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CLASS 10TH
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SKIE CLASSES SRINAGAR CLASS 10TH BIOLOGY #8899880136
 Life Process 3

Process
1
LIFE PROCESSES
Life is not a thing or a material substance. It is a series of processes. The basic functions or
activities performed by living organisms to maintain their life on earth are called life processes.
Physiology is the branch of science which deals with the study of life processes and the functions of
different organs and tissues. The basic life processes are nutrition, respiration, transportation,
excretion, movement, reproduction, growth and control & co-ordination.

NUTRITION
Nutrients: Food contains various organic and inorganic substances. Those which are required by
the organisms to carry out life functions are called nutrients. Nutrients are of various types like
carbohydrates, fats, proteins, vitamins and minerals. The various nutrients carry out different
functions.
Food is an organic substance that when absorbed into the body tissues yield materials for the
regulation of energy, the growth and repair of tissues and regulation of life processes, without
harming the organism. Glucose is the simplest form of food. carbohydrates and fats are known as
energy foods because they only provide energy, proteins and mineral salts are known as Body
building foods because they are used to build up body mussels whereas vitamins are known as
regulating food. Nutrition is a process of intake of nutrients like carbohydrates, fats, vitamins,
minerals and fluids and its digestion, absorption and assimilation by an organism as well as the
utilization of these nutrients for energy purpose by the organism.
HOW DO ORGANISMS GET THEIR FOOD / MODES OF NUTRITION: Modes of nutrition
means methods of obtaining food by an organism. They are mainly classified into three main types
and are:
(a) Autotrophic nutrition
(b) Mixotrophic Nutrition
(c) Heterotrophic nutrition
(a) Autotrophic nutrition: (Auto = self & trophic = nutrition).So autotrophic nutrition means
self nourishing or it is that mode of nutrition in which an organism makes or synthesizes its own food
from the simple inorganic materials like CO2and H 2O with the help of sunlight energy &
Chlorophyll. e.g all the green plants, Algae and some bacteria etc. Autotrophic nutrition is divided
into two categories on the basis of the way of manufacturing of food.
(i) Photosynthesis.
(ii) Chemosynthesis.
(I) PHOTOSYNTHESIS/NUTRITION IN PLANTS (PHOTO-AUTOTROPHIC
NUTRITION OR PHOTOSYNTHESIS): Nutrition in plants takes place by the process of
photosynthesis. The existence of life on earth depends on photosynthesis. Photosynthesis is the only
process on earth by which solar energy is trapped by autotroph’s and converts it into food (glucose). In
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this process energy rich compounds like carbohydrates are synthesized from simple inorganic
compounds like carbon-dioxide, water, chlorophyll in presence of sunlight and with oxygen being
liberated as a by-product. Carbohydrates which are formed during photosynthesis if they are not
used immediately are stored in the form of Starch in plants.
The process by which green plants and some other organisms use chlorophyll, CO2 and H 2O to
synthesize food in presence of Sunlight is known as photosynthesis. Photosynthesis in plants
generally involves the green pigment chlorophyll and generates oxygen as a by-product. The
organisms which shows photosynthesis are referred as photo-autotrophs and this process is also
known as photo-autotrophic nutrition e.g. All green plants show this type of nutrition.
SITE OF PHOTOSYNTHESIS: Photosynthesis takes in green parts of a plant like in leaves &
green stems. Upper side of leaf has specialized cells called as Palisade mesophyll cells, these palisade
mesophyll cells contain many chloroplasts (cell organelle), these chloroplasts contain a green
pigment called as chlorophyll. Chloroplast containing cells are present in more quantity on upper
side than lower side of a leaf. Thus, they are able to get more sunlight energy. Veins in leaf bring
water for photosynthesis.
SOURCES OF RAW MATERIALS FOR PHOTOSYNTHESIS: (conditions necessary for
photosynthesis)
(i) Carbon-Dioxide
(ii) Water
(iii) Chlorophyll
(iv) Sunlight Energy
(i) Carbon-Dioxide: Carbon-dioxide is present in low concentration in atmosphere (0.32%).
Carbon-dioxide enters the leaf through stomata ( a pore present below side of a leaf flanked by two
guard cells). Hydrophyte plants use CO 2 dissolved in water.
(ii) Water: Water is absorbed from the soil through root hair cells. Water moves by osmosis from
root cell to root cell until it reaches the xylem. It is transported up through the xylem vessels to the
leaves. In leaves less water is used up for photosynthesis, rest evaporates from the leaves by the
process of Transpiration. This transpiration results in more water being drawn up from the roots.
(iii) Chlorophyll: Pigments involved in the process of photosynthesis are known as
photosynthetic pigments. Pigments like chlorophyll, Carotenoids, Anthrocyanin and Phycobilins may
be found in a plant cell, but in photosynthesis only chlorophyll is used. Chlorophyll is a green pigment
present in chloroplast. The role of chlorophyll in photosynthesis is vital. Chlorophyll is necessary in
order to convert carbon-dioxide and water by using sunlight, into Glucose and oxygen.
Inner membrane Thylakoid

Outer membrane
Stroma

(Internal Structure of a Chloroplast)

(iv) Sunlight: Chlorophyll traps sunlight energy in the form of Quanta or Photons (packets of
energy emitted by light) and converts it into chemical form of energy i.e ATP (Adenosine
tri-phosphate). Sunlight provides energy required to carry out Photosynthesis. Plants use only 3-6%
of total solar energy.

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HOW FOOD IS SYNTHESIZED DURING PHOTOSYNTHESIS: Just like other organisms,
plants also require food which can supply energy for their various life activities. Green plants
manufacture their own food by the process of photosynthesis. In photosynthesis, energy rich
compounds like carbohydrates are synthesized from simple inorganic compounds like carbon-dioxide,
water, in presence of chlorophyll and sunlight energy accompanied by the liberation of Oxygen gas.
Carbon dioxide is taken from atmosphere by leaves through stomatal pores and water is absorbed by
root hairs which supply this to xylem and finally to leaf veins. In this process light energy is
converted into chemical energy by cholorophyll which is present in the leaf. The process of
photosynthesis takes place in Choloroplast of mesophyll cells of green leaves in a plants. The food
prepared by the green leaves of a plant is in the form of simple sugar called glucose, which undergoes
the process of respiration to release energy, which is used in various metabolic activities. The extra
glucose is stored in the form of starch. The equation for this process can be given as:
Glucose ⎯G⎯yl⎯coly⎯s⎯si → Pyruvate ⎯ O⎯yx⎯ge⎯n → 6H 2O + 6CO 2 + 38 ATP
in cytoplasm (2 molecules) (in mitochondria) (energy)

Photosynthesis occur in two phases or steps:

● Light Phase.

● Dark phase.

