BIOLOGY

CLASS-XI
Members of Review Committee
S.No. Name Designation School

1. Ms. Sarita Singh Vice Dr. B.R. Ambedkar SOSE,

Principal Sector-18, Rohini, Delhi

2. Ms. Iqbal Kaur Lecturer RPVV, Shalimar Bagh, Delhi

3. Ms. Shikha Khatri Lecturer GGSSS, AP-Block, Shalimar
Bagh, Delhi
4. Ms. Leena Saxena Lecturer SKV, H-Block, Ashok Vihar,
Phase-1, New Delhi

5. Ms. Pooja Verma Lecturer School of Excellence, Dwarka,

New Delhi

xiii
xiv
 SYLLABUS
SESSION (2023-24)
CLASS - XI
SUBJECT : BIOLOGY

Orientation and Recapitulation

Discussion on importance of biology, scope of biology and other topics of

interest.

Unit–I Diversity of Living Organisms Marks : 15

Chapter–1 : The Living World

Biodiversity; Need for classification; three domains of life ; taxonomy and

systematics; concept of species and taxonomical hierarchy; binomial nomenclature.

Chapter–2 : Biological Classification

Five kingdom classification; Salient features and classification of Monera,

Protista and Fungi into major groups; Lichens,Viruses and Viroids.

Chapter–3 : Plant Kingdom

Classification of plants into major groups; Salient and distinguishing features

and a few examples of Algae, Bryophyta, Pteriodophyta, Gymnospermae (Topics
excluded - Angiosperms, Plant Life Cycle and Alternation of Generations)

Chapter–4 : Animal Kingdom

Salient features and classification of animals non-chordates upto phyla level

and chordates up to class level (Salient features and at least two examples of each
category).
(No live animals or specimen should be displayed).

xv
 PRACTICALS
1. Study of the parts of a compound microscope. (Spotting)
2. Study of the specimens/slides/models and identification with reasons.
Bacteria, Oscillatoria, Spirogyara, Rhizopus, Mushroom, Yeast, Liverwort, Moss,
Fern, Pine, One monocotyledonous plant, One dicotyledonous plant, One lichen.
(Spotting)
3. Virtual specimens/slides/models and identifying features of - Amoeba,
Hydra, Liverfluke, Ascaris, Leech, Earthworm, Prawn, Silkworm, Honey bee,
Snai, Starfish, Shark, Rohu, Frog, Lizard, Pigeon and Rabit. (Spotting)
Unit–II Structural Organisation in Animals and Plants Marks : 10

Chapter–5 : Morphology of Flowering Plants

Morphology of different plants of flowering plants : root, stem, leaf,

inflorescence, flower, fruit and seed. Description of family Solanaceae.

Chapter–6 : Anatomy of Flowering Plants

Anatomy and functions of tissues systems in dicots and monocots.

Chapter–7 : Structural Organisation in Animals

Morphology, Anatomy and functions of different systems (digestive,

circulatory, respiratory, nervous and reproductive) of frog.

PRACTICALS

4. Study and describe locally available common flowering plants, from family
Solanaceae (Poaceae, Asteraceae or Brassicaceare can be substituted in case of
particular geographical location) including dissection and display of floral whorls,
anther and ovary to show number of chambers (floral formula and floral diagrams),
type of root (tap and adventitious); type of stem (herbaceous and woody); leaf
(arrangement, shape, venation, simple and compound)
5. Preparation and study of T.S. of dicot and monocot roots and stems
(primary). (Core)
6. Different types of inflorescence (cymose and racemose) (Spotting).

xvi
Unit–III Cell : Structure and Function Marks : 15

Chapter–8 : Cell-The Unit of Life

Cell theory and cell as the basic unit of life : Structure of prokaryotic and
eukaryotic cells; Plant cell and animal cell; cell envelope; cell membrane, cell
wall; cell organelles–structure and function; endomembrane system, endoplasmic
reticulum, golgi bodies, lysosomes, vacoules ; mitochondria, ribosomes, plastids,
microbodies; cytoskeleton, cilia, flagella, centrioles (ultrastructure and function);
nucleus.

Chapter–9 : Biomolecules

Chemical constituents of living cells : Biomolecules, structure and function of

proteins, carbohydrates, lipids, nucleic acids, Enzymes– types, properties, enzymes
action. (Topics excluded: Nature of Bond Linking Monomers in a Polymer,
Dynamic State of Body Constituents - Concept of Metabolism, Metabolic Basis
of Living, The Living State)

Chapter–10 : Cell Cycle and Cell Division

Cell cycle, mitosis, meiosis and their significance.

PRACTICALS

7. Tissues and diversity in shape and size of animal cells (squamous epitheliu,
smooth, skeletal and cardiac muscle fibers and mammalian blood smear) through
temporary/permanent slides. (Spotting)
8. Mitosis in onion root tip cells and animal cells (grasshopper) from
permanent slides. (Spotting)
9. Test for the presence of sugar, starch, proteins and fats in suitable plant
and animal materials. (Core)
Unit–IV Plant Physiology Marks : 12

Chapter–13 : Photosynthesis in Higher Plants

Photosynthesis as a mean of autotrophic nutrition; site of photosynthesis,

pigments involved in photosynthesis (elementary idea); photochemical and

xvii
biosynthetic phases of photosynthesis, cyclic and non-cyclic photophosphorylation;
chemiosmotic hypothesis; photorespiration; C3 and C4 pathways; factors affecting
photosynthesis.

Chapter–14 : Respiration in Plants

Exchange of gases; cellular respiration–glycolysis, fermentation (anaerobic),

TCA cycle and Electron Transport System (aerobic); energy relations–number of
ATP molecules generated; amphibolic pathways; respiratory quotient.

Chapter–15 : Plant–Growth and Development

Seed germination; phases of plant growth and plant growth rate; conditions
of growth; differentiation, dedifferentiation and redifferentiation;’ sequence of
developmental processes in a plant cell; growth regulators–auxin, gibberellin,
cytokinin, ethylene, ABA.

PRACTICALS

10. Study of osmosis by potato osmometer. (Core)

11. Study of plasmolysis in epidermal peels (e.g. Rhoeo/lily leaves or fleshy

scale leaves of onion bulb). (Core)

12. Separation of plant pigments, through paper chromatography. (Core)

13. Study of distribution of stomata in the upper and lower surface of leaves.
(Core)

14. Study of the rate of respiration in flower buds/leaf tissue and germinating
seeds. (Core)

Unit–V Human Physiology Marks : 18

Chapter–17 : Breathing and Exchange of Gases

Respiratory organs in animals (recall only); Respiratory system in human;

mechanism of breathing and its regulation in humans–exchange of gases, transport
of gases and regulation of respiration, respiratory volume; disorders related to
respiration–asthma, emphysema, occupational respiratory disorders.

xviii
Chapter–18 : Body Fluids and Circulation

Composition of blood, blood groups, coagulation of blood; composition of

lymph and its function; human circulatory system–structure of human heart and
blood vessels; cardiac cycle, cardiac output, ECG; double circulation; regulation
of cardiac activity; disorders of circulatory system–hypertension, coronary artery
disease, angina pectoris, heart failure.

Chapter–19 : Excretory Products and Their Elimination

Modes of excretion–ammonotelism, ureotelism, uricotelism; human

excretory system–structure and function; urine formation, osmoregulation of
kidney function–renin–angiotensin, atrial natriuretic factor (ANF), ADH and
diabetes insipidus; role of other organs in excretion;’ disorders– uraemia, renal
failure, calculi, nephritis; dialysis, artificial kidney and kidney transplant.

Chapter–20 : Locomotion and Movement

Types of movement–Ciliary, flagellar, muscular; skeletal muscle, contractile

proteins and muscle contraction; skeletal system and its functions; joints; disorders
of muscular and skeletal system–myasthenia gravis, tetany, muscular dystrophy,
arthritis, osteoporosis, gout.

Chapter–21 : Neural Control and Coordination

Neuron and nerves; Nervous system in humans–central nervous system;

peripheral nervous system and visceral nervous system; generation and conduction
of nerve impulse.

Chapter–22 : Chemical Coordination and Integration

Endocrine glands and hormones; human endocrine system–hypothalamus,

pituitary, pineal, thyroid, parathyroid, adrenal, pancreas, gonads; mechanism of
hormone action (elementary idea); role of hormones as messengers and regulators,
hypo–and hyperactivity and related disorders; dwarfism, acromegaly, cretinism,
goiter, exophthalmic goitre, diabetes, Addison’s disease.

Note : Diseases related to all the human physiological systems to be taught in brief.

xix
 PRACTICALS

15. Test for presence of urea in urine. (Core)

16. Test for presence of sugar in urine. (Core)

17. Test for presence of albumin in urine. (Core)

18. Test for presence of bile salts in urine. (Core)

19. Human skeleton and different types of joints with the help of virtual
images/models only. (Spotting)

• Investigatory project and its submission

• REVISION of whole syllabus and Final Practical Exam.

• COMMON ANNUAL SCHOOL EXAMINATION-2024.

xx
 BIOLOGY – XI
Index
S. No. Chapter Name Page No.

1. The Living World 1-6

2. Biological Classification 7 - 20
3. Plant Kingdom 21 - 32
4. Animal Kingdom 33 - 47
5. Morphology of Flowering Plants 48 - 61
6. Anatomy of Flowering Plants 62 - 73
7. Structural Organization in Animals 74 - 88
8. Cell : The Unit of Life 89 - 101
9. Biomolecules 102 - 114
10. Cell Cycle and Cell Division 115 - 125
11. Transport in Plants 126 - 140
12. Mineral Nutrition 141 - 153
13. Photosynthesis in Higher Plants 154 - 169
14. Respiration in Plants 171 - 183
15. Plant Growth and Development 184 - 195
16. Digestion and Absorption 196 - 206
17. Breathing and Exchange of Gases 207 - 217
18. Body Fluids and Circulation 218 - 230
19. Excretory Products and their Elimination 231 - 242
20. Locomotion and Movement 243 - 253
21. Neural Control and Coordination 254 - 265
22. Chemical Coordination and Integration 266 - 277
Solved Sample Paper 278 - 288
Unsolved Sample Paper 289 - 301

xxi
xxii
 Points to Remember
1. Organism (Microorganism, plant and animals) who posseses life is living.
2. Life is a complex organisation expressing itself through chemical reactions
and exhibit characteristics of living organisms.
3. Characteristics of Living Organisms : Growth, reproduction, metabolism,
cellular organisation, consciousness, self-replicating and self regulation.
 Reproduction and growth are NOT defining properties.

 Metabolism (catabolism + anabolism), cellular organisation and

consciousness are defining properties.
 Living organisms are self-replicating, evolving, self-regulating and

interactive systems capable of responding to external stimuli.

4. Biodiversity : The term used to refer to the variety of microorganisms, plants
and animals on earth.
5. Need for classification : To organise the vast number of microorganisms,
plants and animals into categories that could be named, remembered, studied
and understood.
6. Taxonomy : Study of principles and procedures of identification, nomenclature
and classification.
7. Systematics : It deals with classification of organisms based on their
diversities and relationships among them. The term was proposed by Carolus
Linnaeus who wrote ‘Systema Naturae’.
8. Concept of Species : All the members that can interbreed among themselves
and can produce fertile offsprings are the members of same species. This is
the biological concept of species proposed by Mayr.
9. Taxa : Each category (i.e., unit) of classification is called as a taxon.
10. Taxonomic Hierarchy : Classification of organisms in a definite sequence
of taxon or category or rank in a descending order.
Kingdom → Phylum /Division → Class → Order → Family → Genus → Species.

The Living World 1

11. Binomial Nomenclature : Given by Carolus Linnaeus. Each scientific name
has two components-Generic name + Specific epithet.
12. ICBN : International Code for Botanical Nomenclature (for giving scientific
name to plants.)
13. ICZN : International Code of Zoological Nomenclature (for giving scientific
name to animals.)
14. Rule for Nomenclature :
 Latinised names are used.
 First word is genus, second word is species name.
 Printed in italics; if handwritten then underlined separately.
 First word of Genus starts with capital letter while species name starts
with small letter.
15.  Scientific names of some organisms :
Man — Homo sapiens
Housefly — Musca domestica
Mango — Mangifera indica
Wheat — Triticum aestivum
16. Taxonomical aids are the tools for study of taxonomy.
17. Museums in educational institutes (school and colleges) have collection of
skeletons of animals, stuffed and preserved specimens of organisms for study
and reference.
18. Zoological Parks (Places where wild animals are kept in protected environment
under human care) Example : National Zoological Park, Delhi.
19. Herbarium : Store house of dried, pressed and preserved plant specimen
on sheets, kept systematically according to a widely accepted system of
classification, for future use.
20. Botanical Garden : Collection of living plants for reference.
Example : Royal Botanical garden Kew (England), National Botanical

Research Institute (Lucknow), Indian Botanical Garden (Howrah, Kolkata).
21. Keys : (Used for identification of plants and animals on the basis of similarities
and dissimilarities) two types < Indented key, Bracketed key.
22. Couplet : the two alternate characteristic statement used in key to identify
organisation.
23. Each Statement of the key is called a lead.
24.  Flora (Index to plant species found in a particular area.)

2 Biology Class - 11
25.  Manuals (Provide information for identification of name of species in an
area.) It is a handy book.
26.  Monographs (Contain information on any one taxon.)

Question

(SRT) Select Response Type Question (1 mark each)

1. Which of the following botanical garden is the home for great banyan tree?
(a) Acharya Jagadish Chandra Bose Indian Botanic Garden
(b) Narendra Narayan Park
(c) Jawaharlal Nehru Tropical Botanic Garden and Research Institute
(d) Agri Horticultural Society of India
2. When we study about different kinds of organisms and their diversities along
with the relationships among them is called
(a) Nomenclature (b) Systematics
(c) Taxonomic hierarchy (d) Classification
3. Which of the following is not a taxon
(a) Genus (b) Order
(c) Taxonomic key (d) Family

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions  (1 mark each)
4. Define species.
5. Define Life.
6. Name two genus belonging to family Felidae.
7. Assertion: In planaria larva, a fragmented organism regenerates the lost
body part of its body and becomes, a new organism.
Reason: Reproduction is defining feature of life forms.
(a) Both assertion and reason are true, and the reason is the correct
explanation of the assertion.

The Living World 3

 (b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.

Short Answer Question-I (2 marks each)

8. What are the basis of modern taxonomical studies ?
9. Why growth and reproduction cannot be taken as defining property of all
living organisms ?
10. How are museum different from zoological parks?
11. Discuss the advantages of assigning a scientific name to living organism.
12. How systematics is different from taxonomy?
13. Write two significances of taxonomical aids.
14. Explain the concept of species given by Ernst Mayr.
Short Answer Question-II (3 marks each)
15. What is the difference between Botanical Garden and Herbarium ?
16. Keys are analytical in nature and are helpful in identification and classification
of organisms. How ?
17. Define : (a) Genus (b) Family (c) Order
18. Write the taxonomic categories showing hierarchal arrangement in ascending
order.
19. What are botanical gardens? Mention names of three famous botanical gardens.
20. Write a short note on flora, manual, monograph and catalogue.
Long Answer Questions (5 marks each)
21. What are the universal rules of nomenclature ? What does ‘Linn.’ Refers to
in Mangifera indica Linn ?
22. Illustrate taxonomical hierarchy with suitable examples from plant and animal
species.
23. Define classification. What is the significance of classification ? What is the
six kingdom classification ?
24. What is herbarium? How is it prepared? Mention the information that a label
of herbarium sheet carry. What is the advantage of herbarium sheets?
4 Biology Class - 11
25. Who proposed three domain classifications? Explain this concept.

Answers
(SRT) Select Response Type Question (1 mark each)
1. (a) 2. (b) 3. (c)

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 marks each)
4. Members that can interbreed to produce fertile offspring.
5. Life is unique, complete functioning of metabolic activities
6. Felis and Panthera.
7. (c)

Short Answers-I (2 marks each)

8. External and internal structure, structure of cell, development process and
ecological information.
9.  Non-living things can also increase in mass by accumulation of material
on surface (accretion.)

 Many organisms do not reproduce (e.g., mules, sterile worker bees.)
10. Refer point to remember on page no. 2.
11. The scientific name ensures that each organism has only one name. Description
of any organism should enable the people to arriave at the same name. They
also ensure that such a name has not been used for any other known organism.
12. Refer to point to remember on page no. 2.
13. They help in correct classification and identification of organisms. These
are fundamental to studies and essential for training in systematics.
14. Refer to point to remember on page 2.

Short Answers-II (3 marks each)

15. Botanical Garden : Collection of living plants.

The Living World 5

 Herbarium : Collection of dried, pressed and prerserved plant specimens on
sheets.
16. Key is a list of alternate characters arranged in such a manner that by
acceptance and rejection one can easily identify an organisms as to its name
and position. Keys are generally analytical in nature.
17. (a) Genus : Group of related species;
(b) Family : Group of related genera;
(c) Order : Group of related families.
18. Species, genus, family, order, class, phylum/division, kingdom.
19. Refer to points on page 3.
20. Refer to points on page 3.

(CRT) Long Answers (5 marks each)

21. Refer page no. 7, NCERT, Text Book of Biology for Class XI.
‘Linn.’ indicates that the species was first described by Linnaeus.
22. Refer table 1.1, page no. 11, NCERT, Text Book of Biology for Class XI.
23. Grouping organisms on the basis of their similarities and differences.
Significance : – Aids in study, better understanding, predicting the features
of the group known.
Refer ‘Points to Remember’ for six kingdom classification in three domains
of life.
24. Refer page no. 11, NCERT, Text book of Biology class XI.
25. Refer to point to remember on page 1.
 

6 Biology Class - 11
 Points to Remember
Systems of Classification :
 Earliest classification was given by Aristotle.
Divided plants into herbs, shrubs and trees.
Animals into those with red blood and those who do not have it.
 Two kingdom classification : Given by Carolus Linneaeus–Kingdom–
plantae and kingdom–Animalia.
 Five kingdom classification : By R.H. Whittaker, Monera, Protista, Fungi,
Plantae and Animalia are the five kingdoms.
 The main criteria for classification of organisms into five kingdoms include
cell structure, thallus organisation, mode of nutrition, reproduction and
phylogenetic relationships.
Three Domains of Life : Proposed by Carl Woese in 1990, who also proposed
the six kingdom classification for living organisms. The three Domains of
life are Archaea, Bacteria and Eukarya.
1 Kingdom
Archaea → 1. Archaebacteria
2 Prokaryotic organisms in extreme conditions
Domains Bacteria → 2. Eubacteria
of life 3
Eukarya → 3. Protista
→ 4. Fungi Eukaryotic
→ 5. Plantae Organisms
→ 6. Animalia

Biological Classification 7
1. Artificial System of Classification
1. It utilise one or two morphological trail.
2. Homology is never standard.
3. The system does not employ characters from anatomy, cytology,
biochemistry, genetics, etc. for grouping of organisms.
2. Natural System of Classification
1. The system employs several morphological character for grouping of
organisms.
2. It studies homology in all characters including morphology, anatomy, etc.
3. This system gives information about both natural relationship and
phylogeny.
3. Phylogenetic System of Classification
It was proposed by Engler and Prantl. They arranged flowering plants
according to increasing complexity of their floral morphology.
It was based on possible evolution of different traits.
4. Objections to two kingdom system
1. Lichen with dual mode.
2. Fungi remain fixed but nutrition saprophytic.
3. No distribution of unicellular and multicellular organism.
4. No distribution of prokaryotic and eukaryotic organisation.
5. Euglena can move as well as can do photosynthesis.

Kingdom Monera :
 Has bacteria as sole members.
 Cell wall made up of peptidoglycan.
 Bacteria can have shapes like : Coccus (spherical), Bacillus (rod-shaped),
Vibrium (comma shaped) and spirillum (spiral shaped).
 Bacteria found almost everywhere and can be Photosynthetic autotrophs,
Chemosynthetic autotrophs or Heterotrophs.
Archaebacteria
Bacteria
Eubacteria

8 Biology Class - 11
  Archaebacteria
 Halophiles (salt-loving)
 Thermoacidophiles (in hot springs)
 Methanogens (in marsh and in gut of ruminant animals. Produce methane gas.)
 Eubacteria
 Photosynthetic autotrophs like Cyanobacteria (Blue-green algae). Some like
Anabaena and Nostoc have specialized cells called heterocysts for nitrogen
fixation.
 Algae bloom is rich growth of blue green algae over the surface of polluted
water bodies.
 Algae bloom releases neurotoxins, deplete oxygen and makes water unfit
for use.
 Chemosynthetic autotrophs : Oxidise various inorganic substances like
nitrates/nitrites, ammonia and use released energy for their ATP production.
They helps in nutrients recycling of N, P, Fe and S.
 Heterotrophic bacteria : Decomposers help in making curd, production of
antibiotic, N2 fixation, casuse diseases like cholera, typhoid, tetanus and
citrus canker.
Mycoplasmas : Completely lack cell wall. Smallest living cells. Can survive
without oxygen. Pathogenic in animals and plants.

Kingdom PROTISTA

(Comprises of all single celled eukaryotes)
 Forms a link between plants, animals and fungi.
(i) Chrysophytes (Has diatoms and golden algae/desmids)
Fresh water/marine, photosynthetic, microscopic plankton.
 Chief producers in Ocean.
 Cell walls have silica which makes it indestructible and cell walls
overlap to fit together like a soap box.
 Their accumulation forms ‘Diatomaceous Earth” (gritty soil)
 Used in polishing, filtration of oils and syrups.

Biological Classification 9
 (ii) Dinoflagellates :
 Marine, photosynthetic, cell wall has stiff cellulose plates.
 Two flagella–one longitudinal and other transverse in a furrow
between wall plates.
 Example : Gonyaulax multiples rapidly, make sea appear red
(red tides) and produce toxins to kill marine animals.
(iii) Euglenoids :
 Found in stagnant fresh water.
Have protein rich layer ‘pellicle’ which makes body flexible.
 Photosynthetic in presence of sunlight but become heterotrophs if
they do not get sunlight. (Mixotrophic nutrition)
 Example : Euglena
(iv) Slime Moulds :

 Saprophytic protists
 Under suitable conditions form an aggregates called plasmodium,
grows on decaying twigs and leaves.
 During unfavourable conditions, plasmodium differentiates and
forms fruiting bodies bearing spores at their tips.
 Spores have true walls which are extremely resistant and survive for
many years and dispersed by air currents.
(v) Protozoans : Are heterotrops and live as parasites. Have four major
groups.
Amoeboid : Catch prey using pseudopodia, e.g., Amoeba. Entamoeba
are parasite.
Flagellated : Have one or more flagella. Cause disease like Sleeping
Sickness e.g., Trypanosoma.
Ciliated : Have clilia to move food into gullet and help in locomotion.
e.g., Paramoecium.
Sporozoans : Have infective spore like stage in life cycle, e.g.,
Plasmodium which causes malaria.

10 Biology Class - 11
Kingdom Fungi
1. Heterotrophic organisms
2. Non chlorpohyllous hyphae
3. Network of hyphae called mycelium
4. Hyphae which have multinucleated cytoplasm are called coenocytic hyphae
5. Cell wall of chitin and polysaccharides
6. Cosmopolitan. Grow in warm and humid places.
7. Saprophytic, parasitic, symbiotic (Lichen and Mycorrhiza) e.g., Puccinia,
(wheat rust disease), Penicillium, Yeast (unicellular fungus).
8. Reproduction can take place by vegetative means fragmentation, fission
and budding. Asexual reproduction by spores–conidia, sporangiospores or
zoospores. Sexual reproduction by oospores, ascospores and basidiospores–
produced in fruiting bodies.
9. Sexual cycle involves 3 steps :

(i) Plasmogamy (fusion of Protoplasms.)
(ii) Karyogamy (fusion of two nuclei.)
(iii) Meiosis in zygote resulting in haploid spores.
10. Dikaryophase is a condition of having dikaryon in an intervening dikaryotic
stage (n + n i.e., two nuclei per cell) between plasmogamy and karyogamy
in fungi like ascomycetes and basidiomycetes.

Classes of Fungi
(i) Phycomycetes :

 grow on decaying wood or as obligate parasites on plants

 Mycelium aseptate and coenocytic

 Spores produced endogenously in sporangium.

 Asexual reproduction by Zoospores or Aplanospores

 Zygospores are formed by the fusion of gametes.
e.g., Rhizopus, Albugo, Mucor

Biological Classification 11
 (ii) Ascomycetes :

 also known as ‘sac fungi’

 Are saprophytic, decomposers, parasitic or coprophilous (growing on
dung).

 Mycelium branched and septate

 Asexual spores are called conidia produced exogenously on the
conidiophores.
Sexual spores are called ascospores produced endogenously in ascus, produced
inside fruiting body called Ascocarp.
e.g., Aspergillus, Neurospora, Saccharomyces (Unicellular fungi),
Claviceps, morels, truffles
(iii) Basidiomycetes :

 Mycelium septate and branched.

 Generally asexual spores are not found.

 Vegetative reproduction by fragmentation.

 Sexual reproduction by fusion of vegetative or somatic cells to form basidium
produced in basidiocarp.

 Basidium produces four basidiospores exogenously after meiosis.
e.g., Agaricus, Ustilago, Puccinia
(iv) Deuteromycetes :

Taxnomic of Hypha Type of Re- Characteristic Origin of Examples of

Fungi production spore Spore Fungi

Phycomycetes Asptate Asexually Sporangio- Sporangio- Nuisance

spore phore fungi includ-
Zygospore ing genera
Aplanospore Albugo,
Mucor, and
Sexually Zygospore Fussion of Rhizopus
or nuclei
oospore

12 Biology Class - 11
Ascomycetes Septate Asexually Blastospore Budding Penicillium
Aspergillus
Conidium Conidio- Clavicep
phore Neurospora
Sexually Ascospore
Ascus Sacchaaro-
myces
(perfect
yeast)

Basidiomy- Septate Sexually Basidiospore Basidium Mushrooms,

cetes smuts and
rusts

Deuteromy- Septate Asexually Thallospore Thallus Most sapro-

cetes (fungi (hypha) phytes and
imperfecti) pathogens
Conidium Conidio- encountered
phore in medical
mycology
(Imperfect
mould)

 Called as ‘Fungi Imperfecti’ as sexual form (perfect stage) is not known for
them.

 Once sexual form is discovered the member is moved to Ascomycetes or
Basidiomycetes.

 Mycelium is septate and branched.

 Are saprophytic parasitic or decomposers.
e.g., Alternaria, Colletotrichum, Trichoderma.
Viruses :
 They did not find a place in biological classification.
 Not truly living.

Biological Classification 13
  Non-cellular organisms which take over the machinery of host cell on entering
it and become living but as such they have inert crystalline structure appear
non-living. So, difficult to call them living or non-living.
 Virus means venom or poisonous fluid. Pasteur gave the term ‘virus’.
 D.J. Ivanowsky found out that certain microbes caused Tobacco Mosaic
Disease in tobacco plant.
 M.W. Beijerinek called fluid as ‘Contagium vivum fluidum’ as extracts of
infected plants of tobacco could cause infection in healthy plants.
 W.M. Stanely showed viruses could be crystallized to form crystals of protein
which are inert outside their specific host.
 Viruses are obligate parasites.

Structure of Virus :
 It is a nucleoprotein made up of protein coat called Capsid. Capsid is made
up of capsomeres arranged in helical or polyhedral-geometric forms. Have
either DNA or RNA as genetic material which may be single or double
stranded.
 Usually plant viruses have single stranded RNA; bacteriophages have double
stranded DNA and animal viruses have single or double stranded RNA or
double stranded DNA.

Diseases caused in humans :

Mumps, small pox, herpes, influenza and AIDS etc.
In plants, symptoms can be mosaic formation, leaf rolling and curling,
yellowing and vein clearing, dwarfing and stunted growth.

Viroids :
 Infectious agent, free RNA (lack protein coat)
 RNA is of low molecular weight.
 Causes potato spindle tuber disease.
 Discovered by T.O. Diener.

Prions
 They are highly resistant glycoproteins molecule which function as infectious
agent.
14 Biology Class - 11
Lichens :
 Symbiotic association between algal component (Phycobiont) and fungal
component (Mycobiont). Algae provides food via photosynthesis. Fungi
provides shelter and absorb nutrients and water for alga.
 Good pollution indicators as they do not grow in polluted areas. (SO2 rich
areas)

Questions

(SRT) Select Response Type Question (1 mark each)

1. There are specialised cells called heterocysts in Nostoc and Anabaen. The
function of heteocyst is to
(a) To absorb nutrients from thin water film over the body of the organisms
(b) To fix carbon-di-oxide into carbohydrates
(c) To synthesise protein from absorbed nitrogen
(d) To fix nitrogen into products such as ammonia
2. One of following Assomycetes is called model organisms and is used
extensively in genetic research.
(a) Neurospara (b) Saccharomyces
(c) Penicillium (d) Aspergillus
3. Archaebacteria and eubacteria difers in
(a) Eubactria live in harsh environments
(b) Eubacteria have rigid cell wall
(c) Cell wall is absent in eubacteria
(d) Eubacteria are autotrophs only

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Question (1 mark each)
4. Which group comprises of single celled eukaryotes only ?

Biological Classification 15
 5. Which organisms are the chief producers in oceans ?

6. Name the fungus which causes disease in wheat (i) rust (ii) smut.

7. What is the principle underlying the use of cyanobacteria in agriculture ?

8. Define dikaryon stage. Where do you observe this stage?

9. Differentiate between zoospore and zygospore?

Short Answer Question-I (2 marks each)

10. How are bacteria classified on the basis of their shapes ?

11. What is the mode of reproduction in bacteria ?

12. Why are red tides caused and why are they harmful ?

13. Viruses and viroids differ in structure and the diseases they cause. How ?

14. Which class of kingdom fungi has both unicellular as well as multicellular
member ? When is a fungus called coprophilous ?

15. Why two kingdom classification was not sufficient? Explain with the help
of two examples.

16. How flexibility is maintained in the body of Euglena?

Short Answer Question-II (3 marks each)

17. Who gave five kingdom classification ? What was the criteria used for such
classification ?
18. What are the modes of nutrition in fungi ?
19. Some symbiotic organisms are very good pollution indicators and composed
of a chlorophyllous and a non-chlorophyllous member. Describe them.
20. Who gave two kingdom classification? Write its draw backs?
21. Explain how reproduction takes place in phycomycetes?
22. Differentiate between mode of sexual reproduction in ascomycete and
basidiomycetes.

16 Biology Class - 11
Long Answer Questions (5 mark each)
23. Some primitive relatives of animals live as predators or parasites and are
divided into four major groups. Elaborate.

24. Differentiate between various classes of kingdom Fungi on the basis of their
(i) Mycelium, (ii) Types of spores and (iii) Types of fruiting body. Also give
two examples for each class.

25. Describe sexual reproduction in fungi.

26. Draw a labelled diagram of bacteriophage. Write its characters also.

27. Discuss how the system of biological classification has been evolved in past?

Answers
Select Response Type Question (1 mark each)
1. (d) To fix nitrogen into products such as ammonia
2. (a) Neurospora
3. (b) Eubacteria have rigid cell wall

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Kingdom Protista.
5. Diatoms
6. (i) Puccinia, (ii) Ustilago
7. Capability of nitrogen fixation
8. Refer to point to remember on page 10.
9. Motile asexual spores of class phycomycetes are known as zoospores whereas
zygospores are formed by fusion of two gametes.

Short Answers-I (2 marks each)

10. Bacillus (rod-shaped), Coccus (spherical), Vibrio (comma shaped) and
Spirillum (spiral shaped).
Biological Classification 17
11. Mainly by fission; Production of spores in unfavourable conditions. Sexual
reproduction by DNA transfer.
12. Rapid multiplication of dinoflagellates like Gonyaulax. Harmful as they
release toxins which kill marine animals.
13. Refer ‘Points to Remember’.
14. Ascomycetes : Yeast (Unicellular), Penicillum (Multicellular), Coprophilous,
means fungi which grow on dung.

15. Refer page no. 17 and 18, NCERT, Text book of Biology class XI.

16. Instead of cell wall, they have a protein rich layer called pellicle which makes
their body flexible.

Short Answers-II (3 marks each)

17. R.H. Whittaker, Criteria for classification : Cell structure, thallus organisation,
mode of nutrition, reproduction and phylogenetic relationships.
18. Saprophytes, Parasites, Symbionts-Lichens and Mycorrhiza.
19. Lichens, Refer ‘Points to Remember’.
20. Carolous Linnaeus. Refer to points.

21. Refer page no. 23, NCERT, Text Book Biology class XI.

22. Refer page no. 23 and 24, NCERT, Text Book Biology class XI.

Long Answers (5 marks each)

23. Protozoans. Refer page no 21-22, NCERT Text Book of Biology for Class
XI.

24. Refer NCERT Text Book of Biology for Class XI, Page no. 23-24.

25. Refer NCERT text book of Biology for Class XI Page 23. (Plasmogamy,
Karyogamy, Meiosis in zygote, Dikaryophase)

The steps are :

18 Biology Class - 11
 (i) Plasmogamy : fusion of protoplasm of two motile or non-motile gametes.

(ii) Karyogamy : fusion of two nuclei.

(iii) Zygotic Meiosis to form haploid spores.

(iv) Dikaryophase in ascomycetes and basidiomycetes where before

karyogamy two nuclei per cell (dikaryon) are found.

26. NCERT page no. 26 Fig 2.6 (b), for characters refer Page 14 of Support
Material.

27. Refer to point to remember on page 6, 7 and 8.

Case Study (4 Mark each)

Corona viruses are a board family of viruses that cause illnesses ranging
from the common cold to many serious respiratory disorders. SARS-
CoV 19 is a novel Corona Viruses strain that has never been found
in humans before. Corona viruses spread from animals to humans.
Fever, cough, shortness of breath, and breathing difficulties are all
common symptoms of infection. Infection can lead to pneumonia,
severe acute respiratory syndrome, kidney failure, and even death in
more severe cases. Hand washing, coughing with your mouth and nose
covered, and cooking are all standard advice for preventing infection
spread. Close contact with anyone who has respiratory symptoms like
coughing or sneezing should be avoided.

1. Novel corona virus belongs to the category of viruses having :

(a) DNA as genetic material

(b) Double stranded RNA as genetic material

(c) Single stranded DNA as genetic material

(d) Single stand RNA as genetic material

Ans.: (d)
Biological Classification 19
 2. Assertion: An effective antibiotic should be used to prevent the disease
caused by Novel corona virus.

Reason : Effective antibiotic will reduce the chance of getting infection

from viruses including Novel corona virus.

(a) Both assertion and reason are true, and the reason is the correct
explanation of the assertion.

(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.

(c) Assertion is true but reason is false.

(d) Both assertion and reason are false.

Ans.: (d)

3. Read the following statements :

Statement I : The new coronavirus can be transmitted through mosquito bites

Statement II : The COVID-19 virus does not transmit through water while
swimming.

Choose from below the correct alternative.

(a) Only I is true. (b) I and II true.

(c) I is true but II is false. (d) I is false but II is true.

Ans.: (d)
4. Which of the following methods should not be used to prevent infection
from Novel corona virus?
(a) Regular hand washing.
(b) Covering mouth and nose when coughing and sneezing.
(c) Thorough cooking of meat and eggs.
(d) Use of Hand dryers
Ans.: (d)


20 Biology Class - 11
 PLANT KINGDOM

Cryptogamae Phanerogamae
(Plants without seeds & ) (Plants with seeds)
(Sex organs invisible) (Sex organs visible)

Non Vascular Plants Vascular Plants

Gymnospermae Angiospermae
Thallophyta thallus like thread Bryophyta Pteridophyta (Naked Seed) (Seed Enclosed)
Amphibian of (Fern) Sexorgans in ovary
plant Kingdom e.g. Salaginella as cones Flowering
Algae (Moss Plant) Dryopteris Plants
Equisetum

Red Brown Green Cycads Conifers Gnetopsida

Algae Algae Algae Hepaticopsida Anthoceropsida e.g. cycas e.g. pinus e.g. Ginkgo
e.g. Riccia Marchantia
Marchantia Bryopsida
e.g. Funaria

Plant Kingdom
Dicots Monocots
Psilopsida Lycopsida Sphenopsida Pteropsida (twocotyledons) (single cotyledon)
eg. Pea, Gram eg. Wheat, rice

21
 Points to Remember
Classification :
 Artificial System of Classification

 By Carolus Linnaeus, based on androecium structure and vegetative

characters.
 Natural System of Classification

 Based on natural affinities among organisms

 Included external as well as internal features

 By Geroge Bentham and J.D. Hooker

 Phylogenetic System of Classification

 Based on evolutionary relationships between the various organisms

 By Engler and Prantl

 Later on By Hutchinson

Numerical Taxonomy :
 Carried out using computers
 Based on all observable characteristics
 Data processed after assigning number and codes to all the characters.
Advantages : Each character gets equal importance and a number of

characters can be considered.
Cytotaxonomy :
 Based on cytological informations.
 Gives importance to chromosome number, structure and behaviour.

Chemotaxonomy :
 Based on Chemical constituents of the plants.

Algae :
 Chlorophyll bearing, simple, thalloid, autotrophic and largely aquatic
organisms.

22 Biology Class - 11
Importance of Algae :
 Help in carbon dioxide fixation by carrying out photosynthesis and have
immense economic importance.

 At least half of the total carbon dioxide fixation on earth carried out by them.

 Increases dissolved oxygen level in their environment.

 Many species like Laminaria, Sargassum, Porphyra etc. are used as food.

 Agar obtained from Gelidium and Gracilaria which is used in ice-creams

and jellies and to grow microbes.

 Algin obtained from brown algae and carrageen from red algae used
commercially as hydrocolloids.

 Chlorella and Spirullina are unicellular algae, rich in protein and used even
by space travellers.

 Algae are unicellular like Chlamydomonas, colonial like Volvox or or

filamentous like spirogyra and Ulothrix. Occur in water, soil, wood moist
stones etc.

Algae are divided into 3 classes.

(i) Chlorophyceae

 Green algae, Main pigment is chlorophyll ‘a’ and ‘b’.

 Cell wall has inner layer of cellulose and outer layer of pectose.

 Has pyrenoids made up of starch and proteins.

 Pigment and pyrenoids are located in Chloroplast.

e.g., Chlamydomonas, Volvox, Spirogyra, Ulothrix, Chara.

(ii) Phaeophyceae

 Brown algae are brown coloured due to main pigments chlorophyll ‘a’,

‘c’ and fucoxanthin (xanthophyll)

 Cell wall has cellulose with gelantionous coating of algin.

Plant Kingdom 23

 Has mannitol and laminarin (complex carbohydrate) as reserve food

material.

 Body divisible into holdfast, stipe and frond.

 e.g., Ectocarpus, Fucus, Laminaria, Dictyota, Sargassum

(iii) Rhodophyceae

 Red algae are red coloured due to pigments chlorophyll ‘a’, ‘d’ and

r-phycoerythrin.

 Found on surface as well great depths in oceans.

 Cell wall has cellulose.

 Reserve food material is floridean starch.

e.g., Polysiphonia, Porphyra, Gelidium,Gracilaria.

Reproduction in Algae
Vegetative reproduction : by fragmentation
Asexual Reproduction : Flagellated zoospores in Chlorophyceae,
Biflagellated zoospores in Phaeophyceae, By non-motile spores in Rhodophyceae.
Sexual Reproduction : Isogamous, anisogamous or oogamous in
chlorophyceae and Phaeophyceae.
By non-motile gametes and oogamous in Rhodophyceae.

Bryophytes :
 ‘Amphibians of plant kingdom’.
 Occur in damp, humid and shaded places.
 Lack true roots, stem or leaves.
 Main plant body is haploid and thallus like (prostrate or erect)
 Economic Importance : Food for herbaceous animals.
Sphagnum in from of peat is used as fuel and also used as packing material
for trans-shipment of living material, as it has water holding capacity.
Prevents soil erosion, alongwith lichens are first colonizers on barren rock.
 Is divided into two classes Liverworts (thalloid body, dorsiventral, e.g.,

24 Biology Class - 11
 Marchantia) and Mosses (have two stages in gametophyte–creeping, green,
branched, filamentous protonema stage and the leafy stage having spirally
arranged leaves e.g., Funaria, Polytrichum and Sphagnum).

Reproduction in Bryophytes
 Vegetative reproduction by fragmentation.
 Asexual reproduction by gemmae formed in gemma cups.
 Sexual reproduction : Main plant body is haploid, produces gametes and so
called Gametophyte. By fusion of antherozoids produced in antheridium
and egg cell produced in archegonium, results in formation of zygote which
develops into sporophytic structure differentiated into foot, seta and capsule.
Spores produced in a capsule germinate to from free-living gametophyte
(Protonema). Sporophyte is not free living but attached to photosynthetic
gametophyte from which it derives nutrition.

Pteridophytes :
 First terrestrial plants.
 Prefer cool, damp and shady places to grow.
 Grown as ornamentals.
 Used for medicinal purpose, as soil binder.
 Main plant body is sporophyte which is differentiated into true root, stem
and leaves.
 Leaves may be small as in Selaginella or large as in ferms.
 Sporangia having spores are subtended by leaf-like appendages called
sporophylls. (Sporphylls may be arranged to form strobili or cones.)
 In Sporangia, the spore mother cells give to spores after meiosis.
 Spores germinate to form haploid gametophytic structure called prothallus
which is free living, small, unicellular and photosynthetic.
 Prothallus bears antheridia and archegonia which bear antherozoids and
egg cell respectively which on fertilisation from zygote. Zygote produces
multicellular, well differentiated sporophyte.

Plant Kingdom 25
  The four classes are : Psilopsida (Psilotum), Lycopsida (Selaginella),
Sphenopsida (Equisetum) and Pteropsida (Pteris).
Heterospory : Two kinds of spores i.e., large (macro) and small (micro)
spores are produced. e.g.,Selaginella and Salvinia.
Seed Habit : The development of zygote into young embryos takes place
within the female gametophyte which is retained on parent sporophyte. This event
is precursor to seed habit and this is an important step in evolution and is found
Selaginella and Salvinia among the pteridophytes.

Gymnosperms :
 Have naked seeds as the ovules are not enclosed by any ovary wall and
remain exposed.
 Includes shrubs and trees (medium and tall sized).
 Have generally tap roots, stem may be unbranched (Cycas) or branched
(Pinus, Cedrus), leaves–needle like (Pinus) and pinnate (Cycas).
 Roots of Pinus have fungal association in the form of mycorrhiza.
 Cycas have small specialized roots called coralloid root which are associated
with N2 fixing cyanobacteria.
 Heterosporous–Produce haploid microspores and megaspores.
 Male cone has microsporophylls which bear microsporangia having
microspores which develop into reduced gametophyte called pollengrain.
 Female cone has megasporophylls which bear megasporongia having
megaspores which are enclosed within the megasporangium (Nucellus).
One megaspore develops into female gametophyte bearing two or more
archegonia.
 Pollen grains carried in air currents reach ovules, form pollen tube which
reach archegonia and release male gametes which fertilise egg cell and form
zygote which produce embryos. Ovules develop into seeds which are not
covered.

Angiosperms :
 Called flowering plants and have seeds enclosed in fruits.

26 Biology Class - 11
  Divided into two classes–Dicotyledons (have two cotyledons) and
Monocotyledons (have one cotyledon).
 Smallest angiosperm : Wolfia
 Large tree : Eucalyptus (Over 100 meters)
 Stamen has filament and anther. Anthers bear pollen grains. Pollen grains
have two male gametes.
 Pistil has stigma, style and ovary. Ovary has ovule in which female gametophyt
(embryo sac) develops.
 Embryo sac has 7 cells and 8 nuclei.One egg cell 2 synergids, 3 antipodals
and two polar nuclei which fuse to form secondary nucleus.
 Pollen grain is carried by wind, water, insects and other agents reaches to
stigma and produces pollen tube which enters embryo sac.
 Double fertilisation : One male gemate fuses with egg cell (Syngamy) to
form zygote which develops into embryo.
Other male gamete fuses with secondary nucleus (triple fusion) which forms
triploid primary endosperm nucleus (PEN). PEN develops into endosperm which
nourishes the developing embryo.
 Ovules develop into seeds and ovaries into fruits.

Questions
Select Response Type Question (1 mark each)
1. Proteinaceous bodies which are usally surrounded by starch is found in green
algae. What are such bodies called and what is their function?
(a) Pyrenoid body, nitrogen fixation
(b) Pyrenoid body, carbon-di-oxide fixation
(c) Pyretic body, nitrogen fixation
(d) Pyretic body, carbon-di-oxide fixation
2. Peat, a partial decomposed substance used as fuel, leaves/plant used for
trans-shipment of living matrial. Name the plant which serves the mentioned
purpose.

Plant Kingdom 27
ALL IN ONE PCMB #2.0

ALL IN ONE PCMB #1.0

ISC AND ICSE 1.0#

 (a) Marchantia (b) Funaria
(c) Sphagnum (d) Anthoceros
3. Which of the following is not an aquatic pteridophyte?
(a) Salvinia, water moss
(b) Marsilea, water fern
(c) Azolla, mosquito fern
(d) Lycopodium, foot fern

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Question (1 mark each)
4. Define gemma.
5. Which group of plants is regarded as first terrestrial plants ? Why ?
6. Which organism is regarded as one of the tallest tree species ?
7. The gametes and spores of phaeophyceae have a distinct morphology. Give
its name.
8. Which substance has structural similarity to floridean starch ?
9. Name the organism which exhibit heterospory and seed habit.

Short Answer Question-I (2 marks each)

10. Gymnosperms can show polyembryony. Why do you think so ?
11. How is leafy stage formed in mosses ? How is it different from protonema?

Short Answer Question-II (3 marks each)

12. The leaves in gymnosperms are adapted to withstand xerophytic conditions.
Justify.
13. The gametophytes of bryophytes and pteridophytes are different from that
of gymnosperms. How ?
14. Roots in some gymnosperms have fungal or algal association. Give examples,
their names and role in the plants.
15. Why is presence of water a must for fertilisation in pteridophytes ?
16. Draw a neatly labelled diagram of Funaria?

28 Biology Class - 11
17. Differentiate between three classes of algae.
18. Mention any three economic importance of algae.
19. Differentiate between isogamous, anisogamous and oogamous reproduction
in algae.
20. Explain the life cycle of bryophytes.

Long Answer Questions (5 marks each)

21. Explain various classes of Algae.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (b) Pyrenoid body, carbon-di-oxide fixation
2. (c) Sphagnum
3. (d) Lycopodium, foot fern

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Gemma are green, multicullular, asexual buds which develop in receptacles
called as gemma cups.
5. Pteriodphytes. As they possess vascular tissues–xylem and phloem.
6. Sequoia
7. Pyriform (pear-shaped), bear two laterally attached flagella.
8. Amylopectin and glycogen.
9. Selaginella and Salvinia.

Short Answers-I (2 marks each)

10. Have two or more archegonia, so polyembryony can occur.
11. Leafy stage develops from secondary protonema as a lateral bud. Protonema
is creeping, green, branched frequently filamentous stage whereas leafy stage
is upright with spirally arranged leaves.

Plant Kingdom 29
Short Answers-II (3 marks each)
12. Gymnosperms like conifers have : needle shaped leaves to reduce surface
area, thick cuticle and sunken stomata to reduce water loss.
13. Male and female gametophyte have free existence in bryophytes and
pteridophytes but not in Gymnosperms. They remain within sporangia
retained on sporophytes.
14. Pinus has fungal association to form mycorrhiza which helps in absorption
of water and minerals. Cycas has algal association in coralloid roots which
are associated with N2 fixing cyanobacteria.
15. The antheridia produces male gametes, antherozoids which swim in water
to reach archegonia, bearing non-motile egg. Thus fertilisation can occur
only when water is present in the surrounding medium.
16. Refer page no. 34, NCERT, Text book of Biology class XI.
17. Refer page no. 33, NCERT, Text book of Biology class XI.
18. Refer to point to remember on page 18.
19. Refer page no. 30, NCERT, Text book of Biology class XI.
20. Refer page no. 33, NCERT, Text book of Biology class XI.

Long Answers (5 mark each)

21. Rhodophycae/Phoeophyceqe and chlorophyceae with correct explanation.
Case Based Question

Case 1: Bryophytes, or plant amphibians, can be found growing on a

variety of surfaces including rocks, dirt, tree trunks, bones, and rotting wood.
These plants have the ability to live on bare rocks and soil, and so play a
crucial role in xeric plant succession. Mosses are one of the most pollutant-
sensitive components of the plant, and they can be sensitive to both acidity
and nitrogen, which dominate today’s human deposition. Many mosses, like
lichens, have become extinct in urban/industrial settings. Too much nitrogen
can alter morphology, resulting in sparser mats that are more susceptible to
desiccation and less effective in suppressing rivals. Mosses are crucial in
nutrient cycling and nitrogen immobilization in a few ecosystems.