(A) Light phase/ Light reaction/Hill reaction/Photochemical reaction: This is a type or

phase of photosynthesis in which sunlight energy is used to manufacture food and is also called as
light dependent phase. This reaction takes place inside the thylakoid of chloroplast. The main
purpose of the light reaction is to generate organic energy molecules such as ATP & NADPH
(nicotinamide adenine dinucleotide phosphate). This reaction happens in various steps:
(i) Absorption of light energy by chlorophyll: This step takes place in thylakoid region of
chloroplast and involves energy from the sun which is trapped by chlorophyll. Chlorophyll molecule
emits electrons when exposed to sunlight.
(ii) Formation of ATP: ADP present, joins with phosphate group and forms ATP
(Adenosine tri-phosphate). This formation of ATP from ADP is termed as Photophosphorylation.
(iii) Photolysis of water: in this step water splits into Oxygen and Hydrogen gas by sunlight
energy, this process is called as photolysis of water.
 6 Biology-X
(iv) Synthesis of NADPH: The released hydrogen ion from water is available to bind with
NADP and reduces it to NADPH.
(B) Dark phase/Dark reaction/Blackmans reaction/chemosynthetic reaction: This is a
type or phase of photosynthesis in which sunlight energy is not used to manufacture food and is also
called as light independent phase. Instead of sunlight CO2 is used. This reaction takes place in
Stroma region of chloroplast. Dark reaction makes use of ATP & NADPH, which were formed in light
reaction. This phase or reaction is also called as Calvin Benison Cycle. ATP provides energy whereas
NADPH provides electrons to convert CO2 into carbohydrate (glucose).
(b) Mixotrophic Nutrition: Some green organisms like E. viridis & E. gracilis shows
autotrophic mode in presence of Sunlight energy but shows saprotrophic mode (heterotrophic) in
absence of Sunlight energy, This dual mode of nutrition is known as Myxotrophic nutrition.
(c) Heterotrophic nutrition: (Hetero = others & trophe = nutrition). S The heterotrophic
nutrition means nutrition or food obtained from others. Heterotrophic nutrition is that mode of
nutrition in which an organism can’t make or synthesize its own food from simple inorganic materials
like CO2 & H 2O but these organisms depend on other organisms for their food.
All animals have a heterotrophic mode of nutrition .Most bacteria, Protists, Some non-green
plants (parasitic plant like Cuscuta) and fungi also have heterotrophic mode of nutrition. These
organisms take readymade food from plants and other animals. They are unable to manufacture
their food because they do not have chlorophyll so, cant trap sunlight energy. Those organisms which
have Heterotrophic mode of nutrition are called heterotrophs. On the basis of nature of food
heteotrophic nutrition is of three types:

Types of Heterotrophic nutrition

A heterotrophic organism can obtain its food from other organisms in three ways and the ways are:
(a) Saprotrophic nutrition.
(b) Parasitic nutrition.
(c) Holozoic nutrition.
(a) Saprotrophic nutrition: saprotrophic nutrition is that nutrition in which an organism
obtains its own food from dead & decayed matter, and rotten bread etc. The organisms which obtains
nutrition by this method are called saprotrophs. Saprotrophs like fungi and Bacteria release
digestive enzymes to breakdown solid organic food into soluble form. These organisms act as
decomposers in an ecosystem. e.g Fungi (yeast, mushrooms), many bacteria & some flowering plants
like Neottia, Monotropa.
(b) Parasitic nutrition: The parasitic nutrition is that nutrition in which an organism derives
its food from the body of another living organism is called parasitic nutrition. The organism which
obtains the food is called a parasite and the organism whose body food is obtained is called the host.
Some times a parasite may damage or kill its host by a phenomenon known as parasitism. e.g
Roundworms, Fungi, Plasmodium, lice and Tapeworms & some non- chlorophyllous plants are some
examples of parasites. Some Parasites cause diseases in humans and are known as pathogenic
parasites. Some parasites live out side the host and derives their food, these parasites are known as
ectoparasites. E.g of ectoparasites are: Bed-bug, lice & Ticks. Whereas some parasites live inside host
body and these parasites are known as endoparasites. E.g of endoparasites are: Tenia, plasmodium,
malarial parasite & E-Coli bacteria.
Some green organisms like E. viridis & E. gracilis shows autotrophic mode in presence of
Sunlight energy but shows saprotrophic mode (heterotrophic) in absence of Sunlight energy, This
dual mode of nutrition is known as Myxotrophic nutrition.
(c) Holozoic nutrition: Holozoic nutrition means feeding on solid food. The holozoic nutrition is
that nutrition in which an organism takes the complex organic food material into the body by the
process of ingestion. The ingested food is digested and then absorbed into body cells of the organism.

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e.g Human beings and most of animals have holozoic mode of nutrition. Depending upon the source of
food, Holozoic or holotrophs are of following types:
(i) Herbivours: (Herba = plants & vorare = to eat). Thus, herbivours are those living things
which eat only plants or plant products only. So, they are also called as plant eaters. E.g:- Sheep,
deer, horse & rabbit etc.
(ii) Carnivours: (Cornis = meat or flesh & vorare = to eat). Thus, Carnivours are those living
things which eat other animals or animal products only. E.g: Lion, tiger etc.
(iii) Omnivours: (Omni = Both way & vorare = to eat). These are those living things which eat both
plants as well as animals or their products.e.g: Human beings, crow etc.

NUTRITION IN LOWER ORGANISMS

Digestive system is different in various organism. In single celled organisms, the food may be
taken in by the entire surface. As the complexity of the organism increases, different parts became
specialized to perform different functions.
NUTRITION IN AMOEBA AND PARAMECIUM: Amoeba is an important protozoa,
unicellular animal, Omnivoric and holozoic. found in fresh water. It feeds on microscopic organisms
like Bacteria, paramecia, diatoms, dead matter, plants and animals present in water. The mode of
nutrition in amoeba is Holozoic. And the process of obtaining food by amoeba is called phagocytosis.
Amoeba has no mouth and takes food by using temporary finger like projection called pseudopodia.
The different processes involved in the nutrition of amoeba are:-
1. Ingestion: Ingestion is the process of taking food in the body. Amoeba is a unicellular animal,
so it doesn’t have a mouth for ingestion of food. Amoeba ingests the food by encircling it by forming
pseudopodia. When the food is completely encircled, the food is engulfed in the form of a bag called
food vacuole.
2. Digestion: Digestion is the process of breaking the large and insoluble molecules in small and
water soluble molecules. In amoeba, several digestive enzymes react on the food present in the food
vacuoles and break it down into simple and soluble molecules. In the unicellular organisms like
amoeba the enzymes secreted by the cell cytoplasm act upon the food in small food vacuoles which is
then digested this type of digestion is called as “intracellular digestion”.
3. Absorption: The food digested by digestive enzymes is then absorbed in the cytoplasm by the
process of diffusion. While the undigested food remains in the food vacuole. If a large amount of food
is absorbed by amoeba, the excess food is stored in the cytoplasm in the form of glycogen and lipids.
4. Assimilation: During this step the food absorbed by the cytoplasm is used to obtain energy,
growth and repair. This process of utilizing absorbed food for obtaining energy, repair and growth is
called assimilation.
5. Egestion: When a sufficient amount of undigested food gets collected in the food vacuole, it is
thrown out of the body by rupturing cell membrane. The process of removal of undigested food from
the body is called egestion.
In Paramecium which is also a unicellular organism. Paramecium cell has definite shape and food
is taken in from specific spot. Food is moved to this spot by the movement of cilia which cover entire
surface of the cell.
 8 Biology-X

Food particle

Nucleus

Pseudopodia

Food vacuole

Food particle

NUTRITION IN HUMAN BEINGS

(Higher Organisms)
The nutrition in higher organisms like human beings, fishes and other vertebrates takes place
through specialized a modified digestive system. This digestive system is formed of main two parts
and are Alimentary canal and digestive glands. Alimentary canal is further differentiated into many
small organs which perform different functions, so, there is physiological division of labor.
Alimentary canal is also called as digestive tract or Gut, and is about 9 meters long tube open on both
sides. Study of Digestive system is called Gastroenterology. The various organs of Human alimentary
canal are:
Mouth
Buccal cavity / oral cavity
Pharynx
Oesophagus (food pipe)
Stomach / Gaster
Small intestines / Small Bowel
Large intestines / Large Bowel / Colon
Anus.
● Mouth: it is an opening present between two lips.