30 Biology Class - 11
 1. Bryophytes are called amphibian of plant kingdom because.
(a) They live in damp and shady places
(b) They can hop like amphibians
(c) They require water to complete the process of sexual reproduction
(d) They can survive on bare cork.
Ans.: (c)
2. Mosses show sensitivity towards
(a) Soil acidity
(b) Level of nitrogen
(c) Both acidity and Nitrogen
(d) Carbon dioxide level increase in air
Ans.: (c)
3. Assertion : Like lichens, many mosses have become extinct from urban/
industrial environments
Reason : Mosses are among the most sensitive group to both acidity and
Nitrogen
(a) Both assertion and reason are true, and the reason is the correct
explanation of the assertion
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion
(c) Assertion is true but reason is false
(d) Both assertion and reason are false
Ans.: (a)


Plant Kingdom 31
32 Biology Class - 11
 Point to Remember
Basis of Classification :
Animals are classified on the basis of following few fundamental features—
1. Levels of Organisation :
(1) Cellular level : Cells are arranged as loose cell aggregates, e.g.,sponges.
(2) Tissue level : The cells performing the same function are arranged into
tissues, e.g., Coelenterates.
(3) Organ level : Tissues are grouped together to form organs, each
specialised for a particular function. e.g., platyhelminthes.
(4) Organ system level : organs are associated to form functional systems
e.g., Annelids, Arthropods, Molluscs, Echinoderms and Chordates.
Example : Circulatory System.
Open type : Blood pumped out through heart. Not confined to blood vessels.
Cells and tissues are directly bathed in it.
Closed types : Blood is circulated through blood vessels (arteries,veins and
capillaries)
2. Symmetry :
 Asymmetrical : Cannot be divided into equal halves through median plane

e.g., Sponges.
 Radial symmetry : Any plane passing through central axis can divide organism

into identical halves. e.g., coelentrates,Ctenophores and echinoderms.

 Bilateral symmetry : Only one plane can divide the organism into two identical

left and right halves e.g., Annelids and Arthropods.

3. Germinal Layers :
Diploblastic : Cells arranged in two embryonic layers i.e., external ectoderm
and internal endoderm. (Mesoglea may be present in between ectoderm and
endoderm) e.g., porifers and Coelentrates. (Cnidarians)
Triploblastic : Three layers present in developing embryo i.e., ectoderm,
mesoderm and endoderm. e.g., Platyhelminthes to Chordates.
Animal Kingdom 33
 4. Coelom (Body cavity which is lined by mesoderm)
Coelomates : Have coelom e.g., Annelids, Arthropods, molluscs, Echinoderms,
Chordates etc.
Pseudocoelomates : No true coelem as mesoderm is present in scattered
pouches between ectoderm and endoderm. e.,g., Aschelminthes.
Acoelomates : Body cavity is absent e.g., Platyhelminthes.
5. Segmentation (A) True Metamerism : Found Annelida,Arthropoda,
Chordata :
 Segmentation is external as well as a internal in Annelids.

 Segmentation is external in Arthropods.

 Segmentation is internal in chordates.

 Metamerism : If body is externally and internally divided into segments

(metameres) with serial repetition of atleast some organs, then phenomenon is

called metamerism e.g., Earthworm. (B) Pseudometamerism : Found in
tapeworm. The proglottids (segments of tapeworm) budded off from neck
not embryonic in origin.
6. Notochord :
 Rod-like structure formed during embryonic development on the dorsal side.

It is mesodermally derived e.g., Chordates.

 Non-chordates do not have notochord .e.g., porifera to echinoderms.

Phylum Porifera :
 Also called sponges.
 Are usually marine and asymmetrical.
 Have cellular level of organisation and diploblastic animals.
 Food gathering, respiratory exchange and removal of wastes occurs through
water canal system. Digestion intracellular.
 Ostia (minute pores on body), spongocoel (body cavity) and osculum help
in water transport. They are lined by choanocytes (collar cells).
 Body wall has skeleton of spicules or spongin fibres.
 Animals are hermaphrodite. Fertilisation internal. Development is indirect
(i.e., has a larval stage distinct from adult stage) e.g., Sycon, Euspongia.
Spongilla (Fresh water sponge)
Phylum Coelenterata :
 Also called Cnidarians.
 Are usually marine and radially symmetrical.
 Sessile or free swimming.

34 Biology Class - 11
Animal Kingdom 35
  Have tissue level of organisation.
 Are diploblastic (with mesogloea)
 Capture of prey, anchorage and defence occurs through cnidoblasts/cnidocytes
(have stinging capsules nematocytes) present on tentacles.
 Digestion extracellular and intracellular.
 Have a central gastro-vascular cavity and an opening, hypostome.
 Body wall of some composed of calcium carbonate. e.g. corals.
 exhibit two body forms : polyp and medusa e.g., Hydra, Aurelia.
 Alternation of generation between body forms called metagenesis ocurs in
Obelia where :

Medusa Polyp. (Sessile and cylindrical)

(free swimming &
umbrella shaped)
 e.g., Physalia, Adamsia, Pennatula, Gorgonia,Meandrina.
Phylum Ctenophora :
 Also called as sea walnuts or comb jellies.
 Are exclusively marine, radially symmetrical.
 Have tissue level organisation, are diploblastic.
 Digestion both extra and intracellular.
 Body has eight external rows of ciliated comb plates for locomotion.
 Show Bioluminescence (Property of living organisms to emit light).
 Hermaphrodite (sexes are not separate).
 Only sexual reproduction occurs. Exernal fertilization. Indirect development.
e.g., Ctenoplana, Pleurobrachia.
Phylum Plathyhelminthes :
 Also called as ‘flat worms’.
 Have dorsoventrally flattened body. Are mostly endoparasites in animals.
 Are bilaterally symmetrical, triploblastic, acoelomate,with organ level of
orgnisation.
 Absorb nutrients through body surface.
 Parasitic forms have hooks and suckers.
 ‘Flame cells’ help in osmoregulation and excretion.

36 Biology Class - 11
  Sexes not separate.
 Fertilisation internal. Many larval stages present. Planaria has high
regeneration capacity. e.g., Taenia, Fasciola.
Phylum Aschelminthes :
 Also called ‘round worms’.
 May be free living, parasitic, aquatic or terrestrial.
 Are bilaterally symmetrical, triploblastic, pseudocoelomate.
 Alimentary canal complete (has muscular pharynx), wastes removed through
excretory pore.
 Sexes separate. (dioecious)
 Females longer than males.
 Fertilisation internal. Development direct or indirect. e.g., Ascaris,Wuchereria,
Ancylostoma.
Phyum Annelida :
 Are aquatic or terrestrial, free-living or parasitic.
 Are bilaterally symmetrical, triploblastic, organ-system level of organisation
and metamerically segmented body.
 Are coelomate animals.
 Have longitudinal and circular muscles for locomation.
 Have closed circulatory system.
 Nereis (dioecious and aquatic annelid) has lateral appendages called parapodia
for swimming.
 Have nephridia for osmoregulation and excretion.
 Neural system consists of paired gangila connected by lateral nerves to a
double ventral nerve cord.
 Reproduction is sexual.
 e.g., Earthworm (Pheretima) and Leech (Hirudinaria) which are hermaph
rodites (i.e., monoecious).
Phylum Arthropoda :
 Largest phylum of Animalia.
 Are bilaterally symmetrical, triplobastic, segmented externally and organ
system level of organisation, coelomate.
 Body divisible into head, thorax, abdomen and has a chitinous exoskeleton.
Jointed appendages are present.

Animal Kingdom 37
 38
Phylum –
CHORDATA

Sub Phylum – Urochordata Cephalochordata Vertebrata

Biology Class - 11
Division
Agnatha Gnathostomata

Super Class

Pisces Tetrapoda

1. Chondrichthyes 1. Amphibia
Class Cyclostomata
2. Osteichthyes 2. Reptilia
3. Aves
4. Mammalia
 Respiration by gills, book gills, book lungs or tracheal system. Excretion


through malpighian tubules.

 Sensory organs : Antennae, eyes; Organs of balance : Statocysts.

 Fertilisation usually internal. Development is indirect or direct. Are mostly

oviparous.
e.g., Apis, Bombyx, Laccifer, Anopheles, Culex, Aedes, Locusta, Limulus.
Phulum Mollusca :
Second largest phylum of Animalia.


 Terrestrial or aquatic

 Are bilaterally symmetrical, triplobastic and organ system level of organisation,

coelomate.
 Body divisible into head, muscular foot and visceral hump and is covered

by calcareous shell and is unsegmented.

 Mantle : Soft and spongy layer of skin; Mantle cavity : Space between

visceral hump and mantle.

 Respiration and excretion by feather like gills in mantle cavity.

 Head has sensory tentacles. Radula a rasping organ for feeding in mouth.

 Are oviparous, dioecious, have indirect development.

e.g., Plia, Pinctada, Octopus, Sepia, Loligo, Aplysia, Dentalium, Chaetopleura.

Phylum Echinodermata :
 Are spiny bodied organisms with endoskeleton of calcareous ossicles.
 Are exclusively marine, radially symmetrical in adult but bilaterally
symmetrical in larval stage. Organ system level of organisation.
 Triploblastic and coelomate.
 Digestive system complete. Mouth ventral, Anus on dorsal side.
 Food gathering, respiration, locomotion carried out by water vascular system.
 Excretory system is absent.
 Reproduction–sexual, sexes are separate.
 Fertilisation external. Development indirect (free swimming larva)
 e.g., Asterias, Cucumaria, Antedon, Echinus, ophiura.
Phylum Hemichordata :
 Represents small group of worm-like organisms.
 Was earlier placed as sub-phylum of Phyum Chordata.

Animal Kingdom 39
 Bilaterally symmetrical, triploblastic and coelomate with organ system level
of organisation.
 Body cylindrical, has proboscis, collar and trunk.

 Circulatory System–open.

 Respiration by gills, excretion by proboscis gland.

 Sexes separate, external fertiliastion, indirect development.

e.g, Balanoglossus, Saccoglossus.

Phylum Chordata :

 Presence of Notochord.

 Have dorsal hollow nerve cord.

 Have paired pharyngeal gill slits.

 Bilaterally symmetrical, triploblastic, coelomate, organ system level of
organisation.

 Heart is ventral.

 Post anal tail present, closed circulatory system.
(i) Sub-Phyla Urochordata /Tunicata
Notocohord present only in larval tail.


e.g., Ascidia, Salpa, Doliolum

(ii) Sub-phyla Cephalochordata
Notochord extends from head to tail (Persistent)


e.g., Amphioxus.
(iii) Sub-Phyla Vertebrata
Have notochord only during embryonic period.


 Notochord gets replaced by bony or cartilaginous vertebral column.

 Have ventral muscular heart, kidneys for excretion and osmoregulation, paired
appendages (fins or limbs)
Vertebrata have two Division :
(a) Agnatha (Lacks Jaw) : Class : Cyclostomata
 Live as ectoparasites on some fishes.

 Have sucking and circular mouth without jaws.

 Have 6-15 paris of gill slits for respiration.

 No scales, no paired fins.

 Cranium and vertebral column is cartilagenous.

40 Biology Class - 11
  Marine, Migrate to fresh water for spawning and die after spawning.

 Larva returns to ocean after metamorphosis.

e.g., Petromyzon, Myxine

(b) Gnathostomata (Bear Jaws)–divides into two super classes :
Super-class : Pisces
1. Class : Chondrichthyes :
 Have cartilagenous endoskeleton, are marine with streamlined body.

 Mouth ventral.

 Gill slits without operculum (gill cover).

 Skin has placoid scales; jaws–very powerful.

 No air bladder, so swim constantly to avoid sinking.

 Teeth are backwardly directed, modified placoid scales.

 Notochord is persistent throughout life.

 Two chambered heart; poikilotherms (cold-blooded)

 Sexes separate; males have claspers on pelvic fins.

 Internal fertilisation; viviparous.

e.g., Torpedo, Trygon, Scoliodon, Pristis, Carcharodon

2. Class : Osteichthyes
 Have bony endoskeleton, Aquatic

 Mouth is usually terminal. Body-Streamlined

 Four pairs of gill slits covered by operculum, heart two chambered, cold

blooded.
 Skin has cycloid/ctenoid scales.

 Have air bladder which regulates buoyancy.

 Sexes separate.

 Usually oviparous, fertilisation external.

 Development direct.

 e.g., Hippocampus, Labeo, Catla, Betla, Clarias, Exocoetus

Sub-Phylum Vertebrata : Gnathostomata

Super Class : Tetrapoda
1. Class : Amphibia
 Can live in aquatic as well as terrestrial habitats.

 Body divisible into head and trunk, paired limbs.

Animal Kingdom 41
  Skin moist. No scales.

 Tympanum represents ear. Eyes have eyelids.

 Cloaca is the common chamber where alimentary canal, urinary and

reproductive tracts open.

 Respiration by gills, lungs or skin.

 Heart is 3-chambered; cold-blooded; Sexes separate; fertilisation external.

 Oviparous. Indirect development.

 e.g., Bufo, Rana, Hyla, Salamandra, Ichthyophis

2. Class : Reptilia
 Creep or crawl to locomote. Mostly terrestrial.

 Body has dry and cornified skin and epideremal scales or scutes.

 Tympanum represents ear.

 Limbs, when present, are two pairs

 Snakes and lizards shed scales as skin cast.

 Heart 3-chambered but 4-chambered in crocodiles.

 Sexes Separate; fertilisation internal.

 Oviparous. Direct development.

 e.g., Testudo, Naja, Vipera, Calotes, Crocodilus, Hemidactylus

3. Class : Aves
 Presence of feathers except flightless birds and beak (modified jaws)

without teeth.
 Forelimbs are modified into wings.

 Hind limbs have scales, modified for walking, swimmng or clasping.

 Skin is dry as no glands on skin except oil gland at base of tail.

 Endoskeleton bony with air cavities (pneumatic) and hollow bones to

assist in flight.
 Crop and Gizzard—Additional chamber in digestive tract.

 Air sacs are connected to lungs to supplement respiration.

 Warm blooded (homoiothermous), Heart–Four chambered.

 Sexes separate, fertilization internal

 Oviparous. Direct development.

 e.g., Columba, Struthio, Pavo, Corvus, Neophron, Pstittacula,

Aptenodytes.
4. Class : Mammalia
 Have mammary glands to nourish young ones.
 Have two pairs of limbs, adapted to perform special work.

42 Biology Class - 11

 Skin has hairs.

 External ears or, pinna present.

 Different types of teeth in jaw.

 Homoiothermous; Heart–Four chambered, Lungs for respiration.

 Sexes are separate, fertilisation internal.

 Viviparous. Direct development.

 e.g., Rattus, Canis, Elephas, Equus. Oviparous mammal is
Ornithorhynchus.

Questions
(SRT) Select Response Type Question (1 mark each)
1. Which of the following organisms exhibit cellular level of organisation
(a) Sycon (b) Hydra
(c) Obelia (d) Ganyaulax
2. In which of the following organism the indirect development does not occur
(a) Cockroach (b) Saw-fish
(c) Tapeworm (d) Starfish
3. What are the characteristic features of the skin of the members belonging to
class amphibia?
(a) Skin is dry cornified and have scales
(b) The skin is dry without scales
(c) Skin is moist and is without scales
(d) The skin is with scales but moist

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. What is mesogloea ? Where is it found.
5. When is the development of an organism called as ‘Indirect’ ?
6. Why are corals important ?
7. Name the arthropod which is a (i) Living fossil, (ii) Gregarious pest.
8. Which organ helps in excretion in (i) Arthropods, (ii) Hemichordates ?
9. Why the segmentation in flatworms referred as pseudo-segmentations?

Animal Kingdom 43
Short Answer Questions-I (2 marks each)
10. Distinguish between poikilothermous and homoiothermous organisms.
11. Define metagenesis with a suitable example.
12. List the characteristic features of class Mammalia.
13. How will you distinguish between male and female round worms?
14. How the water vascular system of echinoderms is different from porifearans?
Short Answer Questions-II (3 marks each)
15. What is the difference between organisms on the basis of the coelom ? Give
examples for each.
16. Compare the water transport (vascular) system of poriferans and the
echinoderms.
17. What are the feature of class Aves which help them in flying ?
18. Write any three adaptations observed in Aves.
Long Answer Questions (5 marks each)
19. Distinguish between the chordates and non-chordates.
20. Differentiate between class Chondrichthyes and class Osteichthyes.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (a) Sycon 2. (b) Saw-fish
3. (c) Skin is moist and is without scales
CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answers (1 mark each)
4. Undifferentiated layer present between ectoderm and endoderm. It is found
in Coelenterates.
5. Have a larval stage morphologically distinct from adult.
6. Have skeleton composed of calcium carbonatge which gets deposited and
can lead to formation of land forms, e.g., Lakshadweep (a coral island).
7. (i) Limulus (King crab), (ii) Locusta (Locust)
8. (i) Malpighian tubules, (ii) Proboscis gland.
9. Refer to point to remember on page 34.
Short Answers-I (2 marks each)
10. Poikilothermous (cold blooded); Lack ability to regulate their body temperature.
44 Biology Class - 11
 Homoiothermous (Warm) : Can regulate body temperature.
11. Refer ‘Points to Remember’.
12. Refer ‘Points to Remember’.
13. Refer page no. 52, NCERT, Text book of Biology class XI.
14. Refer page no 50 and 54, NCERT, Text book of Biology class XI.
Short Answers-II (3 marks each)
15. Refer ‘Points to Remember”.
16. Refer ‘Points to Remember, NCERT, Text Book of Biology for Class XI.
17. Wings, bones long and hollow with air cavities, air sacs connected to lungs
to supplement respiration.
18. Refer to point to remember on page 36.
Long Answers (5 marks each)
19. Refer Table 4.1, page 55, NCERT, Text Book of Biology for Class XI.
20. Refer ‘Points to Remember’.
21. Based Questions
Case 1: Coral reefs are very beautiful, brightly colored backgrounds for

serene snorkelling experiences. The lovely colors in corals come from a
marine alga referred to as zooxanthellae, which stayinner them. These algae
do photosynthesis for the corals in order that the corals get power to develop
and reproduce. When corals get environmental stresses like warmness or
pollutants, they react via way of means of expelling those algae, leaving a
ghostly, obvious skeleton behind. This is understood as ‘coral bleaching’.
Without zooxanthellae most corals starve and might die. At least 1/4 of the
sector’s marine life desires coral reels round the sector are disappearing
fast. Water pollutants, overfishing and coastal improvement are taking their
tool on coral reefs. At international level, carbon pollutants are warming
our oceans and inflicting corals releases carbon pollutants into the air, that
is heating our planet and warming our oceans. If we keep to pollute the air
and the ocean with carbon emissions at our excessive rate, coral reefs round
the sector will face a catastrophic future in coming decades in our lifetime.
1. To which of the following phylum coral reefs belong?
(a) Echinodermata (b) Platyhelminthes
(c) Cnidaria (d) Porifera

Animal Kingdom 45
Ans.: (c)
2. Corals are made by deposition of
(a) Endoskeleton made up of silica
(b) Exoskeleton made of protein fibre
(c) Exoskeleton made up of calcium carbonate
(d) Endoskeleton made up of protein fibres
Ans.: (c)
3. Which one the following could not be a possible reason for coral bleaching?
(a) Water pollution
(b) Carbon pollution
(c) Soil pollution
(d) Overfishing and coastal development
Ans. : (c)
4. Assertion : Coral reefs are very beautiful, brightly coloured backgrounds for
serene snorkelling experiences
Reason: A marine algae zooxanthellae live inside them and do photosynthesis
(a) Both assertion and reason are correct and reason is correct explanation
of assertion
(b) The assertion is incorrect, but the reason is correct
(c) Both assertion and reason are incorrect
(d) The assertion is correct, but the reason is incorrect
Ans.: (a)
Case II: In 2020, India has battled its worst locust outbreak in decades. The
swarms of desert locusts, known for feeding on green leaves and caused
extensive damage to vegetation.
Locust is a large, tropical grasshopper, with strong powers of flight and
it migrates in vast swarms causing widespread crop loss. Locusts are not
dangerous till the time they are individual hoppers/moths or small isolated
groups of insects, in what is called the “solitary phase”. When the locust
population increases to huge numbers – the behavioural changes are induced
by crowding and they ultimately transformed into a “gregarious” phase.
Achieving gregarious phase, they start forming swarms. A single swarm

46 Biology Class - 11
 contains up to forty to eighty million adults in one square km and these can
travel up to one hundred and fifty km in one day. Locusts are safe to eat
insects. Throughout the world, in many cultures people consume insects and
locusts are also considered a delicacy.
1. Locust belongs to which phyla of animal kingdom :
(a) Insecta
(b) Arthropoda
(c) Mollusca
(d) Cnidaria
Ans.: (b)
2. Assertion : Locust are gregarious pests
Reason : A single swarm contains up to 40-80 million adults in one
square km
(a) Both assertion and reason are correct and reason is correct explanation
of assertion
(b) The assertion is incorrect, but the reason is correct
(c) Both assertion and reason are incorrect
(d) The assertion is correct, but the reason is incorrect
Ans.: (a)
3. Read the following statement
Statement I : The swarms of desert locusts, known for feeding on green leaves
and caused extensive damage to vegetation
Statement II : Locust are not always dangerous and do not usually attack human
(a) Only I if true
(b) I and II are true
(c) I is true but II is false
(d) I is false but II is true
Ans. : (b)
4. Which of the following statement about locust is not true.
(a) Locusts are not edible insects
(b) Locust form swarm
(c) Locust are not harmful in its solitary phase
(d) Locust is a large, mainly tropical grasshopper
Ans. : (a)


Animal Kingdom 47
 Points to Remember
Morphology : The study of various external features, forms and relative
position of different organs of the organism is known as morphology. It may be
further divided into internal and external morphology.
External Morphology : It deals with external forms like shape, size, colour,
structure and relative position of different organs.
Internal Morphology : Further divided into anatomy and histology.
Anatomy : It deals with the study of internal structure exposed after dissection
and opening of various parts of an organ.
Histology : The study of tissues, their composition and structure.
Adaptation : Any alteration in the structure or function of an organism
or any of its part that results from natural selection and by which the organism
becomes better fitted to survive and multiply in its environment.
The Root : The root is underground part of the plant and develops from
elongation of radicle of the embryo.
Characteristics : It is inside the soil, chlorophyll is absent, absence of nodes,
internodes, leaves and buds; positive geotropic and hydrotropic and negative
phototropic.
Main functions of root system :
1. Absorption of water and minerals from the soil.
2. Provides anchorage to plant parts.
3. Stores reserve food material and synthesises plant growth regulators
(cytokinins)

48 Biology Class - 11
 Various types of root

↓
Tap root Fibrous root Adventitious root

↓ ↓ ↓
Originates from radical Originates from base of Originates from parts of
the stem the plant other than radicle
Dicotyledonous plants, Monocotyledonous Banyan tree (Prop roots)
e.g., gram, pea, mango, plants, e.g., wheat, Maize (stilt roots)
mustard. paddy, grasses. Rhizophora (Respiratory
roots)

Regions of Roots
Root Cap : The root is covered at the apex by the thimble-like structure
which protect the tender apical part.
Region of meristematic activity : Cells of this region have the capability
to divide; cells are small, thin walled with dense protoplasm.
Region of elongation : Cell of this region are elongated and enlarged. This
region is responsible for the growth of root in length.
Region of Maturation : This region has differentiated and matured cells.
Some epidermal cells form very fine and delicate thread like structures called
root hairs.
Modifications of Root : Roots are modified for support, storage of food,
respiration.
 For support : Prop roots in banyan tree, stilt roots in maize and sugarcane.
 For respiration : Pneumatophores in Rhizophora (Mangrove).
 For storage of food : Fusiform (radish), Napiform (turnip), Conical (carrot),
Fasiculated fleshy roots (Asparagus).
The Stem : Stem is the aerial part of the plant and develops from plumule
of the embryo. It bears nodes and internodes.
Functions of stem : Exposure of leaves, conduction of water and minerals,
translocation of food, exposure of flowers and fruits.

Morphology of Flowering Plants 49

Modifications of Stem :
In some plants the stems are modified to perform the function of storage of
food, support, protection and vegetative propagation.
 For food storage : Rhizome (ginger, turmeric), Tuber (potato), Bulb (onion),
Corm (Colocasia, Amorphophallus/Zamin-kand)
 For support : Stem tendrils of watermelon, grapevine, cucumber, pumpkins.
 For protection : Axilliary buds of stem of Citrus, Bougainvillea get modified
into pointed thorns. They protect the plants from animals.
 For vegetative propagation : Underground stems of grass (runner), strawberry
(stolons), lateral branches of mint and jasmine, Eichhornia (offsets).
 For assimilation of food : Flattened stem of Opuntia and cylindrical stem
of Euphorbia contains chlorophyll and performs photosynthesis.
The Leaf : Develops from shoot apcial meristem, flattened, green structure
acropetally arranged manufacture the food by photosynthesis. It has bud in axil.
A typical leaf has leaf base, petiole and lamina (leaf blade). In some leguminous
plants the leaf base may become swollen which is called as pulvinus.

Leaf base → bears two lateral outgrowth called stipules

Expanded to enclose stem Swollen

Pulvinus
Sheathing leaf base
Covers stem totally Partially Mimosa
(Gram, wheat) (Butter cup) (Leguminous plant)

Types of Leaf
Simple Compound
(Single leaf blade) (Leaf has number of leaflets)
e.g., mango, peepal

Pinnately Palmately
Compound Compound
(Leaflets present on a common, (Leaflets attached to common
axis the rachis) point i.e. at petiole tip)
(Neem, rose) (Silk, Cotton)

50 Biology Class - 11
 Venation : The arrangement of veins and veinlets in the lamina of leaf.
Types of Venation :
1. Reticulate : Veinlets form a network as in leaves of dicotyledonous plants
(China rose, peepal).
2. Parallel : Veins are parallel to each other as in leaves of monocotyledonous
plants (grass, maize,sugarcane).

Phyllotaxy : The pattern of arrangement of leaves on the stem or branch.

Types of phyllotaxy

Alternate Opposite Whorled

(Single leaf at a node)in (Two leaves at a node) in (More than two leaves in a
alternate manner opposite manner whorl at a node)
e.g., China rose Mustard, e.g., Calotropis, guava e.g., Nerium, Alstonia

Functions of Leaf
photosynthesis, gaseous exchange, transpiration, protection of buds and
conduction.

Morphology of Flowering Plants 51

Modifications of Leaves :
Type Function Example

 Tendrils : (Climbing) — Sweet Pea, Pea

 Spines : (Protection) — Aloe, Opuntia, Argemone
 Pitcher : (Nutrition) — Nepenthes
 Hook : (Support) — Cat’s nail
 Fleshy Leaves : (Storaged food) — Onion and Garlic

Inflorescene
The arrangement of flowers on the floral axis (Peduncle)
Main types of Inflorescence

Main types of Inflorescence

Recemose Cymose

1. It is indefinite inflorescence 1. It is definite inflorescence

2. Main axis continues to grow and 2. Main axis terminates in flowers and the
flowers borne in acropetal succession flowers borne in basipetal succession
e.g. : Radish, Mustard, Amaranthus e.g. : Cotton, Jasmine, Calotropis

Mnemonic : RU = Racemose unlimited growth CL = Cymose limited growth

Special Inflorescence type— Ficus, Salvia, Euphorbia, Sunflower

Flower—Modified shoot meant for reproduction

Flower can be

Bisexual Unisexual
+
if have both Androecium Staminate flower Pistillate flower
(Male + (Female
and Gynoecium flower) flower)
have only have only Gynoecium
Androecium/Stamen Carpel

52 Biology Class - 11
 On the basis of symmetry flower can be :

↓ ↓ ↓
Actinomorphic ⊕ Zygomorphic % Asymmetric
(Radial symmetry) (Bilateral symmetry) (Irregular)
↓ ↓ ↓
Flower can be divided Flower can be divided into Flower cannot be divided
into two equal halves two similar halves only in in two similar halves by
in any radial plane one plane any vertical plane passing
passing through centre through centre
eg : Mustard, Datura, eg : Pea, bean, Gulmohar, eg : Canna
Chilli Cassia
On the basis of floral appendages flower can be :
↓ ↓ ↓
Trimerous Tetramerous Pentamerous
(multiples of 3) (multiples of 4) (multiples of 5)

Thalamus/Receptacle : Swollen end of flower stalk (pedicel) which bears

four whorls of flower viz., Calyx (K), Corolla (C), Androecium (A) and
Gynoecium (G).

On the basis of position of Calyx, corolla and androecium with

resprect to ovary, flower can be:

↓ ↓ ↓
Hypogynous Perigynous Epigynous
(Superior Ovary) (Half inferior ovary) (inferior ovary)
↓ ↓ ↓
G above, K, C, A G at par/same level as K, C, A G below K, C, A
Mustard, China rose, Plum, Rose, Peach Guava, Cucumber
Brinjal ray florets (sun flower)

Morphology of Flowering Plants 53

 Androecium

1 bunch
2 bunch
more than 2 bunches

Bract—Reduced leaf base found at the base of pedicel. Flowers with bracts
are called bracteale and without bracts are called ebracteate.
Perianth : If calyx and corolla are not distinguishable, they are called
perianth.
Example : Lily
Aestivation: The mode of arrangement of sepals or petals in floral bud.
Types of aestivation :
1. Valvate : Sepals or petals just touch one another at the margin, without
overlapping. e.g., Calotropis
2. Twisted : Sepals or petals overlap the next sepal or petal e.g., China rose,
Cotton, lady’s finger.
3. Imbricate : The margins of sepals or petals overlap one another but not in
any definite direction, e.g., Cassia, Gulmohar.
4. Vexillary : The largest petal overlaps the two lateral petals which in turn
overlap two smallest anterior petals, e.g., Bean, Pea.
Placentation : The arrangement of ovules within the ovary.
Types of Placentation :
A. Marginal : Placenta forms a ridge along the ventral suture of ovary, e.g., Pea.
B. Axile : Margins of carpels fuse to form central axis, e.g., China rose, Tomato,
Lemon
C. Perietal : Ovules develop on inner wall of ovary, e.g., Mustard, Argemone
D. Free central : Ovules borne on central axis, lacking septa, e.g., Dianthus,
Primrose

54 Biology Class - 11
 (A) (B) (C)

(D) (E)
E. Basal : Placenta develop at the base of ovary, e.g., Sunflower, Marigold
Placenta : Parenchymatous flattened cushion inside ovary where ovules are
borne.
The fruit : After fertilisation, the mature ovary develops into fruit. The
parthenocarpic fruits are formed from ovary without fertilisation (seedless fruit-
Banana)

Fruit (Ripened Ovary)

Pericarp (Fruit Wall) Seed

Epicarp Mesocarp Endocarp Seed coat Embryo

(outer) (middle) (inner)

Embryonal axis (Plumule + Cotyledons (Store

Radicle) food)

Monocotyledonous seed—Endosperm bulky and stores food, covered by

proteinaceous Aleurone layer. Seed has single large cotyledon–scutellum.
Plumule is enclosed in Coleoptile and Radicle is enclosed in Coleorrhiza.
Dicotyledonous Seed—
Testa (Outer layer)
Seed Coat
Tegmen (Inner Layer)

Morphology of Flowering Plants 55

 Hilum —is a scar on the seed coat through which seeds attached to the fruit.
Micropyle—small pore, above hilum
Cotyledons—two; fleshy, full of reserve food materials
Embryonal axis—Radicle and plumule.
Endospermous seed—endosperm present in mature seed. eg. castor
Non-endospermous seed—endosperm not present in mature seeds, eg. bean,

Questions

(SRT) Select Response Type Question (1 mark each)

1. Which part of Opuntia is modified to form spines?
(a) Root (b) Leaf (c) Flower (d) Stem
2. Which group of plants given below, show pinnately compound leaves?
(a) Silk Cotton, Maple (b) Tulip, Neem
(c) Maple, Acacia (d) Neem, Rose, Acacia
3. Which parts in Ginger and Onion are edible respectively?
(a) Corm & Tuber (b) Bulb & Tuber
(c) Rhizome & Bulb (d) Corm & Rhizome

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Question (1 mark each)
4. In mangroves, pneumatophores are the modified adventitious roots. How
are these roots helpful to the plant ?
5. Why do various plants have different type of phyllotaxy ?

56 Biology Class - 11
 6. State the main function of leaf tendril.
7. Which plant family represent the following floral formula :

K(5) C(5) A5 G(2)

8. The endosperm is formed as a result of double fertilisation (triple fusion).

What is its function ?
9. Which type of venation do you observe in dicot leaf ?
10. In pea flower, the aestivation in corolla is known as vexillary. Give reason.
11. What is the name given to the cotyledon in case of Monocots.
12. Name the part modified for food storage in the following (a) carrot (b) Radish
(c) Potato (d) Dahlia (e) Turmeric (f) Sweet potato
Short Answer Questions-I (2 marks each)
13. Flower is a modified shoot Justify.
14. Name the type of root of the following :
(a) Roots performing the function of photosynthesis.
(b) Roots coming above the surface of the soil to absorb air.
(c) The pillar like roots developed from lateral branches for providing
mechanical support.
(d) Roots coming out of the lower nodes of the stem to provide the support
to the plant.
15. Identify the type of tendrils found in the following plants—
(a) Cucumber (b) Pea (c) Grape vines (d) Water Melon
16. Fill up the blank spaces (a), (b), (c) and (d) in the table given below :

17. Provide the scientific terms for the following :

(i) The leaf without a petiole (stalk).
(ii) The flat and expanded portion of a leaf.
(iii) Orderly arrangement of leaves on the node.
(iv) Lateral appendages on either side of the leaf.

Morphology of Flowering Plants 57

18. Differentiate between peduncle and Pedicel
Short Answer Question-II (3 marks each)
19. Observe the given figure showing various types of placentration. Identify
the type of placentation. Give one example of each.

20. ‘Potato is a stem and sweet potato is a root.’ Justify the statement on the
basis of external features.
21. Define aestivation. Which type of aestivation is found in China rose,
Calotropis Gulmohar and Pea?
22. Give two example of each type of phyllotaxy.
23. Differentiate between :
(a) Actinomorphic flower and Zygomorphic flower
(b) Apocarpous ovary and Syncarpous ovary
(c) Racemose inflorescence and Cymose inflorescence
24. Read & observe the following to answer the questions given below
Seeds either may be monocotyledonous/dicotyledonous. They may vary in
shape, size and period of viability.
(i) In the given structure of a Monocotyledonous seed label the parts a, b,
c,d,e. Give the function of part “a”

(ii) Maize grain is usually called as a fruit and not a seed. Why ?
58 Biology Class - 11
Long Answer Questions (5 marks each)
25. Describe various stem modifications associated with food storage, climbing
and protection.
Direct in the following questions, a statement of assertion (A) is followed
by a statement of reason (R). Mark the correct choice as:
(a) If both (A) and (R) are correct and (R) is the correct explaination of (A).
(b) If both (A) and (R) are true, but (R) is not the correct explanation of (A).
(c) If (A) is true but (R) is false.
(d) If both (A) and (R) are false.
26. Assertion: Underground parts of a plant are not always roots.
Reason: Underground stems of potato are modified to store for
27. Assertion: Calyx can be gamosepalous or polysepalous
Reason: Corolla is composed of petals.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (b) Leaves 2. (d) Neem, Rose, Acacia
3. (c) Rhizome & Bulb

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Pneumatophores is mangroves help in respiration.
5. For proper exposure of leaves to get sunlight.
6. The leaf tendrils help the plant for climbing.
7. Solanaceae
8. Endosperm stores the food.
9. Reticulate venation.
10. In peas, there are five petals. The largest one (standard) overlaps the two
lateral petals (wings) which in turn overlap the two smallest anterior petals
(keel).
11. Scutellum.
12. (a) Fleshy tap root (b) Fleshy tap root ( c) Stem tuber (d) root tuber
(e) Rhizome (f) Fleshy root tuber
Morphology of Flowering Plants 59
Short Answers-I (2 marks each)
13. The flower is considered to be a modified shoot because the internodes
in flower are highly condensed and the appendages such as sepals, petals,
stamens and carpels(pistil) are generally large in number.
14. (a) Assimilatory roots (b) Respiratory roots
(c) Prop roots (d) Stilt roots
15. (a), (c) and (d) stem tendrils
(b) leaf tendril
16. (a) Floral parts are situated below the ovary.
(b) Half inferior
(c) Epigynous
(d) Floral parts are situated above the ovary.
17. (i) Sessile (ii) Lamina
(iii) Phyllotaxy (iv) Stipules
18. Peduncle is the axis of inflorescence which generally bears a number of
flowers.
Pedicel is the stalk of the flower which bears a single flower.
Short Answers SA-II (3 marks each)
19. (a) Marginal placentation — Pea
(b) Parietal placentation — Mustard, Argemone
(c) Free central placentation — Dianthus, Primrose
20. Potato is the swollen tip of an underground stem branch. It has nodes (eyes) which
consist of one or more buds subtended by a leaf scar. Adventitious roots also
arise during sprouting. On the other hand sweet potato is a swollen adventitious
root (tuberous root). It has no nodes, internodes and buds like a stem.
21. The mode of arrangement of sepals or petals in a floral bud is known as
aestivation.
China rose – twisted Calotropis – valvate
Gulmohar – imbricate Pea – vexillary
22. Type of phyllotaxy Examples

(i) Alternate China rose, mustard
(ii) Opposite Calotropis, guava
(iii) Whorled Nerium, Alstonia

60 Biology Class - 11
23. (a) Actinomorphic Flower Zygomorphic flower

(1) Two equal halves are formed (1) Two equal havles are produ-
by any vertical division passing ced only by one vertical
through the centre. division
(2) It has a radial symmetry. (2) It has a bilateral symmetry.

(b) Apocarpous Ovary

Syncarpous Ovary

(1) The flower has several free (1) The flower has fused carpels.
free carpels (ovary).
(2) On maturity it forms fruitlet (2) On maturity it forms a single
of aggregate type. fruit.

(c) Racemose inflorescence

Cymose inflorescence

(1) The main axis has unlimited (1) The main axis has a limited
growth. growth.
(2) Flowers are arranged (2) Flowers are arranged
acropetally i.e., the lower basipetally i.e., the lower
flower are younger flowers are older
24. (i) (a) Endosperm (b) Scutellum
(c) Coleoptile (d) Coleorrhiza
(e) Aleurone layer
Function of (a)—Provide nutrition.
(ii) Maize grain is a single seeded fruit in which the seed covering or testa
is fused with pericarp or fruit wall. A micropyle is not found but base
of style is present.
Long Answers (5 marks each)
25. Stem Modification :
 For food storage : Ginger (Rhizome), Potato (Tuber), Onion (Bulb),
Colocasia (Corm).
 For climbing (support) : Sterm tendril (cucumber,grapevine,watermelon)
 For protection : Thorn (Bougainvillea, Citrus, Duranta) Description :
Refer page 68, NCERT, Text Book of Biology for Class XI.
26. (b) 27. (b)

Morphology of Flowering Plants 61
 Points to Remember
Anatomy : Anatomy is the study of internal structure of organisms. Plant
anatomy includes organisation and structure of tissues.
Tissue is a group is cells having a common origin and usually performing
a common function.
There are two types of tissues (i) Meristematic (ii) Permanent
Meristematic tissues : The meristematic tissue is made up of the cells which
have the capability to divide. Meristems in plants are restricted to specialised
regions and responsible to the growth of plants.

Meristems

Apical meristem Intercalary meristem Lateral Meristem

 Occurs at the tips of  Occurs between  Occurs in the mature

roots and shoots mature tissue region of roots and

shoots
 Primary meristem  Primary meristem  Secondary meristem

 Increase the length of  Occur in grasses and  Appears later than

plant regenerate parts primary meristem

removed by grazers and responsible for
secondary growth
Axillary bud : The buds which are present in the axils of leaves (Consist
of cells left behind from shoot apical meristem) and are responsible for forming
branches of flowers.
Permanent tissues : The permanent tissues are derived from meristematic
tissue, are composed of cells, which have lost the ability to divide and have become
structurally and functionally specialised.

62 Biology Class - 11
 Types of Permanent Tissue

Simple (i) Complex (ii)

Parenchyma Collenchyma Sclerenchyma Xylem Phloem

Parenchyma : Living, thin walled isodiametric cells, with interceullar spaces,

cell wall is made up of cellulose. It performs the functions like photosynthesis,
storage, secretion.
Collenchyma : It is formed of living, closely packed cells. Its cells are
thicknened at the corners due to depositon of celluose and pectin. It provide
mechanical support to the growing parts of the plant. It is either found in
homogenous layer or patches.
Sclerenchyma : It is formed of dead cells with thick and lignified walls.
Provide mechanical support to organs. They have two types of cells : fibres and
sclereids.
(a) Fibers—are thick walled,elongated and pointed cells.
(b) Sclereids—are spherical, oval or cylindrical, highly thickened dead cells
with narrow lumen. Found in walls of nut, pulp of fruits like guava, seed coat of
legumes and leaves of tea.
Xylem : Xylem consists of tracheids vessels, xylem fibres and xylem
parenchyma. It conducts water and minerals from roots to other parts of plant.
(a) Tracheids—Tube like cells with thick and lignified walls and tapering
ends; dead, without protoplasm.
(b) Vessel—long cylindrical structure made up of many cells with large
central cavity, devoid of protoplasm. Present in angiosperms.
(c) Xylem fibres—highly thickened walls; with obliterated lumens; septate
or aseptate.
(d) Xylem parenchyma—living and thin walled; cell walls made up
cellulose, store food material in form of starch or fat.
Radial conduction of water takes place by ray parenchymatous cells
Protoxylem : The first formed primary xylem elements.
Metaxylem : The later formed primary xylem.
Endarch : Protoxylem lies towards the centre and metaxylem towards the
periphery of the organ; in stem

Anatomy of Flowering Plants 63

 Exarch : Protoxylem toward periphery and metaxylem towards centre; in
roots.
Phloem :Phloem consists of sieve tube elements, companion cells, phloem
fibres and phloem parenchyma; Phloem transports the food material from leaves
to various parts of the plant.
(a) Sieve tube elements :
 long tube like structures arranged longitudinally.

 associated with companion cells.

 end walls are perforated to form sieve plates.

 functions of sieve tubes are controlled by the nucleus of companion cells.

(b) Companion cells

 Specialised parenchymatous cells associated with sieve tube elements

 Connected with sieve tube elements by pit fields present between their

common longitudinal walls

 Help to maintain pressure gradient in sieve tubes.

(c) Phloem Parenchyma

 made up of elongated, tapering cylindrical cells with dense cytoplasm and

nucleus.
 cell wall made of cellulose with pits through which plasmodesmatal

connections exist between cells.

 store food material.

(d) Phloem fibers (bast fibers)

 are sclerenchymatous; absent in primary phloem but present in secondary

phloem.
 elongated, unbranched pointed, needle like apices with thick cell walls.

Protophloem : First formed phloem with narrow sieve tubes.

Metaphloem : Later formed phloem with bigger sieve tubes.
The Tissue System :
1. Epidermal tissue system : It includes cuticle, epidermis, epidermal hairs,
root hairs, trichomes and stomata.
(a) Cuticle—Waxy thick layer outside epidermis, prevents the loss of water.
(b) Epidermis : Outer most layer of primary plant body.
(c) Epidermal hair : help in absorbing water and mineral from soil.
(d) Trichomes : help in preventing water loss due to transpiration.

64 Biology Class - 11
 (e) Stomata : Regulate process of transpiration and gaseous exchange.
Stomatal apparatus : The stomatal aperture, guard cells and surrounding
subsidiary cells are together called stomatal apparatus.

Nucleus

2. The ground tissue system : It is made up of parenchyma, collenchyma,

sclerenchyma. In dicot stems and both dicot of monocot roots the ground
tissue is divided into hypodermis, cortex, endodermis, pericycle, medullary
rays and pith.
3. The vascular tissue system : It includes vascular bundles which are made
up of xylem and phloem.

Anatomy of Flowering Plants 65

Anatomy of Root
Dicot Root Monocot Root

1. Cortex is comparatively narrow. 1. Cortex is very wide.

2. Endodermis is less thickened 2. Endodermal cells are highly
casparian strips are more thickened casparian strips are visible
prominent. only in young roots.
3. The xylem and phloem bundles 3. Xylem and phloem are more than 6
varies from 2 to 5. (polyarch).
4. Pith is absent or very small. 4. Well developed pith is present.
5. Secondary growth takes place 5. Secondary growth is absent.
with the help of vascular cambium
and cork cambium.

Casparian Strips—The tangential as well as radial walls of endodermal

cells of dicot roots have deposition of water impermeable, waxy material, suberin
in the form of casparian strips.
Anatomy of Stem
Dicot Stem Monocot Stem

1. The ground tissue is differentiated 1. The ground tissue is made up of similar

into cortex, endodermis, pericycle cells.
and pitch.
2. The vascular bundles are arranged 2. The vascular bundles are scattered
in a ring. throughout the ground tissue.
3. Vascular bundles are open, without 3. Vascular bundles are closed,surrounded
bundle sheath and wedge-shaped by sclerenchymatous bundle sheath,
outline. oval or rounded in shape.
4. The stem shows secondary growth 4. Secondary growth is absent.
due to presence of cambium
between xylem and phloem.

Secondary growth dicot stem—An increase in the girth (diameter) in plants,

vascular cambium and cork cambium (lateral meristems) are involved in secondary
growth.

66 Biology Class - 11
 1. Formation of cambial ring : Intrafascicular cambium + interfascicular
cambium.
2. Formation of secondary xylem and secondary phloem from cambial ring.
3. Formation of spring wood and autumn wood.
4. Development of cork cambium(phellogen)
Cork (phellem) – From outer cells
Cork Cambium (Phellogen)
Sec. cortex (phelloderm) – from inner cells
(Phellogen + Phellem + Phelloderm) = Periderm
Secondary growth in dicot roots : Secondary growth in dicot roots occur
with the activity of secondary meristems (vascular cambium). This cambium
is produced in the stele and cortex, and results in increasing the girth of dicot
roots.
Anatomy of Leaf
Dorsiverntral (Dicot) Leaf Isobilateral (monocot) Leaf

1. Stomata are absent or less abundant 1. The stomtata are equally distributed
on the upper side. on both sides.
2. Mesophyll is differentiated into two 2. Mesophyll is undifferentiated.
parts upper palisade parenchyma
and lower spongy parenchyma.
3. Bundle sheath is single layered and 3. Bundle sheath may be single or
formed of colourless cells. double layered.
4. Hypodermis of the mid-rib region, is 4. Hypodermis of the mid-rib region
collenchymatous. is sclerenchymatous.
5. Stomata have kidney shaped guard 5. Stomata have dumb bell shaped
cells. guard cells.

Spring Wood Autumn Wood

1. Also called early wood. 1. Also called late wood

2. Cambium is active 2. Cambium less active
3. Xylary elements more 3. Xylary elements less
4. Vessels with wide cavities 4. Vessels narrow
5. Light in colour, low density 5. Dark, high denisty

Anatomy of Flowering Plants 67

 Heartwood Sapwood

1. Central or innermost region of stem 1. Peripheral region stem, light in

which is hard, durable and resistant colour
to attack of microorganisms and
insects.
2. Not involved in conduction of water, 2. Involved in conduction of water and
gives mechanical support to stem mineral

Lenticels—Produced when phellogen cuts off parchymatous cells on outer

side. These cells rupture the epidermis forming lens shaped opening called lenticels.
Function—Permit exchange of gases.
Bulliform Cells—Large, empty, colourless adaxial cells with vein in leaves
which maintain turgidity of leaves.

Questions

(SRT) Select Response Type Question (1 mark each)

1. Name the tissue represented by the jute fibers used for making ropes.
(a) Parenchyma (b) Meristematic
(c) Sclerenchyma (d) Aerenchyma
2. Which kind of wood is called early wood?
(a) Spring wood (b) Autumn wood
(c) Late wood (d) Delicate wood
3. Open vascular bundle is made of
(a) Xylem & phloem (b) Xylem, cambium & phloem
(c) Phloem only (d) Xylem only

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Question (1 mark each)
4. State the role of pith in stem.
5. Where are bulliform cells found in leaves ?
6. Why are xylem and phloem called complex tissues ?
7. Which meristem is responsible for longitudinal growth in plants ?
68 Biology Class - 11
 8. What forms’ the cambial ring in a dicot stem during the secondary growth?
9. Name the anatomical layer in the root from which the lateral branches of
root originate.
10. Which tissue of the leaf contains chloroplast ?
11. A plant tissue when stained, showed the presence of hemicellulose and
pectin in cell wall of its cells. Name the tissue.
12. Write the function of phloem parenchyma.
13. Name the cells which make the leaves curl in plants during water stress.
14. Give the function of lenticels.
15. The vascular bundles are surrounded by a thick layer of cells in leaves. What
is the name of cells ?
16. Mention the signfiicance of casparian strips. Where do you find them ?
17. Give the function of companion cells.
Short Answer Questions (SA-I) (2 marks each)
18. Why is cambium considered to be lateral meristem ?
19. Give any four differences between tracheids and vessels.
20. How are open vascular bundles differ from closed vascular bundles ?
21. What are trichomes ? State their functions.
22. Given below are the various types of tissue and their functions. Which out
of these is not a matching pair and why;
(a) Collenchyma : provides mechanical support to the
growing parts of plant.
(b) Sclerenchyma : photosynthesis, storage and secretion.
(c) Chlorenchyma : perform the function of photosynthesis
(d) Xylem : conduction of water and minerals.
23. In which part of the plant you would see the following :
(a) Radial vascular bundle (b) Well developed pith
Short Answer Question (SA-II) (3 marks each)
24. Give the points of difference between lenticels and stomata.
25. Even being a monocotyledonous plant the Palm increases in girth. Why and
how does it take place ?