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● Buccal cavity: Buccal cavity is also called as oral cavity. It is a complex organ of alimentary
canal and is made up of multiple small organs and they are:-
(a) Two lips or Labia: Lips are soft, movable, and serve as the opening for food intake and in the
articulation of sound and speech.
(b) Vestibule: It is the space present between lips and teeth.
(c) Gingiva or Gums: The gums are part of the buccal cavity and they surround the teeth
and provide a seal around them.
(d) Tongue or Lingua / Glossa: Tongue is a thick, muscular and protractible structure in the
mouth. Tongue contains tiny bumps called taste buds or papillae on its surface which give the tongue
its rough texture. Thousands of taste buds cover the surface of the papillae and they are only of four
types; Filliform taste buds which detect sweet taste, Foliate taste buds which detect sour taste,
Fungiform taste buds which detect salty taste & Circum-vallate taste buds which detect Bitter taste
of food.
(e) Teeth: The teeth are the non-living & hardest substances in human body made up of calcium
phosphate. Teeth are present in both the jaws in semicircular fashion. They are embedded in jaws
(Sockets) that is why they are called as Thecodont. In adult humans 32 teeth are present and they are
of four types for performing different functions and are as: Incisors (biting teeth), Canines (cutting
teeth), premolars (first molars or bicuspids) and Molars (second molars or chewing teeth or grinding
teeth). This different type of dentation is known as heterodont. In humans two successive sets of
teeth are developed during the lifetime that is why they are called as Diphyodont. The first set of
teeth is milk teeth or deciduous teeth and the next set is of permanent teeth. Dental formula of
permanent teeth is 2123/2123. The teeth help in Mechanical digestion of food i.e they cut, chew and
grind the food in buccal cavity, which increases the surface area of food to mix digestive enzymes and
digest properly.
(f) Palates: Palates form the roof of the mouth and it divides nasal cavity with the oral cavity.
Palates are of two types in our mouth and are as: Hard palate or bony palate or anterior palate and
another one is soft palate or muscular palate or posterior palate or velum.
(g) Uvula: It is a small piece of flesh that hangs from the top of the inside of the mouth just above
the throat. It arises from soft palate and prevents food from going to nasal cavity and it also secretes
saliva.
(iii) Pharynx or Throat: it is a part present between buccal cavity and food pipe having size of 5
inches. The pharynx is the common passage for deglutition (swallowing) and respiration. It is divided
into three parts; Nasophraynx, Orophraynx & Laryngophraynx.
(iv) Oesophagus or Food pipe: Oesophagus is a long, narrow tube present between mouth and
stomachhaving length of 25 cms. The muscles of stomach contract and expands to allow food into the
stomach by a process called as peristalsis. First opening of food pipe is called Gullet & its last opening
is called gastro-oesophageal opening and this opening is guarded by gastro-oesophageal sphincter.
(v) Stomach or Gaster: It is a thick, muscular and J-shaped digestive organ that is located in
the upper abdomen under ribs. It is the widest part of alimentary canal. It has four main parts
namely; Cardia, Fundus, Body & Pylorus. Pylorus is the last part and is guarded by pyloric sphincter.
(vi) Small intestine or Small Bowel: It is a long approximately 7.5 meters long narrow tube
present between stomach and large intestine. it is the place where most of the digestion and
absorption takes place. The small intestines have three regions
(a) Duodenum: it I s the first part and the smallest part of the small intestine with a length of
30cms & receives bile juice & pancreatic juice.
(b) Jejunum: it is the middle part of small intestine with a length of 2.5 meters. Most of the food
is absorbed in jejunum.
 10 Biology-X
(c) Ileum: it is the longest part of small intestine with a length of 3 meters. The digestive
products which were not absorbed in jejunum are absorbed here in ileum and Vitamin B12 and bile
salts are also absorbed. At the end of ileum is a sphincter known as ileocecal valve.
(vii) Large Intestine or Large Colon or Large bowel: It is a shorter and wider than small
intestine with a length of 1.5 meters & meant for absorption of water and remaining waste materials
is stored here as feces before being removed by defecation. It is made up of six parts:
(a) Colon: It is a tubular structure and is about 1.5 meter. It is further divided into Caecum,
ascending colon, transverse colon, descending colon & Sigmoid colon.
(b) Rectum: Rectum is a doom shaped chamber, present at the end of large intestine. It is meant
for storage of feces for defecation.
(viii) Anus: It lies at the base of gastrointestinal tract and is the opening of the rectum to the
outside of the body. It is guarded by anal sphincter.
The glands which are associated with the human digestive system and form a part of human
digestive system and secrete digestive juices which contain digestive enzymes and they are:-
● Salivary glands: In humans there are 3 pairs of salivary glands (Parotid salivary glands,
submandibular salivary glands & sublingual salivary glands) and they secrete saliva which
performs many functions like lubrication, digestion and immunity. Saliva contains ptyalin or
salivary amylase enzyme, HCO3, antibodies & Lysozyme enzyme.
● Gastric glands: Gastric glands are present in the walls of stomach & are made up of three
types of cells i.e Chief cells or peptic cells which secretes Pepsinogen (inactive enzyme),
Oxyntic cells or parietal cells which secrete Hydrochloric acid (HCl) & mucous cells or goblet
cells secrete mucous.
● Liver: The largest solid organ in the body, lobulated, vital and reddish brown coloured,
situated In the upper part of the abdomen on the right side. Liver produces Bile juice
(yellowish green coloured). Bile juice contains bile salts (Sodium bicarbonate, sodium
taurocholate and sodium glycocholate) & Bile pigments (Bilirubin & Biliverdin). It also stores
glucose in the form of glycogen for energy use until needed.
● Pancreas: A long, flat and yellow coloured digestive gland also called as heterocrine gland
(dual function: exocrine as well as endocrine) present just below the stomach. It secretes
pancreatic juice which contains a number of important digestive enzymes, including trypsin,
pancreatic lipase and pancreatic amylase etc. this juice is alkaline in nature because of high
concentration of bi-carbonate ions(base), this alkaline nature helps to neutralize the acidic
juice from the stomach.
● Intestinal glands: The walls of the small intestine contains intestinal glands (Brunner’s
gland, Payer’s patches & Crypts of Lieberkuhn) which secrete intestinal juice called Succus
entericus this juice contains enzymes called disaccharidases (sucrase, lactase, maltase &
isomaltase).
Process Nutrition in human beings is a vast and long process and takes place in various steps and
are:
Ingestion: Taking of food & putting it into the mouth with the help of hand is called Ingestion.
Digestion: Digestion means breaking down of large substances into smaller pieces. In human
beings digestion of food starts from mouth. The teeth cut the food into small pieces, chew and grind to
increase the surface area of food particles, this is called physical digestion or mechanical digestion.
The salivary glands in our mouth secrete saliva which contains an enzyme called salivary amylase Or
Ptyalin which digests the carbohydrates which is a polysaccharide (made up of many sugars) into
disaccharide (made up of only two sugars), this is called chemical digestion. Our tongue helps in
mixing this saliva with food. The slightly digested food is swallowed and goes down into the food pipe
or esophagus, the walls of the food pipe start contraction and expansion movements called as

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peristaltic movements or peristalsis. Peristaltic movement pushes the food into the stomach via
gastroesophageal sphincter. Chief cells or peptic cells or zymogenic cells of stomach wall secrete
Pepsin enzyme which digests proteins into amino acids. Mucous cells or Goblet cells secrete mucus
which helps to lubricate food so, passage of food becomes easy through intestines and it also protect
stomach wall from hydrochloric acid effect. Oxyntic cells or parietal cells of stomach wall secrete
hydrochloric acid which creates an acid medium inside stomach & kills microbes injected with food
and facilitates the action of the pepsin enzyme to digest proteins into amino acids. The partially
digested food then goes into Duodenum via Pyloric sphincter, this duodenum part receives secretions
of two glands (liver and pancreas). The duct arises from liver is called common Hepatic duct, the duct
arises from gall bladder is called Cystic duct and the duct which arises from pancreas is known as
Pancreatic duct or duct of wirsung. Common Hepatic duct & cystic duct unites to form Common bile
duct (CBD), this common bile duct then passes downwards posteriorly to join the main Pancreatic
duct at Sphincter of Boyden and forms a common duct called as Hepatopancreatic duct. This
hepatopancreatic duct contains both bile juice as well as pancreatic juice. This hepatopancreatic duct
reaches the duodenum and forms Hepatopancreatic ampulla or Ampulla of Vater & this ampulla is
guarded by Sphincter of Oddi. Sodium bi-carbonate of bile juice neutralizes HCl mixed with chime
while as Sodium glycocholate & sodium taurocholate emulsifies the fat into fatty droplet & the
process is known as emulsification. Bilirubin & Biliverdin (waste materials) of bile juice provides
color to the digested food. While as the Trypsinogen of pancreatic juice helps in digestion of
undigested proteins; pancreatic lipase helps in the digestion of Fatty droplets and pancreatic amylase
helps in the digestion of undigested polysaccharides (carbohydrates). The intestinal glands secrete
intestinal juice called Succus entericus, which contains disaccharidase enzymes (maltase, sucrase,
dextrase & Fructase) which finally convert the disaccharides (Maltose, sucrose, dextrose & fructose)
into Glucose (monosacchadise) & Hence
digestion of food is completed. In
multicellular organisms the food passes
through a food pipe known as the alimentary
canal several enzymes act upon the food and Mouth Parotid Salivary
help in digestion and the digestion in this Sublingual
glands
case takes place outside the cell and hence is Submandibular
known as “extra cellular digestion”. The Pharynx
digestion which takes place inside the cell is Trachea
known as intracellular digestion.
Oesophagus
Absorption: The small intestines is the
main region for the absorption of digested
food. The inner surface of the small intestines Stomach
Diaphragm
has numerous fingers like projections called
Liver (cut)
Villi which increase the surface area of for Gall bladder Spleen
rapid absorption of digested food. The Duodenum
molecules of the digested food are so small Common bile duct Large intestine
that they can pass through the walls of the Pancreas
(transverse colon)
small intestine which contain blood vessels. Small intestine

This digested food is now absorbed by walls of

small intestines and goes into our blood. This
Caecum Sigmoid colon
process is called absorption. Appendix
Assimilation: The process of carrying of Rectum
Anus
absorbed food molecules by blood to all the
(Digestive System of Human being)
cells of our body where it becomes
assimilated and is utilized for obtaining energy. The process is known as assimilation.
Egestion/ Defecation: It Also known as defecation. The undigested or unabsorbed food
remained is sent to large intestines where more villi absorb water from this material and remained is
 12 Biology-X
passed out in the form of feces through Anus, the exit of feces is regulated by an anal sphincter. The
process is known as egestion.
DENTAL CARIES: This is also known as tooth decay. Teeth are the hardest material of human
body composed of calcium phosphate. Enamel is the outermost covering of a tooth, below enamel is
present another layer known as dentine and is similar to a bone. This dentine covering surrounds the
pulp cavity which contains blood capillaries, nerves etc.
Dental caries is one among the most common diseases of teeth, mainly it occurs to premolars and
molars due to larger surface area. Generally it is common in those persons whose diets are rich in
carbohydrates which needs less chewing and stick to the teeth. Dental caries is caused by acidogenic
bacteria (acid producing) like streptococcus mutans, in presence of high sugar concentration.
Symptoms of this disease is characterized by softening of enamel and dentine coverings due to
decalcification. Many Bacteria and food particles stick to teeth and form dental plaques to cover the
teeth. Saliva can’t neutralize the acid (formed by bacteria). Finally it leads to existence of cavities in
the teeth and inflammation of pulp with swear pain called as pulpitis. Preventive measures can be to
avoid sugar rich eatables, regular brushing of teeth after meals & vigorous chewing of fibrous foods.

RESPIRATION
Inhalation: Intake of O2 into the body is called Inhalation.
Exhalation: Out put of CO2 from the body is called Exhalation.
Breathing: Intake of oxygen and output of carbon-dioxide is called breathing.
Respiration: The process of respiration involves taking of Oxygen through nose to lungs and
then sent it into the cells ,using it for releasing energy from food and elimination of Carbon -dioxide
and water from the body is known as Respiration. Respiration process can be represented as:
Food + O2 ⎯⎯→ CO2 + H 2O + Energy
(oxygen) (Carbon−dioxide) (water)

The process of respiration takes place inside the cells of the living body. So, it is also known as the
cellular respiration. Respiration is essential for life because it provides energy for carrying out all the
life processes which are necessary to keep the organisms alive. We can study cellular respiration by
taking the example of the complete oxidation of glucose. This molecule is oxidized and broken down
gradually in two distinct stages. The first stage is called glycolysis, which involves anaerobic
respiration.
This takes place in the cytoplasm of the cell. The second stage involves aerobic respiration, which
takes place inside the mitochondria of the cell.
Process of respiration can be divided into two categories and they are:
Types of Respiration: There are two types of respiration and are:

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 Life Process 13
(a) Aerobic Respiration
(b) Anaerobic Respiration
(a) Aerobic respiration: It is that mode of respiration in which an organism uses oxygen for
Respiration is called aerobic respiration. In aerobic respiration the glucose food in the Cytoplasm of
the cell is completely broken down (glycolysis) into two Pyruvate molecules, The two pyruvate
molecules are transported into the Mitochondria of cell where Oxygen Combines with pyruvate
molecules and Combustion reaction takes place. The products formed at the end of the reaction are
Carbon-dioxide, water & Energy. The number of molecules of ATP formed in aerobic respiration is 38.
Hence the energy made available is much greater than in the case of anaerobic respiration.
Inside the mitochondria, when an inorganic phosphate group ( PO3− represented here as Pi) gets
4
attached to a compound called ADP (adenosine di-phosphate), a molecule of ATP (adenosine
tri-phosphate) is formed.
ADP + Pi → ATP
The energy formed during respiration is stored in the form of ATP molecules. Aerobic respiration
produces high amount of energy for use by the organisms. Mitochondria are the sites for aerobic
respiration in the cells. E.g:Human beings and plants. The combustion reaction can be represented as
follows:
Glucose ⎯G⎯yl⎯coly⎯s⎯si → Pyruvate ⎯ O⎯xy⎯ge⎯n → 6H 2O + 6CO2 + 38 ATP
In cytoplasm (2molecules) (in mitochondria) (energy)

(b) Anaerobic respiration: (Fermentation/Intramolecular) It is that mode of respiration in

which an organism doesn’t uses oxygen for respiration is called anaerobic respiration. The
microscopic organisms like yeast and some bacteria have anaerobic mode of respiration. In anaerobic
respiration the organism like yeast break down glucose into ethanol (ethyl alcohol), carbon dioxide
and energy. Anaerobic respiration produces much less energy which gets stored in ATP molecules. In
anaerobic respiration glucose gets converted into two molecules of private, which contains three
carbon atoms. These reactions also produce two molecules of ATP.
The oxidation of glucose in a series of reactions leading to the formation of private is called
glycolysis. Glycolysis means ‘splitting of sugar’. It takes place in all organisms, in the cytoplasm of
the cell. It is the first stage of respiration (both aerobic and anaerobic). After glycolysis, its prod uct
(private) gets converted into different compounds depending on whether further reactions take place
in the presence or absence of oxygen. Glycolysis is the last energy-producing stage in case oxygen is
absent or in low supply, and in cells that lack mitochondria. After glycolysis, further anaerobic
reactions produce different products like lactic acid or ethanol (ethyl alcohol) in different situations.
This step completes the anaerobic respiration of glucose. Anaerobic respiration resulting in the
formation of these products is also called fermentation.
Examples of lactic acid fermentation and alcohol fermentation are given below:
In a low supply of oxygen, yeast converts pyruvate to ethanol and carbon dioxide. Certain bacteria
(which lack mitochondria) convert pyruvate to lactic acid. When our muscles are overworked, blood is
unable to supply oxygen fast enough for producing energy through aerobic means. In this low-oxygen
condition pyruvate gets converted to lactic acid. Accumulation of excess lactic acid in the muscles
causes pain.
This can be represented as:
Glucose ⎯G⎯yl⎯coly⎯s⎯si → Pyruvate ⎯i⎯n a⎯bse⎯nce⎯o⎯
f O 2
⎯→ 2C2H 5 OH + 2CO2 + 2ATP
in cytoplasm (2molecules) in Yeast (Ethanol) (Energy)