Anatomy of Flowering Plants 69

26. Differentiate between endarch and exarch conditions.
27. If you are provided with microscopic preparation of transverse section of a
meristemic tissue and permanent tissue, how would you distinguish them ?
28. Differentiate between aerenchyma and collenchyma on the basis of their
structure and function.
29. Are there any tissue elements in phloem which are comparable to those of
xylem ? Explain.
30. Case Based
Read and observe the following to answer questions given
Stomata are present in the epidermis of leaves, toregulate transpirationo f
gas exchage.
Observe the figure and answer the following questions :
(i) Name parts (a) and (b).
(ii) Are these types of stomata observed in monocot or in dicot plants ?
(iii) Which parts shown in figure constitute the stomatal apparatus ?

Long Answer Questions (5 marks each)

31. (i) What are meristems ?
(ii) Name the various kinds of meristems in plants.
(iii) State the location and functions of meristems.
DIRECTIONS: In the following questions, a statement of assertion(A) is
followed by a statement of the reason(R). mark the correct choice as :
(a) If both (A) and (R) are correct and (R) is the correct explanation of (A).
(b) If both (A) and R are true, but (R( is not the correct explanation of (A).
(c) If (A) is true but (R) is false.
(d) If both (A) and (R) are false.
32. Assertion : Apical meristem of the root is subterminal.
Reason : At the terminal end of the root, the root cap is present.

70 Biology Class - 11
33. Assertion : Aerenchyma helps to maintain buoyancy in hydrophyte plants.
Reason : The large air chambers are present in aerenchyma.
34. Assertion : A simple tissue is made of a single type of cells.
Reason : Various simple tissues are parenchyma, collenchyma and
sclerenchyma.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (c) Sclerenchyma 2. (a) Springwood
3. (b) Xylem combium & phloem

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
1. Sclerenchyma. 2. Monocotyledonous roots.
3. The hard central region of tree trunk made up of xylem vessels, which provide
mechanical strength to stem.
4. Pith stores the food material.
5. Bulliform cells are found in the upper epidermis of monocot leaves.
6. As they are made up of more than one kind of cells.
7. Primary meristem.
8. Fascicular and intrafascicular strips of meristem.
9. Pericycle of mature zone.
10. Mesophyll tissue.
11. Collenchyma.
12. Lateral conduction of food and supply of water from xylem.
13. Bulliform or motor cells.
14. Permit exchange of gases.
15. Bundle sheath cells.
16. Casparian strips are found in endodermis and make them water impermeable.
17. Maintain pressure gradient in sieve tubes.
Short Answers (SA-I) (2 marks each)
18. The cambium is considered as a lateral meristem because it occurs along the
lateral sides of the stem and roots and appears later than primary meristem.

Anatomy of Flowering Plants 71

 Cells of this meristem divide periodically and increase the thickness of the
plant body.

19. Tracheid Vessels

1. A tracheid is formed from a 1. A vessel is made of a number of

single cell. cells.
2. The ends are oblique or 2. The ends are rounded and
tapering. transverse.
3. They are comparatively narrower. 3. They are comparatively wider
4. The lumen is narrower. 4. The lumen is wide.
5. Septa remain intact 5. Septa lacking

20. Open Vascular bundles : These vascular bundles contain a strip of cambium
in between phloem and xylem. Open vascular bundles are collateral and
bicollateral.
Closed Vascular bundles : Intrafascicular cambium is absent. Closed
vascular bundles can be collateral or concentric.
21. Trichomes are multicellular epidermal hairs on the stem, seeds or fruits.
Trichomes help in protection, dispersal of fruits and seeds and reduction in
water loss.
22. (b) Sclerenchyma : photosynthesis, storage and secretion is not a matching pair.
The function of sclerenchyma is to provide mechanical support to
organs.
23. (a) Root (b) Monocot root
Short Answers (SA-II) (3 marks each)
24. Lenticels : Opening that are found in old stems and roots in the cork tissues
containing a number of complimentary cells and they are permanently opened
pores.
Stomata : Opening that are found in leaves and young stems in the epidermis
and have two guard cells. They open and close in response to turgidity of
their guard cells.
25. Palms possess residual meristem below their leaf primordial, which adds
ground parenchyma and vascular bundles. The ground parenchyma can also
undergo further divisions even after the completion of elongation.

72 Biology Class - 11
26. Endarch condition Exarch condition

1. Protoxylem towards pith and 1. Protoxylem towards periphery and

metaxylem towards periphery metaxylem towards pith
2. Found in Stem 2. Found in root.

27. Meristematic tissues are composed of cells that have the capability to divide.
These cells are exist in different shapes without intercellular space. Cells are
thin walled, rich in protoplasm, without vacuoles.
Permanent tissues are derived from meristematic tissue and are composed

of cells have their definite shape, size and function. These cells may be thin
walled (living) or thick walled (dead).

28. Aerenchyma Collenchyma

(a) Parenchymatous tissue containing (a) Tissue contains deposits of

large air space. cellulose and large pectin at the
corner of cells.
(b) Thin walled cells, isodiametric in (b) Consists of oval and polygonal
in shape with intercellular space. cells without intercellular space.
(c) Provides buoyancy to the plant. (c) Provides elasticity and mechanical
strength.

29. (a) The sieve elements of phloem is comparable to the vessel of the xylem because
both lack nucleus.
(b) Pholem fibre is similar to the xylem fibre because both provide tensile strength
to the tissue.
(c) Phloem parenchyma and xylem parenchyma is the living components
of phloem and xylem respectively.
30. (i) a : epidermal cell b : guard cell
(ii) In dicot plants.
(iii) The stomatal apparatus includes the stomatal aperture, guard cells and
the surrounding subsidiary cells.
Long Answers (5 mark each)
31. (i), (ii) and (iii) : Refer ‘Points to remember’
32. (a) 33. (c) 34. (b)
 

Anatomy of Flowering Plants 73

 Points to Remember
Types of Fundamental Animal Tissues

S.No. Type Location Functions

1. Epithelial Tissues Free Surfaces Protection, Secretion,
Excretion, absorption,
Sensory and reproduction
2. Connective Tissues All internal, in organs Holding or binding, support,
in between other tissues, transport and circulation,
below skin and nervous protection and storage.
system.
3. Muscular Tissues Inside movable parts Movements and locomotion
4. Nervous Tissues Central Nervous System Communication and control
& every organ Peripheral
Nervous System.

Animal Tissues

Epithelial Connective Muscular Neural

Epithelial Tissue
(A) Simple :  Composed of single layer of cells.
 Functions as lining for body cavities, ducts and tubes.
1. Squamous  single thin layer of flattened cells.
 found in walls of blood vessels, air sacs of lungs.
2. Cuboidal  single layer of cube like cells.

74 Biology Class - 11
  found in ducts of glands and tubular parts of nephron.
3. Columnar  single layer of tall and slender cells.
 free surface may have microvilli.
 found in lining of stomach and intestine
4. Ciliated  columnar or cubolidal cells with cilia.
 move particles or mucus in specific direction, in
bronchioles, fallopian tubes.
 Made up of more than one layer of cells.
 Provide protection against chemical and mechanical stresses.
 Cover dry surface of skin, moist cavity, pharynx, inner lining of ducts of
salivary glands and pancreatic ducts.
Glandular epithelium

Exocrine glands Endocrine glands

secrete mucus, saliva, oil, milk  secrete hormones.

digestive enzymes
 products released through ducts.  secrete directly into the fluid
bathing the gland.
(B) Compound :
Cell junctions—In nearly all animal tissues, specialised junction provide
structural and functional links between its individual cells.
Three Types of Cell junctions—
1. Tight junctions : Plasma membranes of adjacent cells are fused at intervals.
They help to stop substances from leaking across a tissue.
2. Adhering junctions : Perform cementing function to keep neighbouring
cells together.
3. Gap junction : Facilitate the cells to communicate with each other by
connecting the cytoplasm of adjoining cells for rapid transfer of ions, small
molecules and sometimes big molecules.

Structural Organisation in Animals 75

 Connective tissue : Link and support other tissues/organs of the body.

Connective Tissues

Proper Connective Tissues Specialised Connective Tissues

Loose connective Dense connective Skeletal Fluid Connective

Tissues Tissues Tissues Tissues

Areolar Adipose Dense Dense Bone Cartilage Blood Lymph

regular irregular
eg. Tendon
ligament
Loose Connective Tissue
(has cells and fibres loosely arranged in semi-fluid ground substance)
(i) Areolar Tissue :
 present beneath the skin.

 contains fibroblasts, macrophages and mast cells.

 serves as a support framework for epithelium

(ii) Adipose Tissue :

 located beneath the skin.
 cells are specialised to store fats.

Dense Connective Tissue

Fibres and fibroblasts are compactly packed.
(i) Dense Regular
 Collagen fibres present in rows.
 Tendons attach skeletal muscle to bone.
 Ligaments attach bone to bone.
(ii) Dense Irregular
 Has collagen fibres and fibroblasts oriented differently.
 This tissue is present in the skin.
Specialised Connective Tissues
(i) Cartilage : made up of chondrocytes and collagen fibres; inter cellular
material is solid and resists compression. Present in tip of nose outer ear
joints, etc.

76 Biology Class - 11
 (ii) Bones : Ground substance is rich in calcium salts, collagen fibres and
Osteocytes es are present in lacunae. Bones support and protect softer tissues
and organs. They interact with skeletal muscles to bring about movements.
Bone marrow in some bones is the site of blood cell formation.
(iii) Blood : Fluid connective tissue, consists of plasma and blood cells.
Vascular Tissues

Blood Lymph

Plasma Formed Plasma Leucocytes

Elements

Blood Corpuscles Blood Platelets

Erythrocytes Leucocytes
(RBCs) (WBC)

Granulocytes Agranulocytes

Neutrophils Eosinophils Basophils Monocytes Lymphocytes

MUSCULAR TISSUES
(long, contractile cells called fibres, bring about movement and locomotion)

Skeletal Muscle Smooth Muscle Cardiac Muscle

Striated  Non-striated  Striated with intercalated

disc for communication

 Closely attached to  Forms wall of  Occurs in heart wall

sekeletal bones.  Internal Organs

like blood vessels

stomach, intestine
 long cylindrical  Spindle like  Short cyclindrical

multinucleated fibres uninucleated fibres. uninucleated fibres

Structural Organisation in Animals 77

Neural Tissues
 Neurons are the functional unit and are excitable cells.
 Neurogila cells make up more than half the volume of neural tissue.
They protect and support neurons.
Cockroach— Periplaneta americana (Phylum-Arthropoda, Class-Insecta)
Habitat : Cockroach is a terrestrial, nocturnal, ominivorous, unisexual,
oviparous insect. Body convered by a chitinous, hard exoskeleton of hard plates
called sclerites.
Morphology :
Head : Triangular, formed by fusion of 6 segments. Bears a pair of antennae,
compound eyes. Mouth parts consists of labrum (upper lip), a pair of mandibles,
a pair of maxillae,labium (lower lip), hypopharynx (acts as tongue).
Thorax : 3 segments; prothorax, mesothorax and metathorax.
Bears 2 pairs of wings :
Forewings : tegmina (mesothoracic).
Hindwings : transparent, membranous (metathoracic)
3 pairs of legs in thoracic segments. (one pair in each thoracic segment.)
Abdomen : 10 segments. Bears a pair of long, segmented anal cerci in
both sexes and a pair of short, unjoined anal styles in males only 7th segment is
boat shaped.
Also has anus and genital aperture at the hind end. Genital aperture
surrouonded by external genitalia called gonapophysis or phallomere.
Male Cockroach Female Cockroach
1. Abdomen long and narrow 1. Abdomen short and broad
2. All nine sterna visible 2. Seven sterna visible. (7th sternum
fused with 8th and 9th sterna)
3. Anal style present 3. Anal style absent
Anatomy : Study of the morphology of internal organs.
Alimentary canal : Divided into foregut, midgut and hindgut.
Mouth → Pharynx → Oesophagus → Crop (stores food) → Gizzard (grinding
of food) → Hepatic caecae (at junction of fore and midgut; secretes digestive
juice) → Hindgut (ileum, colon, rectum) → Anus.
78 Biology Class - 11
 Alimentary Canal of Cockroach
Female reproductive system :
A pair of ovaries (with 8 ovarian tubules) → Oviduct → Genital chamber.
Sperms transferred through spermatophores female produces 9–10 Ootheca.
Fertilised eggs encased in capsules called oothecae (contains 14-16 eggs on
an average) development of P. americana paurometabolous incompleted
metamorphosis). Nymph grows by moulting 13 times to reach adult form.
Interaction with man
 Pests as destroy food and contaminate it.
 Can transmit a variety of bacterial diseases (Vector).
Blood vascular system : Open type, visceral organs bathed in haemolymph
(colourless plasma and haemocytes).
Heart consists of enlongated muscular tube and differentiated into funnel shaped
chambers with ostia on either side. Blood from sinuses enters heart through ostia and
is pumped anteriorly to sinuses again. Blood is colourless (haemolymph).
Repiratory system : Network of trachea which open through 10 pairs of
spiracles. Spiracles regulated by sphincters. Oxygen delivered directly to cells.
Excretion and osmoregulation : by malpighian tubules; uricotelic (Uric
acid as excretory proudct).

Structural Organisation in Animals 79

 Nervous system : Consists of series of fused segmentally arranged ganglia
joined by paired longitudinally connectives on the ventral side. Three ganglia in
thorax, six in abdomen. Brain represented by supra-oesophageal ganglion. Each
eye consist s of 200 hexagonal ommatidia.
Reproductive system :
Male reproductive system : Pair of testes (4th-6th segments) → vas deferens
→ ejaculatory duct → male gonophore.
Glands–Seminal vesicle (stores sperms), mushroom shaped gland (6th-7th
segment).
Frog : Rana tigrina (Class : Amphibia)
Cold blooded or poikilotherms. Camouflage with surrounding, undergo
summer sleep (aestivation) and winter sleep (hibernation).
Morphology
The body is divided into head and trunk.
Head : A pair of nostrils above mouth is present, bulged eyes covered with
nictitating membrane (protect eye in water), membranous tympanum on either
side of eyes.
Trunk : Hind legs are large and muscular than forelimb and end in five
digits, Forelimb end in four digits.

Male frog Female frog

Vocal sac present No vocal sac present
Copulatory pad on the first digit of forelimb No copulatory pad present

Anatomy
Digestive system : Mouth buccal cavity pharynx esophagus
stomach intestine rectum rectum opens into cloaca
Stomach secreted HCl and digestive juices for digestion and convert food
into chyme. Duodenum receives chyme from stomach, Pancreatic juice (from
pancreas) and bile (from gall bladder) through common bile duct that help in
digestion. Final digestion and absorption (through microvilli) take place in small
intestine.

80 Biology Class - 11
 Venous system

Respiratory system : Frogs respire both on land and in water.

In Water : through skin via diffusion (cutaneous)
On Land : Air Nostrils Buccal cavity Lungs (A pair of elongated
pink colored sac like structure)
Blood vascular system : Closed type, Heart three chambered (two atria
and one ventricle covered with pericardium), blood contains plasma and cells
(nucleated RBC with hemoglobin, WBC and platelets)
Hepatic and renal portal system (venous connection between kidney and
lower body part) exists along with lymphatic system. Hepatic portal system =
venous connection between liver and intestine.
Excretion and osmoregulation : Ureotelic
Excretory waste though blood reaches to a pair of kidney, then to cloaca via
two ureters and finally reaches urinary bladder (stores urine) Urine is released
via cloacal aperture.

Structural Organisation in Animals 81

 Control and coordination
Chemical coordination
Achieved through hormones secreted by endocrine glands e.g., endocrine
glands found in frog are pituitary, thyroid, parathyroid, thymus, pineal body,
pancreatic islets, adrenals and gonads.
Nervous coordination
Nervous system : consists of central nervous system (Brain and spinal cord),
peripheral nervous system (cranial and spinal nerves) and autonomic nervous
system (sympathetic and parasympathetic).
Brain : Enclosed in brain box (cranium), divided into fore-brain, mid-brain
and hind brain. 10 cranial nerves arise from brain.
Forebrain includes olfactory lobes, paired cerebral hemispheres and unpaired
diencephalon.
Midbrain is characterised by a pair of optic lobes.
Hind-brain consists of cerebellum and medulla oblongata. The medulla
oblongata passes out through the foramen magnum and continues into spinal
cord, which is enclosed in the vertebral column.
Sense organ : different types of sense organs, namely organs of touch
(sensory papillae), taste (taste buds), smell (nasal epithelium), vision (eyes) and
hearing (tympanum with internal ears) present.
Reproductive system :
Male reproductive system : A pair of yellowish ovoid testes Vasa
efferentia (10-12 in number) Enters into kidneys on their side Open into
Bidder’s canal Urinogenital duct Cloaca
Female reproductive system : A pair of ovaries A pair of oviduct
Cloaca
A mature female can lay 2500 to 3000 ova (eggs) at time. Fertilisation is
external and takes place in water. Development involves a larval stage called
tadpole. Development is indirect as tadpole undergoes metamorphosis to form
the adult.

82 Biology Class - 11
 Benefits of frog for mankind :
• They eat insects and protect the crop.
• Maintain ecological balance because these serve as an important link of
food chain and food web in the ecosystem.
• In some countries the muscular legs of frog are used as food by man.
Female reproductive system :
A pair of ovaries (with 8 ovarian tubules) → Oviduct → Genital chamber.
Sperms transferred through spermatophores female produces 9–10 Ootheca.
Fertilised eggs encased in capsules called oothecae (contains 14-16 eggs on
an average) development of P. americana paurometabolous incompleted
metamorphosis). Nymph grows by moulting 13 times to reach adult form.
Interaction with man
 Pests as destroy food and contaminate it.
 Can transmit a variety of bacterial diseases (Vector).

Questions
(SRT) Select Response Type Questions (1 mark each)
1. Name the tissue which contains Haversian canals.
(a) Epithelial tissue (b) Areolar tissue
(c) cartitilage (d) Mammalian Bone
2. Mention any two properties of nervous tissue.
(a) Excitability & conductivity (b) contraction & relaxation
(c) lining & packaging (d) Excitablity & movement
3. Name the large cells present in adipose tissue.
(a) Adipocytes (b) Mast cells
(c) Collagen (d) Fibroblasts

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. Name the cells responsible for clotting of blood.
5. What are exocrine glands ?
6. Differentiate between tendon and ligament.
Structural Organisation in Animals 83
 7. Where are RBC’s formed ?
8. A muscular fiber having no striations and tapers at both ends. Name it.
9. Mention the site,where sclerite is present in cockroach.
10. Name the mouth part of cockroach which is comparable to our tongue.
11. “Sexual dimorphism is found in cockroach”. Explain the statement.
Short Answer Questions–I (2 marks each)
12. What is the function of ciliated epithelium ? Where do we find this
epithelium ?
13. What are the two types of fibres of connective tissues ? Distinguish between
the two.
14. To which tissue do the following belong to :
(a) Osteocytes (b) Chondrocytes
(c) Neuroglia (d) Intercalated discs
15. Give the location of hepatic caecae in cockroach ? What is their function ?
16. Name the locomotory appendages of cockroach on the basis of external
morphology.
17. Differentiate between Male and Female frog.
Short Answer Questions–II (3 marks each)
18. Differentiate between skeletal and smooth muscles.
19. Differentiate between male and female cockroach on the basis of external
morphology.
20. (a) What is open circulatory system ?
(b) Explain the respiratory system of cockroach.
21. (a) Give the common name of Periplaneta americana & Rana tigrina
(b) How many spermathecae found in cockroach ?
(c) What is the position of ovaries in cockroach ?
(d) How many segments are present in the abdomen of cockroach ?
(e) Where do you find malpighian tubules ?
(f) What is mosaic vision ?
22. Name the different cell junctions found in tissues.

84 Biology Class - 11
23. Mention the special features of eye in cockroach.
24. Write the appropriate type of tissue in column B accounting to the functions
mentioned is column A.
Column A Column B
a. Linking and supporting frame work ......................
b. Protective covering .......................
c. Secretion and absorption .......................
25. Diagrammatically represent the blood flow pathway in frog.
26. Explain the mechanism of respiration in frog.
27. What are the benefits of frog for mankind?
28. Neatly draw the labelled diagram of male reproductive system of frog.
29. Why frogs are not seen during peak summer and winters?
Long Answer Questions (5 marks each)
30. (a) What is compound epithelium ? What are their main function ?
(b) Where do we find areolar tissue ?
(c) How is adhering junction different from gap junction ?
31. Make a neat and well labelled diagram showing alimentary canal of cockroach.
32. Assign a term for following :
(a) Animal that secretes urea
(b) Winter sleep.
(c) Camouflaging with environment.
(d) Summer sleep.
(e) the process that tadpole undergoes to become adult.
(f) A small, median chamber passes faecal matter, urine and sperms to the
exterior in frog.
Case Based/Source Based
Read and observe the following, to answer the questions given below
The common Indian frog leads and amphibious life. It can live both on land
and water. Female frogs always lay 2500-3000 eggs in water, the fertilization
is external. They are cold blooded animals, with a three chambered heart.

Structural Organisation in Animals 85

 Direction in the following questions, a statement of assertion (A) is followed
by a statement of reason (R). Mark the correct choice as:
(a) If both (A) and (R) are correct and (R) is the correct explanation of
(A).
(b) If both (A) and (R) are true, but (R) is not the correct explanation of
(A).
(c) If (A) is true but (R) is false.
(d) If both (A) and (R) are false.
33. Assertion: Frog is a ureotelic animal.
Reason: Frog excretes urea.
34. Assertion: Eyes of frog are covered with nictitating membrane
Reason: On either side of the eyes, the membranous tympanum receives
sound signals.

Answers

(SRT) Select Response Type Questions (1 mark each)

1. (d) Mammalian bone. 2. (a) Excitability and conductivity.
3. (a) Adipocytes.

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Blood platelets.
5. Glands which discharge their secretions into ducts.
6. Tendon Ligament

Attach skeletal muscles to bones Attach bone to bone
7. Bone narrow
8. Smooth or non striated muscle fibre.
9. In the exoskeleton all over the body.
10. Hypopharynx
11. Male and female cockroaches show morphological differences.

86 Biology Class - 11
Short Answers–I (2 marks each)
12. Refer ‘Points to Remember’.
13. White and yellow fibres. White fibres are thin, unbranched, inelastic, occur
in bundles and formed of protein collagen. Yellow fibres are thick, straight,
elastic, branched, occuring singly, formed of protein elastin.
14. (a) Bone tissue (b) Cartilage
(c) Neural tissue (d) Cardiac muscle
15. Refer ‘Points to Remember’.
16. Three pairs of legs and two pairs of wings.
17. Refer ‘Points to Remember’.
Short Answers-II (3 marks each)
18. Refer ‘Points to Remember’.
19. Refer ‘Points to Remember’.
20. Refer ‘Points to Remember’.
21. (a) American Cockroach & Frog
(b) One pair, present in 6th segment.
(c) Between 2nd and 6th abdominal terga.
(d) 10 segments.
(e) At the beginning of ileum in cockroach.
(f) Vision where several images of an object are formed by compound eye.
Helps to detect movement of objects very efficiently.
22. (i) Gap junctions
(ii) Tight junctions
(iii) Adhering junctions
23. See text in NCERT at page No. 114.
(i) Situated at dorsal surface of head.
(ii) Each eye consists of about 2000 hexagon ommatidia.
(iii) It can receive several images of an object.
(iv) This kind of vision is known as mosaic vision.
(v) It has high sensitivity but has less resolution.
Structural Organisation in Animals 87
24. (a) Connective tissues
(b) Stratified epithelium
(c) Columnar epithelium
25. Refers ‘Points to Remember’.
26. Refers ‘Points to Remember’.
27. Refers ‘Points to Remember’.
28. Refer to NCERT page 119, figure 7.21
29. Frog are not seen during peak summer and winter. During this period, they
take shelter in deep burrows to protect themselves from extreme heat and cold.
This is known as summer sleep (aestivation) and winter sleep (hibernation)
respectively.
Long Answers (5 marks each)
30. Refer ‘Points to Remember’.
31. Refer Fig. 7. 16 and 7.20 NCERT Text Book of Biology class-XI.
32. A. Ureotelic, B. Hibernation, C. Mimicry, D. Aestivation, E. Metamorphosis,
F. Cloaca.
33. (a)
34. (b)


88 Biology Class - 11
 Cell : The unit of life
No nuclear membrane and
Prokaryotic no membrane bound cell
organelles. Eg.
Ex-bacteria
Basic Unit of Life CELL Two Types
Eukaryotic With nuclear membrane
and membrane bound cell
organelles. Eg.
Ex-human cell

Cell wall Cell Cytoplarm Nucleus Vacuoles

(plant cell) Membrane (Plant Cell)

Outermost Made of Fluid present Consists of Store house

covering of phospholipid between nucleoplasm of water,
plant cell, made bilayer and Nucleus and and nuclear nutrients
up of cellulose proteins Cell membrane membrane mineral salts,
waste

Contains cell organelles

Endo membrane Mitochondria Plastids Ribosomes Cytoskeleten Cillia and Centrosome

System Flegella Centriole

ER, golgi Double Found in Granular Proteinaceous Cilia are Form basal
apparatus, membranous
membranens plant cell & structures, structures smaller body of cilia
lysosomes structure, euglenoids made of made of hair like and flagella,
and produce contains DNA and microtubule, out and spindle
vacuoles energy in the pigments & protein, microfilaments growths fibers during
have co- form of ATP, classified as acts as & intermediate and cell division
ordinated divides by chloroplasts protein filaments, flagella of animal
function so fission, has and factories provide are larger cells
form its own DNA chromoplasts mechanical both help
endo and leucoplasts support, in
membrane ribosomes has DNA & motility and locomotion
system ribosomes
ribo somes maintain
shape of cell
Network of tiny tubular structures scattered in cytoplasm, which divide intracellular
ER – space into two compartments. They
They are
are of two
two types-SER
types– andRER
SER and RER
Golgibodies – Flat disc shaped sacs or cisternae, stacked parallel to each other, near nucleus.
Lysosomes – Membrane bound vescicles formed by packaging in Golgi apparatus

Cell : The Unit of Life 89

 Points to Remember

Cell Theory : Cell Theory was formulated by Schleiden and Schwann, and
was modified by Rudolf Virchow. Cell theory states that :

(A) All living organisms are composed of cells and products of cells.

(B) All cells arise from pre-existing cells.

Cell : Cell is the structural and functional unit of life.

Prokaryotic Cell Eukaryotic Cells

 Generally small sized (1–10 µm)  Generally large sized (5–10 µm)
 Well defined nucleus absent  Well defined nucleus present
 Membrane bound cell organelles  Membrane bounded cell organelles
absent present
 DNA without histone protein  DNA with histone protein

e.g., Bacteria, Mycoplasma, Blue e.g., Amoeba, Euglena and other
green Algae higher organism

Gram Positive Bacteria Gram Negative Bacteria

 Bacteria that take up gram  Bacteria do not take up gram stain
Stain. e.g., Bacillus e.g., Escherichia coli

PROKARYOTIC CELL :
Modification of cell envelope
 Cell envelope consists of tightly bound 3 layered structure – Outermost
Glycocalyx followed by cell well and plasma membrane

 Glycocalyx in form of loose sheath, is called slime layer

 Glycocalyx in form of thick and tough sheath, is called capsule

90 Biology Class - 11
  Mesosomes : Extension of plasma membrane. These can be in the form of
vesicles, tubules and lamellae.
Functions : Cell wall formation, DNA replication and distribution to daughter
cells, respiration, secretion processes, to increase surface area of plasma
membrane and enzyme content.
 Flagella : Extension from cell wall. It is composed of three structures –

filament, hook and basal body. It help in motility of bacteria.

 Fimbriae and Pili : Surface structure of some bacteria which attaches them

to rocks in streams; to host tissues, and conjugating partners respectively.

Genetic Material : It is not covered by nuclear envelope. In addition to
the genomic DNA (the single chromosome/circular DNA), many bacteria have
small circular self replicating, double stranded DNA which is called as plasmid,
plasmid contain genes like antibiotic resistance.
Ribosomes : Associated with plasma membrane of prokaryatic cell, site of
protein synthesis. Several ribosomes may attach to a single mRNA and form a
chain called polyribosomes or polysomes. They translate mRNA into Proteins.
Inclusion Bodies : Stores reserve material, lie freely in cytoplasm not bound
by any membrane. e.g. phosphate granules, cyanophycean granules and glycogen
granules.
Eukaryotic cells
Possess an oragnized nucleus with nuclear envelope and have a variety of
complex locomotory and cytoskeletal structures.
Cell Membrane — Singer and Nicolson (1972) gave ‘fluid mosaic model’.
According to this the quasi-fluid nature of lipid enables lateral movement of
proteins within the overall bilayer; two types of proteins (Peripheral and integral
proteins) with cholesterol, glycolipids and glycoporteins. Erythrocyte membrane
has 52% protein and 40% lipids.
Function—It is selectively permeable and helps in transport of molecule
across it.
Passive transport Active transport
 Transport of molecules from  Transport of molecules from lower to

higher to lower concentration. higher concentration

 It does not utilise energy (ATP).  It utilises energy (ATP)

e.g., diffusion e.g., Na+/K+ ATPase Pump.

Cell : The Unit of Life 91

 Fluid Mosaic Model of Plasma Membrane
Cell Wall is non-living rigid structure which gives shape to the cell and
protects cell from mechanical damage and infection, helps in cell-to-cell interaction
and provides barrier to undesirable macromolecules.
Cell wall of algae is made of cellulose, galactans, mannans and minerals like
calcium carbonate. Plant cell wall consists of cellulose, hemicellulose, pectins
and proteins.
Middle lamella is made of calcium pectate which holds neighbouring cells
together.
Plasmodesmata connect the cytoplasm of neighbouring cells.
Endoplasmic Reticulum (ER)
Consists of network of tiny tubular structure. ER divides the intracellular
space into two distinct compartments–luminal (inside ER) and extra luminal
(cytoplasm).
(i) Rough Endoplasmic Reticulum (RER) :
 Ribosomes attached to outer surface.

Function :  Involved in protein synthesis and secretion.

(ii) Smooth Endoplasmic Reticulum (SER) :  Lack ribosomes.
Function  Site for synthesis of lipid.
Golgi apparatus : First observed by Camillo Golgi (in 1898)
Consist of cisternae stacked parallel to each other. Two faces of the organelle
are convex/cis or forming face and concave/trans or maturing face but inter
connected.
Functions : Performs packaging of materials, to be delivered either to the
intra-cellular targets or secreted outside the cell. Important site of formation of
glycoproteins and glycolipids.

92 Biology Class - 11
 Lysosomes :
Membrane bound vesicular structures formed by the process of packaging
in the golgi apparatus. Contain hydrolysing enzymes (lipases, proteases,
carbohydrases) which are optimally active at acidic pH. Also called ‘Suicidal Bag’.
Function : Intracellular digestion.
Vacuoles : Membrane bound space found in the cytoplasm. Contain water,
sap, excretory product, etc. In plant cell, vacoule occupies 90% of space.
Function : In plants tonoplast (single membrane of vacuole) faciliates
transport of ions and other substances.
Contractile vacuole for excretion in Amoeba and food vacuoles formed in
protists for digestion of food.
Mitochondria : Double membranous structure. Outer membrane smooth and
inner membrane forms a number of infoldings called cristae The inner compartment
is called matrix. The cristae increase the surface area.
DNA (Circular)

OUTER MEMBRANE
RIBOSOME (70S)
CRISTA

MATRIX
INNER MEMBRANE
OUTER MEMBRANE

Mitochondria
Mitochondria

Function : Sites of aerobic respiration. Called ’power houses’ of cell as

produce cellular energy in the form of ATP. Matrix possesses single circular DNA
molecule, a few RNA molecules, ribsomes (70S). It divides by binary fission.
Plastids : Found in plant cells and in euglenoides. Chloroplasts, chromoplasts
and leucoplasts are 3 types of plastids depending on pigments contained.
Types of Plastids

Chloroplast Chromoplast Leucoplast

(Green coloured plastids) (Colourless plastids)
• Contain chlorophyll, and • Carotenoid pigments • Amyloplast (Starch)
carotenoids double stranded (fat souble) like Carotene, • Elaioplasts (oil + fat)
DNA and Xanthophylls and • Aleuroplast
70S ribosomes. Others. (store proteins)
• Trap light energy for • Gives the part of plant a
photosynthesis yellow orange and red colour

Cell : The Unit of Life 93

 Function : Site of photosynthesis, and imparts colours to fruits and flowers.

Chloroplast
Ribosomes
Composed of RNA and proteins; without membrane. Eukaryotic ribosomes
are 80S. S = Svedberg’s unit)
Function : Site of protein synthesis.
Cytoskeleton : Network of filaments.
Proteinaceous structure in cytoplasm made up of microtubules and micro
filaments.
Function : Mechanical support, motility, maintenance of the shape of the cell.
Cilia and Flagella
Cilia are small structures which work like oars which help in movement.
Flagella are longer and responsible for cell movement. They are covered
with a plasma membrane. Core is called axoneme which has 9 + 2 arrangement
of axonemal microtubules.

Centrosome and Centrioles

Centrosome contains two cylindrical structures called centrioles. Surrounded
by amorphous pericentriolar material. Made up of nine evenly spaced peripheral
94 Biology Class - 11
fibrils of tubulin protein (9+0). Centrioles form the basal body of cilia or flagella
and spindle fibres for cell division in animal cells. They produces spindle apparatus
during cell divison.
Nucleus : Double membranous with perinuclear space and nuclear pores;
has Chromatin, nuclear matrix and nucleoli (site for rRNA synthesis). (Named by
Robert Brown – 1831) Perinuclear space : Space between two parallel membrains
of nuclear envelope.
Chromatin DNA + nonhistone proteins. (Named by Fleming)
Nucleoplasm – Nucleolus + Chromatin
Nulear membrane—It is with perinuclear space and nucleopores.
Chromosomes—DNA/RNA + Histone protein/Nonhistone protein.
Centromere : Primary constriction in every chromosome
Kinetochores : Disc shaped structure on the sides of centsomere.
No nucleus in Erythrocytes (RBC) of mammals and sieve tubes in vascular
plants.
Chromosomes (on basis of position of centromere) :
Metacentric : Middle centromere.
Sub-metacentric : Centromere nearer to one end of chromosomes.
Acrocentric : Centromere situated close to its end.
Telocentric :Has terminal centromere.

Metacentric
Telocentric
Sub metacentric Acrocentric

Satellite : Some chromosomes have non-staining secondary constrictions at

a constant location, which gives the appearance of small fragment called satellite.

Cell : The Unit of Life 95

 Questions

(SRT) Select Response Type Question (1 mark each)

1. Name the parts of bacterials flagella.
(a) Filament, hook, basal body
(b) Basal body, nucleus, hook
(c) Filament, hook, cytoplasm
(d) Hook, microtubule, axoneme
2. Name the nutrients stored in elaiopiasts & aleuroplasts respectively.
(a) Fats and oils & proteins (b) Fats & proteins
(c) Proteins & Fats and oil (d) Starch & proteins
3. Name the scientist, who first saw and described a living cell.
(a) Anton Von Leeuwenhoek (b) Robert Brown
(c) Robert Hooke (d) Singer Nicolson

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. What are plasmids ?
5. Name the scientist who first explained that new cells arose from pre-existing
cells (Omnis cellula-e-cellula)
6. What is the composition of plasma membrane of human erythrocyte.
7. Eukayotic ribosomes are 80S. What does ‘S’ stand for ?
8. Write the function of cytoskeleton in a cell ?
Short Answer Questions–I (2 marks each)
9. What are nuclear pores ? State their function.
10. State the cell theory.
11. Differentiate between active and passive transport.
12. Differentiate between RER and SER.
13. List two functions of golgi apparatus.

96 Biology Class - 11
14. List two functions of mesosome.
15. Differentiate between the electron microscopic structure of cilia/flagella and
centriole.
16. Give the specific terms for the following :
(a) Cluster of ribosomes found in cytoplasm
(b) Extensive infolding in the inner membrane of mitochondria
(c) Stacks of closely packed thylakoids
(d) Stalked particles on the inner membrane of mitochondria
17. (a) Write the function of inclusion bodies in prokaryotic cells ?
(b) Where are they present ?
(c) Give two examples of inclusion bodies.
Short Answer Questions–II (3 marks each)
18. With the help of labelled diagram explain the ‘fluid mosaic model’ structure
of cell membrane.
19. Differentiate between a prokaryotic and eukaryotic cell.
20. What are lysosomes ? How are they formed ? Write their functions.
21. Give the structural details of an eukaryotic nucleus along with its diagram.
22. The ribosomes of prokaryoters are of 70 S type ribosomes and while of
eukaryotes are of 80 S type as well as 70 S types.
(a) Give the composition of 70 S type ribosomes and 80 S type ribosome
(two sub units, from each of them are made of)
(b) Name two cell organelles of eukaryotic cells which have their own
independent ribosomes of 70 S type
Long Answer Questions (5 marks each)
23. (a)
Give the structural details of mitochondria.
(b)
Draw its diagram.
(c)
Why is it called ‘powerhouse of the cell’ ?
24. (a)
Diagrammatically represent the types of chromosomes based on the
position of centromere.
(b) What does chromatin contain ?
(c) What is perinuclear space ?

Cell : The Unit of Life 97

 Answers

(SRT) Select Response Type Question (1 mark each)

1. (a) Filament, hook, basal body.
2. (a) Elaioplasts : fats and oils.
Aleuroplasts : proteins.
3. (a) Anton Von Leeuwenhoek

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. The small circular DNA, outside the genomic DNA of bacteria.
5. Rudolf Virchow.
6. 52% proteins, 40% lipids.
7. Sedimentation coefficient (Svedberg unit)
8. Mechanical support, motility, maintenance of shape of cell.
Short Answers–I (2 marks each)
9. Minute pores present in the nuclear envelope; provide passage for movement
of RNA and proteins between nucleus and cytoplasm.
10. Refer ‘Points to Remember’.
11. Refer ‘Points to Remember’.
12. Refer ‘Points to Remember’.
13. Refer ‘Points to Remember’.
14. Refer ‘Points to Remember’.
15. Flegella/Cilia Centriole

(i) Possess (9 + 2) pattern of axoneme : Possess (9 + 0) pattern,
microtubules enclosed by a membrane membrane less organelle
(ii) Each tubule is doublet : Each tubule is a triplet

16. (a) Polyribosome/Polysome (b) Cristae

(c) Grana (d) Fo–F1 particles ...
17. (a) Reserve materials are stored,

98 Biology Class - 11
 (b) They are free in the cytoplasm
(c) e.g.,Phosphate granules, cyanophycean granules, glycogen granules.
Short Answers–II (3 marks each)
18. Refer ‘Point to remember’.
19. Differences in nucleus/chromosomes/mesosome/membrane bound cell
organelles/ribosomes/compartments in cell.
20. Refer ‘Point to remember’.
21. Refer ‘Point to remember’.
22. (a) 70 S ribosomes have 50 S and 30 S sub units; 80S ribosomes have 60
S and 40 S sub units.
(b) Mitochondria and chloropolast.

Long Answers (5 marks each)

23. Points to remember.
24. Points to remember.

Case Based :
25. Read the following and answer question given below:
It is thought that life originated on earth around 4 billion years ago. The
endosymbiotic theory states that some of the organelles in today’s Eukaryotic
cells were once prokaryotic microbes. In this theory the first eukaryotic
cell was probably an Amoeba like cell which ingested prokaryotic cells
which survived within these amoeba host cells. Both organisms established
symbiotic relationship. Mitochondria is formed when bacteria capable of
aerobic respiration were ingested, chloroplast formed when photosynthetic
bacteria were ingested. They eventually lost their cell wall and much of their
DNA.
Some evidences which support this theory are :
· Mitochondria and chloroplast have their own circular DNA, just like
prokaryotes.

Cell : The Unit of Life 99

 · Both have 70s type of ribosomes.
· Both are of the same size as prokaryotic cells and divide by binary fission.
· Both are covered by double layered and contain respiratory enzymes on their
inner surface.
Mitochondria and chloroplasts are semiautonomous organelles as they have
their own DNA and ribosomes. They can synthesise some of their proteins
on their own.
(i) Which feature have the prokaryotes lost during their evolution into
mitochondria and chloroplast?
(a) Cytoplasm (b) Nucleus
(c) ER (d) Cell wall
(ii) Theory of endosymbiosis explains the :
(a) origin of organelles in eukaryotes
(b) how bacteria live
(c) how species evolve
(d) origin of multicellular life
(iii) Host cell received _______ from its endosymbiont and endosymbiont
received ______ from its host :
(a) Energy & shelter (b) Shelter and energy
(c) Motility and reproduction (d) Reproduction and motility
(iv) Which of the following evidence support endosymbiotic theory. Select all
that which applies :
(A) Chloroplasts and mitochondria have their own small circular DNA like
prokaryotes
(B) They divide by binary fission
(C) 70s type of ribosomes in tem
(D) Respiratory enzymes on their inner surface
(a) A & B (b) A, B & C
(c) A, B, C & D (d) B, C, & D

100 Biology Class - 11

Assertion and Reason type Questions (1 mark each)
In each of the following questions, two statements are given, one is Assertion
and other is Reason. Mark the correct answer as :
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both the assertion & reason are false.
26. Assertion : Specialization of cells is useful for organisms.
Reason : It increases the operational efficiency of an organism.
27. Assertion : Eukaryotic cells contain membrane bound organelles.
Reason : Prokaryotic cells do not contain membrane bound organelles.

28. Assertion : Mitochondria and chloroplast are semi autonomous organelles.
Reason : They are formed by the division of preexisting organelles as well

as contain their own DNA but lack protein synthesizing machinery.

Answers:
Ans. 25. (i) (d) Cell wall
(ii) (a) Origin of organelles in eukaryotes
(iii) (a) energy and shelter
(iv) (c) A, B, C and D
Ans. 26. (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.
Ans. 27. (b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
Ans. 28. (c) Assertion in true but reason is false.


Cell : The Unit of Life 101

102 Biology Class - 11
 Points to Remember
Biomolecules : All the carbon compounds that we get from living tissues.
Biomicromolecules : Molecules which have molecular weights less than
one thousand dalton. They are also known as monomers. They are found in acid
soluble fraction.
Biomacromolecules : A biomolecule with molecular weight in the range of ten
thousand daltons and above; found in acid insoluble fraction. e.g. polysaccharides,
nucleic acids, proteins and lipids.
How to analyse chemical composition of living tissues?
Living tissue + Trichloroacetic acid Grinding Thick Slurry

Filter through cheese cloth Filterate (Acid soluble)

Retentate (Acid insoluble)

Primary and secondary metabolites :

 Primary metabolites have identifiable functions and play important roles in
normal physiological process eg. Amino acids, nitrogenous bases, proteins
and nucleic acid.
 Secondary metabolites are product of certain metabolic pathways from
primary metabolites, eg. carotenoids, drugs, alkaloids, essential oils, rubber,
gum, cellulose and resins etc.
Amino acids : Organic compounds containing an amino group and one

carboxyl group (acid group) and both these groups are attached to the same
carbon atom called α carbon and so they are called amino acids.

e.g. (1) In Glycine R = H
(2) In alanine R = CH3
(3) In serine R = CH2 – OH

Biomolecules 103
 Twenty types of amino acids.
Amino acid exists in Zwitterionic form at different pHs.
R R R
| | |
H2N

(A) (B) (C)
(Zwitterionic form)
 Based on the type of side chains number of amino and carboxyl groups,

amino acids can be :

(i) Aromatic – Tryptophan, phenylalanine and Tyrosine are aromatic (give
smell) amino acids.
(ii) Acidic Amino Acids – (aspartic acid, glutamic acid).
(iii) Basic amino acid (Arginine).
(iv) Neutral amino Acids (valine, Proline).
Lipids :
Lipids are not strictly macromolecules as their molecular weight do not
exceed 800 Da but form a part of the acid insoluble pool.
 Water insoluble, containing C, H, O.

 Fats on hydrolysis yield fatty acids.

 Fatty acid has a carboxyl group attached to an R group (contains 1 to 19

carbons).
 Fatty Acids : Saturated : With single bonds in carbon chain, e.g., Palmitic

acid, butyric acid.

Unsaturated : With one or more double bonds, e.g., oleic acid, linoleic acid.
 Glycerol : A simple lipid, is trihydroxy propane.

Some lipid have fatty acids esterified with glycerol.



Example of fatty acid (Palmitic acid) (CH3—(CH2)14—COOH)

 They can be monoglycerides, diglycerides and triglycerides.

Triglyceride, R1, R2, R3 are alkyl

2
groups in fatty acids

104 Biology Class - 11

 Phospholipids are compound lipids with phosphorus and a phosphorylated


organic compound e.g., Lecithin.

Phospholipids (Lecithin) found in cell membrane and lipids made complex
structure in neural tissue.
Nitrogen bases
(Carbon compounds with heterocyclic rings)

Purine : Adenine, Guanine, Pyrimidine : Cytosine, Uracil, Thymine.

Nucleoside : Nitrogenous base + Sugar e.g. Adenosine, guanosine.
Nucleotide : Nitrogenous base + Sugar + Phosphate group. e.g. Adenylic
acid, Guanylic acid. Thymidylic acid.
Nucleic acids : Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
DNA structure (Watson and Crick Model) :
1. DNA is a right handed, double helix of two polynucleotide chains, having
a major and minor groove.
2. The two chains are antiparallel, and held together by hydrogen bonds
(two between A and T and three between C and G).
3. The backbone is formed by sugar-phosphate-sugar chain.
4. The nitrogen bases are projected more or less perpendicular to this,
backbone and face inside.
5. The pitch is 34A°. At each step of ascent, the strand turns 36°. The rise
per base pair is 3.4°A, so one full turn involves ten base pairs.
Protein : proteins are polypeptides.
 They are polymers of aminoacids linked by peptide bond.

 Is a heteropolymer (different monomers repeating ‘n’ number of times).

 Functions : Intercellular ground substance (collagen), as enzyme (Trypsin)

as hormone (Insulin), to fight infections (Antibodies), as sensery receptors,

and to enable glucose transport in cells (GLUT-4)
Structure of Proteins
(a) Primary structure : Is found in the form of linear sequence of amino acids.
First amino acid is called N-terminal amino acid and last amino acid is called
C-terminal amino acid.
(b) Secondary structure : Polypeptide chain undergoes folding or coiling which
is stabilized-by hydrogen bonding. Right handed helices are observed; e.g.,
fibrous protein in hair, nails.

Biomolecules 105
 (c) Tertiary structure : Long protein chain is folded upon itself like a hollow
woollen ball. Gives a 3-dimensional view of protein, e.g., myosin.
(d) Quaternary structure : Two or more polypeptides with their foldings and
coilings are arranged with respect to each other, e.g., Human haemoglobin
molecule has 4 peptide chains - 2 α and 2 β Subunits.
Monosaccharides are joined by glycosidic bond, right end is reducing and
left end is non reducing
Polysaccharides : Are long chain polymers of monosaccharides.
(a) Starch : Store house of energy in plant tissues. Forms helical secondary
structures, made of only glucose monomers.
(b) Cellulose : Homopolymer of glucose. It does not contain complex helices.
Cotton fibre is cellulose.
(c) Glycogen : Is a branched homopolymer, found as storage polysaccharide in
animals.
(d) Inulin : Is a polymer of fructose.
(e) Chitin : Chemically modified sugar (amino-sugars) N-acetyl glucosamine
form exoskeleton of arthropods; homopolymer.
Metabolic Pathways :
(a) Anabolic pathways : Lead to formation of more complex structure from a
simpler structure with the consumption of energy, e.g., Protein from amino
acids., also known as biosynthetic pathways.
(b) Catabolic pathway : Lead to formation of simpler structure from a complex
structure, e.g., Glucose → Lactic Acid + energy
The most important energy currency in living systems is ATP (adenosine
tri – phosphate).
“There is no uncatalysed metabolic conversion in living system”
The living state is a non-equilibrium steady state to be able to perform work.
Without metabolism, there cannot be a living state.
Bonds linking monomers in a polymer
Peptide bond—formed between the carboxyl (–COOH) group of one amino
acid, and the amino (– NH2) group of the next amino with the elimination of water
moiety, (dehydration).
Glycosidic bond—bond formed between two carbon atoms of two adjacent
monosaccharides., by dehydration.
Phosphodiester bond—bond formed in nucleic acids where in a phosphate

106 Biology Class - 11

moiety links the 3–carbon of one sugar of one nucleotide to the 5–carbon of the
sugar of the succeeding nucleotide. (The bond between phosphate group and
hydroxyl group of sugar)
Enzymes : Are biocatalyst.
 Almost all enzymes are proteins.