Some times Anaerobic respiration takes place in Bacteria and in our muscles during heavy
physical exercise and can be represented as follows.
 14 Biology-X
Absence of oxygen
Ethanol+CO2
(Yeast) + Energy

Glucose ⎯G⎯yl⎯coly⎯s⎯si → Lack of oxygen

Pyruvate Lactic acid
in cytoplasm (3-carbon molecule) (In human muscle cells) + Energy

Presence of oxygen
CO2 + water
(In mitochondrial) + Energy
Difference between Aerobic and Anaerobic respiration
Aerobic Respiration Anaerobic Respiration
1. Aerobic respiration takes place in presence of 1. Anaerobic respiration takes place in
Oxygen. absence of Oxygen.
2. Complete breakdown of food occurs in aerobic 2. Partial break down of food occurs in
respiration. anaerobic respiration.
3. End products of aerobic respiration are CO2 , 3. End products of anaerobic respiration are
H 2O & Energy. CO2, Ethanol & Energy.
4. Aerobic respiration produces a high amount of 4. Anaerobic respiration produces much less
Energy. Energy.
5. Glycolysis and Kreb’s cycle occurs in it. 5. It has no Kreb’s cycle but Glycolysis only

RESPIRATION IN PLANTS: Plants like other animals also respire. Plants also need energy.
The plants get energy through the process of respiration in which glucose food breaks down in the
presence of oxygen to form carbon dioxide and water with the release of energy. This energy is used
by the plant for carrying out its various life processes. Thus, Like other organisms, plants also respire
for their survival. The respiration in plants differs from that of animals. In other words, in plants,
each part can independently take in oxygen from air, utilize it to obtain energy, and give o ut carbon
dioxide.
Respiration In Leaves: The leaves of plants
have tiny pores on their surface which are called
stomata. The exchange of gases in the leaves during
respiration takes place through stomata. This happens
as follows: Oxygen from the air enters into a leaf
through stomata and reaches all the cells by the
process of diffusion. This oxygen is used in respiration
in cells of the leaf. The carbon dioxide produced during
diffuses out from the leaf into the air through same
stomata.
The photosynthesis reaction makes glucose and
the respiration reaction break it down. In
photosynthesis, the energy which goes into the
reaction is light energy. In respiration, the energy
which comes out is chemical energy.

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 Life Process 15
Energy stored Energy released

respiration
C6H12O6 + 6O2 6CO2 + 6H2O
photosynthesis

Energy stored Sunlight

Respiration in plants happens throughout the day and night thereby carbon dioxide is produced.
However, during the daytime, the amount of carbon dioxide released is negligible compared to the amount
of oxygen produced as a result of photosynthesis. Hence, one should not sleep under a tree at night.

Respiration in Animals
Different animals have different types of respiratory organs which uptakes oxygen and removes
carbon dioxide out of body. For example, in unicellular organisms such as amoeba and paramecium
exchange of gases takes place through plasma membrane by simple diffusion. In earthworm, leech
and frogs exchange of gases takes place through their moist skin. In insects such as grasshopper and
cockroach respiration is done through spiracles and trachea. In aquatic animals such as fish
respiration takes place through special respiratory organs called gills. While in all the land animals
such as birds, dog, cat, cow and human’s respiration take place through special respiratory organs
called lungs. Now, we shall discuss respiration in amoeba, insects, earthworm, fish and human
beings in detail.

Respiration in Lower organisms (Amoeba & Paramecium)

We know that amoeba is a unicellular organism which O2
lives in fresh water. This organism does not have a CO2
specialized organ to do the process of respiration. So in
Food vacuole
amoeba respiration takes place through its cell membrane
also called plasma membrane. Amoeba gets oxygen gas
dissolved in surrounding water through its plasma Nucleus
membrane by the process of diffusion. The oxygen gas
Contractile
diffused inside the body is used up by amoeba. In the body vacuole
the oxygen gas absorbed is used to break down the complex
food material into simple molecules. During these metabolic reactions in the body of amoeba the
oxygen gas is converted into carbon dioxide gas. The carbon dioxide gas is also liberated in the
surrounding water through the same process of diffusion.
RESPIRATION IN FISHES: Gills mediate the gas
exchange in fish. These organs, located on the sides of the
head, are made up of gill filaments, feathery structures that
provide a large surface for gas exchange. The filaments are
arranged in rows in the gill arches, and each filament has
lamellae, discs that contain capillaries. Blood enters and
leaves the gills through these small blood vessels. Although
gills are restricted to a small section of the body, the
immense respiratory surface created by the gill filaments
provides the whole animal with an efficient gas exchange.
The surrounding water keeps the gills wet.
A flap, the operculum, covers and protects the gills of
bony fish. Water containing dissolved oxygen enters the fish's mouth, and the animal moves its jaws
and operculum in such a way as to pump the incoming water through the gills. As water passes over
 16 Biology-X
the gill filaments, blood inside the capillaries picks up the dissolved oxygen. Since the blood in the
capillaries flows in a direction opposite to the flow of water around the gill filaments, there is a good
opportunity for absorption. The circulatory system then transports the oxygen to all body tissues and
picks up carbon dioxide, which is removed from the body through the gills. After the water flows the
gills, it exits the body behind the fish's operculum.

RESPIRATION IN HUMAN BEINGS

(LUNG RESPIRATION/ PULMONARY RESPIRATION)
The respiratory system (also respiratory apparatus, ventilatory system, gas exchange system) is
a biological system consisting of specific organs and structures used for gas exchange or rid of carbon
dioxide and taking in oxygen. Carbon dioxide, a waste product, goes out of the body. Oxygen, which
the body needs, comes in. The lungs are the main organ to do this. The main organs of this
respiratory system are:-
Nose
Nasal passage
Pharynx
Trachea (Wind pipe)
Bronchi
Lungs &
Diaphragm
The first step in respiration is breathing of oxygen, or inhaling. The second step is gas exchange
in the lungs where oxygen is diffused into the blood and the carbon dioxide diffuses out of the blood.
The third process is cellular respiration, which produces the chemical energy that the cells in the
body need, and carbon dioxide. Finally, the carbon dioxide from cellular respiration is breathed out of
body from the lungs.
The human respiratory system begins from the nose there is a passage behind the nostrils which
is called nasal passage. The O2 for respiration is drawn into our body through the nasal passage the
dust particles present In Oxygen are trapped by nasal hairs to clean air that goes into the lungs. The
part of the throat between the mouth and the windpipe is called as pharynx. From nasal passage air
enters into pharynx which then goes into the windpipe or trachea. The trachea runs down th e neck
and divides into two smaller tubes called bronchi at its lower end. The two bronchi are connected with
two lungs. The lungs are separated from abdominal cavity by a muscular layer called diaphragm.
Each bronchus divides in the lungs to form a large number of smaller tubes called bronchioles. At the
end of these bronchioles tiny air sacs or grape wine like structures are present called alveoli. The
walls of alveoli are surrounded by blood capillaries. It is the alveoli where gaseous exchange takes
place. During breathing the lungs expand, decreasing the air pressure in the lungs. This is caused by
the diaphragm (a sheet of muscular tissue that separates the lungs from the abdomen) and the
muscles between the ribs contracting to expand the chest, which also expands the lungs. As the air
pressure inside the lungs are lower when it has expanded, air from outside at higher pressure comes
rushing into the area of low pressure in the lungs.
The lungs are made of many tubes or branches. As air enters the lungs, it first goes through
branches called the bronchi, then through smaller branches called bronchioles, and finally into the
air sacs. Gas exchange occurs in the air sacs where oxygen is exchanged with carbon dioxide. The
carbon dioxide in the air sacs now need to be exhaled, or breathed out. In the reverse process to
inhaling, the diaphragm and the rib muscles relax, causing the lungs to be smaller. As the air
pressure in the lungs is greater when the lungs are smaller, air is forced out. The exhaled air ha s a
high concentration of carbon dioxide and a low concentration of oxygen. The maximum volume of air
that can be breathed in and breathed out is called the vital capacity of the lungs and is up to five
liters.