 Ribozymes–Nucleic acid that behave like enzymes.

 Has primary, secondary and tertiary structure.

 Active site of an enzyme is a crevice or pocket into which substrate fits.

 Enzymes get damaged at high temperatures.

 Enzymes isolated from thermophilic organisms (live under high temperatures)

are thermostable.
 Enzymes accelerate the rate of reactions many folds.

 Enzymes lower the activation energy of reactions. (Fig. 9.6, Page no. 156,

NCERT Text Book of Biology for Class XI).

 E + S  ES → EP → E + P


where E = Enzymes, S = Substrate, P = Product

Factors affecting enzyme activity :

(a) Temperature : Show highest activity at optimum temperature. Activity
declines above and below the optimum value.
(b) pH : Enzymes function in a narrow range of pH. Highest activity at optimum
pH. (Fig. 9.7, NCERT, Text Book of Biology for Class XI).
(c) Concentration of substrate : The velocity of enzymatic reaction rises with
increases in substrate concentration till it reaches maximum velocity (Vmax).
Further increase of substrate does not increase the rate of reaction as no free
enzyme molecules are available to bind with additional substrate.

Enzyme inhibition : When the binding of a chemical shuts off enzyme

activity, the process is called inhibition and chemical is called inhibitor.

Biomolecules 107
 Competitive inhibition : Inhibitor closely resembles the substrate in its
molecular structure and inhibits the enzyme activity. E.g., inhibition of succinic
dehydrogenase by malonate. (Actual substrate is succinic acid).

Classification of enzymes :
1. Oxidoreductase/dehydrogenases : Catalyse oxidoreduction between 2
substrates. S reduced + S′ oxidised → S oxidised + S′ reduced.
2. Transferases : Catalyse transfer of a group between a pair of substrates.
S – G + S′ → S + S′ – G
3. Hydrolases : Catalyse hydrolysis of ester, ether, peptide, glycosidic, C–C,
P-N bonds.
4. Lyases : Catalyse removal of groups from substrates by mechanisms other
than hydrolysis. leaving double bonds.
5. Isomerases : Catalyse inter-conversion of optical, geometrical or positional
isomers.
6. Ligases : Catalyse linking together of 2 compounds.
C–O, C–S, C–N, P–O
Co-factors : Enzymes becomes catalytically active when it binds to non
protein constituent called co-factors. Protein portion of enzyme is called
apoenzyme.
 Prosthetic group : These are organic compound which tightly bound to the
apoenzyme.

e. g., Haem is prosthetic group in peroxidase and catalase.
 Coenzyme : These are organic compounds whose association with the
apoenzyme is only transient, usually occurring during the course of catalysis.

e.g., Coenzyme Nicotinamide adenine dinucleotide (NAD) and NADP
contain vitamin niacin.
 Metal ions : Metal ions form coordination bond with side chains at the
active site and at the same time form one or more coordination bond with
substrate.

e.g. zinc in enzyme carboxy peptidase.

108 Biology Class - 11

 Questions
(SRT) Select Response Type Question (1 mark each)
1. Purine bases are...
(a) Adenosine & Guanosine (b) Adenine only
(c) Guanine only (d) Adenine & Guanine
2. Bond between two monosaccharides is...
(a) Glycosidic bond (d) Phosphodiester linkage
(c) Peptide bond (d) Coordinate bond
3. Name an element found in protein but not in lipids & carbohydrates.
(a) Hydrogen (b) Carbon
(c) Nitrogen (d) Chlorine

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. What does an enzyme do in terms of energy requirement of a reaction ?
5. What is the function of ATP in cell metabolism ?
6. Name the protein which form the intercellular ground substance.
7. What are biomacromolecules ?
8. Why enzymes are called bio-catalysts ?

Short Answer Questions-I (2 marks each)

9. Differentiate between prosthetic group and coenzyme ?
10. What are glycosidic bonds and peptide bonds ?
11. Why are aminoacids also known as substituted methane?
12. Amino acids exist as zwitter ions. Give its structure. Why is it formed ?
13. Why do starch give blue black colour with iodine ?
14. Why are starch and glycogen more suitable than glucose as a storage
product ?

Biomolecules 109
15. What would happen when salivary amylase which acts on starch in mouth
enter in stomach ?
16. Differentiate between homo polysaccharides and hetero poly saccharides.
17. Why do physicians recommend vegetable oils rich in polyunsaturated fat
for persons suffering from cardiovascular diseases ?
18. Why does the shelf life of fruits and vegetables increase in a refrigerator ?

Short Answer Questions-II (3 mark each)

19. Differentiate between primary and secondary metabolites with examples ?
20. List out some major proteins and their function ?
21. Explain the structure of proteins.
22. Explain Watson-Crick model on DNA structure.
23. Explain peptide bond, glycosidic bond and phospodiester fond.
24. Explain competitive inhibition along with an example.

Long Answer Questions (5 marks each)

25. List the 6 classes of enzymes along with their functions.

Answers
(SRT) Select Resonse Type Question (1 mark each)
1. (d) Adenine & Guanine 2. (a) Glycosidic bond
3. (c) Nitrogen

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer (1 marks each)
4. Lowers the activation energy of reaction.
5. Are the energy currency of cell.
6. Collagen.
7. Refer point to remember.
8. Enzymes are proteins that catalyze metabolic/chemical reactions inside the
living being. That’s why they are called biocatalysts.

110 Biology Class - 11

Short Answer-I (2 marks each)
9. Refer ‘Points to remember’.
10. Refer, ‘Points to remembers’.
11. The α-carbon has 4 substituted groups occupying the 4 valency positions :
H, — COOH, — NH2 and — R group.
12.

3
Due to ionizable nature of — NH2 and — COOH groups.
13. Starch form helical secondary structure which can hold I2.
14. Occupy lesser space as less bulky and can be hydrolysed to glucose when
required.
15. In mouth, salivary amylase changes starch into maltose. Action of amylase
+
stops in stomach as it cannot act in an acidic medium.
16. Homopolysaccharides Heteropolysaccharides
(a) Constituted of single type Constituted by two or more type of
of monosaccharide units monosaccharide unit and their
derivatives
(b) e.g., starch, glycogen, cellulose e.g., Peptidoglycans, chitin
17. Polyunsaturated oils contain fatty acids having one or more double bonds
which does not clog arteries due to high proportion of polyunsaturated fatty
acids.
18. Low temperature prevents growth of food spoiling micro organisms and
also inhibits the action of enzymes present in the food, because, enzymes
are inactivated at low temperature.

Short Answers-I (3 marks each)

19. Secondary metabolites—The metabolites like alkaloids lectins Drugs,
Pigments, Spices and scents etc. which are useful to human welfare and
have ecological importance, are products of certain metabolic pathways.
Primary metabolites—The metabolites having identifiable functions and

play important role in normal physiological processes, e.g., sugars, amino
acids, fats and oils and nucleotides, etc.

Biomolecules 111
 20. Refer Table 9.5, NCERT, text book of biology class XI.
21. Refer ‘Points to remember’.
22. Refer ‘Points to remember’.
23. Refer ‘Points to remember’.
24. Refer ‘Points to remember’.

Long Answers (5 marks each)

25. Refer ‘Points to remember’.

Case study based question (4 marks each)

26. Read the following and answer the question given below:
Enzymes are proteins that act as biological catalysts (biocatalyst). Almost all
enzymes are proteins. Some Nucleic acid behaves like enzymes. They are
called ribozymes. Enzymes have tertiary structure and many crevices called
‘active sites’. Enzymes act upon substrate and change them into products.
Substrate binds to the active sites of enzymes.
26. (i) Which enzyme is used by the biscuit manufactures to lower the protein
level of flour?
(a) Amylases (b) Proteases
(c) Cellulases (d) Xylases
26. (ii) Which of the following statement is/are correct about enzymes?
(a) An enzyme is a protein which acts as a biocatalyst to accelerate the rate
of reaction.
(b) Life would not exist without the presence of enzymes in cells
(c) Enzymes participate in various cellular metabolic processes
(d) All the above
26. (iii) A protein having both structural and enzymatic properties is :
(a) Collagen (b) Trypsin
(c) Myosin (d) Actin

112 Biology Class - 11

 26. (iv) The diagram shows a metabolic pathway :

Enzyme -1 Enzyme -2 Enzyme -3

A B C D

What would happen to the rate of production of ‘D’, if enzyme 1 was not
present?
(a) It would stop
(b) It would be increased
(c) It would be decreased
(d) No effect

Assertion and Reason Type Questions (1 mark each)

In each of the following questions, two statements are given, one is Assertion
and other is Reason. Mark the correct answer as :
(a) Both assertion and reason are true, and the reason is the correct
explanation of the assertion.
(b) Both assertion and reason are true but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both the assertion and reason are false.
27. Assertion : A coenzyme or metal ion tightly bound to enzyme protein is
called prosthetic group.
Reason : A complete catalytically active enzyme together with its bound
prosthetic group is called apoenzyme.
28. Assertion : Secondary metabolites are produced in small quantities and their
extraction from the plant is difficult and expensive.
Reason : Secondary metabolites can be commercially produced by using

tissue culture technique.
29. Assertion : All enzymes are not proteins.
Reason : RNA molecules that possess catalytic activity are called ribozymes.

Biomolecules 113
Answers :
Ans. 26 (i) (b) Proteases
Ans. 26 (ii) (d) All the above
Ans. 26 (iii) (c) Myosin
Ans. 26 (iv) (a) It would stop
Ans. 27 (c) Assertion is true but reason is false.
Ans. 28 (b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
Ans. 29. (a) Both assertion and reason are true, but the reason is the correct
explanation of the assertion.


114 Biology Class - 11

 Points To Remember
Cell cycle : The sequence of events by which a cell duplicates its genome,
synthesises the other constituents of the cell and eventually divides into two
daughter cells.
Interphase (G1 phase + S phase + G2 Phase)

Phases of cell cycle

Karyokinesis (division of nucleus)
M Phase (Mitosis phases)
Cytokinesis (division of cytoplasm)

Interphase : (Resting Phase)

 G1 Phase : Cell metabolically active and grows continuously but does not
replicate DNA
 S Phase : DNA synthesis occurs, DNA content increases from 2C to 4C, but
the number of chromosomes remains same i.e., 2n.
 G2 Phase : Proteins are synthesised in preparation for mitosis while cell
growth continues.
M Phase (Mitosis Phase) : Starts with nuclear division, corresponding to
separation of daughter chromosomes (karyokinesis) and usually ends with division
of cytoplasm, (cytokinesis).
Quiescent stage (G0) In adult animal cells that do not divide and exit G1
phase to enter an inactive stage called G0. Cells at this stage remain metabolically
active but do not proliferate.
e.g., Heart cells

Cell Cycle and Cell Division 115

 I

G2 phase
II cell repeating cell cycle
RNA and
Protein
Synthesis

S Phase G1 Phase
DNA Duplicates Protein Synthesis
Replication of Growth of nucleus
Chromosomes

Mitosis
Since the number of chromosomes in the parent and progeny cells is the
same, it is called as equational division. Mitosis is divided into four sub stages.
1. Prophase : (i) Replicated chromosomes, each consisting of 2 chromatids,
condense and become visible.
(i) Microtubules are assembled into mitotic spindle.
(iii) Nucleolus and nuclear envelope disappear.
(iv) Centriole moves to opposite poles.
2. Metaphase : (i) Spindle fibres attached to kinetochores (small disc-shaped
structures at the surface of centromere) of chromosomes.
(ii) Chromosomes line up at the equator of the spindle to form metaphase
plate.
3. Anaphase : (i) Centromeres split and chromatids separate.
(ii) Chromatids move to opposite poles due to shortening of spindle fibres.
4. Telophase : (i) Chromosomes cluster at opposite poles.
(ii) Nuclear envelope assembles around chromosomes clusters’.
(iii) Nucleolus, Golgi Complex, E.R. reappear.

116 Biology Class - 11

 Cytokinesis : The division of protoplast of a cell into two daughter cells
after karyokinesis (nuclear division)
Animal Cytokinesis :
Appearance of furrow in plasma membrane which deepens and joins in the
centre, dividing cell cytoplasm into two.
Plant cytokinesis : Formation of new cell wall begins with the formation
of a simple precursor — cell plate which represents the middle lamella between
the walls of two adjacent cells.
 When karyokinesis is not followed by cytokinesis, a multinucleated condition
arises. This is called syncytium.
Significance of Mitosis :
1. Growth insert backslash addition of cells.
2. Maintenance of surface/volume ratio. Maintain Nucleo–cytoplasmic ratio.
3. Maintenance of chromosomes number.
4. Regeneration.

Cell Cycle and Cell Division 117

 5. Reproduction in unicellular organisms, lower plants and some insects.
6. Repair and wound healing.
7. Vegetative reproduction in plants takes place by mitosis.
Meiosis :
 Specialised kind of cell division that reduces the chromosomes number by
half. Hence it is called reductional division.
 Occurs during gametogenesis in plants and animals.
 Involves two sequential cycles of nuclear and cell division called Meiosis I
and Meiosis II.
 It results in 4 haploid daughter cells.
 Interphase occurs prior to meiosis which is similar to interphase of mitosis
except the S phase is prolonged.

Meiosis I

Pairing of
Centromere homologous chromosomes
(synapse)
Nucleous

Leptotene Zygotene

crossing Chiasma
over Formation

Pachytene
Diplotene

Terminalisation
occurs
Metaphase
Plate

Diakinesis
Metaphase I

Two Daughter
Nuce I

Anaphase I Telophase I

118 Biology Class - 11

Meiosis I
Prophase I : Subdivided into 5 phases.
(i) Leptotene :
 Chromosomes make their appearance as single stranded structures.
 Compaction of chromosomes continues.
(ii) Zygotene :
 Homologous chromosomes start pairing and this process of association
is called synapsis.
 Chromosomal synapsis is accompanied by formation of Synaptonemal
complex.
 Complex formed by a pair of synapsed homologous chromosomes is
called bivalent or tetrad.
(iii) Pachytene : Crossing over occurs between non-sister chromatids of
homologous chromosomes. The enzymes involved in the process is
‘recombinase’. Recombination between homologous chromosomes is
completed. Exchange of genetic material.
(iv) Diplotene : Dissolution of synaptonemal complex occurs and the recombined
chromosomes separate from each other except at the sites of crossing over.
These X-shaped structures are called Chiasmata. In oocytes of some
vertebrates diplotene can last for month or years.
(v) Diakinesis : Terminalisation of chiasmata.
 Chromosomes are fully condensed and meiotic spindles assembled.
 Nucleolus disappear and nuclear envelope breaks down.
Metaphase I : Bivalent chromosomes align on the equatorial plate.
 Microtubules from opposite poles of the spindle attach to the pair of

homologous chromosomes.
Anaphase I : Homologous chromosomes, separate while chromatids remain
associated at their centromeres.
Telophase I :
 Nuclear membrane and nucleus reappear.
 Cytokinesis follows (dyad of cells).

Interkinesis : Stage between two meiotic divisions, (meiosis I and meiosis II)
generally short lived, No replication of DNA during this.
Meiosis II: (It resembles the normal mitosis).

Cell Cycle and Cell Division 119

 Meiosis II

Prophase II

Chromosome
Aprangedon
Metaphase Plate

Metaphase II

Chromatids
Separate

Anaphase II

Telophase II
Prophase II
Nuclear membrane disappears.
 Chromosomes again become compact.

Metapahse II
 Chromosomes align at the equator.

 Microtubules from opposite poles of spindle get attached to kinetochores of

sister chromatids.
Anaphase II
 Simultaneous splitting of the centromere of each chromosome, allowing

them to move towards opposite poles of the cell, by shortening of microtubules

attached to kinetochores.
120 Biology Class - 11
Telophase II
 Two groups of chromosomes get enclosed by a nuclear envelope.
 Cytokinesis follows resulting in the formation of tetrad of cells i.e., 4 haploid
cells.

Significance of Meiosis
1. Formation of gametes : In sexually reproducing organisms.
2. Genetic variability : Variations are very important for evolution.
3. Maintenance of chromosomal number : By reducing the chromosome
number in gametes. Chromosomal number is restored by fertilisation of
gametes.
Questions
(SRT) Select Response Type Question (1 mark each)
1. Karyokinesis is the division of
(a) nucleus (b) chromosome
(c) cytoplasm (d) protoplasm
2. Cytokinesis is the division of
(a) nucleus (b) chromosome
(c) cytoplasm (d) protoplasm
3. Pairing of homologous chromosomes occurs during
(a) Leptotene (b) diplotene
(c) diakinesis (d) metaphase

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. Name the stage of meiosis during which synaptonemal complex is formed.
5. What is Go phase of cell cycle ?
6. Where does mitosis take place in plants and animals ?
Short Answer Questions-I (2 marks each)
7. Differentiate between cytokinesis of plant and animal cell.
8. What is Chiasmata ? State its significance.
9. Differentiate between chromatin and chromatid.

Cell Cycle and Cell Division 121

10. Give the terms for the following :
(a) The period between 2 successive mitotic divisions.
(b) Cell division in which chromosome number is halved.
(c) Phase in cell cycle where DNA is synthesised.
(d) Division of nuclear material.
11. What happens during S phase of interphase ?
12. Distinguish between metaphase of mitosis and metaphase I of meiosis.
13. What will be the DNA content of a cell at G1 after S and G2 if the content
after M phase is 2C.
Short Answer Questions-II (3 marks each)
14. Differentiate between mitosis and meiosis.
15. List the significance of mitosis.
16. Describe the following :
(a) Synapse (b) Bivalent (c) Leptotene
Long Answer Questions (5 marks each)
17. With the help of labelled diagram, explain the following :
(a) Diplotene (b) Anaphase of mitosis
(c) Prophase I of meiosis
18. What is cell cycle ? Explain the events occurring in this cycle.
19. With the help of labelled diagrams, explain various stages of mitosis cell division.
20. (a) Write a note on significance of meiosis.
(b) Differentiate between anaphase 1 of meiosis and Anaphase of mitosis.
(c) In which phase of interphase duplication of DNA will occur ?

Answers
(SRT) Select Response Type Question (1 mark each)
1. (a) Nucleus 2. (b) cytoplasm 3. (a) Leptotene

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Zygotene.
5. Cells which enter a stage where they are metabolically active but no longer
proliferate.
122 Biology Class - 11
 6. Plant – Meristematic tissue; Animals–somatic cells.
Short Answers-I (2 marks each)
7. Refer ‘Points to Remember’.
8. Refer ‘Points to Remember’.
9. Chromatin Chromatid :
(a) Diffuse, deep staining hereditary material longitudinally split half of a
chromosome, light staining hereditary material.
(b) Metabolically inert Metabolically active.
10. (a) Interphase
(b) Meiosis
(c) S phase
(d) Karyokinesis
11. Refer ‘Points to Remember’ :
12. Metaphase Metaphase I
(a) Chromosome align along (a) Bivalent chromosomes arrange
the equator of the cell along the equatorial plane.
(b) Figure from points to remember (b) Figure from points to remember

13. G1 – 2C, S1 – 4C, G2 – 4C
Short Answers-II (3 marks each)
14. Mitosis Meiosis

(a) Occurs in Somatic cells (a) Occurs in germ cells

(b) Number of chromosomes (b) Number of chromosomes reduces
remain same in daughter cells to half in daughter cells.
(c) No exchange of genetic (c) Exchange of genetic material occurs
material due to crossing over
(d) Involve single division (d) Involve two successive division

15. Refer ‘Points to Remember’.

16. Refer ‘Points to Remember’.
Long Answer (5 marks each)
17. Refer ‘Points of Remember’.
18. Refer ‘Points of Remember’.

Cell Cycle and Cell Division 123

19. Refer ‘Points of Remember’.
20. (a) Refer ‘Points of Remember’
(b) Refer ‘Points of Remember’.
(c) During S phase or synthesis phase.
Case Study based Question (4 marks each)
21. Read the following and answer any four questions from 21 (i) to 21 (v) given
below :
The sequence of events by which a cell duplicates its genome, synthesizes
the other constituents of the cell and eventually divides into two daughter
cells is termed cell cycle. Cell cycle is divided into interphase and M Phase.
Interphase is divided into three phases- G1 phase, S phase and G2 phase. In
G1 phase, cell prepares proteins and enzymes. In S phase, DNA replication
and centrioles duplication takes place. After S phase, chromosome number
of the cell does not change but amount of DNA becomes double (4C). In G2
phase synthesis of protein especially tubulin, which is used in the formation
of spindle fibres, occurs.
21. (i) How many chromosomes and DNA content will the onion cell have in
G1 phase, after completing S phase and after M phase respectively, if onion
plant possess 14 chromosomes initially?
(a) 14 / 2C, 28 / 4C and 14 / 4C
(b) 14 / 2C, 14 / 4C and 14 / 2C
(c) 14 / 2C, 14 / 2C and 14 / 2C
(d) 28 / 4C, 28 / 4C and 14 / 2C
21. (ii) Choose the correct option for a human cell before it enters prophase?
Number of Chromatids Number of Chromosomes
(a) 46 92
(b) 46 46
(c) 92 46
(d) 92 92
21. (iii) Non-dividing cells like muscles, neurons are in ______ phase
(a) G1 (b) G2
(c) G0 (d) M Phase
21. (iv) How many mitotic divisions are required to form 128 cells from a single
onion root tip cell (mitosis)?
124 Biology Class - 11
 (a) 14 (b) 21
(c) 6 (d) 7
Assertion and Reason Type Questions (1 mark each)
In each of the following questions, two statements are given, one is Assertion
and other is Reason. Mark the correct answer as :
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true but the reason it not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both the assertion and reason are false.
22. Assertion : Daughter somatic cells formed by mitosis are genetically similar
to parental cell.
Reason : Chromosomes do not undergo crossing over in mitosis.

23. Assertion : Meiosis–II is similar to mitosis.
Reason : Meiosis–I cannot occur in haploid cells.

24. Assertion : Interphase is called resting stage.
Reason : In interphase the cell is metabolically inactive.
Answers :
Ans. 21 (i) (b) 14 / 2C, 14 / 4C and 14 / 2C
Ans. 21 (ii) (c) 92, 46
Ans. 21 (iii) (c) G0 phase
Ans. 21 (iv) (d) 7
Ans. 22 (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.
Ans. 23. (b) Both assertion and reason are true but the reason it not the correct
explanation of the assertion.
Ans. 24 (c) Assertion is true but reason is false.


Cell Cycle and Cell Division 125

 wall

126 Biology Class - 11

 Points To Remember
Translocation (Long distance transport) : Transport of substances in plants
over longer distances through the vascular tissue (Xylem and Phloem) The
transport of water and mineral in Xylem is unidirectional while transport of organic
and mineral nutrients in phloem is multi-directional.

Means of transport (Short distance transport) : The transport of material

into and out of the cells is carried out by a number of methods. These are diffusion,
facilitated diffusion and active transport.

(i) Diffusion : Diffusion occurs from region of higher concentration to region

of lower concentration. It is passive and slow process. No energy expenditure
takes place. No membrane required

Factors affecting diffusion : Permeability of membrane, Temperature,

pressure, gradient of concentration and the size of substances.

(ii) Facilitated diffusion : The diffusion of hydrophilic substances along

the concentration gradient through fixed membrane transport protein without
involving energy expenditure. For this the membrane possess aquaporins and ion
channels. No ATP energy is utilized in this process.

Porins—The proteins that form huge pores in the outer membranes of the
plastids, mitochondria and some bacteria which allow the small size molecules
to pass through.

Aquaporins—Proteins that facilitate diffusion of water molecules through/

across the plasma membrane of cell.

Methods of Facilitated Diffusion

Symport Antiport Uniport

(Two molecules cross the (Two molecules move (Single molecule moves
membrane in the same in opposite direction at across membrane indpen-
direction at the same time.) the same time.) dent of other molecules.)

Transport in Plants 127

 Transport Proteins—They are present in the membrane. They allow the
passage of substances through membrane.
(i) Carrier Proteins—They bind to the particular solute particle to be
transported and deliver these to other side of membrane.
(ii) Channel Proteins—Ion Channel—They are specific for different ions like
K+, Cl–,
Water Channel—Surrounded by eight proteins called Aquaporins and allow
passage of water or water soluble substance.
(iii) Active transport : Active transport is carried by the mobile carrier
proteins (known as protein pumps) of membrane. Active transport uses energy to
pump molecules against a concentration gradient from a low concentration to
high concentration (uphill-transport). It is faster than passive transport.
Different Transport Mechanisms
S. Property Simple Faciliated Active
No. Diffusion Transport Transport

1. Required Special No Yes Yes

membrane protein
2. Uphill transport No No Yes
3. Requires ATP Energy No No No

 Water potential—(ψw)–Greater the concentration of water in a system,

greater is its kinetic energy and greater is the water potential. It is measured
in pascal (Pa) or mega pascal.
 If two systems are in contact, then there is movement of water from the
solution with higher potential to lower water potential.
 Solute potential—(ψs)–Magnitude of lowering of water potential, when a
solute is added to the water.
 Pressure Potential—(ψp)—Magnitude of increase of water potential, when
pressure greater than atmospheric pressure is applied to pure water or a
solution.
 Water potential of pure water is zero (0).
 Solute potential is always negative (–) and pressure potential is always
positive (+).
ψw = ψs + ψp

128 Biology Class - 11

  Osmotic Pressure—External pressure applied to prevent the diffusion of
water. It depends upon solute concentration.
 Numerically, osmotic pressure is equal to osmotic potential. Osmotic pressure

has positive (+) sign. Osmotic potential has negative (–) sign.
Turgor Pressure—Due to osmotic entry of water, the protoplasm of a plant
cell presses the cell wall towards the outside with a force, it is called Turgor
Pressure.
Diffusion Pressure—The pressure exerted by the tendency of the particles
to diffuse from the area of higher concentration to lower concentration. It is directly
proportional to the concentration of particles of diffusing substance.
Osmosis : Osmosis is movement of solvent or water molecules from the
region of their higher chemical potential to the region of their lower potential
across a semipermeable membrane.
Water molecules move from higher water potential to lower water potential
until equilibrium is reached.
Plasmolysis : Process of shrinkage of protoplasm away from its cell wall
due to exosmosis in hypertonic solution. If a plasmolysed cell is placed in water
or a hypotonic solution it becomes turgid.
Hypotonic solution : The external solution which is more dilute than the
cytoplasm. Cell kept in hypotonic solution become turgid.
Hypertonic solution : The external solution, which is more concentrated
than the cytoplasm. Cell kept in hypertonic solution get plamolysed
Isotonic solution : When the external solution balances the osmotic pressure
of the cytoplasm. Cell kept in isotonic solution become flaccid.
Casparian strip : It is the tangential as well as radial walls of endodermal
cells having the deposition of water impermeable suberin.
Imbibition : Imbibition is the phenomenon of absorption of water by the
solid particles of an adsorbent causing it to enormously increase in volume without
forming a solution.
Some examples of Imbibition :
(i) If a dry piece of wood is placed in water, it swells and increases in its volume.
(ii) If dry gum or pieces of agar-agar are placed in water, they swell and their
volume increases.
(iii) When seeds are placed in water they swell up.
(iv) Swelling of wooden door during rainy season.
Conditions essential for imbibition
1. Water potential gradient between the surface of the adsorbent and the imbibed
liquid, is essential.
2. Affinity between the adsorbent and the imbibed liquid.

Transport in Plants 129

 Transport of water in plants : Water is absorbed by root hairs by diffusion.
Then water moves upto xylem by two pathways–apoplast and symplast pathway.
Apoplast Pathway—Movement occurs through the intercellular spaces or
walls of the cell, without entering the cytoplasm. This movement is fast. In roots,
movement of water occurs via apoplast except at the carparian strip, most of water
enters through apoplast.
Symplast Pathway—Water enters the cell through cell membrane and travels
intercellularly through plasmodesmata. This movement is slow. At casparian strip
region water moves only through symplast.

Apoplastic And Symplastic Pathways of Water Transport

Ascent of Sap—Upward movement of water in the form of dilute solution
of mineral ions from roots to the top aerial parts of plants through tracheary
elements of xylem against the gravitational force is called ascent of sap. It involves
two theories—
(i) Cohesion–Tension-Transpirtation pull theory.
(ii) Root pressure theory.
(1) Cohesion-Tension-Transpiration pull theory—
(i) Continuity of water column—The transport of water to the top of trees
occurs through xylem vessels. The forces of adhesion and cohesion maintain a
thin and unbroken column of water in the capillaries of xylem vessels through
which it travels which is travels upward. Water is mainly pulled by transpiration
from leaves.
(ii) Transpiration Pull—Transpiration accounts for loss of 99% of water in
the form of water vapours from the surface of leaves. The loss is mainly through stomata.
 Pull of water as a result of tension created by transpiration is the major diving force

of water movement upward in a plant. This movement is called ascent of sap.

Three physical properties of water which affect the ascent of xylem sap due
to transpiration pull.
(iii) Cohesion force or Tensile strength of water—
130 Biology Class - 11
  Cohesion—Mutual attraction between water molecules.
 Adhesion—Attraction of water molecules to polar surface.

 Surface tension—Attraction of water to each other in liquid phase to a

greater extent than to water in gaseous phase.

(2) Root pressure Theory : A hydrostatic pressure existing in roots which
pushes the water up in xylem vessels upto certain height to herbaceons plant.
Guttation : The water loss in its liquid phase in the form of water droplets
at night and early morning through special openings of vein near the tip of leaves.
These opening are called hydathodes.
Transpiration : The loss of water through stomata of leaves and other aerial
parts of plants in form of water vapours.
Factors affecting transpiration : Temperature, light, relative humidity, wind
speed, number and distribution of stomata, water status of plant, canopy structure.
Significance of transpiration—Advantages—Helps in ascent of sap,
removal of excess water, cooling effect, distribution of mineral salts, supply water
for photosynthesis.
Disadvantages—May cause reduced growth, wilting (loss of turgidity),
reduced yield and waste of energy.
Since there are advantages as well as disadvantages of transpiration so—
‘Transpiration is called a necessary evil’.
Opening and closing of stomata—Opening and closing of stomata happens
due to following two reasons—
(i) Change in the turgidity of guard cells.
(ii) Orientation of cellulose microfibrils in the cell wall of guard cells.
Endosmosis—When a cell is placed in water or hypotonic solution, water
enters into the cell. This in called endosmosis. Due to it the volume of cell increases
and it creates turgor pressure.
Exosmosis—When a cell is placed in hypertonic solution, water comes out
of the cell, this is called exosmosis. It decreases volume of the cell.
Uptake and transport of mineral nutrients—Ions are absorbed by the
roots by passive and active transport. The active uptake of ions require ATP energy.
Specific proteins in membranes of root hair cells activity pump ions from the soil
into the cytoplasm of epidermal cells and then xylem. The further transport of
ions to all parts of the plant is carried through the water stream. Older dying leaves
export much of their mineral content to younger leaves. Elements phosphorus,
sulphur, nitrogen and potassium are most readily mobilised. Structural components
such as calcium are not remobilised.

Transport in Plants 131

 Mass flow : Mass flow is the movement of substances (water, minerals and
food) in bulk from one point to another as a result of pressure differences between
two points.
The pressure or mass flow Hypothesis :
Leaf Mesophyll Cells
Photosynthesis
↓
Glucose
↓
Sucrose
↓
Rise in Osmotic Pressure
↓
Endosmosis
↓
Rise in turgor pressure of Mesophyll Cells
↓
Mass flow of H2O and Sucrose due to turgor gradient
ATP

ADP + Pi
“In mass” comes in companion cell
Loading
and then into sieve tube cells
↓
Water comes in sieve tube cell from
Xylem and increase turgor Pressure gradient

ATP

ADP + Pi
Sucrose comes to Root cell and
convert into starch or energy or get Unloading
consumed in Respiration

132 Biology Class - 11

 ↓
Decrease in osmotic pressure of Root Cells
↓
Water moves to Root Xylem
Mycorrhiza—A mycorrhiza is a symbiotic association of a fungus with a
root system. The fungal hyphae absorb mineral ions (phosphorous) and water
from the soil, and provide them to the roots of plant, in turn the roots provide
sugars and nitrogen containing compounds to the mycorrhizae.

Questions
(SRT) Select Response Type Question (1 mark each)
1. Which part of the root is related with the absorption of water ?
(a) root tip (b) terminal root
(c) root hair (d) leaf
2. What makes the raisins to swell up when kept in water ?
(a) Endasomonis (b) diffusion
(c) Exosmosis (d) Guttation
3. Casparian strip is made of a substance which is impervious to water. Name
this substance.
(a) Lignin (b) cellular
(c) Subenin (d) Pectin

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. What will happen to water potential when a solute is added to water ?
5. A plant cell when kept in a solution got plasmolysed. What was the nature
of the solution.
6. Mention two ways of absorption of water by root hairs in plants.
7. Which form of sugar is transported through phloem ?
8. Give one example of imbibition.
9. A flowering plant is planted in an earthen pot and irrigated. Urea is added
to make the plant grow faster, but after some time the plant dies. Give its
possible reason.

Transport in Plants 133

10. Why is energy required to develop root pressure ?
11. Correct the statements :
(a) Imbibition is a special type of diffusion when water is absorbed by
living cell.
(b) Most of water flow in the roots occurs via symplast.
(c) Cells shrink in hypotonic solution and swell in hypertonic solution.

Short Answer Questions-I (2 marks each)

12. A well watered potted herbaceous plant shows wilting in the afternoon of a
dry sunny day. Give reason.
13. Do different species of plants growing in the same soil show the same rate
of transpiration at a particular time ? Justify your answer.
14. What is casparian strip ? Write its significance in plants.
15. Xylem transport is unidirectional and phloem transport bi-directional
why ?
16. How is transpiration different from guttation ? Give two points.
17. Suggest two methods to increase the life of cut plants in a vase.
18. Write the chemical composition of xylem and phloem sap.
19. Transpiration is a necessary evil in plants. Explain.
Short Answer Questions-II (3 marks each)
20. Why is solute potential always negative ? Explain.
ψw = ψs + ψp
21. Water has a very important role in sustaining the life list properties of water
which make it useful for all biological processes on earth.
22. When any dry plant material or seeds is/are kept in water, they swell up.
(a) Name the phenomenon involved in this change.
(b) Define this phenomenon.
(c) Give two conditions essential for the phenomenon to occur.
23. Differentiate between temporary and permanent wilting. Do any of them
indicate the water status of the soil ?
24. Observe the diagram and answer the following :

134 Biology Class - 11

 (a) Which of these guard cells show a higher water content, A or B ?
(b) Are these types of guard cells found in monocots or dicots ?
(c) Name the element which play an important role in the opening and
closing of stomata.
25. What is mycorrhiza ? How is the mycorrhizal association helpful in absorption
of water and minerals in plants ?
26. Observe the given figure and give the answers of the following :
(a) Identify the process occurring in (I), (II) and (III).
(b) Differentiate between the process II and III.
(c) How many types of aquaporins form the water channels in the cell
membrane.

27. Give scientific term for the following statements/processes :

(a) Movement of water in roots exclusively, through the cell wall
(b) The positive hydrostatic pressure developed inside the cell or cell wall.
(c) A solution having relatively less concentration.
(d) Loss of water vapour from the aerial parts of the plants in the form of
water vapours.

Transport in Plants 135

 (e) Movement of a molecule across a membrane independent of other
molecule.
(f) Water loss in its liquid phase through the special opening of veins near
the tip of leaves of many herbaceous plants.
Long Answer Questions (5 marks each)
28. Minerals are present in the soil in sufficient amount. Do plants need to adjust
the types of solutes that reach the xylem ? Which molecules help to adjust this?
How do plants regulate the type and quantity of solutes that reach xylem.
29. How do plants absorb water ? Explain transpiration pull model in this regard.
30. (a) Describe the pressure flow hypothesis of translocation of sugar in plants.
(b) Explain the mechanism of closing and opening of stomata.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (a) root tip 2. (a) Endosmosis 3. (a) Suberin

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer (1 mark each)
4. Water potential will decrease.
5. Hypertonic.
6. Apoplast and symplast pathway.
7. Sucrose.
8. Swelling of seed when put in water/moist soil.
9. Due to exosmosis i.e., water comes out the plant.
10. Every activity requires energy. Root pressure develops due to activity of
living cell.
11. (a) Osmosis is a special type, of diffusion when water is absorbed by living
cells.
(b) Most of the water flows in the roots occurs via the apoplast.
(c) Cells shrink in hypertonic, solution and swell in a hypotonic solution.
Short Answers-I (2 marks each)
12. During noon, the rate of transpiration becomes higher than the rate of water
absorption by plant. It causes loss of turgidity and leads to wilting.

136 Biology Class - 11

13. Rate of transpiration is not same because transpiration is affected by numbers
and distribution of stomata, and their opening.
14. Band of suberised matrix on the inner side of endodermis water molecule
are unable to panetrate it.
15. In xylem movement of water is always from roots to leaves. In phloem
movement of food is from source to sink and vice versa.

16. Transpiration Guttation

(i) Loss of water by a plant in form (i) The loss of water in the form of
of vapours. liquid droplets from the plant.
(ii) Occurs through the general (ii) Occurs at the margins and the
surface of leaves (stomata) and tips of the leaves.
the young stems.

17. (a) By adding cytokinin into water of the vase.

(b) Preventing entry of air in the cut plants by immediately immersing the
cut end in water.
18. Xylem Sap-Water, traces of all minerals.
Phloem sap-5-10% sucrose, 1% amino acids, traces of bound mineral,
hormones, other organic substances and rest is water.
19. Refer to ‘Points of Remember’ (Significance and disadvantages of
Transpiration)

Short Answers-II (3 marks each)

20. Refer to ‘Points of Remember’. (Solute Potential, Pressure Potential and
Water potential)
21. Refer to ‘Points of Remember’, (Cohesion, Adhesion and surface tension)
22. (a) Imbibition.
(b) Refer to ‘Points to Remember.’
(c) Condition necessary to imbibition.
(i) Water potential between the absorbent and the liquid imbibed.
(ii) Affinity between the adsorbent and the liquid imbibed.
Transport in Plants 137
23. Temporary wilting Permanent wilting

(i) Plant recovers from temporary (i) Automatic recovery is not

wilting after sometimes. possible. It may recover if water
is provided soon.
(ii) Much damage is not caused. (ii) Much damage is caused.
(iii) It commonly occurs during (iii) It occurs throughout day and
mid-day only. night.

When wilting is permanent, water present in soil is largely in unavailable

form. The soil contains 10-15% water depending, upon its texture.
24. (a) A (b) Dicots
(c) K+ (Potassium ions)
25. Refer points to remember.
26. (a) (i) Uniport (ii) Antiport (iii) Symport
(b) Refer ‘Points to Remember’.
(c) 8 types of aquaporins.
27. (a) Apoplast pathway (b) Turgor pressure
(c) Hypotonic (d) Transpiration
(e) Uniport (f) Guttation

Long Answers (5 marks each)

28. Refer ‘Points to remember’.
29. Refer ‘Points to remember’.
30. (a) Refer points to remember.
(b) Refer ‘Points to remember’.
Assertion Reasoning
The following question consists of 2 statements- Assertion (A) and Reason (R).
Answer the question by selecting the appropriate option below :
(a) Both A and R are true and the reason is a correct explanation of the
assertion

138 Biology Class - 11

 (b) The assertion is true but the reason is false
(c) Both the assertion and reason are false
(d) The assertion if false but the reason is true
31. Assertion (A) : Facilitated diffusion occurs due to channel proteins.
Reason (R) : The proteins are of extrinsic type.
32. Assertion (A) : Transpiration is considered as a necessary evil.
Reason (R) : Ascent of sap occurs due to three physical properties of water

SOLUTIONS
Assertion Reasoning
31. (b) 32. (b)
Source-based/Case-based/Passage-based/Integrated Assessment questions
Read the following and answer questions from given below :
33. Translocation in plants occurs by mass f low. This was a hypothesis first
given by Munch and then was elaborated by Crafts. According to this theory,
organic solutes are translocated ‘en masse’ through the sieve tubes from the
source to the sink. The hypothesis fails to explain the bidirectional movement
of metabolites which is common in plants. Munch and Crafts could not
explain how osmotic pressure is maintained in and balanced in mesophyll
cells and that of root hair. This hypothesis placed sieve tube and protoplasm
in a secondary role of mass f low whereas xylem and movement of water
plays important role in maintaining turgor pressure for the mass flow. Turgor
pressure gradient is established across the protoplasm between the cells of
the source and the cells of the sink.
(i) What are the source and sink referred to?
(ii) Why does water move from the xylem into the lumen of sieve tubes
and causes turgor pressure gradient?
(iii) The movement of sugars at the sink is removed by ___________ (active/
passive transport). Choose the correct option.
(iv) Food prepared in leaves is moved from higher concentration to lower
concentration. (T/F).

Transport in Plants 139

 (v) Bidirectional movement occurs in which part of the transporting tissue(s)
present in plants?
SOLUTIONS
Source-based/Case-based/Passage-based/Integrated Assessment questions
33. Solution
(i) Source is leaves, sink is the storage organs such fruits, or other parts of
the plant.
(ii) As the solute concentration increase, the water from xylem moves into
the lumen of sieve tubes due to osmosis and causes turgor pressure gradient.
(iii) Active transport
(iv) True
(v) Phloem


140 Biology Class - 11

Vesicles Containng Rhizobia

2+
Zn

Mineral Nutrition 141

 Points To Remember
Biological nitrogen fixation: Conversion of atmospheric nitrogen into
organic compounds by living organisms.
Flux : The movement of ions is called flux. Influx is inward movement of
ions into the cells and efflux is the outward movement of ions.
Necrosis : Death of tissues particularly leaf tissue due to deficiency of Ca,
Mg, Cu, K.
Mineral Nutrition : Plants require mineral elements for their growth and
development. The utilization of various absorbed ions by a plant for growth and
development is called mineral nutrition of the plant.
Hydroponics : Soil-less culture of plants, where roots are immersed in nutrient
solution (without soil) is called hydroponics. The result obtained from hydroponics
may be used to determine deficiency symptoms of essential elements.
Passive Transport : Absorption of minerals with concentration gradient by
the process of diffusion without the expense of metabolic energy.
Essential Elements There are 17 essential elements
In addition to the 17 essential elements, Na, Si, Co and Si are required by
some higher plants.
Criteria for essentiality specificity, irreplaceable, direct
involvement :
Role of Minerals Elements in Plants
MACRO NUTRIENTS
Element Obtained as Functions Deficiency
symptoms
—
Mainly as NO 3 some
Nitrogen (N) Constituent of Stunted growth
as NO or NH + proteins, nucleic Chlorosis,
2 4
acids, vitamins and dormancy of apical
hormones. causal buds.
Phosphorus (P)
Phosphate ions Constituent of cell Poor growth of
— 2—
(H2PO4 or HPO4 ) membrane. Required plant.
for the synthesis
of nucleic acids, Leaves dull green,
nucleotides, ATP delay in seed
NAD and NADP germination purple
for phosphory- or red spots on
lation reactions. leaves, premature
leaf fall.

142 Biology Class - 11

Potasium (K) K+ Helps to maintain an Stunted growth;
anion-cation balance yellow leaves
in cells. Involved in of mottled
protein synthesis, in appearance of
opening and closing leaves. Premature
of stomata; activation death.
of enzymes; mainte-
nance of turgidity of
cells.
Calcium (Ca) Ca2+ Required in formation Stunted growth,
of mitotic spindle; chlorosis of young
involved in normal leaves.
functioning of cell
membranes; activates
certain enzymes; as
calcium pectate in
middle lamella of the
cell wall.
Magnesium (Mg) Mg2+ Activates enzymes in Chlorosis between
phosphate metabolism, the leaf veins,
constituent of necrosis, purple
chlorophyll; maintains colours spots on
ribosome structure. older leaves.
2–
Sulphur (S) SO 4 Constituent of two Chlorosis of
amino-acids-Cysteine younger leaves,
and methionine and stunted growth
proteins, coenzymes,
vitamins and
ferredoxin.

MICRO NUTRIENTS
Element Obtained as Functions Deficiency
symptoms
Iron (Fe) Fe3+ Constituent of Chlorosis of
Ferredoxin and leaves
cytochrome; needed
for synthesis of
chlorophyll.
Manganese (Mn) Mn2+ Activates certain Chlorosis, grey
enzymes involved spots on leaves.
in photosynthesis,
respiration and nitrogen
metabolism.

Mineral Nutrition 143

Zinc (Zn) Zn2+ Activates various Malformation of
enzymes like leaves
carboxylases. Required
for synthesis of auxins.
Copper (Cu) Cu2+ Activates certain Stunted growth,
enzymes. Essential for inter-veinal
overall metabolism chlorosis in leaves.
Necrosis of the tip
of young leaves,
drybark of shoot.
Boron (B) BO33–, B4O72– Required for uptake Death of stem
of water and Ca, for and root apex,
membrane functioning, loss of apical
pollen germination, cell dominance,
elongation carbohydrate abscission of
translocation. flowers, small size
2+
MoO2 of fruits
Molybdenum (molybdate ions) Activates certain Nitrogen
(Mo) metabolism. deficiency inter-
veinal chlorosis
retardation of
growth
Chlorine (Cl) Cl– Maintains solute Wilted leaves;
concentration along stunted root
with Na+ & K+; maintain growth and
anion-cation balance reduced fruiting.
in cells; essential for
oxygen evolution in
photosynthesis.
Critical Concentration : The concentration of the essential element below
which plant growth is retarted. The element is said to be deficient when present
below the critical concentration.
Deficiency symptoms : Chlorosis, necrosis, stunted growth, premature fall
of leaves and buds and inhibition of cell division.
Toxicity of micronutrient : Any mineral ion concentration in tissues that
reduces the dry weight of tissues by 10% is considered toxic. Toxicity of one
element may lead to deficiency of other element since the former may inhibit the
uptake of latter., e.g., Mn competes with Fe, Mg for uptake and also inhibits Ca
translocation to shoot apex. Therefore Mn toxicity symptoms are actually same
as deficiency symptoms of Fe, Mg and Ca.

144 Biology Class - 11

Role of microbes in nitrogen cycle :
 Rhizobium, Azotobacter, Rhodospirillum; Fix atmospheric nitrogen
 Nitrosomonas and/or Nitrococcus : Conversion of ammonia to nitrite
 Nitrobacter : Conversion of nitrite into nitrate.
 Pseudomonas and Thiobacillus : reduce nitrate into nitrogen.

SOIL nitrogen (N) Pool

Nitrogen Cycle
Nitrogen fixation— (N2) into ammonia.
Ammonification—The process of decomposition of organic nitrogen of
plants and animals (proteins) into ammonia.

Ammonifying
Protien in Dead Plants and Animals  → NH
Bacteria 3

Nitrification—The ammonia so formed may volatilise and re-enter the

atmosphere, or some of the ammonia may be converted first into nitrite and then
into nitrate by soil bacteria
Nitrosomonas
Nitrosomonas → 2NO – + 2H O + 2H +
2NH 3 + 3O 2  2 2

Nitrobactor
2NO 2 – + O 2  → 2NO3 –

Mineral Nutrition 145

 The Nitrate so formed can be easily absorbed by the plants and transported
to leaves. In leaves, nitrate is reduced to ammonia to form amino-acids, because
nitrate can not used by plants as such.
– Nitrate reductase – Nitrite Amino acid
NO3 NO2 NO13
Reductase Synthesis
H2O
NADH2 NAD
NADH2 NAD

Denitrification—Process of reduction of the nitrate present in soil to nitrogen.

It is carried out by bacteria like Pseudomonas and Thiobacillus.
Nitrogen fixation = N2 → NH3
Biological Nitrogen Fixation—Reduction of nitrogen to ammonia by living
organisms. Certain prokaryotes are able to fix nitrogen because of presence of
‘nitrogenase’ enzyme in them.
Nitrogen fixing microbes may be
(a) Free living—(i) Aerobic—Azotobacter
(ii) Anaerobic—Rhodospirillum
(b) Cyanobacteria—Nostoc, Anabaena
(c) Symbiotic—(i) With leguminous plants—Rhizobium
(ii) With non-leguminous plants—Frankia
Enzyme nitrogenase—The enzyme nitrogenase is Mo-Fe protein and
catalysis the conversion of atmospheric nitrogen to ammonia (First stable product
of nitrogen fixation)
Leg-hemoglobin—A pink colour pigment, similar to hemoglobin of
vertebrates and functions as an oxygen scavenger and protects nitrogenase from
oxygen.
Steps of nodule formation :
(a) Rhizobium bacteria present in soil contact a susceptible root hair.
(b) Infection of the root hair cause it to curve and deformed due to chemical
secretion.
(c) An infection thread is produced carrying the bacteria into the cortex of the
root.
(d) The bacteria get modified into rod-shaped bacteroids and cause inner cortical
and pericycle cells to divide Plant produces cytokinin and auxin to stimulate
cell division and enlarges to form nodules.