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The inhaled air goes down to the air sacs at the end of each bronchiole. The air sacs are called
alveoli, they have a large surface area, and are moist, thin, and close to a blood supply. The inhaled
air has a much greater concentration of oxygen than carbon dioxide whilst the blood flowing to the
lungs has a more carbon dioxide than oxygen. This creates a concentration gradient between the air
in the air sacs and the blood, meaning there is more oxygen in the air than the blood.
As the alveolar membrane, oxygen can easily diffuse in and out. Oxygen at high concentration in
the alveoli diffuses into the haemoglobin of blood (where oxygen concentration is low) and forms
oxy-haemoglobin, and carbon dioxide at high concentration in the blood diffuses into the air sacs
where carbon dioxide concentration is low (So, haemoglobin is called respiratory pigment). It is the
alveoli where gaseous exchange takes place. As the blood passes through the tissues of the body, the
O2 present in it diffuses into the cells. The oxygen in the blood is passed to all the cells and is used by
the cells in the body. The O2 combines with the digested food present in the cells and releases energy
from it. CO2 gas is produced as a waste product during respiration in the cells. The carbon dioxide is
finally sent back from cells to alveoli through same path and is exhaled out from the body.
The breathing rate in an adult man at rest is about 15-18 times per minute.

(Respiratory System of Human Being)

Pulmonary venule

Pulmonary arteriole

Alveolus

Capillary network

TRANSPORTATION
Transportation: In Biology, transportation is a life process in which a substance absorbed in
one part of the body of an organism is carried to other parts of its body. Large organisms need
transport systems in their bodies to supply all their cells with food, O2, H 2O, & other materials.
Special tissues and organs are need for the transport of substances in plants and animals.
 18 Biology-X
Transportation in Plants
Transport system in plants is less elaborate than in animals. Plants are less active, so their cells
don’t need to be supplied with materials so quickly. All the cells of a plant can get O2 for respiration &
CO2 for photo synthesis from atmosphere directly. So the only substances which are to be supplied to
a plant through a transport are water & minerals. Another job of the transport system of plant is to
transport food prepared in the leaves to the various parts of the plant. In case of plants, the biggest
concern is the transport of water and it terminates at the limiting factor depending on its growth. To
overcome this problem, a tree uses several processes like Translocation, Storing, Absorption and
Utilization of water. The process of transportation in plants involves the following processes
● Diffusion: It is a physical process that involves the movement of solute particles from the
region of their higher concentration to the region of their lower concentration. Transport of
materials within the cell is by diffusion. The entry of carbon dioxide into the stomata is by
diffusion.
● Osmosis: It is a physical process in which the solvent (water) moves from the region of its
higher concentration to the region of its lower concentration across a semi-permeable
membrane. This is to say that water moves from a dilute to a concentrated solution. Water is
absorbed into the root cells by osmosis.
● Transpiration: It is defined as the loss of excessive water from internal tissues of aerial parts
in the form of vapours. The important part among them is leaf. Plants retain only small
amounts of absorbed water in their body because most of it is lost by the process of
transpiration.
● Translocation: Translocation is defined as the process in which movement of water, mineral
salts and organic substances from one part of a plant to other. Translocation of food material
takes place from leaves to all other parts of the parts of the plant through phloem tissues.

The plant have two types of conducting tissues for transportation and are Xylem & phloem:
(a). Xylem OR Wood: which carries H 2O &
minerals from roots towards leaves. The xylem Xylem tissue
vessel is a long non living tube which runs like a Ground Vessel
Tracheid element
drain pipe through the plant. A xylem vessel is tissue cell
made of many hallow dead cells called xylem
elements joined end to end, so an open tube is
formed. Xylem vessel runs from the roots of the
plant right up to the leaves. It transports water
& other minerals from roots towards leaves. Pits

This transportation process takes place by

transpiration pull theory, which states that:
Water is pulled from above and not pushed from
below through roots, As there is gravitational
Nucleus
force downside but still two forces are there Vessel elements Tracheids
which helps to pull the water upward I.e. Cohesive and adhesive forces.
In cohesive force water molecules cling together to form a chain in plants. Where as in Adhesive
force helps in attachment of these water chains to various parts and walls of the xylem. This suction
is actually pulling water upward so called transpiration pull. The continuous evaporation of H 2O or
transpiration from the cells of a leaf creates a kind of suction which pulls up water through the xylem.
The main function of xylem is to transport water, and some soluble nutrients including minerals and
inorganic ions, upwards from the roots to the rest of the plant. Xylem cells form long tubes that
transport materials, and the mixture of water and nutrients that flows through the xylem cells is
called xylem sap.

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 Life Process 19
(b) Phloem: Phloem is composed of several cell types including sclerenchyma, parenchyma,
sieve elements and companion cells. These sieve plates are areas with many pores through which
adjacent cells are connected by a continuous cytoplasm. which carries food from leaves to other parts
of a plant . Like xylem , phloem is made of many cells joined end to end to form long tube. The cells in
phloem which are joined end to end are called sieve tubes. Sieve tubes which form phloem are living
cells which contain cytoplasm but no nucleus. Each sieve tube cell has a companion called next to it
companion cell has a nucleus and many other cell organelles. Phloem is the vascular tissue
responsible for the transport of food nutrients such as glucose, amino acids, proteins and mRNAs
from source tissues (ex-photosynthetic leaf cells) to sink tissues (except Non-photosynthetic root cells
or developing flowers). i.e from leaves to all other cells of the plant by the process called translocation.
Phloem shows bi-directional movement of food particles.
Phloem

Parenchyma
Cells

Sieve
Tube

Companion
Cell

Plasmodesmata

TRANSPIRATION: Transpiration is the process of water loss from leaves of plants through
stomata. Transpiration mostly occurs in leaves through special structures present on them called as
stomata. Transpiration always occurs against the gravity. Transpiration involves mainly the xylem
cells which become active during absorption process by the roots. Opening of stomata is controlled by
K + ion.
Types of Transpiration:
● Stomatal Transpiration: Stomatal transpiration is the evaporation of water from a plant’s
stomata. Most of the water that is transpired from a plant is transpired this way; at least 90%
of the water transpired from a plant’s leaves exits through the stomata.
 20 Biology-X
Stoma closed
Stoma open

Nucleus

Chloroplasts

Vacuole

Guard cell

Cell wall

Stoma

● Cuticular Transpiration: Cuticular transpiration is the evaporation of water from a plant’s

cuticle. The cuticle is a waxy film that covers the surface of a plant’s leaves.
● Lenticular transpiration: Is the type of transpiration which occurs through the small pores
called as lenticels present in the bark.

Transport of food & other substances in Plants

Leaves make food by the process of photosynthesis. Every part of the plant needs food for their
growth. So, the food manufactured in the leaves is transported to all the other parts through phloem.
The transport of food from the leaves to other parts of the plant is called translocation. Food is
transported by a special mechanism called as pressure flow hypothesis. Pressure flow hypothesis is
the one which explain the translocation of food molecules by phloem. The mechanism of translocation
involves certain steps.
As sugar is synthesized in the leaves by the process of photosynthesis, a high concentration of
organic substance inside the phloem cells of the leaf creates a diffusion gradient by which more water
is sucked into the cells.
Phloem sap with lot of sugar moves from sugar sources (leaves) to sugar sinks with the help of
turgor pressure. Sugar sources are the organs of the plant which synthesize sugars. Sugar sinks are
the ones from where the sucrose is removed from the phloem.
Hydrostatic pressure increases in the phloem sieve tubes, pressure flow begins and the sap moves
through the phloem.
Osmotic pressure at the sink is reduced. Sucrose from the phloem sap is removed and given to the
cells which utilize it by converting it into energy or starch or cellulose.

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 Life Process 21
XYLEM PHLOEM

Companion Source
cell (leaf cell)
Water

Sleve-tube elements

Water
Companion SINK
cell (root cell)

Transportation in Animals: in all living beings the nutrients and gases are transported to all
parts of the body. This is essential to carry on various life processes. In case of unicellular and small
multicellular organisms transport takes place by diffusion. However, in large multicellular
organisms, as the distances between different body parts have increased, they need an elaborate and
efficient system for transportation of materials. In large animals, such a system is called circulatory
system in which a fluid circulates in all parts of the body. Annelids are the first metazoans to have a
well developed circulatory system. In many invertebrates this fluid is the haemolymph (blood
without colour), where as in all vertebrates and in some higher invertebrates this fluid is the blood.

Transport in Humans
Human beings have two systems responsible for transportation Blood circulatory system and
lymphatic system.

Human circulatory system

The various organs of the circulatory system are:
Heart
Blood vessels.
Blood.

Human Heart
It is a clenched fist sized, thick, muscular and contractile organ. It is surrounded by a thin,
transparent layer called Pericardium. This pericardium protects heart from mechanical shock. In
circulatory system the heart acts as a pump to push out blood. The arteries, veins & capillaries acts
as pipes or tubes through which the blood flows.
The heart is roughly triangular in shape. It is made of special muscle called cardiac muscle. The
size of the heart is about the same as our clenched fist. The heart has four chambers inside it. The
upper right chamber of the heart is called right atrium & left one is called left atrium & the lower
right chamber is called right ventricle & the left one is called left ventricle. Right and left auricles are
separated by a thin layer called interarticular septum. The right atrium or auricle receives
deoxygenated blood (rich in carbon dioxide) from most of the body parts by superior vena cava or
 22 Biology-X
main vein, while as left auricle receives oxygenated blood (rich in oxygen) from the lungs by
pulmonary vein. interarticular septum prevents the mixing of two types of blood. And the two
ventricles transport blood to the entire body. Ventricles are larger and thick walled than auricles
because these have to pump blood to various organs of the body. Right and left ventricles are
separated from each other by a thick muscular layer called as interventricular septum which also
prevents mixing of two types of blood. Both auricles are connected with ventricles by atrioventricular
valves. The right atrium gives deoxygenated blood to right ventricle through a valve called tricuspid
valve or V2. Similarly, the left atrium gives oxygenated blood to left ventricle through a valve called
as bicuspid valve or V1. These valves prevent the back flow of blood into atria when these ventricles
contract. When right ventricle contracts de-oxygenated blood from it passes to lungs by pulmonary
aorta or pulmonary vein & is guarded by seminal valves, while as contraction of left ventricle passes
the oxygenated blood to all the parts of body through systemic aorta or main artery & is guarded by
seminal valve also. The job of the heart is to pump the blood to the whole body. Ventricles pump the
blood to rest of the body with high pressure so ventricles are made up of thicker wall than atria. The
chambers of the heart are separated by a partition called septum.
Arteries: Arteries are the thick walled blood vessels which carry blood from the heart to all the
parts of the body. Arteries carries Oxygenated blood.
Capillaries: The capillaries are thin walled & extremely narrow tubes of blood vessels which
connect arteries with veins.
The exchange of various materials like O2, food, CO2 etc between the blood & the body cells
takes place through capillaries.
Veins: Veins are thin walled blood vessels which carry blood from all the parts of body back to the
heart. Vein carries De-oxygenated blood.
The main difference between the artery & the vein is that an artery carries blood from the heart
to the body organs where as a vein carries blood from the body organs back to the heart.
The blood carrying O2 in it is called oxygenated blood. The blood having no O2 in it is called
deoxygenated blood.

Internal View of the Heart

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 Life Process 23
How heart works/ Blood flow
All blood enters the right side of the heart through two veins: The superior vena cava (SVC) and
the inferior vena cava (IVC). The SVC collects blood from the upper half of the body. The IVC collects
blood from the lower half of the body. Blood leaves the SVC and the IVC and enters the right atrium
(RA). When the RA contracts, the blood goes through the tricuspid valve. and into the right ventricle
(RV). When the RV contracts, blood is pumped through the pulmonary valve, into the pulmonary
artery (PA) and into the lungs where it picks up oxygen. Because blood returning from the body is
relatively poor in oxygen. It needs to be full of oxygen before being returned to the body. So the right
side of the heart pumps blood to the lungs first to pick up oxygen before going to the left side of the
heart where it is returned to the body full of oxygen.
Blood now returns to the heart from the lungs by way of the pulmonary veins and goes into the
left atrium (LA). When the LA contracts, blood travels through the mitral valve and into the left
ventricle (LV). The LV is a very important chamber that pumps blood through the aortic valve and
into the aorta. The aorta is the main artery of the body. It receives all the blood that the heart has
pumped out and distributes it to the rest of the body. The LV has a thicker muscle than any other
heart chamber because it must pump blood to the rest of the body against much higher pressure in
the general circulation (blood pressure).

Double Circulation
A circulatory system in which the blood
travels twice through the heart in one
complete circulatory cycle is called double
circulation.
In human being heart is four chambered
which consists of two Atria and two
Ventricles, left side and the right side of the
heart are completely separated to prevent
the mixing of oxygenated blood with
deoxygenated blood. Such a separation
allows a highly efficient supply of oxygen to
the body cells which is necessary for
producing a lot of energy.

BLOOD
Study of blood is called Hematology & its
specialist is called hematologist. Blood is
actually a tissue. It is thick because it is
made up of a variety of cells, each having a
different job. In fact, blood is about 80%
water and 20% solid. The circulatory system
is the route by which the cells in your body
get the oxygen and nutrients they need, but
blood is the actual carrier of the oxygen &
nutrients. Blood is made mostly of plasma,
which is a yellowish liquid that is 90% water. In addition to the water, plasma contains salts, sugar
(glucose), and other substances. And, most important, plasma contains proteins that carry important
nutrients to the body’s cells and strengthen the body’s immune system so it can fight off infection.
The average man has between 10 and 12 pints of blood in his body. (one pint of blood is equal to 525
ml) The average woman has between 8 and 9 pints.
 24 Biology-X
Blood is actually a tissue. It is thick because it is made up of a variety of cells, each having a
different job. In fact, blood is about 80% water and 20% solid. Blood is made mostly of plasma, but 3
main types of blood cells circulate with the plasma:
● Red blood cells: Red blood cells are also called erythrocytes & they help in carrying oxygen
from lungs to the cells due to having Hemoglobin present in them. The body creates these cells
at a rate of about 2.4 million a second, and they each have a life span of about 120 days.
● White blood cells: white blood cells are also called leucocytes & they helps in fighting against
infection. These cells form our immune system. WBC's are of various types depending upon
the shape of their nucleus.
● Platelets: Platelets are also called thrombocytes. they help in blood clotting. Clotting stops
the blood from flowing out of the body when a vein or artery is broken. So, maintenance of
Platelets in normal range is must because if injury occurs, naturally the loss of blood from the
veins has to be stopped. In addition to avoid this, the blood has platelet cells which plug these
leaks by helping to clot the blood at the time of injury.