146 Biology Class - 11

(e) Division and growth of cortical and pericycle cells lead to nodule formation.
Vesicles containing Rhizobia

Mechanisms of N2 fixation
It require 4 components—
(a) A strong reducing agent like FADH2, NADPH2
(b) Nitrogenase enzyme
(c) ATP (as energy service)
(d) Nitrogen gas molecule (as substrate)
N2 + 8e– + 8H+ + 16 ATP 2NH3 + H2 + 16 ADP + 16Pi
Fate of Ammonia :- At physiological pH, the ammonia is protonated to form
NH4+, which is quite toxic to plants and hence can not accumulate in them. It is
used by plants in following ways–
(a) Reductive amination :- α – ketoglutaric acid + NH­4+ + NADP
glutamate
Dehydrogenase
glutamate + H2O + NADP

(b) Transamination :- Transfer of amino group from one amino acid to the keto
group of a keto acid to form amino acid with the help of enzyme transaminase.

(c) Formation of Amides :- The hydroxyl part of the acid is replaced by another
amino radicle to form amides. e.g. asparagine and glutamine are formed from
aspartic acid and glutamic acid.

Mineral Nutrition 147

 Questions

(SRT) Select Response Type Question (1 mark each)

1. Name one symblotic nitrogen fixing bacteria.
(a) Rhizobium (b) E. coli
(c) Pseudomones (d) Nitrosomonas
2. .... & .... are examples of macronutriesnt.
(a) S & Ca (b) Zn & Ca
(c) Fe & B (d) C & A
3. Death of tissue, due to deficiency of Ca, Mg, Cu, K is....
(a) Chlorosis (b) Wilting
(c) Plasmolysis (d) Necrosis

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. Which substance impart pink colour to the root nodule of a leguminous plant
and also mention its role ?
5. What is the term used for mineral deficiency symptom in plants in which
leaves become yellow in different pattern ?
6. Define hydroponics.
7. Give the name of an insectivorous angiosperm plant.
8. Give the name of one non-symbiotic nitrogen fixing prokaryote.
9. Name the green house gas produced in rice fields.
10. Name the element which is essential for the photolysis of water during
photosynthesis.
11. Why do deficiency symptoms appear in older leaves first?

Short Answer Questions-I (2 marks each)

12. Differentiate between two types of absorption of minerals in plants from
soil.
148 Biology Class - 11
13. Name the following :
(a) Bacteria which converts ammonia into nitrite.
(b) Bacteria which oxidises nitrite into nitrate.
14. How does Leghemoglobin protect the enzyme nitrogenase ?
15. Name the enzyme found in root modules for N2 fixation ? Name the pink
coloured pigment required for its functioning.

Short Answer Questions-II (3 marks each)

16. Write the deficiency symptoms of the following three elements :
(a) Phosphorus
(b) Magnesium
(c) Potassium
17. Describe the following three deficiency symptoms and co-relate them with
concerned mineral deficiency :
(a) Phosphorus
(b) Magnesium
(c) Potassium
18. Explain in brief the steps involved in biological nitrogen fixation.
19. Describe the two main processes of synthesis of amino acids from Ammonium
ion (NH4+) in plants.
20. Define critical concentration, also mention four deficiency symptoms of
nutrients in plants.
21. Write a short note on toxicity of micronutrient. Give an example which show
toxicity of one element may lead to deficiency of other element.
Long Answers (5 marks each)
22. Describe all the steps of nitrogen cycle in nature.
23. Describe with diagrams how root nodules are formed in leguminous plants.
24. Explain adaptations in leguminous root nodules for N2 fixation.

Mineral Nutrition 149

 Answers

(SRT) Select Response Type Question (1 mark each)

1. (a) Rhizobium 2. (a) S & Ca
3. (d) Necrosis

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Leghemoglobin. It is an oxygen scavenger, which protects the enzyme
nitrogenase.
5. Necrosis.
6. The technique of growing plants in a nutrient solution without soil is called
hydroponics.
7. Nepenthes (Pitcher plant)
8. Azotobacter
9. Methane (CH4)
10. Calcium
11. It happens because the elements are mobilized to the younger parts of the
plant from older leaves.

Short Answers-I (2 marks each)

12. Refer ‘Points to Remember’.
13. (i) Nitrifying Bacteria—Nitrosomonas.
(ii) Nitrifying Bacteria—Nitrobacter
14. Refer to page no. 203.
15. Enzyme-Nitrogenase
Pink coloured pigment-Leghaemoglobin

Short Answers-II (3 marks each)

16. Refer to ‘Points to Remember’.
17. Refer to ‘Points to Remember’.

150 Biology Class - 11

18. Refer to ‘Points to Remember’.
19. Refer to ‘Points to Remember’ (Fate of Ammonia)
20. Refer to ‘Points to Remember’.
21. Refer to ‘Points to Remember’.

Long Answers (5 marks each)

22. Refer to ‘Points to Remember’.
23. Refer to ‘Points to Remember’.
24. Refer to ‘Points to Remember’.
Assertion Reasoning (1 mark each)

The following question consists of 2 statements - Assertion (A) and Reason
(R). Answer the question by selecting the appropriate option below :
(a) Both A and R are true and the reason is a correct explanation of the
assertion
(b) The assertion is true but the reason is false
(c) Both the assertion and reason are false
(d) The assertion is false but the reason is true
25. Assertion (A) : Leguminous plants are grown alternatively with grain crops
to replenish nitrogen in the soil.
Reason (R) : Rhizobium is a symbiotic bacterium that can fix nitrogen while
living in the roots of leguminous plants
26. Assertion (A) : If any mineral concentration in tissues that reduces the dry
weight of tissues by about 10 percent is considered toxic.
Reason (R) : It is difficult to analyse the symptoms of mineral toxicity
27. Assertion (A) : Calcium is required by meristematic and differentiating
tissues.
Reason (R) : It is essential fo rthe formation of the mitotic spindle and cell
wall formation.
28. Assertion (A) : Hydroponic is a soil-less method to grow plants.
Reason (R) : Commercial production of vegetable such as tomato, seedless
cucumber and lettuce is done only with the help of hydroponics.

Mineral Nutrition 151

29. Assertion (A) : Influx of nutrients always occurs via facilitated diffusion.
Reason (R) : Energy is always required when there is an influx.
Solution
Assertion Reasoning
25. (a)
26. (b)
27. (a)
28. (c)
29. (d)
Source-based/Case-based/Passage-based/Integrated assessment questions
(4 marks each)
Read the following and answer any four questions from (i) to (v) given below :
30. Soil is the reservoir of nutrients and the properties of soil depend upon the
type of minerals present. In addition to essential mineral elements, there
are some other minerals too that are grouped according to their biochemical
behaviour and physiological functions in plants metabolism. Biogeochemical
cycles replenish mineral nutrients in the soil. One of such important nutrients
is nitrogen, plants cannot use nitrogen directly from the atmosphere. Many
microbes play an important role in the absorption and recycling of nitrogen
in an ecosystem. As plants use minerals, the soil becomes deficient in
some nutrients. They are either added artificially or are enhanced using
biofertilizers. These biofertilizers help plants to absorb certain minerals either
symbiotically or non-symbiotically.
(i) Which of the following is a micronutrient?
(a) Carbon
(b) Nitrogen
(c) Iron
(d) Oxygen
(ii) What will happen if one of the micronutrients is available in the plant
in excess?
(iii) In which of the following forms nitrogen is absorbed by the plants?
(a) Nitrates and dimeric nitrogen
(b) Nitrates and nitrites

152 Biology Class - 11

 (c) Nitrites and ammonia
(d) Dimeric nitrogen and ammonia
(iv) Name any two symbiotic nitrogen-fixing microbes.
(v) Deficiency of ____________ leads to premature fall of leaves and they
turn dark green in colour.
(a) Phosphorous
(b) Iron
(c) Nitrogen
(d) Potassium
Solution
Source-based/Case-based/Passage-based/Integrated assessment questions
(i) (c) Iron
(ii) It will cause mineral toxicity and will interfere with the metabolism of other
micronutrients.
(iii) (b) Nitrates and nitrites
(iv) Frankia, Rhizobium
(v) Phosphorous
 

Mineral Nutrition 153

 Higher Plants

154 Biology Class - 11

 Points To Remember
Photosynthesis : Photosynthesis is an enzyme regulated anabolic process
to manufacture organic compounds inside the chlorophyll containing cells from
carbon dioxide and water with the help of sunlight as a source of energy.

Sun Light
Sunlight
6CO 2 + 12H 2 O C6 H12 O6 + 6H 2 O + 6O 2 ↑
Chlorophyll + enzymes

Historical Perspective
Josheph Priestley (1770) : Showed that plants have the ability to take up
CO2 from atmosphere and release O2. (Candle with bell jar and mouse expt.)
Jan Ingenhousz (1779) : Release of O2 by plants was possible only in sun-
light and only by the green parts of plants. (Expt. with aquatic plant in light & dark)
Theodore de Saussure (1804) : Water is an essential requirement for
photosynthesis to occur.
Julius Von Sachs (1854) : Green parts in plant produce glucose which is
stored as starch.
T.W. Engelmann (1888) : The effect of different wavelength of light on
photosynthesis and plotted the first action spectrum of photosynthesis.
C.B. Van Niel (1931) : Photosynthesis is essentially a light dependent
reaction in which hydrogen from an oxidisable compound reduces CO2 to form
sugar. He gave a simplified chemical equation of photosynthesis.
Sun Light
Sunlight
2H 2 A + CO 2 2A + CH 2 O + H 2 O

Hill (1937) : Evolution of oxygen occurs in light reaction.

Calvin (1954-55) : Traced the pathway of carbon fixation.
Hatch and Slack (1965) : Discovered C4 pathway of CO2 fixation.
Site for photosynthesis : Photosynthesis takes place only in green parts of
the plant, mostly in leaves. Within a leaf, photosynthesis occurs in mesophyll cells
which contain the chloroplasts. Chloroplasts are the actual sites for photosynthesis.
The thylakoids in chloroplast contain most of pigments required for capturing solar
energy to initiate photosynthesis : The membrane system (grana) is responsible for
trapping the light energy and for the synthesis of ATP and NADPH. Biosynthetic
phase (dark reaction) is carried in stroma.

Photosynthesis in Higher Plants 155

 Importance of Photosynthesis—(1) Synthesis of organic compounds (2)
Change of radiant energy into chemical energy (3) Useful products are obtained
from plants gums, oils timber fire wood, resins rubber, fibers and drugs, etc. (4)
Balance the percentage of O2 and CO2 in atmosphere (5) Fossil fuels like coal,
natural gas and petroleum have been formed inside the earth indirectly as a product
of photosynthesis.
Pigments involved in photosynthesis :
Chlorophyll a : (Bright or blue green in chromatograph). Major pigment,
act as reaction centre, involved in trapping and converting light into chemical
energy. It is called universal photo-synthetic pigment.
Chlorophyll b : (Yellow green)
Xanthophylls : (Yellow)
Carotenoids : (Yellow to yellow-orange)
 In the blue and red regions of spectrum shows higher rate of photosynthesis.

Light Harvesting Complexes (LHC) : The light harvesting complexes are

made up of hundreds of pigment molecules bound to protein within the photosystem
I (PS-I) and photosystem II (PS-II). Each photosystem has all the pigments (except
one molecule of chlorophyll ‘a’) forming a light harvesting system (antennae).
The reaction centre (chlorophyll a) is different in both the photosystems.

e–

e–

Light Harvesting Complex

156 Biology Class - 11
 Photosystem I (PS-I) : Chlorophyll ‘a’ has an absorption peak at 700 nm
(P700).
Photosystem II (PS-II) : Chlorophyll ‘a’ has absorption peak at 680 nm
(P680),
Process of photosynthesis : It includes two phases-Photochemical phase
and biosynthetic phase. (Formerly known as Light reaction and dark reaction)
(i) Photochemical phase (Light reaction) : This phase includes-light
absorption, splitting of water, oxygen release and formation of ATP and NADPH.
It occurs in grana region of chloroplast.
(ii) Biosynthetic phase (Dark reaction) : It is light independent phase,
synthesis of food material (sugars). (Calvin cycle). It occurs in stroma region of
chloroplast.
Photophosphorylation : The process of formation of high-energy chemicals
(ATP and NADPH) in presence of light.
Non-Cyclic photophosphorylation : Two photosystems work in series–First
PSII and then PSI. These two photosystems are connected through an electron
transport chain (Z. Scheme). Both ATP and NADPH + H+ are synthesised by
this process. PSI and PSII are found in lamellae of grana, hence this process is
carried here.

Photosynthesis in Higher Plants 157

 The electron transport (Z-Scheme) : In PS II, reaction centre (chlorophyll
a) absorbs 680 nm wavelength of red light which make the electrons to become
excited. These electrons are taken up by the electron acceptor that passes them to
an electron transport system (ETS) consisting of cytochromes. The movement of
electron is down hill. Then, the electron pass to PS I and move down hill further
to NADP+. NADP+ in then reduced to NADPH + H+.

The splitting of water : It is linked to PS II. Water splits into H+, [O] and
electrons. 2H2O 4H+ + O2 + 4e–

Cyclic photophosphorylation : Only PS-I works, the electron circulates

within the photosystem. It happens in the stroma lamellae (possible location)
because in this region PSII and NADP reductase enzyme are absent. Hence only
ATP molecules are synthesised. It occurs when only light of wavelengths beyond
680 nm are available for excitation.
Chemiosmotic Hypothesis :
Chemiosmotic hypothesis explain the
mechanism of ATP synthesis in chloroplast.
In photosynthesis, ATP synthesis is linked
to development of a proton gradient across
a membrane. The protons are accumulated
inside of membrane of thylakoids (in
lumen). ATPase enzyme has a channel
of that allow diffusion of protons back
across the membrane. This release energy
to activate ATPase enzyme that catalyses
the formation of ATP.

158 Biology Class - 11

 Chloroplast
Biosynthesis phase in C3 plants :
ATP and NADPH, the products of light reaction are used in synthesis of food.
The first CO2 fixation product in C3 plant is 3-phosphoglyceric acid or PGA. The
CO2 acceptor molecule is RuBP (ribulose bisphosphate). The cyclic path of sugar
formation is called Calvin cycle on the name of Melvin Calvin, the discover of
this pathway. Calvin cycle proceeds in three stages.
(1) Carboxylation : CO2 combines with ribulose 1, 5-bisphosphate to form
3 PGA in the presence of RuBisCo enzyme (present in stroma)
(2) Reduction : Carbohydrate is formed at the expense of ATP and NADPH.
It involves 2ATP for phsophorylation and 2NADPH for reduction per CO2
molecule fixed.
(3) Regeneration : The CO2 acceptor ribulose 1, 5-bisphosphate is formed
again.
6 turns of Calvin cycles and 18 ATP molecules are required to synthesize
one molecule of glucose.

ATP
ATP
+
NADPH

Triose
Phosphate ADP +
Pi + NADP+

Photosynthesis in Higher Plants 159

 6CO2 + 6 RuBP + 18ATP + 12NADPH C6H12O6 + 6RuBP +
18ADP + 18Pi + 12NADP
Input Output
6CO2 One Glucose
18 ATP 18 ADP
18NADPH 12 NADP
The C4 pathway : C4 plants such as maize, sorghum, sugarcane have a four
carbon compound special type, of leaf anatomy, they tolerate higher temperatures.
In this pathway, oxaloacetic acid (OAA) is the first stable product formed. It is
4 carbon atoms compound, hence called C4 pathway (Hatch and Slack Cycle).
The leaf has two types of cells : mesophyll cells and bundle sheath cells (Kranz
anatomy). Initially CO2 is taken up by phosphoenol pyruvate (PEP) in mesophyll
cell and changed to oxaloacetic acid (OAA) in the presence of PEP carboxylase.
Oxaloacetate is reduced to maltate/asparate that reach into bundle sheath cells.
The decarboxylation of maltate/asparate occurs with the release of CO2
and formation of pyruvate (3C). In high CO2 concentration RuBisCO behaves as
carboxylase and not as oxygenase, hence the photosynthetic losses are prevented.
RuBP operates now under Calvin cycle and pyruvate transported back to mesophyll
cells and changed into phosphoenol pyruvate (PEP) to keep the cycle continue.

Figure 13.9 diagrammatic representation of the Hatch and Slack Pathway

Photorespiration : The light induced respiration in green plants is called

photorespiration. In C3 plants some O2 binds with RuBisCO and hence CO2 fixation
is decreased. In this process RuBP instead of being converted to 2 molecules of
PGA binds with O2 to form one molecule of PGA and phosphoglycolate.

160 Biology Class - 11

 There is neither synthesis of ATP nor NADPH2 or sugar. Rather it results in
release of CO2 with utilisation of ATP. The biological function of photorespiration
is not known yet.

C4 Plants :
(1) Lack Photorespiration
(2) Show response to high light intensities
(3) Have greater productivity of biomass.
Adaptations in C4 Plants :
(i) Kranz Anatomy
(ii) Occurrence of two types of cells
(iii) Dimorphic chloroplast
(iv) Presence of RuBisCO in Bundle Sheath cells and PEPcase in mesophyll
cells.
(v) Mechanism to increase CO2 concen-tration near RuBisCO in Bundle Sheath
cells.
CAM (Crassulacean Acid Metabolism) Plants—Stomata open at night.
e.g., Cacti, Bryophyllum, Pineapple.
Law of Limiting Factors : If a chemical process is affected by more than
one factor, then its rate will be determined by the factor which is nearest to its
minimal value. It is the factor which directly affects the process if its quantity is
changed. Factors affecting photosynthesis :
1. Light : Rate of photo-synthesis increases at low light intensities. At high
intensities of light beyond a point the rate of CO2 fixation decreases. Longer
hours of light duration favour more photosynthesis rate.
2. Carbon dioxide : Increase in CO2 concentration causes increases in CO2
fixation. It is the major limiting factor for photosynthesis.
3. Temperature : The rate of photosynthesis at optimum temperature is, high.
It is 20°C-25°C For C3 plants and 30-45°C for C4 plants.
4. Water : Water is one of the reactant in photosynthesis, but it effects the rate
of CO2 fixation. Low water content causes the stomata to close and reduces
the CO2 availability.

Photosynthesis in Higher Plants 161

 Questions
(SRT) Select Response Type Question (1 mark each)
1. Which of the following pathway is following by Pineapples in order to fix
carbon-di-oxide efficiently?
(a) TCA cycle (b) CA cycle
(c) CAM pathway (d) C3 cycle
2. How many molecules of ATP are required for synthesis of one molecules of
glucose in C3 and C4 pathway?
(a) 12 and 18 respectively (b) 30 and 18 respectively
(c) 16 and 30 respectively (d) 18 and 30 respectively
3. As the light intensity increases, the rate of photosynthesis increases. During
high light intensities the rate of photosynthesis decreases due to
(a) 
Increase incident light beyond a point causes the breakdown of
chlorophyll
(b) Increase incident light beyond a point causes less absorption of minerals
(c) Increase incident light beyond a point will block xylem vessels
(d) Increase incident light beyond a point will use carbon-di-oxide and will
not be available for photosynthesis.
CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answer Questions (1 marks each)
4. Which one of the photosystems can carry on photophosphorylation
independently ?
5. Name two photosynthetic pigments belonging to carotenoids.
6. Name the most abundant enzyme found in the world.
7. Name the scientist who proposed the C4 pathway. Name one such plants.
8. Where does carbon fixation occur in chloroplast ?
9. Which compound acts as CO2 acceptor in Calvin cycle ?
10. Name the end products of light reaction.
11. Does the photosynthesis occur in moon light ? Why ?
12. Which part of sunlight is most suitable for photosynthesis.

162 Biology Class - 11

Short Answer Questions-I (2 marks each)
13. Why does the rate of photosynthesis decline in the presence of continuous
light ?
14. Why do green plants start evolving carbon dioxide instead of oxygen on a
hot sunny day ?
15. Fill in the space, left blank in the given table to bring the difference between
C3 and C4 plants :

S.No. Characteristics C3 plants C4 plants

1. Cell type mesophyll ...(a)... and mesophyll

Phosphoenol
2. CO2 acceptor ...(b)... pyruvate (PEP)
3. First CO2 fixation 3-PGA ...(c)...
product
4. Optimum ...(d)... 30° C to 45° C
temperature

16. State two functions of accessory pigments, found in thylakoids.

17. Why do C4 plants are more expensive (in energy requirement) than C3
plants ?
18. What is limiting factor ? State the law of limiting factors.

Short Answer Questions-II (3 marks each)

19. The figure shows the effect of light on the rate of photosynthesis. Based on
the graph, answer the following questions :
(i) At which point(s) A, B or C in the curve, light is a limiting factor ?
(ii) What could be the limiting factor(s) in region A ?
(iii) What do region C and D represent on the curve ?

Photosynthesis in Higher Plants 163

20. When and why does photorespiration take place in plants ? How does this
process result in a loss to the plant ?
21. What are the steps that are common to C3 and C4 photosynthesis ?
22. Two potted plants were kept in an oxygen free environment in transparent
containers, one in total darkness and the other in sunlight. Which one of the
two is likely to survive more ? Justify your answer by giving the reason.
23. (a) In the diagram shown below, label A, B and C. What type of
phosphorylation is possible in this ?

(b) Give any two points of difference between cyclic and non-cyclic
photophosphorylation.
24. Name the pigment found in tomato, carrots, chillies etc. which gives red
colour to them. Is it a photosynthetic pigment ?
25. Chloroplast and mitochondria are believed to be semi-autonomous organelles.
Justify the statement.
26. Mention the conditions under which the C4 plants are superior to C3 plants.

Long Answer Questions (5 marks each)

27. Describe C4 pathway in a paddy plant. How is this pathway an adaptive
advantage to the plant ?
28. Explain, the process, of biosynthetic plase of photosynthesis occurring in
chloroplast.
29. (a) Give steps to ATP synthesis in chloroplasts through chemiosmosis.
(b) Schematically represent non-cyclic photophosphoryation in plants.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (c) CAM pathway

164 Biology Class - 11

 2. (d) 18 and 30 respectively
3. (a) 
Increase incident light beyond a point causes the breakdown of
chlorophyll

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer (1 mark each)
4. PS-I.
5. Carotene and xanthophylls.
6. RuBisCO.
7. Hatch and Slack. Maize and Sorghum.
8. Carbon fixation takes place in stroma.
9. Ribulose 1, 5 bisphosphate.
10. ATP, NADPH and O2.
11. No, the moonlight is unable to perform light reactions of photosynthesis
(ATP-NADPH Synthesis as it is 1/50,000 the intensity of sunlight and not
strong enough to enable plants to photsynthesise.
12. Blue and Red regious of light spectrum.

Short Answers-I (2 marks each)

13. Increase incident light beyond a point causes the breakdown of chlorophyll.
14. On a hot suny day, enzyme RuBP carboxylase becomes active and its
affinity for CO2 decreases and for O2 increases. Consequently more and
more photosynthetically fixed carbon is lost by photorespiration.
15. (a) Bundle sheath
(b) RuBP
(c) OAA (oxaloacetic acid)
(d) 20°C-25°C
16. (a) Absorption of light and transfer of energy to chlorophyll ‘a’.
(b) Protect chlorophyll ‘a’ from photo oxidation.
17. Because they require more energy (30 ATPs) in synthesizing one glucose
molecule as compared to C3—(18ATPs).
Photosynthesis in Higher Plants 165
18. Limiting Factor—A factor which is deficient to such an extent that increase
in its concentration directly increase the rate of the process.
(For the law of limiting factors see text in NCERT Book.) Page 222

Short Answers-II (3 marks each)

19. (i) ‘B’
(ii) CO2 and temperature
(iii) ‘C’ represents to constant rate of photosynthesis, ‘D’ is the light saturation
intensify at which rate of photosynthesis is maximum.
20. Refer NCERT, Text Book Biology for class XI.
21. Hints :

(a) Photolysis of H2O and photophosphorylation occurs in both C3 and C4
plants.
(b) In both, dark reaction occurs in stroma.
(c) Calvin cycle results in the formation of starch in both the plants.
(d) During dark reaction both types of plants undergo the phases of
carboxylation and regeneration :
22. Hints :

 The plant in sunlight will survive for longer period.

 Light is essential for photosynthesis.

23. (a) (A) e– acceptor

(B) Electron transport system
(C) Chlorophyll P700

(b) Refer A Page no. 212, NCERT Text Book of Biology for Class XI.

24. Carotenoid : It is an accessory photosynthetic pigment which takes part in

harvesting light energy only if chlorophyll is present.

25. Mitochondria and chloroplast both contain DNA and can reproduce
independently of the cell and chloroplasts even have a built in feeding
mechanism both have their own ribosomes of 70S type and capable of
synthesising their own kind of proteins.

166 Biology Class - 11

26. C4 Plant grow in regions with high temperatures and intense light. The rate
of transpiration in C4 plant is 25% of a C3 plant, thus they conserve water
and have greater photosynthetic rate gives greater rate of growth in intense
sunshine and high temperature.

Long Answers (5 marks each)

27. Refer Page no. 218, NCERT Text Book of Biology for Class XI.

28. Refer Points to Remember.

Hints : Three stages of Calvin cycle : Carboxylation, Reduction and

Regeneration.

29. (a) Refer Page no. 213 (Chemiosmotic Hypothesis), NCERT Text Book of
Biology for Class XI.

(b) Refer Fig. 13.5 (Z-Scheme of light reaction), NCERT Text Book of
Biology for Class XI.

Assertion Reasoning (1 mark each)

The following question consists of 2 statements - Assertion (A) and Reason (R).
answer the question by selecting the appropriate option below :
(a) Both A and R are true and the reason is a correct explanation of the
assertion
(b) Both A and R are true and the reason is not a correct explanation of the
assertion
(c) The assertion is true but the reason is false
(d) Both the assertion and reason are false
(e) The assertion is false but the reason is true
30. Assertion (A) : C4 cycle is found in CAM plants.
Reason (R) : Photorespiration does not occur in C4 plants.
31. Assertion (A) : Higher the concentration of O2 in the atmosphere, lower is
the photosynthesis are.
Reason (R) : Lower respiration rate is due to oxidation of RuBisCo.
Photosynthesis in Higher Plants 167
32. Assertion (A) : For the formation of one molecule of glucose, 6 molecules
of CO2 and 12 molecules of NADPH+ + H+ and 18 ATP are used.
Reason (R) : In light reaction ATP and NADPH2 are formed.
Solution:
Assertion Reasoning
30. (e)
31. (a)
32. (b)
Source-based/Case-based/Passage-based/Integrated assessment question
(4 marks each)
Read the following and answer any four questions from (i) to (v) given below :
33. Photosystems are of two types, PS 1 and PS 11, and are found in thylakoid
membranes. Each photosystem consists of a light harvesting complex and
each LHC is made up of hundreds of pigment molecules bound to proteins.
Each photosystem has all the pigments complexes except one molecule of
chlorophyll a.,a single chlorophyll forms a reaction centre. Each photosystem
absorbs different wavelengths of light. In PS I the reaction centre chlorophyll
a has an absorption peak at 700 nm, hence is called P700, while in PS II it
has absorption maxima at 680 nm, and is called P680. It was named PSII
because it was discovered after PSI was discovered. Only light reaction takes
place in these systems. PSII is the first system which traps light and the most
important function is splitting of water and molecular oxygen. The electron
is released while the splitting of water. These electrons are passed through
PSII and PSI before ending up in NADPH as they move down in the electron
transport chain. NADPH, thus produced is used in the dark reaction of
photosynthesis.
(i) Photosystem I and II respectively are found in _____________
(a) Inner and outer surface of thylakoid in mitochondria
(b) Outer and inner surface of thylakoid in mitochondria
(c) Inner and outer surface of thylakoid in chloroplast
(d) Outer and inner surface of thylakoid in chloroplast

168 Biology Class - 11

 (ii) Will photolysis of water occur in PSI? (Yes/No)
(iii) What is the correct sequence?
I. Antenna molecule 700
II. NADPH
III. PSI
IV. PSII
V. Thylakoid membrane
(a) I, II, III, IV, V
(b) II, III, IV, I, V
(c) V, IV, III, I, II
(d) V, III, IV, I, II
(iv) The dark reaction cannot take place during the day. (True/False)
(v) Which one of the following is not true about the light reaction in
photosynthesis?
(a) Photosystems are arrangements of chlorophyll and other pigments
packed into thylakoids
(b) Photolysis of water occurs in PSI
(c) NADP is reduced
(d) Magnesium ions are required for the formation of chlorophyll
Solution:
Source-based/Case-based/Passage-based/Integrated assessment questions
33. (i) (d) Outer and inner surface of thylakoid in chloroplast
(ii) No
(iii) (c) V, IV, III, I, II
(iv) False (dark reaction takes place both during the day and the night)
(v) (b) Photolysis of water occurs in PSI

 

Photosynthesis in Higher Plants 169

 Points To Remember
Aerobic respiration : Complete oxidation of organic food in presence of
oxygen thereby producing CO2, water and energy.
Anaerobic respiration : Incomplete breakdown of organic food to liberate
energy in the absence of oxygen.
ATP Synthetase : An enzyme complex that catalysis synthesis of ATP during
oxidative phosphorylation.
Biological oxidation : Oxidation in a series of reaction inside a cell.
Cytochromes : A group of iron containing compounds of electron transport
system present in inner wall of mitochondria.
Dehydrogenase : Enzyme that catalyses removal of H+ atom from the
substrate.
Electron acceptor : Organic compound which receive electrons produced
during oxidation-reduction reactions.
Electron transport : Movement of electron from substrate to oxygen through
respiratory chain during respiration.
Fermentation : Breakdown of organic substance that takes place in certain
microbe like yeast under anaerobic condition with the production of CO2 and
ethanol.
Glycolysis : Enzymatic breakdown of glucose into pyruvic acid that occurs
in the cytoplasm.
Oxidative phosphorylation : Process of formation of ATP from ADP and
Pi (Inorganic phosphate) using the energy from proton gradient.
Respiration : Biochemical oxidation food to release energy.
Respiratory Quotient : The ratio of the volume of CO2 produced to the
volume of oxygen consumed.
Proton gradient : Difference in proton concentration across the tissue
membrane.

170 Biology Class - 11

Respiration in Plants 171
 Mitochondrial matrix : The ground material of mitochondria in which
pyruvic acid undergoes aerobic oxidation through Kreb’s cycle.
Electron Transport Chains (ETC)—A series of co-enzymes and electron/
carriers where electrons can pass along increasing redox potential losing a bit of
energy at every step of transfer.
Abbreviations
ATP — Adenosine-tri-phosphate
ADP — Adenosne-di-phosphate
NAD — Nicotinamide Adenine dinucleotide
NADP — Nicotinamide Adenine dinucleotide Phosphate
NADH — Reduced Nicotinamide Adenine dinucleotide
PGA — Phosphoglyceric acid
PGAL — Phospho glyceraldehyde
FAD — Flavin adenine dinucleotide
ETS — Electron transport system
ETC — Electron transport chain
TCA — Tricarboxylic acid
OAA — Oxalo acetic acid
FMN — Flavin mono nucleotide
PPP — Pentose phosphate pathway
Cellular Respiration—The process of oxidation/breakdown of food materials
within the cell to release energy. Respiratory substrate to be oxidized during
respiration is usually glucose, but these can also be proteins, fats or organic acids.
In plants, respiratory gaseous exchange occurs through stomata and lenticels :
Overall cellular respiration is :
C6H12O6 + 6O2 6CO2 + 6H2O + Energy (36ATPs)
Aerobic Respiration
Overall mechanism of aerobic respiration can be studied under the following
steps :
(A) Glycolysis (EMP pathway) in cytoplasm
(B) Oxidative Decarboxylation—(Gateway Reaction)—in Mitochondrial
matrix
(C) Kreb’s cycle (TCA—cycle)—Matrix of mitochondria
(D) Oxidative phosphorylation

172 Biology Class - 11

 A. Glycolysis : The term has originated from the Greek word, glycos =
glucose, lysis = splitting, or breakdown means breakdown of glucose molecule
to pyruvic acid. It was given by Embden Meyerhof and Parnas. It is a chain of 10
reactions to convert glucose into pyruvate. It is common for aerobic and anaerobic
respiration.
Steps for Glycolysis—(EMP Pathway)
1. Phosphorylation of Glucose into Glucose-6-phosphate (ATP used)
2. Isomerisation of Glucose-6-Phosphate into fructose-6-phosphate
3. Second phosphorylation in which Fructose-6-phosphate changes into Fructose-1,
6-biphosphate (ATP used)
4. Splitting of Fructose-1, 6-biphosphate into DHAP (dihydroxy acetone phosphate)
and PGAL
5. Isomerisation of DHAP into PGAL
6. Oxidation of PGAL into 1, 3-biphosphosphoglycerate (NADH Produced)
7. Synthesis of ATP and converssion of 1, 3-biphosphoglycerate into 3-phospholycerate
8. Isomerisation of 3-phosphoglycerate into 2-phospholycerate
9. Dehydration of 2-phosphoglycerate into PEP (Removal of water)
10. Substrate level ATP synthesis and formation of Pyruvic Acid.

 It is also called Embden—Meyerhof—Paranas pathway. (EMP pathway)

 It is common in both aerobic and anaerobic respiration.

 It takes place outside the mitochondria, in the cytoplasm.

 One molecule of glucose (Hexose sugar) ultimately produces two molecules
of pyruvic acid through glycolysis.’

 During this process 4 molecules of ATP are produced while 2 molecules
ATP are utilised. Thus net gain of ATP is of 2 molecules.
Input and Output of glycolysis
S. No. Input Output
1. Glucose, (6—C), 1 Pyruvate, (3—C), 2 molecules
molecule
2. 2 ATP 2 ADP
3. 4 ADP + 2 Pi 4 ADP + 2H2O
4. 2 NAD+ 2 NADH (H+)

Net out put ...... 2 Pyruvate + 2ATP + 2NADH (+ H+) OR 2 Pyruvate + 8 ATP
The pyruvate, so produced, may under go (i) Lactic acid fermentation, (ii)
Alcoholic fermentation (iii) Aerobic Respiration (Krebs Cycle)
Respiration in Plants 173
 B. Oxidative decarboxylation : Pyruvic acid is converted into Acetyl CoA
in presence of pyruvate dehydrogenase complex.
Mg2
Pyruvic acid + CoA + NAD+ pyruvate Acetyl CoA + CO2 + NADH
dehydrogenase
Mg2+
+ H+
2
pyruvate The Acetyl CoA enters in TCA cycle.
dehydrogenase

C. Tri Carboxylic Acid Cycle (Kereb’s cycle) or Citric acid Cycle : This
cycle starts with condensation of acetyl group with oxaloacitic acid and
water to yield citric acid which under goes a series of reactions.

 It is aerobic and takes a place in
mitochondrial matrix.

 Each pyruvic acid molecule
produces 4 NADH + H+, one
FADH2, one ATP.

 One glucose molecule has been

broken down to release

CO2 and eight molecules
of NADH + H+, two molecules
of FADH2 and 2 molecules
of ATP.
Compensation Point : It is the

value of a factor at which the rate
of photosynthesis controlled by it is just equal to the rate of respiration
and photorespiration so that there is not net exchange of gases between the
phtosynthetic organ and the environment.
At compensation point the photosynthetic tissue manufacture only such
amount of food which of sufficient for it to remain alive. No food is supplied
to rest of the plant. Therefore, net photosynthesis is zero.

(D) Oxidative Phosphorylation

The synthesis of ATP from ADP and inorganic phosphate using energy from
proton gradient is called oxidative phosphorylation. This takes place in
elementry particles present on the inner membrane of cristae of mitochondria.
174 Biology Class - 11
 This process in mitochondria is catalysed by ATP synthestase (complex V).
This complex has two major components F0 and and F1- F0 acts a channel
for proton and F1 acts as an ATP synthetase.

Electron Transport System and Oxidative Phosphorylation

Name of Complex Components of ETS

Complex I FMN and FeS are prosthetic groups and NADH
dehydrogenase
Complex II FADH2 dehydrogenase (succinate dehydrogenase), FeS,
UQ
Complex III Cytochrome bc, complex–cytochrome b, cytochrome C,
FeS, UQ
Complex IV Cytochrome oxidase–Cytochrome a1, cytochrome a3 which
posses two copper centres.
Complex V F0–F1 particles, Flow of protein through F0 channel induces
F1 partcile to function as ATP synthetase.

Respiratory Balance Sheet :

Glucose + 6O2 + 36ADP + 36Pi → 6CO2 + 6H2O + 36 ATP
Total ATP Production

Process
Total ATP produced
1. Glycolysis 2ATP + 2NADH2 (6ATP) = 8ATP
2. Oxidative decarboxylation 2NADH2 (6ATP) = 6ATP
3. Kreb’s Cycle 2GTP (2ATP) + 6NADH2 (18ATP)
+ 2FADH2 (4ATP) = 24 ATP
Energy production in prokaryotes during aerobic respiration = 38 ATP
Energy poroduction in eukaryotes during aerobic respiration = 38 – 2 = 36
ATP
In eukaryotes 2 ATP are used in transporting 2 molucules of NADH + H+
formed in glycolysis from cytoplasm to mitochandria for oxidation through ETS
shuttle.
(2) Anaerobic Respiration—In anaerobic respiration, Glycolysis is followed
by formation of ethanol or lactic acid in the cytoplasm.

Respiration in Plants 175

 Fermentation : It is the process of anaerobic respiration which occurs in
yeast and some bacteria. Fermentation involves incomplete oxidation of food into
enthanol and carbon-dio-oxide. It results in the production of 2 ATP molcules.

(i) Conversion of Acetyl CoA into fatty acid and PGA.

(ii) Synthesis of chlorophyll and cytochromes from Succinyl CoA
(iii) Synthesis of Amino acids from OAA and α-ketoglutaric acid
(iv) Synthesis of Alkaloid from OAA.
Enzymes involved-Pyruvic acid decarboxylase, Alcohol dehydrogenase
Anaerobic respiration in muslces : During vigrous exercise a person feels
pain and fatigue in his muscles. This is due to accumulation of lactic acid in
muscles. When oxygen is inadequate pyruvic acid is reduced to lactic acid in
presence of enzyne-lactic dehydrogenase.
Lactic dehydrogenase

During rest lactic acid is reconverted to pyruvic acid.

Amphibolic Pathway :
During the process of cellular respiration Carbohydrates, fats and proteins
are broken down to release energy and hence respiration is a catabolic process/
catabolic pathway. From this pathway many compound are withdrawn for synthesis
of substrates. Some anabolic processes are formation of pyruvic acid from amino
acids, and formation of Acetyl CoA from Fatty acid. Thus, Respiratory pathway is
involved in both catabolism and anabolism, it is better to consider the respiratory
pathway as an amphibolic pathway.

RQ (Respiratory quotient)
(a) RQ = 1 (When carbohydrate is used as substrate)
C6H12O6 + 6O2 → 6CO2 + 6 H2O + Energy
(b) RQ is less than 1 (i.e., < 1) (When fats are used as substrate)

176 Biology Class - 11

 2C51H98O6 + 145O2 → 102CO2 + 98 H2O + Energy
Tripalmitin

R.Q. ⇒ = 0.7
(c) RQ is 0.9 for proteins.
(d) RQ is more than 1 (i.e., > 1) for organic acids.
(e) RQ is inifinite in case of anerobic respiration, because CO2 is evolved but
O2 is not consumed.

Questions

(SRT) Select Response Type Question (1 mark each)

1. Which of the following is the terminal acceptor of electrons?
(a) Cytochrome-b (b) Carbon-di-oxide
(c) Hydrogen (d) Oxygen
2. Which of the following is correct name of the molecule which acts as the
acceptor and substrate entrant in Kreb cycle?
(a) Oxaloacetate and acetyl Co-A
(b) Acetyl Co-A and Oxaloacetate
(c) Citric acid and malic acid
(d) Pyruvic acid and Acetyl Co-A
3. Respiratory quotient is ..................... and RQ of fats and proteins is .............
and .................. respectively.
(a) Ratio between the volume of oxygen consumed to the volume of carbon-
di-oxide evolved, 0.5, 0.9
(b) Ratio between the volume of carbon-di-oxide consumed to the volume
of oxygen evolved, 0.5, 0.9
(c) Ratio between the volume of oxygen consumed to the volume of carbon-
di-oxide evolved, 0.9, 0.5
(d) Ratio between the volume of carbon-di-oxide consumed to the volume
of oxygen evolved 0.9, 0.5

Respiration in Plants 177

 CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answer Question (1 mark each)
4. How many ATP molecules are produced from a molecule of glucose on it
complete oxidation in eukaryotes ?
5. Where does ETC found in eukaryotic cell ?
6. Name the enzyme which convert sugar into glucose and fructose.
7. How many molecules of ATP are produced by the oxidation of one molecule
of FADH2 ?
8. Why do the person with sufficient white fibres get fatigued in a short
period ?
9. Write the name of end product of glycolysis.
10. Name the first product formed in Kreb’s cycle.
11. Which intermediate undergoes lysis in glycolysis ?
12. Write the other two names of Krebs cycle.
13. Name the first chemical produced in Krebs cycle.
14. What is Electron Transport Chain ? (ETC).
15. F0–F1 Protein complexes participate in the synthesis of ..........

Short Answer Questions-I (2 mark each)

16. Differentiate between aerobic respiration and anerobic respiration.
17. Mention two steps of glycolysis in which ATP is utilised.
18. Why does anaeriobic respiration produces less energy than aerobic respiration?
19. Distinguish between glycolysis and fermentation.
20. What are respiratory substrates ? Name the most common respiratory
substrate.

Short Answer Questions-II (3 marks each)

21. Pyruvic acid is the end product of glycolysis. What are the three metabolic
fates of pyruvic acid under aerobic and anaerobic conditions ?
178 Biology Class - 11
22. Give the schematic representation of an overall view of TCA cycle.
23. Where does electron transport system operative in mitochondria ? Explain
the system giving the role of oxygen ?
24. Give a brief account of ATP molecules produced in aerobic respiration in
eukaryotes.
25. Discuss the respiratory pathway is an amphibolic pathway.
26. Exapnd ETC., ETS and TCA.

Long Answer Questions (5 marks each)

27. What is glycolysis ? Where does glycolysis takes place in a cell ? Give
schematic representation of glycolysis.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (d) Oxygen
2. (a) Oxaloacetate and acetyl Co-A
3. (a) Ratio between the volume of oxygen consumed to the volume of carbon-
di-oxide evolved, 0.5, 0.9

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. 36 ATP.
5. Mitochondrial membrance.
6. Invertase.
7. 2 ATP molecules.
8. due to formation of Lactic acid.
9. Pyruvic acid.
10. Citric acid.
11. Fructose, 6-bisphosphate.

Respiration in Plants 179

12. (i) Citric acid cycle (ii) Tricarboxylic acid cycle.
13. Citrate
14. See text (Points to remember)
15. ATP

Short Answers-I (2 mark each)

16. Refer NCERT Text Book Chapter 14 (14.3 and14.4).

17. (i) Phosphorylation of Glucose into Glucose-6-phosphate.

(ii) Phosphorylation of Fructose-6-phosphate into Fructose-1,6-biphosphate.

18. Refer NCERT Text Book Chapter 14.

19. Refer NCERT Text Book.
20. Refer NCERT Text Book.

Short Answers-II (3 marks each)

21. (i) Aerobic conditions–CO2 + H2O + Energy
(ii) Anaerobic conditions–(fermentation)
(a) In muscles – Lactic acid + Energy
(b) Yeast-Ehtanol + CO2 + Energy
22. Refer NCERT Text Book Fig. 14.3.
23. Refer NCERT Text Book.
24. Refer notes.
25. Refer NCERT Text Book.
26. Seet text (abbreviations).

Long Answers (5 mark each)

27. Refer NCERT Text Book.

Assertion Reasoning (1 mark each)

The following question consists of 2 statements - Assertion (A) and Reason (R).
answer the question by selecting the appropriate option below :

180 Biology Class - 11

 (a) Both A and R are true and the reason is a correct explanation of the
assertion
(b) Both A and R are true and the reason is not a correct explanation of the
assertion
(c) The assertion is true but the reason is false
(d) Both the assertion and reason are false
(e) The assertion is false but the reason is true
28. Assertion (A) : More ATPs are produced during aerobic respiration than
anaerobic respiration.
Reason (R) : Site for aerobic respiration is mitochondria and that of anaerobic
respiration is cytoplasm.
29. Assertion (A) : Respiration is called an amphibolic pathway.
Reason (R) : In respiration both anabolism and catabolism occur on many
substrates.
30. Assertion (A) : During carbon-di-oxide fixation, the acetyl-coA comes from
glycolysis.
Reason (R) : Acetyl-coA gives energy for the formation of glucose.

Solution:
Assertion Reasoning

28. (b)

29. (a)

30. (d)

Source-based/Case-based/Passage-based/Integrated assessment question

 (4 marks each)
Read the following and answer any four questions from (i) to (v) given below :
31. Electron transport chain is the final stage of aerobic respiration which is
located on the mitochondrial membrane. There are two mitochondrial
membranes, outer and inner. All proton pumps are located on the inner
mitochondrial membrane which is arranged into folds called cristae. These
folds increase the surface area available for the transport chain. Electron

Respiration in Plants 181

 transport chain is the series of redox reactions in which there is transfer of
electrons from electron donors to electron acceptors. The energy is released
and stored within the reduced hydrogen carriers which are then used to
synthesise ATP. This is called oxidative phosphorylation. Oxidative
phosphorylation occurs in distinct steps. First, the proton pumps create an
electrochemical gradient called as proton motive force, second, ATP synthase
uses the subsequent diffusions of protons, this step is called chemiosmosis.
ATP is synthesised in this step. Third and final, oxygen accepts electrons
and protons to form water.
(i) The correct series of electron acceptors present in mitochondrial
membrane is
(a) Cyt c, b, a, a3
(b) Cyt b, c, a, a3
(c) Cyt a, a, b, c
(d) Cyt b, c, a3, a
(ii) How may ATPs will be produced from three molecules of NADPH and
two molecules of PADH2?
(a) 5
(b) 9
(c) 13
(d) 18
(iii) In amphibolic pathway fatty acids will produce
(a) Glucose-6-phosphate
(b) Glucose-1-6-phosphate
(c) Pyruvate
(d) Acetyl coA
(iv) The F0-F1 complex acts as a site for ATP synthesis when protons enter
inner membrane space. (T/F)

182 Biology Class - 11

 (v) Ubiquinone (UQ) transfers its electrons to
(a) Cytochrome b in complex III
(b) Cytochrome a in complex IV
(c) FAD in Complex II
(d) Mitochondrial matrix
Solution:
Source-based/Case-based/Passage-based/Integrated assessment questions
31. (i) (b) Cyt b, c, a, a3
(ii) (c) 13
(iii) (d) Pyruvate
(iv) False, F0-F1 complex is acts as site for ATP synthesis when protons
leave inner membrane space.
(v) (a) Cytochrome b in complex III


Respiration in Plants 183

184 Biology Class - 11
 Points To Remember
Seed Germination : The seed germinates only when favourable conditions
for growth exists in the environment. In absence of favourable conditions it goes
into a period of suspended growth or rest, called dormancy.
Abscission : Shedding of plant organs like leaves, flowers and fruits etc.
from the mature plant.
Apical dominance : Suppression of the growth of lateral buds in presence
of apical bud.
Dormancy : A period of suspended activity and growth usually associated
with low metabolic rate. Some, seeds undergo a period of dormancy and can
germinate only after dormancy period gets over.
Phytochrome : A pigment, found in plants which control the light dependent
developmental process.
Phytohormone : Chemicals secreted by plants in minute quantities which
influence the physiological activities.
Senescene : The last phase of growth when metabolic activities decrease.
Vernalisation : A method of promoting flowering by exposing the young
plant to low temperature.
Growth : An irreversible permanent increase in size, volume and weight of
an organ or its parts or even of an individual cell.
Quiescence : Non-germination of a viable seed due to non-availability of
proper environmental conditions.
Vivipary : It is the germination of seed while it is still attached to the parent
plant and is nourished by it. e.g., Rhizophora and Sonneratia. As the germinating
seed forms a seedling. It fall down into the mud due to increase in weights. In the
mud, lateral roots develops for anchorage.
Heterophylly :Occurrence of more than one type of leaves in plants e.g.,
larkspur, coriander leaves of juvenile plant are different in shape from mature plant.
Bolting : Elongation of internodes prior to flowering in plants like cabbage.
Photoperiodism : Response of Plants to relative periods of day/night to
induce flowering.
According to duration of exposure of plants to light, plants are divided in
3 categories :
1. Long Day Plants (LDP)—Plants which need exposure to light for period
exceeding critical duration e.g., wheat, rice, cucumber.

Plant Growth and Development 185

 2. Short Day Plants (SDP)—Plants which need exposure to light for period
less than the critical length e.g., Cabbage.
3. Day Neutral Plants (DNP)—There is no correlation between exposure to
light duration & induction of flowering e.g., Tomato.
Abbreviations
IAA Indole acetic acid
NAA Napththalene acetic acid
ABA Abscisic acid
IBA Indole-3 butyric acid
2,4-D 2,4 dichlorophenoxy acetic acid
PGR Plant growth regulator

Seed Dormancy Quiescence

It is the condition of seed when it is The condition of a seed when it is

unable to germinate in spite of the unable to germinate because the
availability of all environmental condi- conditions for germination are not
tions suitable for germination. It can be available, such as moisture,
due to immature embryo or pressure temperature etc.
of growth inhibitors.

Measurement of growth : Plant growth can be measured by a variety of

parameters like increase in fresh weight, dry weight, length, area, volume and
cell number.
Phases of growth : The period of growth is generally divided into three
phases, namely, meristematic, elongation and maturation.
(i) Meristematic : New cell produced by mitotic division at root-tip and shoot-
tip thereby show increase in size. Cells are rich in protoplasm and nuclei.
(ii) Elongation : Zone of elongation lies just behind the meristematic zone of
roots and concerned with enlargement of cells.
(iii) Maturation : The portion lies proximal to the zone of elongation in roots.
The cells of this zone attain their maximum size in terms of wall thickning
and protoplasmic modification.
Growth rate : The increased growth per unit time is termed as growth rate.
The growth rate shows an increase that may be arithmetic or geometrical.

186 Biology Class - 11

 Height
of
Plant
Time
Fig. Linear growth curve

Growth Mathematical expression Curve

In Arithmetic growth : L1 = L0 + rt Linear curve

Only one daughter cell continues L1 = Length at time t
to divide mitotically while other L0 = Length at time zero
differentiate and matures. r = growth rate

Sigmoid Growth Curve

Geometrical growth Formula Shape of curve
The initial growth is W1 = W0ert Sigmoid or
slow (lag phase) and increase W0 = Initial size S-curve
rapidly there-after at an W1 = Final Size
exponential rate (log phase) r = growth rate
In both, the progeny cells divide t = time of growth
mitotically and continue to do so. e = base of natural
However, with limited nutrient logarithms
supply, the growth slow down
leading to stationary phase.

Sigmoid growth curve

Lag phase : Growth is slow in initial
stage.
Exponential phase : Period of
maximum growth Lag Phase
Stationary phase : When the nutrients
become limiting, growth slows down.
Fig. Sigmoid growth curve
Plant Growth and Development 187
 Relative Growth : The growth per unit time as percentage of initial size

RGR = × 100

Differentiation : A biochemical or morphological change in meristemic

cell (at root apex and shoot apex) to differentiate into permanent cell is called
differentiation. e.g. loss of protoplasm by tracheary elements.
Dedifferentiation : The phenomenon of regeneration of permanent tissue to
become meristematic is called dedifferentiation. eg. formation of interfascicular
cambium and cork combium from parenchymatous cells.
Redifferentiation : Meristems/tissue are able to produces new cells that
once again lose the capacity to divide but nature to perform specific functions.
e.g. secondary cortex, secondary xylem etc.

Conditions or factors influencing Growth

1. Nutrition 2. Availability of water 3. Temperature 4. Oxygen 5. Light
6. Gravity 7. Stress factors like minerals, water or temperature etc.
Phytohormone or Plant Growth-Regulator
Growth promoting hormones : These are involved in growth promoting
activities such as cell division, cell enlargement, flowering, fruiting and seed
formation. e.g., Auxin, gibberellins, cytokinins.
Growth inhibitor : Involved in growth inhibiting activities such as dormancy
and abscission. e.g., Abscisic acid and Ethylene.
Hormones Functions

1. Auxins (Growth Promoters) 1. Apical dominance, cell elongation,

Promote flowering prevent premature
e.g. Indole 3-Acetic Acid, leaf and fruit falling, initiate rooting
2, 4-D and 2, 4, 5,-T etc. in stem cutting, as weedicide, induce
parthenocarpy.
2. Gibberellins 2. Delay senescence, speed up malting
process, increase in length of axis
 GA 3 (C19 H 22 O6 ) 
(grape stalk), increase in length of stem
eg. GA 4 , GA 7 , GA19 and 
e.g,
(sugarcane), bolting in beet, cabbages and
 GA 20 etc.  many plants with rosette habit.

188 Biology Class - 11

3. Cytokinins (Growth Promoters) 3. Promote cell division, induce cell
e.g. Zeatin (trans 6-purine) enlargement, reduce apical dominance,
 DMAA-Dimethylalyl  induce growth in auxiliary bud,
  chlorophyll preservation, lateral shoot
adenine and Isopentyl  growth, adventitious root formation.
 
adenine (IP) etc. 
4. [Ethylene (H2C = CH2) 4. Promotes senescence and abscission
A gaseous PGR which acts as of leaf and fruits, promotes ripening
growth promoters as well growth of fruits, break seed and bud domancy,
inhibitor (mainly as growth initiate germination in peanut, sprouting
inhibitor) of potato tuber, promotes root growth and
root hair formation.
5.
Abscisic acid (ABA) 5. Inhibit seed germination, stimulate closer
eg. (Abscisin II, Dormin) of stomata, increase tolerance to various
stress, induce dormancy in seed and bud,
promotes ageing of leaf (senescence).
Can delay the ripening of stored fruits as
it absorbs the ethylene.

Vernalisation : The phenomenon in which flowering is either quantitatively or

qulitatively dependent on exposure to low temperature. eg wheat, barley, rye, bi-
ennial plants like sugarbeet cabbage, carrots. It prevents precocious reproductive
development late in the growing season and enables the plant to have sufficient
time to reach maturity

Questions

(SRT) Select Response Type Question (1 mark each)

1. The cause of ‘BAKANE’ disease of rice
(a) Gracilaria (b) Gibberella fujikuroi
(c) Geledium (d) Anabena
2. Which plant hormone was first isolated from human urine.
(a) Ethylene (b) ABA
(c) Auxin (d) Cytokinin

Plant Growth and Development 189

 3. The only gaseous plant hormone is
(a) Gibberllins (b) Dormin
(c) Zeatin (d) Ethylene

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Question (1 mark each)
4. How does abscisic acid acts as stress hormone in drought condition ?
5. A farmer observed some broad-leaved weeds in a wheat crop farm. Which
plant hormone would you suggest remove them ?
6. Name the plant growth regulators you should use to (a) Increase the yield
of sugarcane (b) Promote lateral growth (c) Cause sprouting of potato tuber
(d) Inhibit seed germination.
7. Why do lateral buds start developing into branches when apical bud is
removed ?
8. Flowering in certain plant occur only when they are exposed to low temperature
for a few weeks. Name this phenomenon.
9. A hormone released by an over ripe apple in a wooden box will cause ripening
of all other apples too. Name the hormone, and to which class it belongs to?
Short Answer Question-I (2 marks each)
10. How will you induce lateral branching in a plant which normally does not
produce them ? Give reason.
11. What induces ethylene formation in plants ? Give any two different action
of ethylene on plants.
12. What is meant by abscission ? Name phytohormone involved in it.
13. What is meant by apical dominance ? Which hormone control it ?
14. Differentiate between photoperiodism and vernalization.
15. Name a hormone which is :
(a) gaseous in nature (b) responsible for phototropism (c) used for killing
dicot weeds (d) Induces flowering in long day plants.
Short Answer Questions-II (3 marks each)
16. A primary root grows from 5 cm to 19 cm in a week. Calculate the growth
rate and relative growth over the period.

190 Biology Class - 11

17. Where are the following hormones synthesised in plants (a) IAA
(b) gibberellins (c) cytokinins.
18. What would be expected to happen if :
(a) GA3 is applied to rice seedling?
(b) a rotten fruit get mixed with unripe fruits?
(c) you forget to add cytokinin to the culture medium?
19. Which growth hormone is responsible for the following :
(a) induce rooting in a twig
(b) quick ripening of a fruit
(c) delay leaf senescence
(d) ‘bolt’ a rosette plant
(e) induce immediate stomatal closure in leaves
(f) Induce growth in axillary buds.
20. Define differentiation, dedifferentiation and redifferentiation.
21. Where are auxins generally produced in a plant ? Name any one naturally
occurring plant auxin and any one synthetic auxin.
22. Define growth rate. Name two types of growth. Draw the growth curves for
these two types.
23. Mention various parameters taken into consideration for measuring the
growth.

Long Answer Question (5 marks each)

24. Enlist the five categories of phytohormone. Write atleast two uses of each.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (b) Gibberella fujikuroi.
2. (c) Auxin.
3. (d) Ethylene.

Plant Growth and Development 191

 CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answer (1 mark each)
4. ABA cause rapid closure of stomata, preventing loss of water by transpiration.
5. 2.4-D.
6. (a) Gibberellin (b) Cytokinin
(c) Ethylene (d) Abscisic acid
7. Due to inhibition of the activity of auxin the apical dominance is removed.
8. Vernalisation.
9. Ethylene, plant growth inhibitor.

Short Answers-I (2 marks each)

10. When apical bud is removed, lateral branches are produced. Du to removal
of apical bud, the auxin is destroyed, thus inducing the lateral buds to grow
rapidly.
11. Refer NCERT Book
12.  Premature fall of leaf and fruit is called abscission.

 Abscisic acid
13. Refer NCERT Book
14. Refer NCERT Book
15. (a) Ethylene C2H2 (b) Auxin (c) 2, 4-D (d) Gibberellin

Short Answers-II (3 marks each)

16. (a) Growth = 19 – 5 = 14 cm, Period = 7 days

Growth rate = = 2cm/day

(b) Inititial growth = cm

Growth rate per day = 2 cm

Relative growth rate = × 100 = 40%

192 Biology Class - 11

17. (a) 1AA = Shoot apex
(b) Gibberellin – young leaves of buds, root tips
(c) Cytokinins – Root apical meristan
18. (a) Hyper elongation of internodes of rice seedlings will occur.
(b) Unripe fruits will lead to early ripening and ultimately it will result in
rottening.
(c) Shoot but formation will not occur.
19. Refer Points to Remember of Support Material
20. Refer Points to Remember of Support Material
21. Refer Points to Remember of Support Material
22. Refer Points to Remember of Support Material
23. Refer Points to Remember of Support Material

Long Answers (5 marks each)

24. Refer NCERT Text Book Page no. 241-250.

Assertion Reasoning (1 mark each)

The following question consists of 2 statements - Assertion (A) and Reason
(R). Answer the question by selecting the appropriate option below :
(a) Both A and R are true and the reason is a correct explanation of the
assertion
(b) Both A and R are true and the reason is not a correct explanation of the
assertion
(c) The assertion A is true but the reason R is false
(d) Both the assertion A and reason R are false
(e) The assertion A is false but the reason R is true
25. Assertion (A) : Plant growth regulators are phytohormones, they are required
for various metabolic activities for growth in plants.
Reason (R) : Auxins, if applied on Pinus, will not induce flowering.
26. Assertion (A) : Plant growth is measurable.
Reason (R) : Growth only means addition of dry weight in the plant.

Plant Growth and Development 193

 (a) Both A and R are true and the reason is a correct explanation of the
assertion
27. Assertion (A) : ‘r’ in logistic growth means exponential growth.
Reason (R) : It is also known as the efficiency index.
28. Assertion (A) : Heterophylly in larkspur is due to dedifferentiation.
Reason (R) : There is no role of environment in plasticity.
29. Assertion (A) : Cytokinin is produced in actively dividing cells.
Reason (R) : It helps in producing new leaves and shoots in plants.
Solution:
Assertion Reasoning
25. (b) (Plant growth regulators regulate growth but will not induce flowering)
26. (c) (Growth is measured by a variety of parameters some of which are: increase
in fresh weight, dry weight, length, area, volume and cell number)
27. (e) (‘r’ is relative growth rate)
28. (d)
29. (a)
Source-based/Case-based/Passage-based/Integrated assessment questions
 (4 marks each)
Read the following and answer any four questions from (i) to (v) given below :
30. The process by which prolonged exposure to cold temperatures. 4°C or less,
promotes f lowering is called vernalisation. It was first studied in 1918 by
Gassner. It is believed that due to prolonged cold treatment, a hypothetical
hormone like substance vernalin is produced in meristematic regions which
induce f lowering. Some monocarpic plants, which die when they f lower,
require vernalisn to f lower, mostly requiring two seasons to complete the
life cycle. Such plants are biennials or winter annuals. Cold exposure is a
most for such plants to flower. Some monocarpic plants that are annuals but
they do not require any cold treatment for flowering, such plants are called
summer annuals. Many perennial such as stone fruit plants also require cold
treatment to flower. Winter cereals such as autumn wheat also require cold

194 Biology Class - 11

 treatment to flower. If such wheat is grown in spring, it will continue growing
vegetatively and will f lower only after the upcoming winter season.
Vernalisation can be reversed. It is done for sowing seeds of onions which
are stored in cold storage for long. Applying plant growth regulators which
cause bakanae disease can also help some seeds to germinate and skip
prolonged cold periods.
(i) Which hypothetical precursor hormone is believed to be produced in
meristematic regions of plants after vernalisation?
(a) Photolin (b) Vernalin
(c) florigen (d) morphactin
(ii) The plants which die after flowering are called _____________?
(a) Polycarpic plants (b) Bicarpic plants
(c) Monocarpic plants (d) Plietesialic plants
(iii) Spring wheat does not require prolonged cold treatment for
flowering. (T/F)
(iv) Name any two monocarpic plants that require vernalisation.
(v) Which of the following plant growth regulators can replace vernalisation?
(a) Gibberellin
(b) Auxin
(c) Cytokinin
(d) Ethylene
Solutions:
Source-based/Case-based/Passage-based/Integrated assessment questions
30. (i) (b) Vernalin
(ii) (c) Monocarpic plants
(iii) True
(iv) Sugarbeet, cabbage, carrots (any two)
(v) (a) Gibberellin


Plant Growth and Development 195

 Absorption
Points To Remember
Digestion : The process in alimentary canal by which the complex food is
converted mechanically and biochemically into simple substances suitable for
absorption and assimilation in the body of animals/organisms.
Food : A substance which is taken and digested in the body to provide
material for growth, repair & energy for reproduction and resistance from disease
or regulation of body processes.
Thecodont : The teeth embedded in the sockets of the jaw bone, e.g., in
mammals.
Diphyodont : The teeth formed twice in life time e.g., in mammals.
Heterodont : Different types of teeth. An adult human has 32 permanent
teeth which are of four different types.

Crown

Root

(for tearing) (cutting) (grinding) (churning & grinding)

Different Types of Teeth

DENTAL FORMULA OF HYMANS

Milk Teeth Permanent Teeth

I C PM M. Upper half jaw I C PM M.
2 1 2 0 ] x 2 = 10
]
+ = 20
2 1 2 0 ] x 2 = 10
Lower half jaw 2 1 2 3 ] x 2 = 16
]
+ = 32
2 1 2 3 ] x 2 = 16

196 Biology Class - 11

 Peristalsis : The involuntary movement of the gut by which the food bolus
is pushed forward.
Deglutition : The process of swallowing of food bolus. It is partly voluntary
and partly involuntary.
Ruminants : The herbivours animals (e.g., cow, buffalo etc.) which have
symbiotic bacteria in the rumen of their stomach, which synthesize enzymes to
hydrolyse cellulose into monosaccharides.
Diarrhoea : The abnormal frequent discharge of semisolid or fluid faecal
matter from the bowel.
Vomiting : The ejection of stomach contents through the mouth, caused by
antiperistalsis.
Dysentery : Frequent watery stools often with blood and mucus, along with
pain and fever. Loss of water causes dehydration.
Chyme : The semifluid mass, into which food is converted by gastric
secretion, which passes from the stomach into the small intestine.
Gastric : Anything associated with stomach is given a prefix ‘gastric’.
Proenzyme : The inactive forms of enzymes.
Sphincter : A flap like structure at various junctions of the alimentary canal
which facilitates one way traffic (movement of material) in the alimentary canal.
Bolus : The masticated food mixed with saliva.
Hepatic : Anything associated with liver is given a prefix ‘hepatic’.
Goblet cells : The cells of intestinal mucosal epithelium which secrete mucus.
Glisson’s capsule : The connective tissue sheath which covers the hepatic
lobules of liver.
Hepatic lobules : The structural and functional units of liver containing
hepatic cells which are arranged in the form of cords.
Sphincter of Oddi : The sphincter which guard the opening of common
hepatopancreatic duct.
Villi : The small finger-like folding in the small intestine which increase the
surface area for absorption of digested food.

Digestion and Absorption 197

 Crypts of Lieberkuhn–pits of intestine/tubular intestinal glands.
Succus entericus—Intestinal juices, secreted in small intestine.

Basic Steps of Holozoic Nutrition :

(1) Ingestion : Intake of food.
(2) Digestion : Breaking down of complex organic food materials into simpler,
smaller water soluble molecules.
(3) Absorption and assimilation : Absorption of digested food into blood or
lymph and its use in the body cells for synthesis of complex components.
(4) Egestion : Elimination of undigested food as faeces :
Digestive glands : (A) Salivary gland—3 types are (i) Parotids (cheek)

(ii) Sublinguals (Below the tongue) (iii) Submaxillary or submandibular
(lower jaw) Secrete saliva which contains ptyalin (Salivary Amylase).
(B) Pancreas : A dual gland that secretes pancreatic juice and also secretes
Hormones. Located between limbs of U shaped duodenum.
(C) Liver : In abdominal cavity (1.2–1.5 kg.)
2 lobed ® Hepatic lobules ® Hepatic cells (arranged as cords) ® Secrete bile
® Goes to hepatic ducts ® bile stored in gall bladder.

198 Biology Class - 11

 COMPLETE PROCESS OF DIGESTION

1 1 1
1
1
2 2

2 3 2
3
3

3
JUICE

3
4 4 Enterokinase
4
4
4 Activates
Pancreatic
enzymes

ABSORPTION OF FATS
• Fatty acids and monoglycerides and Glycerol (insoluble).
• Micelles (tiny spheres with hydrophilic ends) formed.
• Absorbed by epithelial cells of small intestine (simple diffusion)
• They are reformed into very small protein coated fat globules called chylo-
microns.
• Chylomicrons transported into lymph vessels (lacteals) in the villi.
• Lymph vessels release the absorbed substances into bloodstream
• Malnutrition—When a person is not getting enough food or getting unbal-
anced diet.

PEM—Protein Energy Malnutrition

Kwashiorkar Marasmus
The word means ‘rejected child’ Word marasmus means wasting
away
 It is a disorder found in children  Child remaining under-nourished

1-5 years of age, where child is suffer from marasmus. Usually

weaned off mother’s milk very early. found in children below the age
of 1 year.
 Children get low protein and low  It is caused by deficiency of

carbohydrate diet are affected. protein & carbohydrate & fat.

Digestion and Absorption 199

 DIGESTION AND ABSORPTION
Part of Name of glands Enzymes/ Substrate End Products pH
alimentary secretion
canal
Buccal cavity Salivary glands Salivary Starch Maltose Slightly acidic
amylase
oesophagus – – – – –
Stomach Gastric glands Gastric Juice Activates pep- Pepsin Highly Acidic
(mucosal) HCL sinogen
Pepsin Protein Peptone
Renin (in calves caesin (milk Ca++ & paracae-
& infants) protein) sinate
Mucus (protects stomach walls)
Small Liver (through Bile Juice Fats Emulsify fats Alkaline
intestine. duct)
(duodenum) Pancreas Pancreatic Juice Alkaline
(through duct) Trypsin Proteins Peptones/
polypeptides
Carboxypepti- Milk proteins/ Dipeptides or
dase peptides amino acids
Amylase Starch Glucose
Lipase Lipids Fatty acids &
Glycerol
Nucleases RNA, DNA nucleotides
Intestinal Succus entericus Alkaline
mucosa Enterokinase Trypsinogen Trypsin
Dipeptidase Dipeptides Amino acids
Lipase Lipids Fatty acids + Glycerol
Maltase/sucrase/ Maltose/ Glucose/
lactase sucrose/lactose Fructose/
Galactose
Nucleotidase/ Nucleotides/ Nucleoside/free
Nucleosidase Nucleosides base
Small ABSORPTION OF DIGESTED FOOD
Intestine Passive Facilitated
Active Diffusion
(lleum) diffusion Diffusion
Movement of
molecules as Diffusion of some ions and polar
against concen. gradient
per conc. gradi- molecules
ent
No ATP utilised ATP used membrane proteins required
glucose, amino
acids, chloride amioacids, glucose, sodium Fructose and some amino acids
ions

200 Biology Class - 11

Symptoms
Kwashiorkar Marasmus
1. Stunted growth 1. Low body weight
2. Dry & scaly skin 2. Wasting of muscles
3. Odema (retention of water in tissues) 3. Prominent ribs
4. Match stick legs 4. Sunken eyes
5. Protrude Belly 5. Lean body with thin limbs
6. Mental retardation

Cure
Feeding the child with protein rich Child should be given protein
diet including milk, soyabean, diet with enough quantity of
egg etc. carbohydrates & fats.

Calorific Value : Amount of heat energy released by 1 gm of substrate after
complete oxidation.
Calorific value of Carbohydrates is 4.1 k.cal/g = 17.1 kj/g
Protein is 5.6 kcal/g = 23.4 kj/gm
Fats is 9.4 kcal/g (app.) = 39.2 kj/gm

Questions

(SRT) Select Response Type Question (1 mark each)

1. The hardest substance in the body is:
(a) Keratin (b) Enamel
(c) Collagen (d) Fibrin
2. Choose the correct option for lacteal and its function
(a) Lymph vessel of villi, absorption of protein
(b) Lymph vessel of stomach of protein
(c) Lymph vessel of villi, absorption of vitamin
(d) Lymph vessel of villi, absorption of fats
3. Smallest projection of tongue is:

Digestion and Absorption 201

 (a) Goblet cells (b) Serosa
(c) Papillae (d) Appendix

Very Short Answer Questions (1 mark each)

4. Mention the function of epiglottis.
5. Write the names of major parts of stomach.
6. Name the enzyme that digest fats. Mention the end products of fat digestion.
7. In which part of alimentary canal absorption of water, simple sugars and
takes place ?
8. Why are proteases generally released in inactive form ?
9. Trypsinogen is an inactive enzyme of pancreatic juice. An enzyme,
enterokinase, activates it. Which tissue/cell secrete this enzyme ? How is it
activated ?
10. What is the role of insulin ?
11. Name any one country where children affected from PEM are found more.

CONSTRUCTED RESPONSE TYPE (CRT)

Short Answer Questions-I (2 marks each)
12. What is emulsification ? Where and how does it occur ?
13. Name three parts of large intestine. Which vestigial organ arises from the
first part of it ?
14. Name the digestive gland which acts as both exocrine and endocrine. Also
name the products which are secreted by it.
15. The wall of alimentary canal is made up of four layers. Give the names of
these four layers.
16. Hydrochloric acid is found in our stomach. What purpose does it serve in
alimentary canal ?
17. In which part of the digestive system the absorption of following substances
takes place ?
(a) Certain drugs
(b) Glucose, fructose and fatty acids
(c) Water, some minerals and drugs
(d) Simple sugar and alcohol
18. Differentiate between chylomicron and micelles.

202 Biology Class - 11

Short Answer Question-II (3 mark each)
19. In the following diagram of duct system of liver, gallbladder and pancreas, label
a, b, c, d, e and f :

20. Give a diagrammatic representation of transverse section of gut.

21. Draw the sketch of anatomical regions of human stomach and label any four
parts in it.
22. How does the nervous system control the activities of gastro-intestinal
tract ?

Long Answer Question (5 marks each)

23. Draw a labelled figure of digestive system of human.
24. Give a summary of cause and symptoms of following disorders of digestive
system :
(a) Jaundice (b) Vomiting
(c) Diarrhoea (d) Constipation
(e) Indigestion

Answers

(SRT) Select Response Type Question (1 mark each)

1. (b) Enamel
2. (d) Lymph vessel of villi, absorption of fats
3. (c) Papillae, Some Papillae have taste buds.

Digestion and Absorption 203

 CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answer (1 mark each)
4. Prevent the entry of food into the glottis.
5. Cardiac, fundic, pyloric.
6. Lipase, fatty acids and glycerol.
7. Large intestine, small intestine and stomach respectively.
8. If released in active form, without the presence of food they will start digesting
the membranes and muscular walls of the alimentary canal.
9. Intestinal Mucosa.

(In active) (Active)

10. Metabolism of sugar.
11. African countries– Somalia & others.
Short Answer Questions–I (2 marks each)
12. The process of breakdown of large fat droplets into smaller ones. It occurs
in duodenum of small intestine. It is brought about by bile salts through
reduction of surface tension of large fat droplets.
13. Caecum, colon and rectum. Vermiform appendix.
14. Pancreas. Exocrine secretion is pancreatic juice containing enzymes and
endocrine secretions are hormones : Insulin and glucagon.
15. Serosa, muscularis, submucosa and mucosa.
16. (i) Killing of germs present in food
(ii) Conversion of inactive pepsinogen into active form pepsin.
17. (a) Mouth & large intestine (b) Small intestine
(c) Large intestine
(d) Stomach

18. Chylomicron Micelles

1. Protein coated water soluble Formed by combination of fatty acid,

fat droplets released into the monoglycerides and bile salts.
lymph.
2. In this form fats lipids are put In this form digested fats are absorbed
into circulation in intestinal cells in alimentary canal.

204 Biology Class - 11

Short Answers Questions–II (3 marks each)
19. Refer Fig. 16.6, Page no. 261 (NCERT Text Book, XI Biology).
20. Refer Fig. 16.4, Page no. 260 (NCERT Text Book, XI Biology).
21. Refer Fig. 16.3, Page no. 259 (NCERT Text Book, XI Biology).
22. (a) Sight/smell of food ® secretion of saliva.
(b) Neural signal ® gastric intestinal secretion.
(c) CNS and local control over muscular movement.

Long Answers (5 marks each)

23. Refer Fig. 16.1, Page no. 258 (NCERT Text Book, Class XI Biology).
24. Refer Page no. 265-266 (NCERT Text Book, Class XI Biology).
Case-based/Value based questions :
26. When I do not sleep... then the metabolic activities of my body get affected
badly. Various food components once ingested, voluntarily by me are passed on
to my oesophagus. This proces now is an involuntary action which is now called
peristalsis. My stomach works hard to grind the food which was chewed up by my
mouth, it also secretes HCl to make surroundings acidic, so as to help in protein
digestion. My liver gets filled up by the toxicity from the proteins (ammonia),
which were completely digested in the small intestine. My hard working liver also
converts fats into an energy source for the body. My intestines look forward to
the much-needed rest they need, after their villi have absorbed the final products
of digestion and passed it over to my blood. My pancreas screams for help as the
Insulin secreted by it, unable to control the increase of the glucose in my blood..
My brain starts getting electrocuted by constantly responding to the huge variety
of stimuli being fed into my system continuously... thus increasing my stress. So
dear eyes close yourself on time and sleep peacefully. This much needed sleep
on time, provides the much-needed rejuvenation to the metabolism of our body!
1. What is the end product of the digestion of proteins in the intestines, which
is passed on to the blood?
(a) Monosaccharides (b) Amino acids
(c) Fatty acids (d) Nucleosides
2. Define metabolism.
(a) Sum total of catabolic processes

Digestion and Absorption 205

 (b) Sum total of anabolic processes
(c) Sum total of catabolic and anabolic processes.
(d) None of the above
3. Which hormone is secreted by the pancreas?
(a) Salivary amylase
(b) Insulin
(c) Glucagon
(d) Insulin and glucagon
4. Why sleeping on time is essential for the body?
(a) To have a perfect circadian rhythm
(b) To rejuvenate metabolism
(c) To pass time
(d) Both (a) & (b)
Assertion reasoning questions: Select Response Type-II Question (1 Mark each)
DIRECTIONS, a statement of assertion (A) is followed by a statement of
the reason (R). Mark the correct choice as :
(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) true, but (R) is not the correct explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
27. Assertion : The innermost layer lining the lumen of the small intestine is
mucosa and is called villi.
Reason : It increases the surface area of the small intestine.
28. Assertion : The teeth help in the mastication of food.
Reason : The hard chewing surface of the teeth is made up of enamel.
Solutions :
26. 1. (b)
2. (c)
3. (d)
4. (d)
27. (a)
28. (a)


206 Biology Class - 11

 Points To Remember
Breathing : (External respiration) The process of exchange of O2 from the
atmosphere with CO2 produced by the cells.
Carbamino haemoglobin : Compound formed in RBCs when CO2 combine
with haemoglobin.
Inspiration : Oxygen from fresh air taken in by lungs and diffused into the
blood.
Expiration : CO2 given up by venous blood in the lungs is sent out to exterior.
Respiration : The sum total of physical and chemical processes by which
oxygen and carbohydrates (main food nutrient) etc are assimilated into the system
and the oxidation products like carbon dioxide and water are given off.
Diaphragm : A muscular, membranous partition separating the thoracic
cavity from the abdominal cavity.
Hypoxia—Shortage of oxygen in tissues.
Partial Pressure—The pressure contributed by an individual gas in a mixture
of gases. It is represented as pO2 for oxygen and pCO2 for carbondioxide.
Pharynx : The tube or cavity which connects the mouth and nasal passages
with oesophagus. It has three parts (i) Nasopharynx (anterior part) (ii) Oropharynx
(middle part) and (iii) Laryngopharynx (posterior part which continues to larynx)
Adam’s Apple : The projection formed by the thyroid cartilage and surrounds
the larynx at the front of the neck.
Tidal volume (TV) : Volume of air taken in/given out during normal
respiration (500 mL.)
Inspiratory Reserve Volume (IRV) : Additional volume of air inspired by
a forcible inspiration. 2500mL to 3000mL.
Expiratory Reserve Volume (ERV) : Additional volume of air, a person
can expire by a forcible expiration.
Residual volume (RV) : Volume of air remaining in the lungs even after a
forcible expiration (1100 mL to 1200 mL)

Breathing and Exchange of Gases 207

 PULMONARY CAPACITIES : Use in clinical diagnosis.
Inspiratory capacity (IC) = (TV + IRV) Total volume of air a person can
inspire after a normal expiration.
Expiratory Capacity—Total Volume of air a parson can expire after a
normal inspiration E.C. = TV + ERV
Functional Residual Capacity—Volume of air that will remain in lungs
after a normal expiration (FRC) = (ERV + RV)
Vital Capacity (VC) = (ERV + TV + IRV) or the maximum volume of air
a person can breath out after a forced inspiration.
Total Lung Capacity : It includes RV, ERV, TV and IRV or vital capacity
+ residual volume.
Pulmonary—Anything associated with the lungs is given the prefix
‘pulmonary’

Steps involved in respiration—

(i) Breathing or pulmonary ventilation (intake of atmospheric air and releasing
out CO2 rich alveolar air)
(ii) Diffusion of gases (O2 and CO2) across alveolar membrane & blood vessel
(capillaries).
(iii) Transport of gases by the blood.
(iv) Diffusion of O2 and CO2 between blood and tissues.
(v) Utilisation of O2 by the cells for catabolic reactions and resultant release of
CO2.
208 Biology Class - 11
Respiratory organs in animals :
(i) Protozoans, annelids Frogs—Body surface
(ii) Fishes, tadpole stage of frog and many other aquatic animals—Gills (Branchial
Respiration)
(iii) Insects and a few other arthropods—Tracheal tubes
(iv) All land vertebrates (amphibians, reptiles, aves and mammal)—Lungs.
(Pulmonary Respiration)
Conditions required for (cutaneous respiration)
Skin should be moist and thin. It should be highly vascularised.
Mechanism of Breathing

Inspiration Expiration
Contraction of diaphragm and external Relaxation of diaphragm and sternum
intercostal muscles
↓ ↓
Increase in the volume of thoracic Decrease in the volume of thoracic
chamber chamber
↓ ↓
Lungs expand Lungs contract
↓ ↓
Pressure inside the lungs fall Pressure inside the lungs increase
↓ ↓
Air rushes into lungs from Atmosphere Air rushes out from lungs in
to Atmosphere

Breathing and Exchange of Gases 209

Human Respiratory Tract :

A pair of external nostrils → nasal chamber through nasal passage → pharynx
→ glottis → larynx → trachea → Left and right primary bronchi → secondary
and tertiary bronchi → bronchioles → vascularised bag like structures
(alveoli) or air-sacs. Each lung is covered with double layered membrane
known as pleura with pleural fluid between them.

Physiology of Respiration :
(a) Exchange of gases—Diffusion of gases takes place from the region of higher
partial pressure to lower (lesser) partial pressure)
(i) pO2 in alveolar air = 104 mm Hg.
(ii) pO2 in venous blood = 40 mm Hg.
O2 diffuses from alveoli to venous blood.
(iii) pCO2 in venous blood = 45 mm Hg.
pCO2 in alveolar air = 40 mm Hg.
CO2 diffuses from venous blood to alveoli
Inspired air Expired air

Alveolar air
Alveolus
PO2 = 104 mm Hg
PCO2 = 40 mm Hg
CO2 O2

Pulmonary
artery CO2 O2
Pulmonary
vein

Systemic veins Systemic arteries

Carrying (carrying oxygenated)
deoxygenated blood
blood
PO2 = 40 mmHg PO2 = 95 mmHg

PCO2 = 45 mmHg O2 PCO2 = 40 mmHg

CO2

Body tissue

210 Biology Class - 11

(b) Transport of O2 by the blood — (i) About 3% of O2 in dissolved state
through plasma.

(ii) As oxyhaemoglobin : 97% of O2 diffuses from plasma into RBCs.

Haemoglobin carry 1-4 molecules of O2.
LUNGS Hb4 O8
Hb4 + 4O2 Oxyhaemoglobin
TISSUE

Oxygen dissociation curve

• A sigmoid curve showing relationship between the % of saturation of
haemoglobin with oxygen in blood and pO2 of the blood.
• Fully saturated each gram of haemoglobin combines with nearly 1.34 ml of
oxygen.
• H+ concn., CO2 tension, temperature affect the curve. Increase in their
concentration decreases the affinity of hemoglobin for oxygen.

(c) Transport of CO2

(i) As solution – 7% of CO2 dissolves and carried by the plasma.
(ii) As Bicarbonate – 70% of CO2 in RBCs combines with water form carbonic
acid. Carbonic acid dissociates into bicarbonate ions and H+, Carbonic
anhydrase enzyme help in these reactions.
Carbonic H2CO3 Carbonic HCO– + H+
CO2 + H2O 3
anhydrase anhydrase

(iii) As carbaminohaemoglobin – 23% CO2 combines in RBC with amino group

of haemoglobin, form carbaminohaemoglobin.

Regulation of Respiration
• Respiratory rhythm centre in medulla of brain responsible for this regulation.
• Pneumotaxic centre in pons region moderates function of respiratory rhythm
centre.
• Chemosensitive area adjacent to rhythm centre is highly sensitive to CO2
and H+ ions.

Breathing and Exchange of Gases 211

 • Increase in CO2 and H+ ions activates this centre, which in turn signal the
rhythm centre to make necessary adjustments and respiratory process by
which these substances can be eliminated.
Disorders of Respiratory System
• Emphysema– chronic disorder in which alveolar walls damaged due to
cigarette smoking
• Asthma–difficulty in breathing due to inflammation of bronchi or bronchioles,
• Occupational disorders– people working in stone grinding or breaking
industries, the dust produced damage the defence system of body leading
to servere lung damage.

Questions

(SRT) Select Response Type Question (1 mark each)

1. The organ in human respiratory system producing sound is
(a) Pharynax (b) Alveoli
(c) Larynx (d) Ear drum
2. One Haemoglobin molecule carries
(a) 2 oxygen molecule (b) 3 oxygen molecule
(c) six oxygen molecule (d) oxygen moelcule
3. The double membranous layer which surround the lung is
(a) Mucosa (b) Muscularis
(c) Pleura (d) Serosa

Very Short Answer Questions (1 mark each)

4. Which organ of our respiratory system acts as primary site of exchange of
gases ?
5. Cigarette smoking causes emphysema. Give reason.
6. Name the principle or process of exchange of gases.
7. What is the role of oxyhaemoglobin after releasing molecular oxygen in the
tissues ?
8. Name the muscles which facilitate breathing.
9. How is the entry of food prevented in the respiratory tract?

212 Biology Class - 11

10. About 97% of O2 is transported by RBCs in the blood. How does the remaining
3% of O2 transported ?
Short Answer Questions (2 marks each)
11. Draw a labelled diagram of a section of an alveolus with a pulmonary
capillary.
12. Following is the table showing partial pressure (in mm Hg) of oxygen and
carbondioxide) at different parts involved in diffusion in comparison to those
in atmosphere. Fill in the blank – a, b, c and d.
Respiratory Atmospheric Alveoli Blood Blood Tissue
gases air (Deoxygenated) (Oxygenated)

O2 (a) 104 40 (d) 40

CO2 0.3 (b) (c) 40 45

13. Name the organs of respiration in the organisms.

(a) Flatworms (b) Birds (c) Frog (d) Cockroach
14. What are occupational respiratory disorders ? What are their harmful effects
? What precautions should a person take to prevent such disorders ?
15. How is respiration different from breathing ?
Short Answer Questions-II (3 marks each)
16. Explain the role of neural system in regulation of respiration is human.
17. How is carbon dioxide transported in blood?
Long Answer Questions (5 marks each)
18. With the help of labelled diagram explain the structure of human respiratory
system.
19. Explain the mechanism of breathing with the help of labelled diagram
involving both stages—inspiration and expiration.
20. Explain the process of exchange of gases with the help of a diagrammatic
representation in human respiratory system.
Case Based/Source/Competency focussed Question
 (4 Marks each)
21. Breathing is a physical phenomenon where oxygen from the atmosphere is
exchanged with the carbon dioxide produced by the cells. Various organisms

Breathing and Exchange of Gases 213

 have different mechanisms for breathing depending upon their needs and
habitat. For example, lower invertebrates like sponges exchange gases by
simple diffusion while earthworms use cuticle and insects have a network
of tubes to transport atmospheric air within the body. Special vascularized
structures called gills are used by aquatic arthropods and molluscs whereas
vascularised bags called lungs are used by terrestrial forms for the exchange
of gases. Fishes use gills while birds and mammals have lungs and amphibians
use their moist skin to exchange gases.
1. Assertion (A) : Breathing is different from respiration.
Reason (R) : Breathing is physical and respiration is biochemical.

(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) are true, but (R) is not the explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
2. Why is the mechanism of breathing different for different organisms?
(a) To meet their needs
(b) To help them adapt to their environment
(c) To suit their mode of life
(d) All of the above
3. What special name is given to the vascularised bags of terrestrial animals
and vascularised structures of aquatic arthropods and molluscs?
(a) Gills and lungs respectively
(b) Lungs and trachea respectively
(c) Lungs and gills respectively
(d) Gills and trachea respectively
4. How do lower invertebrates like sponges exchanges gases?
(a) Diffusion
214 Biology Class - 11
 (b) Osmosis
(c) Breathing
(d) Cuticle exchange
5. Assertion : The larynx is called the sound box.
Reason : The larynx is a cartilaginous box that helps in sound production.

(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) are true, but (R) is not the explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
(Select Response Type) Assertion reasoning type questions :(1 marks each)
DIRECTIONS : In the following questions, a statement of assertion (A) is
followed by a statement of the reason (R). Mark the correct choice as :
(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) are true, but (R) is not the explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
22. Assertion : Most fishes, when out of water die of suffocation.
Reason : Atmospheric air contains far less oxygen content then the dissolved

oxygen in water.
23. Assertion : Aerobic animals are not truly aerobic.
Reason : They produce lactic acid anaerobically.

24. Assertion : During inspiration pressure of air falls in the thorax.
Reason : There is a rise in the volume of the thorax during inspiration.

25. Assertion : Symptoms of emphysema develops when a person living on
planes ascends and stays on a mountain.

Breathing and Exchange of Gases 215

 Reason : Air pressure and partial pressure of oxygen increases with the rise

in altitude.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (c) Larynx (Sound box)
2. (d) Four molecules of O2.
3. (c) Pleura. It reduces the friction and the two pleura together protect the
lungs.

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Alveoli of lungs.
5. Cigarette smoking damages alveolar walls due to alveolar sacs abnormal
distension, leading to decreased respiratory surface for exchange of gases.
6. Diffusion.
7. Amino group of reduced haemoglobin combines with CO2 forming
carbaminohaemoglobin to transport CO2.
8. External and internal intercostals muscles, situated between ribs.
9. During swallowing a cartilaginous flap like structure called epiglottis covers
the glottis and prevents the entry of food into respiratory tract.

10. In simple solution form through plasma.

Short Answers-I (2 marks each)

11. Refer fig 17.4, page 273 (NCERT Text Book Class XI Biology)
12. Refer table 17.1, page 272 (NCERT Text Book Class XI Biology)
13. (a) Body surface (b) lungs (c) skin and lungs (d) Network of trachea
14. Refer Topic 17.6 at page 275 (NCERT Text Book Class XI Biology)

216 Biology Class - 11

15. Slow oxidation of food to release energy is called respiration while breathing
is a biophysical process which is the first step of respiration.

Short Answers-II (3 marks each)

16. Refer Support Material Points to remember.

17. Refer Support Material Points to remember.

Long Answers-II (5 marks each)

18. Refer Support Material Points to remember.
19. Refer Support Material Points to remember.
20. Refer Support material ‘Points to remember’ of this chapter.
21. 1. (a)
2. (d)
3. (c)
4. (a)
5. (a)

Short Answers-II (3 marks each)

22. (c)
23. (a)
24. (a)
25. (d)


Breathing and Exchange of Gases 217

 Points To Remember
Blood : A special connective tissue that circulates in principal vascular
system of man and other vertebrates consisting of fluid matrix, plasma and formed
elements (Blood = Plasma + All blood cells).
Plasma : (Blood – All blood cells = Plasma) The liquid part of blood which
is straw coloured, viscous fluid and contains about 90-92% of water and 6-8%
proteins.
Lymph : A clear yellowish, slightly alkaline, coagulable tissue fluid,
containing white blood cells (Only lymphocytes), a liquid resembling blood
plasma.
Serum : Blood plasma from which fibrinogen and other clotting factors
have been removed. [Plasma– (fibrinogen & other clotting factor)] = blood serum.
Heart Beat : The rhythmic contraction and relaxation of the heart, which
includes one systole (contraction phase) and one diastole (relaxation phase) of
the heart. Heart beat count of healthy person is 72 times per minute.
Stroke Volume : The volume of blood pumped out by the heart during a
systole. It is approximately 70 ml.
Cardiac output : The amount of blood pumped by heart per minute is called
cardiac or heart output. The value of cardiac output of a normal person is about
72 × 70 = 5040 mL or about 5L per minutes.
Cardiac Cycle : The rhythmic contraction and dilation of different parts of
heart in one beat.
Systole : Contraction of heart muscles.
Diastole : Relaxation of heart muscles
Formed Elements : Erythrocytes, leukocytes and platelets are called blood
corpuscles or formed elements.

218 Biology Class - 11

TYPES OF BLOOD CELLS THEIR NUMBER, STRUCTURE & FUNCTIONS
Name and Number/ Structure Life Span and Function
Percentage Formation

(A) Erythrocytes RBCs Red colour Formed from birth Transport of oxygen
- 4.5 to 5.5 million Circular, biconcave onward by red bone and some amount
per cubic millimetre of denucleated, elastic marrow Life-120 days of carbon dioxide
blood lack of cell organelles excess RBCs are through haemoglobin
like ER, ribosomes, stored in spleen
mitochondria etc.
(B) Leucocytes Colourless rounded Formed in red bone Acts as soldiers
(WBCs) 5000-8000 or irregular, marrow, Lymph scavenger and some
per cubic mm of nucleated 12 to nodes, spleen and help in healing
blood 20mm wide thymus, life-1-4 days

(i) Agranulocytes Large rounded Lymph nodes, Non Phagocytic

(a) Lymphocytes 20-45% nucleus, 6-10 mm spleen, thymus red secrete antibodies
of leucocytes bone marrow, life few
days to months or
even years
(b) Monocytes 6-8% of Largest of all (12-15 Red Bone marrow, phagocytic, very
leucocytes, mm) bean shaped life 10-20 hours motiles engulf
nucleus germs
(ii) Granulocytes
(a) Eosinophils 2-3% bilobed nucleus, Red Bone marrow, play role in immunity
of leucocytes granules in cytoplasm life 4 to 8 hrs. in non phagocytic
blood
(b) Basophils 0-5% of Three lobed nucleus Red Bone marrow, release heparin and
leucocytes (s-shaped) life 4 to 8 hours in histamine
blood
(c) Neutrophils 60-65% Many lobed nucleus Red Bone marrow, phagocytic, engulf
of leucocytes fine granules life 4 to 8 hours in germ and dead cells
blood
(C) Platelets Colourless, rounded Red Bone marrow help in blood clotting
thrombocytes or oval, or irregular worn out ones
1,50,000-3,50,000 per non-nucleated phagocytized in blood
cubic mm of blood fragments

Body Fluids and Circulation 219

 Blood Pressure—The resistance offered by the lumen of the artery to the
flow of Blood.
Hypertension : The condition when blood pressure is higher than normal
(120/80 mmHg)
Electrocardiograph : (ECG) the machine used to record electrocardiogram.
Electrocardiogram ECG : The print out of pattern of heart beat taken on
a graph paper from Electrocardiograph. (ECG machine)
Lymph (Tissue Fluid)
The colourless mobile fluid connective tissue drains into the lymphatic
capillaries from the intercellular spaces. It is formed by squeezing of blood through
capillaries, within tissues. Its flow is unidirectional i.e., from tissues to heart.
Composition : It is composed of fluid matrix, plasma having only lymphocytes
of white blood corpuscles or leucocytes.
Functions : (i) It drains excess of tissue fluid from extra cellular spaces
back into the blood.
(ii) It contain lymphocytes and antibodies.
(iii) It transport digested fats.
Blood Clotting : Coagulation of Blood : (Cascade process)
(Stimulus)® Injured Tissue Blood Platelets
Releases Disintegrate
↓ and release ↓
Thromboplastins Platelet thromboplastin
Ca++ Proteins Ca+ Proteins

↓ ↓
Thrombokinase
Inactivates heparin and
catalyses
Ca++
Prothrombin Thrombin
↓ Catalyses
Fibrinogen Fibrin
↓ Fibrin + entangled and
damaged elements of blood
↓
Clot or Coagulum
220 Biology Class - 11
Functions of Blood
Transport, of food, respiratory gases (O2 and CO2), hormones, metabolic
intermediates, waste products, supply of raw materials, regulation of water balance,
regulation of pH and body temperature, and provides immunity.
Blood Groups : Based on presence of Antigens and Antibodies in blood.

Blood Antigen (on Anti body : (in Possible recipients Possible donors Remarks
Group the Surface plasma) having blood group having blood
of R.B.Cs) group

A A Anti B A, AB O, A —

B B Anti A B, AB O, B, —

AB A and B None AB O, A, B, AB Universal

recipient

O None Anti A and O, A, B, AB O Universal
Anti B Donor

Rh (Rhesus) Group :
• Rh positive (Rh + ve) – Rh antigen similar one present in rhesus monkey.
Observed on the surface of RBCs (nearly 80% of humans)
• Rh negative (Rh–ve) – those in whom this antigen is absent.
• Compatibility is crucial during transfusion and pregnancy because if Rh -ve
person is exposed to Rh +ve blood it forms specific antibodies against Rh
antigens.
Rh incompatibility in pregnancy
1st PREGNANCY
Rh+ve (Father) First newborn Rh +ve (safe)
No mixing of two bloods due to placenta
Rh-ve (Mother) Foetal maternal blood mixes during delivery But mother (Rh-ve) prepares
Rh+ve (Foetus) antibodies
against Rh factor
2nd PREGNANCY
Rh+ve (Father)
Antibodies leak into the blood of foetus Destroy foetal RBCs
Rh-ve (Mother)
Leads to erythroblastosis foetalis
Rh+ve (Foetus)

Body Fluids and Circulation 221

 → SAN (Sino-atrial node) : A patch of tissues present in the right upper
corner of the right atrium, acts as pacemaker due to having a unique property of
self excitation.

→ AVN (Atrio Ventricular Node) : A mass of tissues seen in the lower

left corner of the right atrium close to the atrio-ventricular septum. Fresh wave of
contraction generated here, passes over both the ventricles simultaneously along
the bundle of HIS.

Human Heart

] = Pericardium
Human Heart
 It is the mesodermally derived organ situated in thoracic cavity in between
the two lungs. Protected by a double membrane covering called Pericardium.
 Four chambers–two (left and right) atria, and two ventricles (left and right)
 Inter-atrial septum separates the two atria and inter ventricular septum
separates the two ventricles, while the atria and ventricles are separated by
atrioventricular septum.
 The valves between right atrium and right ventricle is tricuspid while between
left atrium and left ventricle is bicuspid or mitral value.
 The opening of the right ventricle into the pulmonary artery and the opening
of left ventricle in to aorta are guarded by semilunar values.

222 Biology Class - 11

  The valves allow the flow of blood only in one direction, i.e., from atria to
ventricles and from ventricles to pulmonary artery or aorta.
Heart Valves
Tricuspid Valve : The valves formed of three muscular flaps or cups, which
guard the opening between the right atrium and the right ventricle.
Bicuspid Valve (Mitral Valve) : The valves which guard the opening
between the left atrium and the left ventricle, made up of two flaps.
Semilunar Valves : The valves present at the opening of the right and the
left ventricles and allow the entry of blood into pulmonary artery and the aorta
respectively.
ECG
Electrocardiogram ECG : The graphic record of the electric current
produced by the excitation of the cardiac muscles. It is composed of a ‘P’ wave,
‘QRS’ wave. (complex) and ‘T’ wave.
Standard ECG and Reading of ECG : ‘P’ Wave represents the electrical
excitation (or depolarisation) of the atria and leads to the contraction of both the
atria.

Diagrammatic presentation of a standard ECG.

‘QRS’ complex : represents the depolarisation of the ventricles, which

initiates the ventricular contraction.
‘T’ Wave : represents the return of the ventricles from excited to normal
state (repolarisation). The end of T-wave marks the end of sytole.

Double circulation :
Right Deoxygenated Oxygenated
Ventricle Lungs Left
Blood Blood Auricle
Pulmonary Circulation

Systemic circulation
Right Deoxygenated Oxygenated
Body
Auricle Blood (Except Lungs Blood Left
Ventricle

Body Fluids and Circulation 223

CARDIAC CYCLE : The rhythmic contraction and dilation of different parts
of heart in one beat.
Systole : contraction of heart muscles.
Diastole : relaxation of heart muscles.
q Joint diastole :-All chambers of heart in relaxed state.
• Tricuspid and bicuspid valves– open
• Blood from pulmonary vein and vena cava flows into left and
right atrium respectively.
q Atrial systole :- contraction of atrias
• SAN generates action potential to stimulate atrias to contract
simultaneously
• Blood flows to respective ventricles
q Ventricular systole : contraction of ventricles
• AV node and AV bundle conduct the wave of contraction to the
ventricles via bundle of HIS.
• Ventricles contract as a closed chamber (as AV valves and
semilunar valves are close).
• Pressure of blood opens the semilunar valves and blood flows to
respective arteries.
q Joint diastole : Relaxation of all chambers.
HEART SOUNDS
• Closure of bicuspid and tricuspid valves produces first heart sound
‘lub’
• Closure of semilunar valves produces second heart sound ‘dub’
Disorders of circulatory System
Hypertension (High blood Pressure) : It results from narrowing of arterial
lumen and reduced elasticity of arterial walls in old age. It can cause rupturing of
capillaries. It is a silent killer.
Coronary Artery Disease : (CAD) Atherosclerosis. The supply of the blood
to heart muscles is affected. It is caused by deposits of Calcium, fat, cholesterol
and fibrous tissues to make the lumen of arteries narrower.
Angina Pectoris : Caused due to arteriosclerosis, when not enough oxygen
is reaching the heart muscle due to which the person experiences acute chest pain.

224 Biology Class - 11

 Heart attack : Caused when the heart muscle is suddenly damaged by an
inadequate blood supply.
Cardiac arrest : The state in which the heart stops beating.
Arteriosclerosis : The state of hardening of arteries and arterioles due
to thickening of the fibrous tissue and consequent loss of elasticity. It causes
hypertension.

Questions

(SRT) Select Response Type Question (1 mark each)

1. Which instrument is used to measure blood pressure?
(a) Barometer (b) Sphygmomanometer
(c) BOD meter (d) none of these
2. State true or false
“A lymph node is specialized structure in lymphatic vessel concerned with
filtration of foreign bodies by the lymphocytes.”
3. QRS complex of Electron cardio gram represents
(a) Ventricular systole (b) Joint diastole
(c) Joint systole (d) Ventricular diastole
4. The carbonic acid in RBCs is synthesised by the enzyme
(a) RUBISCO (b) Lipase
(b) Carbonic anhydrase (d) Acetyl co transferase.

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
5. What is systemic circulation ?
6. Give two examples of extra-cellular fluids.
7. What name is given to the blood vessels which generally bring blood to an
organ ?
8. Which adrenal hormone accelerates heart beat under normal conditions ?

Body Fluids and Circulation 225

 9. Name the blood vessel that carries blood from the intestine to liver.
10. Define cardiac cycle.
11. Name the protein found in RBCs.
12. What happens to a person suffering from hemophilia ?

Short Answer Questions-I (2 marks each)

13. Explain when and how the two sounds of heart are produced.
14. Define joint diastole. What are constituents of the conducting system of
human heart ?
15. Give the names of various types of formed elements present in the blood.
Short Answer Questions-II (3 marks each)
16. Why is the SA node called pacemaker of the heart ? Write its full from.
17. Draw a diagram showing schematic plan of blood circulation in human.
18. In the following diagram of section of a human heart, label a, b, c, d, e
and f.

19. What is lymph ? Describe its circulation in brief.

20. What is stroke volume ? What is its relation with cardiac output ?
21. A person suffering from fever is advised to take blood test. What may happen
to his WBC count and why ?

226 Biology Class - 11

Long Answer Questions (5 marks each)
22. Neena is having blood group A-ve while her husband’s blood group is O +ve.
Their first child is having blood gp. A +ve. Her second child was born with
severe anemia and jaundice. What could be the reason ? How this situation
could have been avoided ?
23. Draw a diagram to show the internal structure of human heart. Lable any
two heart chambers, any two heart valves and chordae tendinae in it.
24. Describe the structure of human heart.
25. What is cardiac cycle ? Describe the event that occur during it.
26. Explain Rh grouping and its incompatibility in humans.

Case Based/Competency Based Questions(5 marks each)

27. Blood is a fluid connective tissue made up of fluid matrix plasma, and formed
elements, Red blood cells, (erythrocytes) white blood cells (leukocytes),
and platelets (thrombocytes) constitute the formed elements. The blood of
humans is grouped into A, B, AB and O systems based on the presence or
absence of two surface antigens A, B on the RBCs. Another blood grouping
is also done based on the presence or absence of another antigen called
Rhesus factor (Rh) on the surface of RBCs. The spaces between cells in the
tissues contain a fluid derived from the blood called tissue fluid this fluid
called lymph is almost similar to blood except for the protein content and
the formed elements.
1. Why is blood called a fluid connective tissue?
(a) Because of fluid matrix plasma
(b) Because of osteocytes
(c) Because of the solid matrix
(d) None of the above
2. Name the formed elements of blood.
(a) RBCs, WBCs only (b) Platelets only
(c) Plasma only (d) RBCs, WBCs and Platelets
3. Which blood group is considered a universal donor and why?
(a) A (b) B
(c) AB (d) O

Body Fluids and Circulation 227

 4. Name the complication which arises when a Rh+foetus is developing the
womb of a Rh-mother.
(a) Erythroblastosis foetalis
(b) Angina
(c) Cardiac arrest
(d) None of the above
5. Give the basic difference between tissue fluid and blood.
(a) Tissue fluid has no proteins
(b) Tissue fluid has no RBCs
(c) Tissue fluid has no WBCs and platelets
(d) All of the above

Assertion & Reason Question (SRT)  (1 marks each)

DIRECTIONS : In the following questions, a statement of assertion (A) is
followed by a statement of the reason (R). Mark the correct choice as :
(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) true, but (R) is not the correct explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
28. Assertion : Blood coagulates in uninjured blood vessels.
Reason : Uninjured Blood vessels release an anticoagulant Heparin.

29. Assertion : Left atrium possess the thicket muscles.
Reason : Left atrium receives blood from the lungs.

30. Assertion : In the human heart there is no mixing of oxygenated and
deoxygenated blood.
Reason : The presence of valves in the heart allows the movement of blood

in one direction.

Answers
(SRT) Select Response Type Question (1 mark each)
1. (b) Sphygmomanometer. 2. True

228 Biology Class - 11

 3. (a) QRS waves denotes ventricular contraction
4. (c) Carbonic anhydrase.
Very Short Answer (1 mark each)
5. The kind of blood circulation that is concerned with the supply of oxygenated
blood from the left ventrical to all body parts and return of oxygenated blood
to the right atrium of heart.
6. Interstitial fluid and blood plasma.
7. Afferent blood vessel.
8. Noradrenalin.
9. Hepatic portal vein.
10. A regular sequence of three events (i) auricular systole (ii) ventricular systole
and (iii) Joint diastole during the completion of one heart beat.
11. Haemoglobin.
12. The person suffering from haemophilia lacks clotting factors in blood, which
result the defective clotting mechanism. In case of injury the person is at a
risk of blood loss.
Short Answer-I (2 mark each)
13. (i) ‘Lubb’ the first sound which is low pitched, is caused by the closure of
bicuspid and tricuspid valves.
(ii) ‘Dub’ the second sound which is high pitched, is caused by the closure
or semilunar valves.
14. In a cardiac cycle when both atria and ventricles are in a diastole and are
relaxed simultaneously is called a joint diastole.
Conducting system constitutes : SA node → AV node → Bundle of His →
Purkinje fibres.
15. Erythrocytes, lymphocytes, monocytes, neutrophils, eosinophils, basophils
and platelets.
Short Answer-II (3 marks each)
16. SA node being self excitatory initiate a wave of contraction in the heart.
SA node — Sino–Atrial Node.
17. Refer Support material Points to remember.

Body Fluids and Circulation 229

18. Refer Support material Points to remember.
19. Refer Points to remember of support material.
20. During one cardiac cycle or one heart beat the volume of blood pumped by
the heart is called stroke volume. This is normally 70 mL.
In one minute the heart beats about 72 times and the amount of blood pumped
per minute is called cardiac output. This is usually 4900 mL. or 5 litres.
21. The WBC count of this person may show an increase from the normal range.
As pathogens may be present in his body, so the body is producing more
WBCs to fight against those pathogens. WBC count is a good tool to asses
the presence of infection in a sick person.
Long Answer (5 marks each)
22. During her first pregnancy after exposure with blood of her first Rh +ve
child, her body prepared antibodies against Rh antigen in her blood. In second
pregnancy these Rh antibodies from mother leaked into the blood of foetus
(Rh +ve) and destroyed foetus RBCs. It could cause of severe anemia and
Jaundice could be fetal to the foetus.
This situation could have been avoided if she had got herself administered
anti Rh antibodies, immediately after first delivery to kill Rh antibodies
entered in mother’s blood from foetus.
23. Refer Points to remember.
24. Refer Points to remember.
25. Refer Points to remember.
26. Refer Points to remember.
Case Based Question (4 marks each)
27. 1. (a) 2. (d) 3. (d)
4. (a) 5. (d)
Assertion & Reason Question (SRT)  (1 marks each)
28. (d)
29. (d)
30. (b)

230 Biology Class - 11
 Points To Remember
Excretory Products : Ammonia (most harmful) it needs large amount of
water for excretion. Urea (less harmful) and Uric acid (least harmful) needs least
amount of water for excretion.
MODE OF EXCRETION
(On the basis of type of excretory end products)

Ammonotelism Ureotelism Uricotelism

• Excretion of ammonia • Excretion of urea • Excretion of Uric acid
• Bony Fishes, Aquatic • Mammals, Many • Snails, Reptiles,
Amphibians & Aquatic Terrestrial Amphibians Birds & Insects.
Insects. & Marine Fishes
Human Excretory System:
Pair of kidney, pair of Ureter, Urinary bladder and Urethra.
Nephron And Its Structure:
The structural and functional unit of kidney is nephron. Each kidney contains
about one million of nephrons. A nephron consist of glomerulus (tuft of capillaries-
JGA juxtra glomerulus apparatus), and renal tubule. Renal tubule consist of
bowman’s capsule, proximal convulated tubule (PCT), loop of henle, distal
convulated tubule (DCT) and collecting Duct.
Structure of Kidney :
Size 10-12 cm in length, 5-7 cm in width, 2-3 cm thick, average weight about
120-170 g.
 The blood vessels, ureters and nerves enter the kidney through hilum

(a notch).
 The outer layer of kidney is a tough capsule.

 The outer zone of kidney is cortex and the inner is medulla.

 The medulla is divided into few conical masses (medullary pyramids)

projecting into calyces.

Excretory Products and their Elimination 231

  The cortex extends between medullary pyramids called columns of Bertini.
Glomerular Filtration :
The filtration of blood in glomerulus, about 1100-1200 ml of blood is filtered
by the kidney per minute.
Glomerular Filtration Rate (GFR) :
The amount of filtrate formed by the kidney per minute is called GFR. In a
healthy individual it is about, 125 ml/minute, i.e. 180 litres per day.
Types of Nephrons :
(i) Juxtamedullary Nephron—About 15% of total nephrons, Glomeruli are
found in inner region of cortex, large in size, long loop of Henle and found
deep in medulla, associated with vasa recta control plasma volume when
water supply is short.
(ii) Cortical Nephron—About 85% of total nephron mainly lie in renal cortex,
glomeruli found in outer cortex, short loop of Henle, extends very little in
medulla. They do not have vasa recta or vasa recta is highly reduced.
Functions of Tubules :
(i) PCT—absorption of all essential nutrients and 70-80% of electrolytes and
water, helps to maintain the pH and ionic balance of body fluids by selective
secretion of H+, ammonia and K+ into filtrate.
(ii) Henele’s Loop—reabsorption in this segment is minimum, it plays a
significant role in maintenance of higher molarity of medullary interstitial
fluid.
(iii) DCT—conditional reabsorption of Na+ and water takes place here,
reabsorption of HCO3– and selective secretion of H+ and K+ and ammonia
to maintain the pH and sodium-potassium balance in blood.
(iv) Collecting duct—Large amount of water is absorbed from this region to
produce concentrated urine, it plays a role in maintenance of pH and ionic
balance of blood by selective secretion of H+ and K+ ions.
Steps of Urine Formation
1. Glomerular Filtration—Blood is filtered by glomerulus through three
membranes i.e., endothelium of blood vessel, filtration slits of Bowman’s
capsule and basement membrane between these two layers. This filtration
is called ultrafiltration as all constituents of plasma comes into filterate except
proteins.

232 Biology Class - 11

 2. Reabsorption—90% of filtrate is reabsorbed by the renal tubules by active
or passive mechanism.
It is evident by the fact that out of 180L of filtrate formed per day only 1.5
L of urine released.
3. Secretion—Tubular cells secrete H+, K+, ammonia into the urine. It maintains
acid-base balance of body fluids.

Mechanism of concentration of the Filtrate (Countercur-

rent Mechanism) :
NCERT-Class XI Biology
 This mechanism is said to be countercurrent mechanism because the out

flow (in the ascending limb) runs parallel to and in the opposite direction of
the inflow (in the descending limb).
 NaCl is transported by the ascending limb of Henle’s loop which is exchanged

with the descending limb of vasa-recta. (Capillaries running parallel to loop

of hence)
 NaCl is returned to the interstitium by the ascending portion of vasa recta.

 Henle’s loop and vasarecta as well as the counter current in them help to

maintain an increasing osmolality towards the inner medullary interstitium

i.e., from 300 mosmol/L in cortex to about 1200 mosmol/L in inner medulla.
 Small amount of urea enter, the thin segment of ascending limb of Henle’s

loop which is transported back to the interstitium by the collecting tubule.

 This mechanism helps to maintain a concentration gradient in the medullary

tubule interstitium.
ADH (ANTIDIURETICHORMONE)
(VASOPRESSIN)

Decrease in body fluid volume Increase in body fluid volume

Activation of osmoreceptors Switch off the osmoreceptors

Stimulation of hypothalamus. Signal to hypothalamus

Release of ADH (from posterior pituitary gland) Supress the ADH release

Facilitates water reabsorption from DCT. Reduce water reabsorption

Prevent Diuresis
(Excessive loss of water from body

Excretory Products and their Elimination 233

  It helps in an easy passage of water from the collecting tubule to concentrate
the filtrate i.e. urine.

Renin Angiotensin System

Fall in GFR
↓ Renin from JG cells
Angiotensinogen → Angiotensin I → Angiotensin II
↓ Acts on
Adrenal Cortex
↓ Secretes aldosterone
Reabsorption of Na+ and water
from DCT
↓
Increase in GFR
Atrial natriuretic factor (ANF)
• Increase in blood flow to Atria of heart release of ANF.
• Causes vasodilation and thus decrease blood pressure.
• ANF acts as a check on renin-angiotensin mechanism.
Micturition :
The expulsion of urine from the urinary bladder is called micturition. It is a
reflex process but can be controlled voluntarily up to some extent in grown up
children and adults.
 The CNS (Central Nervous System) sends the signal which cause the

stretching of the urinary bladder when it gets filled with urine.

 In response, the stretch receptors on the walls of the bladder sends signals

to the CNS.
 The CNS passes on motor message to initiate the contraction of smooth

muscles of the bladder and simultaneous relaxation of the urethral sphincter

causing the release of urine.
And cause release of urine by contraction of smooth mucle of urinary bladder.
Urine is slightly acidic in pH 6.0 and yellow in colour due to urochrome
pigment derived from breakdown of haemoglobin from worm out RBCs.
 An adult human excretes on an average 1 to 1.5 Litres of urine per day.

 On an average 25-30 gram of urea is excreted out per day.

234 Biology Class - 11

Role of other organs in excretion :
 Lungs—removes CO2 (18L/day) and water.
 Liver—secretes bilirubin, biliverdin etc. helps to eliminate these substances
along. with cholesterol, vitamins, drugs and degraded steroid hormones
through digesive wastes.
 Sweat and sebaceous glands—These glands of skin help to eliminate small
amount of urea, NaCl and lactic acid etc. through sweat while sebaceous
glands help to eliminate some substances like steroids, hydrocarbons and
waxes through sebum.
 Saliva—It can help to eliminate small amount of nitrogenous wastes.

Disorders of Excretory system :

 Uremia—The accumulation of urea in blood due to malfunctioning of kidney.
Hemodialysis—The process of removal of urea from the blood artificially.

In this process the blood from an artery is passed into dialysing unit after
adding an anticoagulant like heparin. The blood passes through coiled
cellophane tube, surrounded by dialysing fluid. The nitrogenous wastes form
the concentration gradient and the blood becomes clear. This blood is pumped
back to the body through vein after adding anti-heparin to it.
 Renal calculi—The formation of insoluble mass of crystallised salts (oxalates
or phosphates of calcium).
 Glomerulonephritis—Inflammation of glomeruli of kidney.
Kidney Transplantation
 Kidney transplantation is done in a patient in which both the kidneys fail to work
i.e. at total failure of kidney. Kidney transplantation is the ultimate method for
treatment of renal failure. In case of kidney transplantation both the damaged kidneys
of patient are removed by surgery. And a functional kidney from a healthy donar
preferably from close relative is taken and transplanted in the body of patient. After
successful transplantation the patient and donar can survive on one kidney.
Precautions taken for successful transplantation of Kidney :
1. Kidney should be taken from a healthy donor preferably from close relative.
2. Matching of blood group and other factor and compatibility should be done
carefully before transplantation.

Excretory Products and their Elimination 235

3. The patient (recipient) has to take some prescribed medicines
immunosuppressants through out the life to suppress the immune system.

Questions

(SRT) Select Response Type Question (1 mark each)

1. Which gland secrete sebum?
(a) lacrymal (b) Adrenal
(c) sebaceous gland (d) Thymus
2. A part of Henle’s Loop is impermeable to water that is
(a) decending limb (b) ascending limb
3. State true or false:
Sodium chloride, lactic acid, glucose are the constituent of the human sweat
beside water.
CONSTRUCTED RESPONSE TYPE (CRT)
Very Short Answer Questions (1 marks each)
1. Which gland secretes sebum ?
2. One part of loop of Henle’s is impermeable to water. Name it.
3. Besides water, name any two contents of human sweat.
4. Explain the function of vasa recta.
5. Name two types of nephrons found in human kidney.
6. Define GFR (Glomerular Filtration Rate).
7. The mechanism of concentration of filtrate is also known as counter current
mechanism. Justify the statement.
8. What is micturition ?
9. Write the function of hormone ‘renin’ produced by kidney.
10. Name the excretory product of (i) reptiles (ii) Prawns (iii) Tapeworm
(iv) Marine fish (v) Insects (vi) Birds.
11. What is vasa recta ?
Short Answer Questions-I (2 marks each)
12. Mark the odd ones in each of the following—
(a) Renal pelvis, medullary pyramid, renal cortex, ureter.
(b) Afferent arteriole, Henle’s loop, vasa recta, efferent arteriole.
(c) Glomerular filtration, antidiuretic hormone, hypertonic urine, collecting duct.
(d) Proximal convoluted tubule, distal convoluted tubule, Henle’s loop
renal corpuscle.

236 Biology Class - 11

13. In the following diagram of longitudinal section of kidney (Fig.–i) identify
and label a, b, c and d respectively.

fig. (i) fig. (ii)

14. In the diagram (Fig.-ii) showing malpighian body (renal corpuscle) identify
and label p, q, r, s.
15. Name two metabolic disorder which can be diagnosed by analysis of
urine.
Short Answer Questions-II (3 marks each)
16. In the following diagram (Fig.-3) showing structure of a nephron label a, b,
c, d, e and f.

17. Describe the hormonal feed back circuit in controlling the renal functions.
18. Give three points of difference between Rennin and Renin.

Excretory Products and their Elimination 237

19. What are ammonotelic, ureotelic and uricotelic animals ? Give an example
of each type of these.
20. Why is urine formation less during summers ?
Long Answer Questions (5 marks each)
21. Draw a labelled diagram of human urinary system and write one function
each of adrenal gland, ureter, urinary bladder, kidney and urethra.
22. Describe how urine is formed in the nephron through filtration reabsorption
and secretion.
OR
Explain the steps involved in the process of urine formation.
23. Distinguish between (i) Uricotelism and Ureotelism (ii) Sebum and sweat
(iii) Proximal and distal convoluted tubules (iv) Ascending and descending
limbs of Henle’s loop (v) Cortical and Medullary nephrons.

24. Explain the process of reabsorption and secretion of major substances at

different parts of nephron with the help of schematic diagram.

Case Based/Competency Based Question (4 marks)

25. For the regulation of glomerular filtration rate (GFR) the kidneys have a
built-in mechanism. One such efficient mechanism is known as renin-
angiotensinogen system and is carried out by the distal convoluted tubule
and the afferent a arteriole at the location of their contacts. Fall in GFR can
stimulate the JG cells to release renin which can stimulate the glomerular
blood flow and thereby bring the GFR back to normal. An increase in blood
flow in the atria of the heart can cause the release of the Atrial natriuretic
factor (ANF). This causes vasodilation of blood vessels and thereby decreases
the blood pressure. ANF mechanism, therefor, acts as a check on renin-
angiotensin mechanism.
1. Why is GFR called ultrafiltration?
(a) As it is very efficient
(b) As it is using ultraviolet rays of filtration
(c) As all constituent of plasma come into filtrate except proteins
(d) All of the above

238 Biology Class - 11

 2. Where is JGA located?

(a) Below renal corpuscle

(b) At Henle’s loop

(c) At the contact region between distal convoluted tubule and afferent
arteriole.

(d) Below glomerulus

3. Give the causes of the release of ANF.

(a) Decrease in blood flow to the atria of the heart

(b) Increase in blood flow to the atria of the heart

(c) Decrease in blood flow to the ventricle of the heart

(d) Increase in blood flow to the ventricle of the heart

4. Which mechanism can act as a check on renin-angiotensin mechanism?

(a) Self-check and control

(b) Atrial natriuretic factor

(c) Parasympathetic system

(d) Vasopressin factor

5. What do JG cells release to control GFR?

(a) Renin

(b) Rennin

(c) Angiotensin

(d) Antidiuretic hormone

(SRT) Assertion reasoning type questions-II (1 marks each)
DIRECTIONS : In the following questions, a statement of assertion (A) is
followed by a statement of the reason (R). Mark the correct choice as :
(a) If both (A) and (R) are correct and (R) is the correct explanation of (A)

Excretory Products and their Elimination 239

 (b) If both (A) and (R) true, but (R) is not the correct explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
26. Assertion : In cortical nephrons vasa recta is absent or highly reduced.
Reason : Cortical nephrons are mainly concerned with the concentration of
urine.
27. Assertion : Compared to uric acid, urea is a more toxic excretory substance.
Reason : Birds and insects are uricotelic animals.
28. Assertion : Vasopressin increases the water permeability of the distal
convoluted tubule.
Reason : In absence of ADH, water reabsorption is considerably reduced.

Answers
(SRT) Select Response Type Question (1 mark each)
1. (c) Sebaceous glands (wax-glands)
2. (b) Ascending limb
3. True

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer (1 mark each)
4. It helps to retain reabsorbed ions and urea in the interstitial fluid of the
medulla, to maintain its high osmotic pressure.

5. (i) Juxta medullary nephron (ii) Cortical nephron

6. The amount of filtrate formed by the kidney per minute.

7. In the ascending limb, the outflow runs parallel to and in the opposite direction
of the inflow in the descending limb.

8. The act of passing out urine from urinary bladder.

9. Renin is used to convert angiotensinogen to angiotensin.

240 Biology Class - 11

10. (i) Uric acid (ii) Ammonia (iii) Ammonia (iv) Urea (v) Uric Acid
(vi) Uric acid.

11. Capillary network running parallel to loop of Henle is known as Vasa recta.

Short Answer-I (2 marks each)

12. (a) Ureter (b) Henle’s loop (c) Glomerular filtration (d) Renal Corpuscle.

13. Refer fig. 19.2, page 292 (NCERT Class XI-Biology)

14. Refer fig. 19.4 page 293 (NQERT class XI-Biology)

15. Glycosuria, Ketonuria

Short Answer-II (3 marks each)

16. Refer fig. 19.3, page 292, (NCERT class XI-Biology)
17. Refer content 19.5, page 297 (NCERT class XI-Biology).

18. Rennin Renin

(i) It is a proteolytic enzyme. (i) It is a hormone that acts as an enzyme.
(ii) It helps in the digestion of milk (ii) It converts the protein angiotensinogen
protein. into angiotensin
(iii) It is secreted as an inactive (iii) It is secreted as renin.
form Prorennin which is
activiated to rennin by HC1.
(iv) Its secretion is stimulated by (iv) It secretion is stimulated by a reduction
food. of Na+ level in tissue fluid.

19. Refer content given in the beginning of the chapters of NCERT Text Book
page 290 class XI-Biology or Points to remember of this support material.
20. Due to sweating in summers blood volume is decreased. ADH is secreted
from hypothalamus which increase reabsorption from D.C. tubules thus
amount of urine is decreased.

Excretory Products and their Elimination 241

Long Answer (5 mark each)
21. Support Material Points to Remember.
22. Refer content points to remember of this support material.
23. Refer the content given in Points to remember of this chapter of support
material.
24. Refer Support material points of remember.

25. 1. (c) 2. (c)

3. (c) 4. (b)

5. (a)

SRT Questions II Answers.

26. (c)

27. (b)

28. (b)



242 Biology Class - 11

 Points To Remember
Arthritis : an inflammatory joint disease characterised by inflammation of
joints.
Coccyx : tail bone formed by fusion of four coccygeal vertebrae in man.
Dicondylic Skull : A Skull with two occipital condyles.
Endo Skeleton : A skeleton present in side the body.
Fascicle : Bundles of muscles fibres held together by connective tissue.
Fascia : Collagenous connective tissue layer that surrounds muscle bundles.
Floating ribs : The ribs that remain free anteriorly, (last 2 pairs)
False ribs : 8th, 9th and 10th pair of ribs not directly joins the sternum but
to seventh pair of ribs, hence called pseudoribs.
Myoglobin : A red colored pigment present in sarcoplasm of muscle.
Sarcomere : A portion of myofibril between two successive ‘Z’ lines.
Sarcolema : The plasma membrane of a muscle.
Gout : Inflammation of joints due to accumulation of uric acid crystal.
Suture : immovable joints between skull bones.
Synovial joints : Freely movable joints between limb bones.
Patella : A seasmoid bone acting as kneecap.
Intervertebral disc : Fibro cartilaginous pad present between the vertebrae
that act as shock absorbers.
Tendon—Connective tissue made of yellow fibrous tissue which connect
muscle to bone. It is not flexible.
Ligament—Connective tissue made of white fibrous tissue which joins two
bones. It is flexible.
LMM : Light meromyosin
HMM : Heavy meromyosin
Types of Movement :

Locomotion and Movement 243

 1. Amoeboid movement : These movements takes place in phagocytes where
leucocytes and macrophages migrate through tissue. It is affected by
pseudepodia formed by the streaming of protoplasm (as in amoeba)
2. Ciliary movement : This movement occurs in internal organs which are
lined by ciliary epithelium.
3. Muscular Movement : This movement involves the muscle fibers, which
have the ability to contract and relax.
Properties of Muscle : (i) Excitability (ii) Contractility
(iii) Extensibility (iv) Elasticity
Types of Muscles :
(a) Skeletal muscles or striated muscles—These are involved in locomotion
and change of body postures. These are also known as voluntary muscles.
(b) Visceral muscles or smooth muscles—These are located in inner walls of
hollow visceral organs, smooth in appearance and their activity are not under
control of voluntary nervous system. They are called involuntary muscles.
(c) Cardiac muscles—The muscles of heart, involuntary in nature, striated and
branched, These are uninucleated.
Characteristic Skeletal Muscle Smooth Muscle Cardiac Muscle

Location Muscles attached with muscles found in the inner wa- Muscles found only
skeletal components lls of hollow visceral organs in heart.
Appearance Striated having light and unstriped, smooth in Striated in
dark bands. Multi- appearance with tapering appearance and
nucleated ends. Uninucleated branched, uninucleated
Control They are controlled by They are not under the not under the
our will hence called control of our will hence direct control of
voluntary muscles. called involuntary muscles. nervous system.

Structure of myofibril :
 Each myofibril consist of alternate dark and light band.
 Dark band—contain myosin protein and is called A-band or Anisotroic band.
 Light band—Contain actin protein and is called I Band or Isotropic band.
 I Band is bisected by an elastic fiber called ‘Z’ line. Actin filament (thin
filament) are firmly attached to the ‘Z’ lines.
 Myosin filament (thick filament) in the ‘A’ Band are also held together in
the middle of T Band by thin fibrous membrane called ‘M’ line.
 The portion between two successive ‘Z’ lines is considered as functional
unit of contraction and is called a sarcomere.

244 Biology Class - 11

Structure of Actin and Myosin Filament
I-Band

Thin
filament

Thick
filament

1. Actin filament : An actin filament is made of two ‘F’ actins which are
helically wound to each other. Two filaments of tropomyosin protein also
run close to ‘F’ actins throughout its length. A complex protein Troponin is
distributed at regular intervals on tropomyosin which mask the actin binding
site for myosin.
2. Myosin filament : Each myosin filament is a polymer of meromyosin. Each
meromyosin has two components—a globular head with a short arm and a
tail. Head is made of heavy meromyosin while tail is made of light meromyosin.
The head with its short arm project outward at regular distance and angle
from each other and is known as cross arm. The head has an active site for
actin and binding site for ATP.
Red muscle fibres :
— These are red in colour due to presence of high content of myoglobin.
— These contain plenty of mitochondria.
— Sarcoplasmic reticulum is less in these fibres.
— Show slow but sustained contractions for longer periods.

Locomotion and Movement 245

White muscle fibres
— These are pale or whitish due to presence of less content of myoglobin.
— These contain fewer mitochondria
— Sarcoplasmic reticulum is more/high
— During sternous exercise, lactic acid accumulates in large quantity so muscle
fatigues

Mechanism or Muscle contraction : Sliding filament theory

The contraction of muscle fiber takes place by the sliding of actin (thin
filament) on myosin (thick filament)
 Muscle contraction is initiated by a signal sent by the CNS via a motor
neuron.
 Impulse from motor nerve stimulates a muscle fiber at neuro muscular
junctions.
 Neurotransmitter releases here which generates an action potential in
sarcolema.
 This causes release of Ca++ into sarcoplasm. These Ca++ binds with troponin,
thereby remove masking of active site.
 Myosin head binds to exposed active site on actin to form a cross bridge,
utilising energy from ATP hydrolysis.
 This pulls the actin filament towards the centre of ‘A’ band.
 ‘Z’ lines also pulled inward thereby causing a shortening of sarcomere i.e.
contraction.
 I band get reduced, whereas the ‘A’ band retain the length.
 During relaxation, the cross bridge between the actin and myosin break.
Ca++ pumped back to sarcoplasmic cisternae. Actin filament slide out of ‘A’
band and length of I band increase. This returns the muscle to its original
state.

246 Biology Class - 11

Vertebral formulae of man C7T12L5S(5) C(4) = 33
Human skeleton – 206 bones

Axial skeleton (80 bones) Appendicular

skeleton (126 bones)

skull (29 bones) vertebrae (33) 1

cranium-8 face-14 Cervical-7 Sternum Ribs
Ear ossicle-6 Thoracic-12 1 12 pairs (24)
Hyoid-1 Lumber-5
sacral-1 (5-fused to form 1 sacrum)
Caudal-1 (4-coccygeal fused to form 1 coccyx)

Girdles (6 bones) Limbs (120 bones)

Pectoral (2) (Shoulder girdle) Pelvic (Hip girdle) (2)

Clavicle 2 Scapula 2 Coxal (2) Sacrum (2)

= Ilium + Pubis + Ischium

Fore limbs (60 bones) (30 in each limb) Hind limbs (60 bones) (30 in each limb)
Humerus 2×1 = 2 Femur 2 × 1 = 2
Radius 2×1 = 2 Tibia 2 × 1 = 2
Ulna 2×1 = 2 Fibula 2 × 1 = 2
Carpals 2×8 = 16 Patella 2 × 1 = 2
Meta Carpals 2×5 = 10 Tarsals 2 × 7 = 14
Phalanges 2 × (2+3+3+3+3) = 28 Metatarsals 2 ×5 = 10
Digits = 2 × (2 + 3 + 3 + 3 + 3) = 28
Joints

Fibrous joints Cartilaginous joints Synovial joints

do not allow allow very slight Freely
movement movement movable

e.g., joints between e.g., joint between

the bones of skull adjacent vertebrae

Ball and socket Hinge Pivot Gliding Saddle

Joints Joints Joints Joints Joints
e.g., between humerus e.g., knee e.g., Atlas e.g., between e.g., between
and pectroal girdle Joint and axis carpals Carpals and meta
between femur Elbow joint carpals of thumb
and pelvic girdle

Locomotion and Movement 247

 Questions

(SRT) Select Response Type Question (1 mark each)

1. What is the total number of bones present in the left pectoral Jaden and left
arm respectively. In human beings?
(a) 4, 30 (b) 2, 30
(c) 4, 30 (d) 2, 32
2. Skeletal muscles show striation because of
(a) Pattern of troponin and tropomyosin
(b) pattern of actin and kinetin
(c) pattern of actin and myosin
(d) none of these
3. Which pair of ribs are called floating ribs
(a) 9th and 10th (b) 11th and 12th
(c) 7th and 6th (d) 10th and 11th

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. Name the proteins making up dark and light bands of myofibrils.

5. Write the name of chemical that causes fatigue in the muscles.

6. What lubricates the freely movable joints at the shoulder ?

7. Name the longest bone of human body.

8. Give the name of first vertebra.

9. Define a sarcomere.

10. Name the cup shaped bone that constitutes the knee cap.

11. Which muscle fibre work during long flight of eagle ?

12. Name the cavity in the girdle into which the head of femur fits ?

248 Biology Class - 11

Short Answer Questions-I (2 marks each)
13. Write any two difference between cardiac muscle and skeletal muscle.

14. Distinguish between red fibre and white fibre.

15. Name the two types of girdles found in human body and write their role.

16. State the role of calcium ions and ATP in muscle contraction.

17. Name the bones of fore limb (hand) of human body. Give their number in
each limb.
Short Answer Questions-II (3 marks each)
18. What makes the synovial joints freely movable ? List any four types of
synovial joints.
19. Name the category of bones forming the ribcage. How are these articulated
to each other to form the cage ?
20. How are actin and myosin filament arranged in a muscle fibre ?
21. Mention the factor which is responsible for the following :
(i) Tetany (ii) Gout (iii) Osteoporosis
Long Answer Questions (5 mark each)
22. Explain the important steps of sliding filament theory of muscle contraction.
Case Based/Competency based/Value based question
 (4 mark each)
23. The muscle fiber is a syncytium. A characteristics features of the muscle
fiber is the presence of a large number of parallelly arranged filamenls in the
sarcoplasm called myofilaments or myofibril. Each myofibril has alternate
dark and light bands on it. Visceral muscles are located in the inner walls of
hollow visceral organs of the body. They do not have any striation and are
smooth in appearance. Many cardiac muscle cells assemble in a branching
pattern to form cardiac muscle.
(i) Why is muscle fiber called a syncytium?

Locomotion and Movement 249

 (a) As it is aseptate
(b) As it has more than one nuclei
(c) As it has more than one sarcoplasm
(d) As it has dark and light bands
(ii) Give a characteristic feature of muscle fiber.
(a) Presence of myofilaments
(b) Absence of myofilaments
(c) Presence of branching pattern
(d) Spindle shaped appearance

(iii) Name some visceral organs of the human body.

(a) Femur, legs, arms
(b) Oesophagus
(c) Stomach
(d) Both (b) & (c)
(iv) Which type of muscle are located in the inner walls of hollow visceral organs?
(a) Skeletal muscles
(b) Smooth muscles
(c) Cardiac muscles
(d) Smooth muscles & cardiac muscles
(v) Skeletal muscles and smooth muscles are .....
(a) Involuntary and voluntary respectively
(b) Voluntary and involuntary respectively
(c) Both involuntary
(d) Both voluntary
(SRT) Assertion reasoning type questions-II:
DIRECTIONS : In the following questions, a statement of assertion (A) is
followed by a statement of the reason (R). Mark the correct choice as :

250 Biology Class - 11

 (a) If both (A) and (R) are correct and (R) is the correct explanation of (A)
(b) If both (A) and (R) true, but (R) is not the correct explanation of (A)
(c) If (A) is true but (R) is false
(d) If both (A) and (R) are false
24. Assertion : Fatigue is the inability of muscles to relax.
Reason : It is due to lactic acid accumulation by repeated contractions.
25. Assertion : Rapid spasm in the muscle is termed as tetany.
Reason : Tetany is caused by an increase in the blood calcium level.
26. Assertion : Radius is shorter than the ulna.
Reason : It has a large olecranon process.
27. Assertion : First seven pairs of ribs are called true ribs.
Reason : These ribs are not connected ventrally to the sternum.
28. Assertion : Inflammation of a skeletal joint may immobilize the movement
of joints.
Reason : Uric acid crystals in the joint cavity and ossification of articular
cartilage leads to this condition.

Answers
(SRT) Select Response Type Question (1 mark each)
1. (b) Left pectoral girdle has 2 bones. Left Arm has 30 bones.

2. (c) Due to distribution pattern of actin and myosin protein.

3. (b) These ribs are not ventrally attached to sternum

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Actin and myosin

Locomotion and Movement 251

 5. Lactic acid
6. Synovial fluid
7. Femur
8. Atlas
9. A portion of myofibril between two successive ‘Z’ lines.
10. Patella
11. Red muscle fibre
12. Acetabulum
Short Answers-I (2 marks each)
13. Refer Points to remember of support material.
14. Refer Points to remember
15. Pectoral and Pelvic girdle bones help in articulation of the upper and lower
limbs respectively with the axial skeleton.
16. Calcium (Ca++) ions binds with troponin, thereby remove masking sites.
ATP hydrolysis gives energy to Myosin head to bind with active site of actin.
17. Refer Points to remember
Short Answers-II (3 marks each)
18. Refer content points to Remember of support
19. Refer content points to Remember of support
20. Refer content points to Remember of support
21. Refer content points to Remember of support
Long Answer (5 marks each)
22. Refer Points to remember
23. (i) (b)
(ii) (a)
(iii) (d)

252 Biology Class - 11

 (iv) (b)
(v) (b)
(SRT) Assertion Reason II Answers

24. (a)
25. (c)
26. (b)
27. (c)
28. (a)


Locomotion and Movement 253

 Points To Remember
Coordination : Process through which two or more organs interact and
complement the functions of one another surrounding the brain.
Action potential : A sudden change in the electrical charges in the plasma
membrane of a nerve fibre.
Aqueous humour : The thin watery fluid that occupy space between lens
and cornea in eye.
Blind spot : A spot on retina which is free from rods and cones and lack the
ability for vision.
Cerebrospinal fluid : An alkaline fluid present in between inner two layers
of meninges, surrounding the brain and spinal cord.
Cerebellum : A part of hind brain that controls the balance and posture of
the body.
Cochlea : A spirally coiled part of internal ear which is responsible for
hearing.
Corpus callosum : A curved thick bundle of nerve fibres that joins two
cerebral hemisphere.
Depolarisation : A condition when polarity of the plasma membrane of
nerve fibre is reversed.
Endolymph : The fluid filled within membranous labyrinth.
Eustachian Tube : A tube which connect ear cavity with the pharynx.
Fovea : An area of highest vision on the retina which contain only cones.
Meninges : Three sheets of covering of connective tissue wrapping the brain.
Gray Matter : This is the area of processing : Contains cell bodies and their
dendrites (of neurons)
White matter : It provides communication between the grey matter and the
rest of the body. Consists of bundles of axons.

254 Biology Class - 11

 Medula oblongata : Posterior most part of the brain which is continuous
with spinal cord and control respiration, heart rate,swallowing,vomiting.
Pons : Thick bundles of fibres on the ventral side of brain below cerebellum.
Foramen magnum : A big aperture in the skull posteriorly through which
spinal cord emerges out.
Spinal cord : A tubular structure connected with medulla oblongata of brain
and situated in the neural canal of the vertebral column, covered by meninges.
Synaptic cleft : A narrow fluid filled space which separates two membranes
of the two neurons at the synapse.
Synaptic vesicles : These are membrane bound vesicles in the axoplasm of
the axon terminal and they store neurotransmitter.
Neurotransmitter : These are chemicals stored in synaptic vesicles, diffuse
to reach the membrane of next neuron for its stimulation.
Synapse : A physiological junction between axon of one neuron and dendrite
of next neuron.
CNS—Central neural system
PNS—Peripheral neural system
ANS—Autonomic neural system
Neural System

Central neural System Peripheral neural System

Brain Spinal cord Cranial nerve Spinal nerve

12 pairs 31 pairs
Nerve fibres of PNS

Afferent fibres Tansmit impulse Efferent fibres Transmit impulse

from Tissue/organ to CNS from CNS to Peripherel tissue/organ
Division of PNS

Somatic neural System Automatic neural system Transmit

Relays impulse from CNS impulse from CNS to involuntary
to Skeletal muscle organs and smooth muslces
Neural Control and Coordination 255
Visceral Nervous System : whole complex of nerves, fibres, ganglia and plexuses
by which impulses travel from CNS to the viscera and from viscera to CNS
Cell body = Cytoplasm with nucleus, cell organelles and
Nissl’s granules
Parts of Neuron Dendrites = Short fibres which branch rapidly and project
out of cell
Axon = Single, long fibre, branched at distal end
(Refer fig. 21.1, page 317, NCERT - Biology, Class-XI)
Multipolar = : One axon and two or more dentrites
: Found in cerebral Cortex
Neuron Bipolar = : One axon and one dendrite
: Found in retina of eye
Unipolar = : Cell body with axon only
: Found usually in the embryonic stage

Conduction of Nerve Impulse

Polarization : Resting potential
• Before stimulation axoplasm contain –vely high concentration of K+
and low concentration of Na+ Inner surface is –vely charged.
• Fluid outside axon – low concentration of K+ and high concentration of
Na+. Outside the membrane is + vely charged.
• Most membrane channels are closed.
Depolarization: Action potential
• Stimulation of nerve.
• Permeability of membrane to Na+ increases.
• Na+ channels opens allowing Na+ to diffuse into the cell quickly.
• As a result inside become +ve and outside -ve.
Repolarization : Normalising
• K+ gates open in order to allow K+ to diffuse out of the axon. This
restores the membrane. (+ve outside -ve inside)

256 Biology Class - 11

Transmission of Impulses at Synapse
(i) At electrical synapses : Here the membrane of pre and post-synaptic neuron
are in very close proximity. Electric current can flow directly from one neuron
into other across these synapses, like impule conduction along a single axon.
(ii) At chemical synapses : Here the membrane of pre and post-syneptic neuron
are separated by fluid filled space called synaptic cleft. Neurotransmitter are
involved here.
When an impulse arrives at the axon terminal, it stimulates the movement
of the synaptic vesicles towards membrane and they fuse with the plsama membrane
and release their neurotransmitter in the synaptic cleft. These chemicals bind to
specific receptors, present on the post-syneptic membrane. Their binding opens
ion channels and allow the entry of ion which generate new potential in post
synaptic neuron.
Human brain : Human brain is the major portion of central neural system.
Which is well protected by the skull.
The brain is surrounded by three cranial meninges—
(i) Duramater—outer layer
(ii) Arachnoid—middle layer
(iii) Piamater—Inner layer-remain incontact with brain
Parts of Brain

Fore brain Mid brain Hind brain

(a) Cerebrum (a) Cerebellum
(b) Thalamus (b) Pons
(c) Hypothalamus (c) Medulla oblongata
Functions of pars of brain :
Cerebrum : Centre of intelligence, memory and imagination, reasoning,
judgement, expression of will power.
Thalamus : Acts as relay centre to receive and transmit general sensation
of pain, touch and temperature.
Hypothalamus : Centre for regulation of body temperature, urge for eating
and drinking.
Midbrain : Responsible to coordinate visual reflexes and auditory reflexes.
Cerebellum : Maintains posture and equilibrium of the body as well as
coordinates and regulates voluntary movement.

Neural Control and Coordination 257

 Pons : Relays impulses between medulla oblongata and cerebral hemisphere
and between the hemisphere of cerebrum and cerebellum. It also heps to regulate
breathing.
Medulla oblongata : Centre that control heart beat, breathing, swallowing,
salivation, sneezing, vomitting and coughing.
Reflex action : It is spontaneous, autonomic and mechanical response to a
stimulus that occurs at the level of spinal cord, without involvement of brain.
Reflex arc : The flow of nerve impulse along the specific, path during reflex
action. It consist of—
(a) A receptor
(b) An Afferent neuron (sensory neuron)
(c) An inter neuron
(d) An efferent neuron (motor neuron)
(e) An effector organ
Sensory neuron
Stimulus Receptor
(REFLEX - ARC) Inter neuron of spinal cord
Response Effector organ
motor neuron
Organ of Sight-Eye
Layer Component Function
1. External layer Sclera Protects and maintain shape of the
eye ball
Cornea Outermost transparent portion of
eye which allows light to enter
2. Middle layer Choroid Absorb light and prevent light from
being reflected within the eye ball.
Ciliary body Holds lens, regulate shape of the
lens.
Iris Control amount of light entering.
3. Inner layer Retina Vision in dim light, colour vision,
vision in bright light. Sends the
image to brain through optical
nerves.
(Refer-Fig. 21.6, Page 323 NCERT-Biology, Class XI)

258 Biology Class - 11

Organ of Hearing–Ear
Portion of the ear Component Function
1. External ear Pinna Collect sound waves
External Direct sound waves towards ear drum,
auditory canal ear wax prevents the entry of foreign
bodies.
2. Middle ear Tympanic Acts as resonator that reproduces
membrane the vibration of sound.
Ear ossicles Transmit sound waves to internal ear.
Eustachian tube Helps in equalising the pressure
on either side of ear drum.
3. Internal ear Cochlea Hearing organ.
Vestibular Balancing of body.
apparatus
(Refer Fig. 21.7, page 325-NCERT-Biology, Class XI)

Organ to smell – Nose (Factor Organ)

NOSE
Olfactory Epithelium
Olfactory Receptors – Receives sense of smell (air/chemicals)
(mucus coated)

Olfactory Neurons

Olfactor bulbs (limbic system of brain)

Organ to Taste – Tongue (Gustatory Organ)
TONGUE
Papillae

Taste buds

Gustatory Nerves

Brain (integrates the differential inputs from taste buds).

Neural Control and Coordination 259

 Questions

(SRT) Select Response Type Question (1 mark each)

1. Name the fluid present in the membranous Labyrinth
(a) hemolymph (b) endolymph
(c) myolymph (d) peri lymph
2. Name the area of retina where only cones are densely packed
(a) Sclera (b) choroid
(c) fovea (d) iris
3. Name the innermost meanings of the brain?
(a) duramater (b) arachnoid
(c) piamater (d) pieuron

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. To which part of the brain communication and memory are associated ?
5. Name the bundle of fibres that connect two cerebral hemisphere in human
being.
6. Name the photo pigment present in the rod cells.
7. Why do impulses flow only in one direction ?
8. Where is hypothalamus located in the brain ?
9. Which cells are responsible for scotopic vision?

Short Answer Questions-I (2 marks each)

10. Distinguish between electrical synapses and chemical synapses.
11. What is iris ? Give the function of iris.
12. What is organ of corti ? Where is it located ?
13. Differentiate between cerebrum and cerebellum.
14. What is synapse ? Name its two types.

260 Biology Class - 11

15. Fill in the blanks in the different columns A to D :

Part/Organ Function

Pinna ........(A).........
........(B)......... Equalise the pressure on either side of ear drum.
Cone cells ........(C).........
........(D)......... regulate amount of light to pass into the eye.

16. Why are grey matter and white matter contained in human nervous system
named so ?
Short Answer Questions-II (3 marks each)
17. Observe the diagram given below and answer the following questions :

(i) Label the parts A, B, C & D.

(ii) Give the function of C and D.
(iii) Name the layers which wrap this organ.
18. What is a synapse ? How does the nerve impulse cross the chemical
synapse ?
19. Give the function of the following :
(i) Cerebrum (ii) Hypothalamus (iii) Mid brain
20. What is meant by reflex action ? Name the components of a reflex arc in
correct sequence from receptor upto effector. Support your answer by a
diagram.
21. Draw a diagram of V.S. of human eye and label the following :
Iris, Retina, Cornea, Blind spot, Ciliary body and Vitreous chamber.

Neural Control and Coordination 261

Long Answer Questions (5 mark each)
22. Describe in detail, how conduction of nerve impulse takes place through a
nerve fibre.
Case Study based questions :
23. Read the following and answer any four questions from 23 (i) to 23 (v) given
below :
Ajinomoto, the most popular ingredients commonly used in Chinese dishes
as a taste enhancer is otherwise known as mono sodium glutamate (MGS).
Excessive consumption of Ajinomoto can cause various harmful effects such
as hypertension, effect on Brain and nerves, nausea, headache, sleeping
disorders and cancer. As glutamate can serve as a neurotransmitter, high
intake of MSG can adversely affect the brain and nerves. In our body
neurotransmitters are involved in carrying nerve impulses across a chemical
synapse. Common neurotransmitters are epinephrine, adrenaline,
acetylcholine, dopamine and GABA. When an impulse arrives at the axon
terminal, it stimulates the movement of synaptic vesicles towards the
presynaptic membrane, where they fuse and release their neurotransmitters
in the synaptic cleft. Now these neurotransmitters bind to their specific
receptors present on the postsynaptic membrane, which opens ion channels.
Thus signal is transmitted across the synapse. In electrical synapse signal
can flow directly from one neuron to another.
(i) Identify the harmful effects of excessive consumption of ajinomoto :
(a) Hypertension
(b) Headache
(c) Effects nerves
(d) All of them
(ii) Ajinomoto serves as a _________ neurotransmitter :
(a) Glutamate
(b) GABA
(c) Dopamine
(d) Acetyl choline
(iii) Interaction between neurons occurs commonly across junctions called :

262 Biology Class - 11


(a) Action potential (b) Synapse
(c) Axon terminal (d) Juxtaposition
(iv) Receptor site for neurotransmitters are present on :
(a) Presynaptic membrane
(b) Tips of axons
(c) Postsynaptic membrane
(d) Membrances of synaptic vesicles
(v) Assertion : Transmission of nerve impulse across a synapse is accomplished
by neurotransmitters.
Reason : Transmission across a chemical synapse usually requires

neurotransmitters because there is a small space, synaptic cleft that separates
one neuron from another.
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false
(d) Both the assertion and reason are false
(SRT) Assertion and Reason type Questions-II : (1 mark each)
In each of the following questions, two statements are given, one is Assertion and
other is Reason. Mark the correct answer as :
(a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false
(d) Both the assertion and reason are false

Neural Control and Coordination 263

24. Assertion : The space between the cornea and the lens is called the vitreous
chamber.

Reason : The space between the lens and retina is called the aqueous chamber.

25. Assertion : The Eustachian tube helps in equalizing the pressure on either
side of the ear drum.

Reason : The Eustachian tube connects the middle ear cavity with the pharynx.

Answers

(SRT) Select Response Type Question (1 mark each)

1. (b) Endolymph 2. (c) Fovea
3. (c) Piameter

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answers (1 mark each)
4. Cerebrum
5. Corpus callosum
6. Rhodopsin
7. Because each synapse allows impulse to cross it in a single direction.
8. At the base of thalamus.
9. Rods
Short Answers-I (2 marks each)
10. Refer Point to remember of support material.
11. Refer Point to remember of support material.
12. Refer Point to remember of support material.
13. Refer Point to remember of support material.
14. Junction between two nerves Chemical synapse and electrical synapse
15. (A) To collect sound waves (B) Eustachina tube
(C) Colour vision (D) Iris
16. Refer Point to remember of support material.

264 Biology Class - 11

Short Answers-II (3 marks each)
17. (i) A : Cerebrum C : Cerebellum
B : Corpus callosum D : Medulla oblongata
(ii) C : Balancing of body and maintain posture
D : Vomiting , coughing, breathing, salivation or any other correct answer
(anyone).
(iii) Pia mater, arachnoid and dura mater.
18. Refer Point to remember of support material.
19. Refer Point to remember of support material.
20. Refer Point to remember of support material.
21. Refer Point to remember of support material.

Long Answer (5 marks)

22. Refer Point to remember of support material.
23. (i) (d) All of them
(ii) (a) Glutamate
(iii) (b) synapse
(iv) (c) post synaptic membrane
(v) (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion

Assertion Reason Type II Answer.

24. (d) Both the assertion and reason are false
25. (a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
 

Neural Control and Coordination 265

 Points To Remember
Endocrine glands : These are ductless glands which secrete hormones
directly into the blood stream.
Hormones : Non-nutrient chemicals synthesised in trace amount by
Endocrine glands, that act as intracellular messengers and are specific in their
action which are transported by blood from site of production to site of action.
Hypothalamus :
 It is basal part of diencephalon.
 Has neurosecretory cells called nuclei which produce hormones to regulate
the synthesis and secretion of pituitary gland hormones.
 Two types of hormones released are :
Releasing hormones : Stimulate secretion of pituitary hormones, e.g.,

Gonadotrophin releasing hormone stimulates pituitary gland to synthesise
gonadotrophins.
Inhibiting hormones : Inhibit secretions of pituitary hormones, e.g.,
Somatostatin inhibits secretion of growth hormone.
Pituitary Gland :
 Located in bony cavity called as sella tursica.
 Attached to hypothalamus by a stalk.
 Divided anatomically into : Adenohypophysis (Anterior lobe) and
Neurohypophysis (Posterior lobe).
 Hormones released from hypothalamic neurons reach anterior pituitary
through portal system and through neurons in Posterior pitutary.
 Posterior pituitary is under neural control of hypothalamus.

266 Biology Class - 11

 1. Pituitary Gland
Pituitary Gland

Adenohypophysis (Anterior lobe) Neurohypophysis (Posterior lobe)

(It stores hormones secreted by hypothalamus
Pars distalis Pars intermedia
Pars nervosa
Secretes MSH

Oxytocin Vasopressin
GH PRL TSH ACTH LH FSH
(ADH)
Adenohypophysis : (Anterior lobe of Pituitary)
 Growth hormone (GH) : Oversecretion leads to gigantism and low secretion
causes dwarfism and Proper secretion leads to proper growth of body.
 Prolactin (PRL) : Growth of mammary gland and formation of milk in
them.
 Thyroid stimulating hormone (TSH) : Stimulates synthesis and secretion
of thyroid hormones from thyroid gland.
 Adrenocorticotrophic hormone (ACTH) : Stimulates synthesis and
secretion of steroid hormones called glucocorticoids from adrenal cortex.
 Luteinizing hormone (LH) : Synthesis and secretion of hormones called
androgens in males, and helps in ovulation and maintenance of corpus luteum
in females.
 Follicle stimulating hormone (FSH) : Regulate spermatogenesis in males,
and growth and development of ovarian follicles in females.
Neurohypo physis (Posterior lobe of Pituitary)
 Oxytocin helps in contraction of uterus during child birth and milk ejection
from mammary gland in females.
 Vasopressin : Acts on kidney and stimulates reabsorption of water and
electrolytes by distal tubules to reduce water loss through urine. It is also
called as Anti Diuretic Hormone (ADH).
Diabetes insipidus : Impairment of synthesis of ADH
(i) Diminished ability of kidney to conserve water.
(ii) Water loss and dehydration.
(iii) Can be overcome by taking more water.

Chemical Coordination and Integration 267

Excessive Secretion of Growth Hormone
 Acromegaly : It is a condition when the pituitary gland makes too much
growth hormone. It is due to a tumour in pituitary gland. Person suffering
from acromegaly (acro means tip and megaly means enlargement) may
gradually develop a long face with protruding lower jaw, enlarged nose and
wider spacing between teeth and enlarged hands and feet.
2. Pineal Gland :
 Located on dorsal side of forebrain.

 Secretes Melatonin for regulation of 24-hours rhythm, sleep-wake cycle,

menstrual cycle, pigmentation etc.

3. Thyroid Gland :
 Has two lobes on either side of trachea interconnected by isthmus (connective

tissue).
 Composed of follicles and stromal tissues.

 Follicular cells synthesise thyroxine (T ) and tri-iodothyronine (T ).

4 3
 Iodine is necessary for normal functioning of thyroid.

 Goitre (Hypothyroidism) : Enlargement of thyroid gland; Hypothyroidism

may lead to mental retardation and stunted growth (cretinism) Deaf-mutism

in the baby if it occurs during pregnancy.
 Hyperthyroidism : Occurs due to cancer or due to development of nodules

in thyroid glands, affects body physiology as abnormally high levels of

thyroid hormones is synthesised. Basic metabolic rate increases.
 Exophthalmic goitre : It is a form of hyperthyroidism, characterised by

enlargement of thyroid gland, protrusion of eye balls and increased BMR

 Thyroid hormone controls carbohydrates, proteins & fats metabolism.

 Also secretes a protein hormone called Thyrocalcitonin (TCT) which regulates

blood calcium level.

4. Parathyroid Gland :
 Present on back side of thyroid gland. Each lobe of thyroid gland has its one

pair.
 Secrete peptide hormone called parathyroid hormone (PTH) which increases

calcium levels in blood so called hypercalcemic hormone.

 PTH stimulates bone resorption, and reabsorption of calcium from blood

and reabsorption of calcium by renal tubules, thus increasing blood Ca++

level.

268 Biology Class - 11

 5. Thymus Gland
 Located on dorsal side of heart and aorta.

 Secrete peptide hormones called Thymosins which play role in differentiation

of T-lymphocytes (help in cell mediated immunity.)

 Thymosins also produce antibodies and provide humoral immunity.

 Immunity of old people usually becomes weak as thymus gets degenerated

with age.
6. Adrenal Gland
 Located at anterior part of each kidney.

 Has centrally located adrenal medulla and at periphery in adrenal cortex.

 Adrenal medulla.

1. Adrenal medulla secretes adrenaline (epinephrine) and nor adrenaline

(norepinephrine), commonly called as catecholamines or emergency
hormones or hormones of fight or flight.
2. These hormones increase heart beat, rate of respiration, breakdown of
glycogen thus increase blood glucose level, breakdown of lipids and protein,
alertness, raising of hairs, sweating etc.
 Adrenal Cortex-(3 layers) : Zona reticularis (inner layer)
Zona fasciculata (middle layer)
Zona glomerulosa (outer layer)
 Adrenal cortex secretes :
1. Androgenic steroids : (Secreted by Zona reticularis)
 Secreted in small amounts.

 Play role in growth of axial pubic and facial hair during puberty.

2. Glucocorticoids : (Secreted by fasciculata)

 Involved in carbohydrate metabolism.

 Stimulates gluconeogenesis, lipolysis and proteolysis.

 e.g., Cortisol which is also involved in cardio-vascular and kidney functions.

 It also suppresses immune response and stimulates RBC production.

3. Mineralocorticoids : (Secreted Zona glomerulosa)

 Regulate balance of water and electrolytes in body.

+
 e.g., Aldosterone which also helps in reabsorption of Na and water. Excretion

of K+ and phosphates ions from renal tubules.

Chemical Coordination and Integration 269

  When adrenal cortex is damaged, it does not produce enough cortisols (which
regulate body’s reaction to stressful situations) and aldosterone.
 It result in Addison’s disease. Symptons of addison’s disease are weak
muscles, extreme fatigue, increased skin pigmentation, weight loss, sores in
mouth and depression.
Two major adrenal insufficiency
Primary adrenal insufficiency where our immune system mistakes adrenal
for an antigen and tries to damage it.
 Secondary adrenal insufficiency-when pituitary gland can’t produce ACTH

7. Pancreas : It is called composite/dual gland. As it acts as Exocrine and

endocrine gland i.e. has both exocrine and endocrine function.
 Contains about 1-2 million islets of Langerhans which has glucagon secreting

α-cells and insulin secreting β-cell.

 Glucagon : Peptide hormone, stimulates glycogenolysis by acting on liver

cells. Also, stimulates gluconeogenesis. Hence called hyperglycemic

hormone.
 Insulin : Peptide hormone, acts on hepatocytes and adipocytes to enhance

cellular glucose uptake, stimulates conversion of glucose to glycogen

(glycogenesis), so decrease blood glucose level. Hence called hypoglycemic
hormone.
 Deficiency of insulin causes diabetes mellitus in which loss of glucose occurs

through urine. Excessive hunger and thirst (polydipsia) are other symptoms
of Diabetes.
 Insulin and glucagon are antagonistic hormones i.e. play opposite role.

Glycogenolysis : Breaking of glycogen into glucose.

Gluconeogenesis : Formation of glucose from substances other than glycogen.
Glycogenesis : Conversion of glucose into glycogen.
8. Testis :
 A pair of testis composed of seminiferous tubules and interstitial cells is

present in the scrotal sac of males.

 Leydig cells (interstitial cells) produce androgens (mainly testosterone) which

regulate development and maturation of male accessory sex organs, formation

of secondary sex characters and play stimulatory role in spermatogenesis.
Male sexual behaviour (libido) is influenced by androgens.
270 Biology Class - 11
 9. Ovary : A pair of ovaries which produce one ovum in each menstrual cycle
are present in abdomen in females.
 Ovary composed of ovarian follicles and stromal tissue.

 Estrogen synthesised by growing ovarian follicles helps in stimulation of

growth of female secondary sex organs, female behaviour, mammary gland

development and female secondary sex characters.
 Ruptured follicle form corpus luteum which secretes progesterone.
Progesterone supports pregnancy and stimulates alveoli formation and milk
secretion in mammary glands.
Hormones secreted by tissues which are not endocrine
glands :
(a) Heart : Atrial wall secrets Atrial Natriuretic factor (ANF) which decreases
blood pressure by dilation of the blood vessels.
(b) Kidney : Juxtaglomerular cells secretes erythropoietin which stimulates
erythropoiesis (RBC formation).
(c) Gastro-intestinal tract : It secretes four peptide hormones.
 Gastrin : Acts on gastric glands and stimulates secretion of hydrochloric

acid and pepsinogen.

 Secretin : Acts on pancreas and stimulates secretion of water and bicarbonate

ion.
 Cholecystokinin (CCK) : Act on pancreas and gall bladder to stimulate

secretion of pancreatic juice and bile juice respectively.

Gastric inhibitory peptide (GIP) : Inhibits gastric secretion and motility.
Mechanism of hormone action : By hormone receptors of two kinds, i.e.,
(a) Located on membrane of target cell
 These are membrane bound receptors.

 Form hormone receptor complex.

↓
Leads to biochemical changes in tissue.
↓
Release of second messengers like (cyclic AMP, IP3, Ca2+ etc.) which regulate
cellular metabolism.

Chemical Coordination and Integration 271

(b) Located inside the target cell

 These are intra cellular receptors.

 Hormones (steroid hormones iodothyronines etc.) interact with them and

cause physiological and developmental effects of regulating gene expression.

Questions

(SRT) Select Response Type Question (1 mark each)

1. Which to system coordinate and regulate physiological function of our body?
(a) muscular system and endocrine system
(b) neural system and muscular system
(c) neural system, and endocrine system
(d) endocrine system and reproductive system
2. What is the role of melanocyte stimulating hormone?
(a) act on hepatic cells
(b) act on melanocytes and regulate pigmentation of skin
(c) act on ovarian follicles
(d) act on osteocytes
3. Name the hormone which act antagonistically in order to regulate calcium
level in blood?
(a) Glucocorticoid and adrenocortical
(b) Thyrocalcitonin and parathyroid hormone
(c) Mineralocorticoid and Thyrocalcitonin
(d) Parathyroid hormone and glucocorticoid

CONSTRUCTED RESPONSE TYPE (CRT)

Very Short Answer Questions (1 mark each)
4. Give the names of any one glucocorticoid and one mineralocorticoid.
5. How does Atrial natriuretic factor decrease blood pressure ?

272 Biology Class - 11

 6. Which structure is formed from ruptured follicle in females ? What is its
role ?

7. Immunity of old persons becomes very week. Give reason.

Short Answer Questions-I (2 marks each)

8. What happens if a person suffers from prolonged hyperglycemia ?

9. What are the two modes through which the hypothalamus causes the release
of hormones by pituitary gland ?

10. Androgen regulates the development, maturation and other important

functions in human male. List them.

11. Mr. Akshay notices that his shoe size has progressively increased. He also
observes that shape of his face is gradually changing with protruding lower
jaw. What can be the cause for all changes. Name the disorder.

Short Answer Questions-II (3 marks each)

12. Define hormone and classify them on basis of their chemical nature.

13. How do oxytocin, progesterone and estrogen differ from each other ?

14. What are the disorders caused and the effects produced due to malfunctioning/
improper secretion from thyroid gland ?

15. Name the disease/disorder caused by :

(a) Excessive secretion of Thyroid hormone in adults.

(b) Insufficient amount of insulin secreted by pancreas.

(c) Damage of adrenal cortex.

Long Answer Questions (5 mark each)

16. ‘The master gland regulates a number of physiological functions in our body.’
Give reasons and explain.

Chemical Coordination and Integration 273

 Answers
(SRT) Select Response Type Question (1 mark each)
1. (c) Nerual system and endocrine system.
2. (b) Acts on melanocytes and regulates pigmentation of skin.
3. (b) Thyrocalcitonin (TCT) and parathyroid hormone (PTH).

Very Short Answers (1 mark each)

4. Glucocorticoid—Cortisol; Mineralocorticoid—aldosterone.
5. By dilation of the blood vessels.
6. Corpus luteum which secrets progesterone.

7. Thymus gland degenerates with age.

Short Answer Questions-I (2 marks each)

8. Gets affected by diabetes mellitus which causes loss of glucose through urine
and formation of harmful ketone bodies.
9. Through hypothalamic neurons control anterior pituitary gland. Through
neural regulation controls posterior pituitary gland.
10. Refer Points to Remember.
11. Increased secretion of growth hormone Acromegaly

Short Answers Questions-II (3 marks each)

12. Refer Points to Remember of this support material
13. Oxytocin causes milk ejection and contraction of uterus at time of child birth.
Progesterone–causes milk secretion and maintains pregnancy.
Estrogen : Refer Points to Remember.
14. Refer Points to Remember.
15. (a) Exophthalmic goitre (b) Diabetes
(c) Addison’s disease

274 Biology Class - 11

Long Answers Questions-II (3 mark each)
16. Explain the role of pituitary gland + Refer Points to Remember.

Case Study based question :

17. Read the following and answer any four questions from 17 (i) to 17 (v) given
below :
Xenoestrogens are found in a variety of everyday items. Its sources are
plastic, pesticides, insecticides, beauty products etc. Many of us don’t think
twice about the make up we wear, container we use to pack a lunch.
Unfortunately this may be altering the way our body works naturally because
they all contain endocrine disruptors called Xenoestrogens. Xenoestrogens
are a subcategory of endocrine disruptor that specifically has estrogen like
effects. Estrogen is a natural hormone synthesized by the growing ovarian
follicles in females. It helps in the growth of female secondary sex organs
and female secondary sex characters. It is also important for bone growth
and reproduction in men and women. When xenoestrogen enter the body
they increase the total amount of estrogen in the body resulting in a
phenomenon called estrogen dominance. As they are not biodegradable they
are stored in our fat cells. This leads to breast cancer, prostate cancer, obesity,
infertility, miscarriages and diabetes.
(i) Xenoestrogen mimics the action of _______ and its excess causes______.
(a) Progesterone, bone and prostate cancer
(b) Estrogen, breast and prostate cancer
(c) Cortisol, brain and blood cancer
(d) Thyrocalcitonin, bone and lung cancer
(ii) Estrogen is secreted mainly by :
(a) GI tract
(b) Pancreas

Chemical Coordination and Integration 275

 (c) Growing ovarian follicles
(d) Thymus
(iii) Select the function/functions performed by estrogen in females :
(a) Growth of female secondary sex organs
(b) Bone growth
(c) Female secondary sex-characters
(d) All of these
(iv) What measures, as an individual you would take to reduce your exposure to
these harmful exenoestrogens?
(a) Eat local and organic food
(b) Use beauty products made from natural ingredients
(c) Do not use plastic lunch box and water bottles
(d) All of these
(v) Assertion : Estrogen belongs to the class of steroid hormones.
Reason : Cholesterol is the precursor used in synthesizing estrogen hormone.

(a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.

(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.

(c) Assertion is true but reason is false

(d) Both the assertion and reason are false

(SRT) Assertion and Reason type Questions-II : (1 mark each)

In each of the following questions, two statements are given, one is Assertion
and other is Reason. Mark the correct answer as :

(a) Both assertion & reason are true, and the reason is the correct

276 Biology Class - 11

 explanation of the assertion.

(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.

(c) Assertion is true but reason is false

(d) Both the assertion and reason are false

18. Assertion : Hormone thyrocalcitonion has antagonistic effect to that of

parathyroid hormone (PTH).

Reason : Thyrocalcitonin decreases the blood calcium level while parathyroid

hormone increases blood calcium level.

19. Assertion : Immunity of old person becomes weak.

Reason : Thymus degenerates in old individuals.

Answers :

17. (i) (b) Estrogen, breast and prostate cancer

(ii) (c) Growing ovarian follicles

(iii) (d) All of these

(iv) (d) All of these

(v) (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion

18. (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.
19. (a) Both assertion & reason are true, and the reason is the correct
explanation of the assertion.



Chemical Coordination and Integration 277

 Practice

Solved Sample Paper

Subject : BIOLOGY (044) (Theory)
Class : XI
Time : 3 Hrs.] [MM : 70

INSTRUCTION :
• Section - A contains 16 questions of 1 mark each.
• Section - B contains 5 questions of two marks each.
• Section - C contains 7 questions of three marks each.
• Section -D contains 2 questions of four marks each.
• Section-E contains 3 questions of 5 marks each.
• There is no overall choice. However, internal choice has been provided in
some questions. Attempt only one of the alternatives in such questions.
• Wherever necessary, neat and properly labelled diagram should be drawn.

Section -A

Question 1 to 12 is Selected Response type questions.

1. As we go from species to Kingdom in a taxonomical hierarchy, the
number of common characteristics

278 Biology Class - 11

 (a) will decrease (b) will increase
(c) remain same (d) may increase or decrease
2. The given statement describes a group of organisms.
(i) Instead of a cell wall they have a protein rich pellicle making a body
flexible.
(ii) They have two flagella a short and a long one
(iii) They show mixotrophic nutrition
(iv) They are connecting link between plants and animals.
Which of the following group is referred here?
(a) Dinoflagellates (b) Slime moulds
(c) desmids (d) Euglenoids
3. Isogamous condition with non-flagellated gametes is found in
(a) Chlamydomonas (b) Volvox
(c) Spirogyra (d) Fucus
4. Flame cells are the excretory structures for
(a) Annelids (b) Coelenterates
(c) platyhelminthes (d) Echinoderms
5. In a flower if all the sepals are united then the condition is said to be
(a) Gamosepalous (b) gamopetal JUS
(c) polypetalous (d) polysepalous
6. Stomatal apparatus is made of and
(a) Stomatal aperture, guard cells and subsidiary cells.
(b) Slomatal aperture and guard cells only
(c) Guard cells and subsidiary cells only
(d) Stomatal aperture and subsidiary cells only
Paper 279
 7. Which is the common opening for passing out fecal matter, urine and
sperms to the exterior in frogs?
(a) Anus (b) cloaca
(c) urethra (d) ostia
8. Select the incorrect statement regarding S- phase of interphase.
(a) occurs between Gl and G2
(b) DNA replicates in the nucleus
(c) Centrioles duplicate in the cytoplasm
(d) As DNA is doubled number of chromosome also doubles
9. Keratin present in hairs show secondary structure known as
(a) Parallel beta sheet (b) antiparallel beta sheet
(c) Alpha helix (d) none of these
10. Frogs respire through
(a) Moist skin (b) lungs
(c) Gills in larval stage (d) All three
11. Renal corpuscle or Malphigian body is-
(a) Glomerulus only
(b) only Bowman's capsule
(c) Glomerulus along with Bowman's capsule
(d) Glomerulus with afferent arteriole
12. Multipolar neuron has
(a) One Dendron and one axon
(b) Many dendrons and one axon
(c) one Dendron and many axons
(d) many dendrons and no axon
280 Biology Class - 11
Question No 13 to 16 consists of two statements- Assertion and Reason.
Answer these questions selecting the appropriate options given below:
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion & reason are false.
13. Assertion: Two kingdom Classification was insufficient.
Reason: Majority of organisms failed to fall into either of the categories
in two kingdom classification.
14. Assertion: Only red algae are able to flourish at the great depths of sea.
Reason: Red algae have the pigments r-phycoerythrin and r-phycocyanin.
15. Assertion: In alternate phyilotaxy the arrangement of leaves is such that
a single leaf arises at each node in alternate manner.
Reason: Alternate phyilotaxy is seen in China rose and mustard plant.
16. Assertion: Collenchymatous cells show thickening of hemicellulose and
pectin at the corners.
Reason: Collenchyma is thick walled dead tissue.

Section -B

17. With respect to ribcage explain the following:

(a) True ribs (b) Floating ribs
18. (i) Name the four main components of xylem.
(ii) Which of these is most suitable for carrying water?

Paper 281
 OR
How open vascular bundles differ from closed vascular bundles?
19. Identify and name the following:
(i) Unit membrane which bounds a vacuole.
(ii) Animal cell that loses nucleus at maturity.
20. What is the difference between a virus and viriods?
21. Draw a well labelled diagram of Funaria.
OR
Tabulate 4 major differences between liverworts and mosses.

Section -C

22. Answer the following:

(i) What is radula?
(ii) Name the excretory organs of insects.
(iii) What is bioluminescence?
OR
Give an example for each of the following:
(i) A fish possessing electric organ
(ii) An oviparous mammal
(iii) Animal which exhibits alternation of generation
(iv) An animal with Cnidoblasts
(v) An animal having canal system and spicules
(vi) An organ, which regulates buoyancy in fishes
23. Comment on the "9 + 2" arrangement of a flagellum with the help of
suitable diagran

282 Biology Class - 11

24. Give 3 reasons why plants can survive without respiratory organs.
OR
(i) What is oxidative phosphorylation? Where does it occur inside the
mitochondria?
(ii) Explain the role of oxygen in ETS.
25. Draw a well labelled diagram of a human nephron. Label any 6 parts.
26. Explain the following terms
(a) Turn over number (b) Denaturation
(c) Activation Energy.
27. Describe the arrangement of floral members in relation to their insertion
on thalamus.
28. Draw a diagram to show the structure of a neuron and label any 6 parts
in it.

Section - D

29. Jetlag is a temporary sleep problem that can affect anyone who quickly
travels across several time zones. Your body has its own internal clock,
called circadian rhythms. They signal to your body when to stay awake
and when to sleep. You will be surprised to know that our internal body
clock is regulated by melatonin hormone which is produced by Pineal
gland. When light is low during night time, the hypothalamus signals
the pineal gland to release melatonin. When people are exposed to blue
light coming from their mobiles and laptops at night, it delays/ stops the
release of melatonin which makes it hard for them to sleep.
(i) What is the location of Pineal Gland in our body?
(ii) List 4 functions of melatonin hormone.
(iii) Is Pineal an endocrine gland or exocrine Gland? Give reason.

Paper 283
 30. Fruits are one of the best natural food usually consumed raw. Natural
fruit ripening is a physiological process which makes fruit edible and
nutritious. Unfortunately, nowa¬days artificial fruit ripening is done
using Calcium Carbide (CaCz) which is popularly known as "masala",
its use is banned under Food safety and Standards Regulations, 2011.
When calcium carbide reacts with water it produces acetylene gas (also
called carbide gas) which quickens the ripening process. It is said to
have the same effect as ethylene the natural ripening hormone. Calcium
carbide contains traces of arsenic and phosphorus and thus not good for
our health.
(i) Name the plant growth regulator (PGR) which performs natural
fruit ripening.
(ii) Write a short note on discovery, 2 physiological functions performed
by this PGR.
Section -E
31. (i) Write a short note on "Kranz anatomy".
(ii) Which group of plants possesses Kranz anatomy?
(iii) Does this group of plants show photorespiration9 If no, explain how
is it possible?
OR
Describe Z scheme of light reaction in plants. Why this process is called
so? Also mention the location where it occurs?
32. (i) How does cytokinesis in plant cells differ from that in animal cells?
(ii) The plant cell cannot undergo cytokinesis by an invaginating
cleavage furrow. Why?
OR
(i) Name and explain the three stages of cell cycle associated with
interphase.

284 Biology Class - 11

 (ii) Why Meiosis-II is necessary? Explain.
33. (i) What is basis of ABO blood grouping in humans?
(ii) Rh factor plays a crucial role in child's birth born out of a marriage
between Rh-woman and Rh+ man. Explain how?
OR
Answer the following:
(i) Name 2 leucocytes which show phagocytic action.
(ii) Name the ions and type of blood cells involved in blood clotting.
(iii) One can determine the heart beat rate by counting the number of i n
an ECG.
(iv) Name the leucocytes which have coarse granules, bilobed nucleus
and take acidic stain.
(v) Name the organ which acts as graveyard of RBC's.
17. (iii) False ribs- last 2 pairs (11* and 12*) which are not connected
\ entrally. 1 -1 I8.(i) Vessels, tracheids. xylem fibres and xylem
parenchyma
(iii) Vessels 1X
OR
Refer NCERT Textbook Page No 901 X
7 = 1
1 =2
20. Refer NCERT Textbook Page No 25 and 26. 2=2
21. Refer Fig No 32 (c) in NCERT Textbook Page No 34 X 4=2
OR
X4 = 2
1X1X
Paper 285
 Vz
Liverworts Mosses
1. Plani bodv is dorsiventral Plant body has radial symmetry
is ihallus like. Plant body is foliose.
3. Lizoids Multicellular rhizoids
4. Example- Marchantia Example - Fun aria
22. (i) (ii)
Section- C
Physiological Functions - Refer NCERT Textbook Page No 250 2
Section -E
31. (i) Bundle sheath cells form a 'wreath' around vascular bundles. 1
(ii) It is found in C-4 plants. 1
(iii) Refer NCERT Textbook Page No 220 (4th para in
photorespiration). 3
OR
(i) Refer NCERT Textbook Page No 212 for explanation of Z scheme
light reaction. 3
(ii) It is called so because the diagram, when first drawn, was in the
form of letter 'Z'.
(iii) Location - Membrane of thylakoid 1
32. (i) Refer NCERT Textbook Page No 166 under the heading
cytokinesis. 3
(ii) The plant cell cannot undergo cytokinesis by an invaginating
cleavage furrow due to the presence of rigid cell wall made up of
cellulose. 2

286 Biology Class - 11

 OR
(i) Explain Gi, S and G2 phase of cell cycle, Refer to NCERT Textbook
Page No 163.(3)
(ii) Meiosis - II separates sister chromatids. Meiosis -II resembles
mitosis but it is very important as it serves to increase the number of
daughter cells from two to four and also reduces the amount of DNA
to half. 2
33. (i) ABO grouping is based on the presence or absence of two surface
antigens on the RBCs namely A and B. 2
(iii) Refer NCERT Textbook Page No 281 under the heading Rh
grouping. 3
OR
(i) Neutrophils and Monocytes 5=5
(ii) Calcium ions and Platelets
(iii) QRS Complexes
(iv) Eosinophil or Acidophil
(v) Spleen
(iii) The property of a living onanism to emit light. Example -Phylum
Ctenophora 1×3=3
OR
(i) Torpedo
(ii) Echidna
(iii) Obelia
(iv) Hydra
(v) Euspongia
(vi) Air bladder '/2 x 6 = 3

Paper 287
 23. Refer Fig 8.10(b) in NCERT Textbook Page No 137(diagram -1,
explanation -2 Marks) 3
24. (i) Each plant part takes care of its own gas-exchange needs.
(ii) They do not present great demand for gas exchange as leaves
produce oxygen.
(iii) Distance that gases must diffuse is not great. 1×3 = 3
OR
Refer NCERT Textbook Page No 233 2 +1
25. Refer Fig 19.3 in NCERT Textbook Page No 292. Vi x 6 = 3
26. (i) Turnover- Number of substrate molecules transformed per minute
by a single enzyme into products.
(ii) Denaturation- implies destruction of the tertiary structure of a
protein molecule and the formation of random polypeptide chains.
(iii) Activation Energy- is the difference in average energy content
of'substrate' from that of transition state. 1×3=3
27. Explain Epigynous, Hypogynous and perigynous condition.
1 + 1+1
28. Refer Fig 21.1 in NCERT Textbook Page No 317 >/2 x 6 = 3
Section- D
29. (i) Pineal gland is located on the dorsal side of forebrain. 1
(ii) Melatonin regulates 24- hours' diurnal (circadian) rhythm, sleep
wake cycle, metabolism, pigmentation, menstrual cycle and defense
capability. (Write any 4) 2
(iii) As pineal lacks duct, thus it is ductless or endocrine gland. 1
30. (i) Ethylene hormone is responsible for natural fruit ripening. 1
(ii) Discovery of ethylene- Refer NCERT Textbook Page No 248 (4th
paragraph) 1

288 Biology Class - 11

 Unsolved Sample Paper
Subject : BIOLOGY (044) (Theory)
Class : XI
Time : 3 Hrs.] [MM : 70

INSTRUCTION :
• Section - A contains 16 questions of 1 mark each.
• Section - B contains 5 questions of two marks each.
• Section - C contains 7 questions of three marks each.
• Section -D contains 2 questions of four marks each.
• Section-E contains 3 questions of 5 marks each.
• There is no overall choice. However, internal choice has been provided in
some questions. Attempt only one of the alternatives in such questions.
• Wherever necessary, neat and properly labelled diagram should be drawn.

Section -A

Question 1 to 12 is Selected Response type questions.

1. Growth occur .................. in plants and .................. in animals.
(a) Continuously, only upto a certain age
(b) Only upto a certain age, continuously
(c) Continuously, continuously
(d) Twice, never
2. Which of the following are autotrophs?
(a) Photosynthetic bacteria (c) both a and b
(b) chemosynthetic bacteria (d) None of them
Paper 289
 3. Phylogenelic system of classification is based on
(a) Morphological features (b) Anatomical features
(c) Floral characters (d) Evolutionary relationships
4. Which of the following feature of bony fish is missing in cartilaginous
fishes?
(a) Placoid scales (c) cold blooded
(b) Operculum (d) unpaired fins
5. Vexillary aestivation is characteristic of the family
(a) Fabaceae (c) Poaceae
(b) Asteraceae (d) Solanaceae
6. Fibres and sclereids are the types of
(a) Collenchyma (c) Parenchyma
(b) Sclerenchyma (d) Aerenchyma
7. In frog, a triangular structure calledjoins the right
(a) Conus arteriosus, ventricle (c) Conus arteriosus, auricle
(b) Sinus venosus, auricle (d) Sinus vcnosus, ventricle
8. Lipid gets precipitated under acid insoluble fraction during analysis of
chemical composition of tissues due to
(a) Its high molecular weight
(b) Its low molecular weight
(c) Its polymeric nature
(d) on grinding, it is broken into pieces and form vesicles
9. The exchange of genetic material between non-sister chromatids of
homologous chromosomes occurs during
(a) Anaphase -I (b) Mctaphase-1
(c) Prophase-I (d) Telophase -I

290 Biology Class - 11

 10. Urea is
(a) More toxic than uric acid (c) more toxic than ammonia
(b) Equally toxic to ammonia (d) Non-toxic
11. Sodium- Potassium exchange pump
I. needs ATP to workII. Expels 3 Na+ ions for every 2 K+ imported
III. Works against concentration gradient
IV. Maintains resting potential
(a) Only I. and II. are correct
(b) Only I., III. And IV. are correct
(c) Only II. and IV. are correct
(d) All are correct
12. The majority of CO2 is transported as-
(a) Carbaminohaemoglobin (b) Carbonates
(c) Bicarbonates (d) Dissolved state in blood
Question No 13 to 16 consists of two statements- Assertion and Reason SRT.
Answer these questions selecting the appropriate options given below:
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion & reason are false.
13. Assertion: Both words are separately underlined in binomial
nomenclature.
Reason: Underlining indicates their Latin origin.
14. Assertion: Chlorella is utilised to keep the air pure in space vehicles.
Reason: The space travelers feed on chlorella soup.
Paper 291
 15. Assertion: Monoadelphous stamens are found in pea.
Reason: Dialdelphous stamens are found in China rose.
16. Assertion: Frog has short alimentary canal.
Reason: Frogs are carnivores.

Section -B

17. List 2 roles of fungi in our daily lives.

OR
What are the characteristics of euglenoids? (Write any 4)
18. Draw a well labelled diagram of T.S. of monocot stem.
19. What role does Ca2" ions play in the contraction of muscles?
OR
Differentiate between red and white muscle fibres.
20. List 2 ways which prove that Sphagnum is economically important for
us.
21. Why are lysosome called "suicidal bags of the cell"?

Section-C

22. (a) List 2 similarities between Chondrichthyes and Osteichthyes.

(b) Also tabulate 4 differences between them.
23. Describe various stem modifications associated with food storage,
climbing and protection.
24. (a) How many types of plastids are present in a plant cell on the basis of
pigments present in them?
(b) Are these different types of plastids interchangeable? If yes, give an
example where they are getting converted from one type to another.

292 Biology Class - 11

 OR
Justify the statement."Mitochondria are powerhouses of the cell".
25. Draw a graph depicting relationship between substrate concentration and
velocity of reaction. Define Km value. What is the correlation between
Km and efficiency of enzyme?
OR
What is competitive inhibition? Explain its application in the
Pharmaceutical sector.
26. Give the schematic representation of glycolysis. Also give a brief account
of total ATP produced in it.
27. Describe the 3 steps involved in the formation of urine.
28. Explain the process of polarization of the membrane of a nerve fibre.

Section - D

29. Agent Orange is a chemical herbicide and defoliant which was used
by U.S. military during the Vietnam War from 1961 to 1971. Jt is a
mixture of 2, 4, 5-T and 2, 4-D. The government of Vietnam says that
upto three million people have suffered illness because of exposure to
Agent Orange.
(a) Expand 2. 4-D.
(b) To which group of plant growth regulators does 2, 4-D belongs?
(c) Write a note on 2 physiological functions performed by this group
of plant growth regulators.
30. Thyroid diseases are, arguably, among the commonest endocrine
disorders worldwide. India too, is no exception. Four main thyroid
diseases are - hypothyroidism, hyperthyroidism, Goiter and Hashimoto's
disease. Hypothyroidism affects approximately 11% of the population

Paper 293
 of India. Any irregularity with the thyroid can lead to various health
problems in the long run.
(a) How does hypothyroidism during pregnancy affects the foetus?
(b) Mention 2 functions performed by thyroid hormones in humans?
(c) Mention the 2 forms in which thyroid hormone are secreted in our
blood

Section -E

31. (i) Draw flowchart of C-4 Cycle.

(ii) Rubisco is an enzyme that acts both as a carboxylase and oxygenase.
Why do you think Rubisco carries out more carboxylation in C-4
plants?
32. Draw a well labeled diagram to show the internal structure of human
heart and label any 8 parts in it.
OR
Answer the following questions:
(i) SA Node is called 'pacemaker of human heart'.
(ii) Name the 2 Heart sounds. How are they produced?
(iii) Why human heart is considered myogenic?
33. Why mitosis is called equational division? Explain its four phases with
suitable well-labelled diagram.
OR
(i) Comment on the statement - Telophase is reverse of prophase.
(ii) Comment on the statement - Meiosis enables the conservation
of specific chromosome number of each species even though the
process per se, results in a reduction of chromosome number.

294 Biology Class - 11

 Unsolved Practice Paper-II
Subject : BIOLOGY (044) (Theory)
Class : XI
Time : 3 Hrs.] [MM : 70

INSTRUCTION :
(i) All questions are compulsory.
(ii) The question paper has 5 sections and 33 questions. Section–A, Section–B,
Section–C, Section–D & Section-E.
(iii) Section-A contains 16 questions of 1 mark each.
(iv) Section-B contains 5 questions of 2 marks each.
(v) Section-C contains 7 questions of 3 marks each.
(vi) Section-D contains 2 case based questions of 4 marks each.
(vii) Section-E contains 3 questions of 5 marks each.
(viii) There is no overall choice. However, internal choice has been provided in
some questions. Attempt only one of the alternatives in such questions.
(ix) Wherever necessary, neat and properly labelled diagrams should be
drawn.

Section-A
Question 1 to 12 is Selected Response type questions.
1. Match the column (Kingdom and cell wall) and select the correct option.
Kingdom Cell Wall
(A) Monera (1) Peptidoglycan
(B) Protista (2) Cellulose
(C) Fungi (3) Pellicle
(D) Plantae (4) Chitin
(a) Al B2 C3 D4 (b) Al B3 C4 D2
(c) A4 B3 C2D1 (d) A3Bl C4 D2
Paper 295
2. In mitochondria, protons accumulate in
(a) Outer membrane (b) Inner membrane
(c) Matrix (d) Peri-Mitochondrial space
3. Which one is stress hormone?
(a) C2H4 (b) GA3
(c) IAA (d) ABA
4. Serum differs from blood in
(a) Lacking clotting factors (b) Lacking antibodies
(d) Lacking albumins (d) Lacking globulins (d)
5. Which of the following is correct?
(a) CNS includes brain and spinal cord
(b) CNS is the site of information, processing and control
(c) PNS comprises of all the nerves of the body associated with CNS
(d) All three
6. Enzyme amylase belongs to-
(a) Oxidoreductases (b) transferase
(c) Hydrolases (d) Isomerases
7. Incomplete double circulation is found in-
(a) Mammals (b) Non-ehordates
(c) Amphibians and reptiles (d) Birds
8. Electrical potential difference across the depolarized membrane is called
(a) Resting potential (b) Action potential
(c) Solute potential (d) Osmotic potential
9. Which stage is marked by terminalisation of chiasmata?
(a) Zygotene (b) Pachytene
(c) Diplotcnc (d) Diakinesis
10. Different cells have different sizes. Arrange the following cells in an
ascending order according to their size and select the correct option

296 Biology Class - 11

 (1) Mycoplasma (2) Ostrich egg
(3) Human RBC (4) Bacteria
(a) 1,4,3,2 (b) 2,1,3,4
(c) 1,2,3,4 (d) 3,2,1,4
11. Bryophytes are not characterised by
(a) Well developed root system and vascular tissue
(b) Rhizoids
(c) Alternation of generation
(d) Presence of chlorophyll
12. Common characteristics between flatworms, roundworms and earthworms
is
(a) Parasitism (b) acoelomate nature
(c) Triploblastic (d) Pseudocoelomate
Question No 13 to 16 consists of two statements- Assertion and Reason.
Answer these questions selecting the appropriate options given below:
(a) Both assertion & reason are true, and the reason is the correct explanation
of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct
explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion & reason are false.
13. Reason: To maintain unequal distribution ol Na' and K' ions, neurons use
electrical energy.
Reason: To maintain unequal distribution of Na' and K* ions, neurons us.
14. Assertion: Left atrium possesses ihe thickest muscles.
Reason: Left atrium receives blood from the superior and inferior vena
cava.
15. Assertion: A cell membrane shows fluid behaviour.

Paper 297
 Reason: A membrane is a mosaic of lipids and proteins.
16. Assertion: Bryophytes exist in 2 phases - gametophyte and sporophyte.
Reason: Sporophyte in bryophytes is nutritionally independent.

Section-B
17. What is the correct way of writing a scientific binomial name? Illustrate
with an example.
18. List 4 peculiar features that are present in parasitic platyhelminthes.
OR
How do earthworm and Ascaris differ with respect to coelom?
19. "Inspiration in humans is a negative pressure phenomenon". Justify.
OR
"In mammals, the lungs replace the skin very effectively as respiratory
organs". Explain giving any 2 reasons.
20. The digestive system of frog is made of following parts. Arrange them in an
order beginning from mouth.
Mouth, oesophagus, buccal cavity, stomach, cloaca, intestine, rectum,
cloacal aperture
21. Which are chiasmaia? State their significance.

Section-C
22. Tabulate 6 differences between Kingdom Monera and Kingdom Protista.
23. (i) Define Placentaiion.
(ii) How can you differentiate between free central and axile placentaiion.
24. Briefly describe the life cycle of bryophytes with the help of a flowchart.
25. Answer the following:
(i) Mention the (>pc of ribosome* found in mitochondria and p last ids
(ii) Would our expect the cells that form hairs lo contain more ribosomes
than the cells vesica itore lais? Why?
OR

298 Biology Class - 11

 How do neutral solutes move across the plasma membrane? Can the polar
molecules also move across it in the same way? If not, then how are these
transported across the membrane?
26. (i) What are the end products of light reaction?
(ii) Chlorophyll 'a' is the primary pigment for light reaction. What are
accessory pigments? What is their role in photosynthesis?
27. "Auxin and cytokinin show synergistic as well as antagonistic action in
plants". Justify the statement with the help of an example.
28. Give reason for the following statements:
(i) Steroid hormones act within the cells.
(ii) Hormones released by posterior Pitutary are not its own products.
(iii) Adrenals are called 'glands of emergency'.
OR
Name the 2 pancreatic hormones responsible for maintaining sugar level in
the human body. How do they maintain sugar level in the blood?

Section-D
29. Fermentation occurs in yeast cells, bacteria and in the muscles of animals
under anaerobic condition. Cellular respiration begins with glycolysis where
a 3-C compound, pyruvic acid is formed as the end product. There are 2
main types of fermentation. In lactic acid fermentation sugar is converted
into lactic acid by lactobacillus and muscle cells. Lactobacillus is used in
setting curd due to its unique property. In alcoholic fermentation, pyruvate
is broken down into ethyl alcohol and carbon dioxide by yeast.
Due to this properly, yeast is used in making bread and wine.
(i) Lactic acid fermentation occurs in:
(a) Muscles under anaerobic condition
(b) Some bacteria
(c) Aerobes
(d) Both (a) and (b)

Paper 299
 (ii) Differentiate between alcoholic fermentation and lactic acid fermentation
(write any 3 points).
OR
Only 2 ATPs molecule are formed from one glucose molecule during
fermentation. Explain how is it possible?
30. Around 10% of the Indian population suffers from chronic kidney disease
and every year 1 lakh cases of kidney failure are being reported. Most
common causes of kidney-failure are diabetes, high blood pressure, recurrent
dehydration, renal infection etc. With the help of a machine called dialysis
machine, blood can be filtered and purified. It assists in maintaining balance
of electrolytes and fluids, removing nitrogenous waste from blood when
kidney fails to perform and carry out its functions.
(i) What is the composition of the membrane that is used in dialysis
machine?
(ii) What happens to the plasma proteins during haemodialysis?
(iii) What is a dialysis machine? When is it needed?

Section-E
31. (i) Why are xylem and phloem called "complex tissue"?
(ii) Name the 4 major components of phloem.
(iii) From which part of the plant Jute, hemp and flex fibres are obtained.
OR
(i) Explain the 3 types of meristem present in plants.
(ii) What is the difference between fibres and sclereids? Give one example
of each.
32. (i) List 4 features of DNA structure.
(ii) A DNA fragment has total 1,000 nucleotides, out of which 240 are
adenine containing nucleotides. How many pyrimidine bases this DNA
possesses?

300 Biology Class - 11

 OR
Explain any 5 classes of enzymes with suitable example.
33. Explain in detail the mechanism of muscle contraction as given by Sliding
filament theory.
OR
(i) What are the 3 types of muscles? Write 2 characteristic features about
the structure and function of each of them.
(ii) Name the cells/ tissue in the human body which-
(a) Exhibit amoeboid movement
(b) Exhibit ciliary movement

Paper 301
 Notes
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
________________________________________________
_____________________________________________________________________________________________________________________________________________