Lymphatic System
There is another system of tiny tubes called lymph LYMPHATIC SYSTEM

vessels & lymph glands in the human body which transports Tonsils
the liquid called lymph from the body tissues to the Lymph Thymus
circulatory system called lymphatic system. Lymphatic vessels
system consists of three parts.
Liver Spleen
Lymph vessels
Lymph glands &
Lymph.
Lymph: Lymph is another medium of circulation in the
human body but it flows only in one direction. Lymph Bone
Lymph nodes
contains two formed elements i.e Plasma and Leucocytes Marrow
(WBC). So lymph is blood minus RBC, Platelets and some
proteins.
Functions of Lymph:
1. Lymph acts as a "middle man" which transports
oxygen, food materials, hormones, etc, to the body cells and
brings carbon dioxide and other metabolic wastes, from the body cells to blood and then finally pours
the same into the venous system.
2. Body cells are kept moist by the lymph.
3. Lymph nodes produce lymphocytes. Lymph takes lymphocytes and antibodies from the lymph
nodes to the blood.
4. It destroys the invading microorganisms and foreign particles in the lymph nodes.
5. Lymph maintains the volume of the blood, as soon as the volume of the blood reduces in the
blood vascular system, the lymph rushes from the lymphatic systems to the blood vascular system.
Difference between blood and Lymph

Blood Lymph
1. It is red in colour. 1. It is almost colourless.
2. it flows in blood vessels. 2. It flows in lymphatic vessels.
3. It contains RBC’s, WBC’s and platelets. 3. It contains only WBC’s (lymphocytes) and
not RBC’s and platelets.

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 Life Process 25
4. Plasma is rich in blood proteins. 4. It lacks blood proteins except for the
lymph to liver.
5. It carries oxygen from lungs to various parts and 5. It is not a carrier of oxygen or carbon
brings carbon dioxide from different parts back dioxide.
to lungs.

EXCRETION
Excretion: The process of removal of toxic wastes from the body of an organism is called
excretion. Excretion is a process by which metabolic waste is eliminated from an organism. In
vertebrates this is primarily carried out by the lungs, kidneys and skin. Excretion is an essential
process in all forms of life. For example, in mammals urine is expelled through the urethra, which is
part of the excretory system. In unicellular organisms, waste products are discharged directly
through the surface of the cell (Diffusion).
Green plants produce carbon dioxide and water as respiratory products. Plants can get rid of
excess water by transpiration and guttation. It has been shown that the leaf acts as an 'excretophore'
and, in addition to being a primary organ of photosynthesis, is also used as a method of excreting
toxic wastes via diffusion.
In animals, the main excretory products are carbon-dioxide, ammonia (in ammoniotelics), urea
(in ureotelics), uric (in uricotelics), guanine (Guanotelics).
Aquatic animals usually excrete ammonia directly into the external environment, as this
compound has high solubility and there is ample water available for dilution.
In terrestrial animals ammonia-like compounds are converted into other nitrogenous materials
as there is less water in the environment and ammonia itself is toxic.
Birds excrete their nitrogenous wastes as uric acid in the form of a paste. Although this process is
metabolically more expensive, it allows more efficient water retention and it can be stored more
easily in the egg.
In insects, a system involving Malpighian tubules is utilized to excrete metabolic waste.
Metabolic waste diffuses or is actively transported into the tubule, which transports the wastes to the
intestines. The metabolic waste is then released from the body along with fecal matter. The excreted
material may be also called as ejecta.
The accumulation of toxic wastes in the body harms an organism. So, far an organism to lead a
normal life, the toxic wastes being produced in its body must be removed continuously. Excretion
takes place in animals as well as in plants.

Excretion in Human Beings (Urinary System)

The excretory system in human beings consists of following main organs:
(a) Two kidneys
(b) Two ureters
(c) Urinary bladder
(d) Urethra
(a) Kidneys: Kidneys are been shaped and are located at the back of our body just above the
waist. Every person has a pair of kidneys. The blood in our body is constantly passing through our
kidneys. The renal artery brings the dirty blood into the kidneys. The function of the kidneys is to
remove the poisonous substances like urea, other waste salts & excrete them in the form of a yellow
liquid called urine.
Like in lungs each kidneys is made up of a large number of excretory units called nephrons. The
nephron has a cup shaped bag at its upper end called Bowman’s capsule. The lower end of bowman’s
 26 Biology-X
capsule is tube shaped and it is called a Tubule. The Bowman’s capsule contains a bundle of
capillaries which is called Glomerulus. The function of glomerulus is to filter the blood passing
through it.

Kidney Anatomy

(b) Ureters: The ureter is a tube that carries urine from the kidney to the urinary bladder. There
are two ureters, one attached to each kidney. The upper half of the ureter is located in the abdomen
and the lower half is located in the pelvic area. The ureter is about 30 cm long in the average adult.
The tube has thick walls composed of a fibrous, a muscular, and a mucus coat, which are able to
contract.
(c) Urinary bladder: The urinary bladder is a muscular sac in the pelvis, just above and behind
the pubic bone. When empty, the bladder is about the size and shape of a pear. Urine is made in the
kidneys and travels down two tubes called ureters to the bladder. The bladder stores urine. The
bladder is lined by smooth involuntary muscles that stretch to hold urine. The normal capacity of the
bladder is 400-600 ml.
(d) Urethra: is a duct that transmits urine from the Renal artery
Renal vein
bladder to the exterior of the body during urination (urine
pass out). The urethra is held closed by the urethral
Left
sphincter (a muscular structure that keep urine in the Right kidney kidney
bladder until voiding can occur). The female urethra is
Dorsal aorta
much shorter than that of the male, being only 4 cm (1.5
inches) long. In the human male, the urethra is about 8
inches (20 cm) long. Ureter

Urinary bladder

Urethra
The Human Excretory system

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 Life Process 27
Structure and function of a Nephron
Each kidney is made up of a large number of excretory units called Nephrons. Histologically, each
kidney is composed of approximately 1 million of Uriniferous tubules or nephron. Nephron is the
structural and functional unit of the kidney. Each nephron has two major portions:
● A Renal corpuscle (Malpighian body)

● A Renal tubule

(A) RENAL CORPUSCLES (MALPIGHIAN BODY): A renal corpuscle consists of a

glomerulus & Bowman’s capsule (glomerular capsule). The glomerulus is a capillary network that
arises from an afferent arteriole. Ultra filtration process takes place at glomerulus. Ultra filtration is
the filtration of blood plasma in the glomerulus. The glomerular filtrate thus formed contains both
useful as well as harmful substances into it. After ultra filtration blood that is not filtered enters into
efferent arteriole. The diameter of the efferent arteriole is smaller than that of the afferent arteriole,
which helps maintain a fairly high blood pressure in the glomerulus. Bowman’s capsule is double
walled cup like structure and it encloses the glomerulus. Bowman’s capsule is named after it’s
identifier, English physician and physiologist, Sir William Bowman (1816-1892). The wall of
glomerulus and the Bowman’s capsule consists of a single layer of flattened epithelial cells.
Glomerular capsule consists of three layers:-
(i) Outer parietal layer: consists of squamous epithelium cells with minute pore of 12nm
diameter called fenestration
(ii) Middle basement membrane: which is selectively permeable
(iii) The inner visceral layer: of large nucleated cell called podocytes. Podocytes bears finger
like projections known as podocels. The areas between the two podocels is filtration slit underlying
basement membrane.
(B) RENAL TUBULES: The renal tubule continues from Bowman’s capsule and consists of the
following parts: proximal convoluted tubule (in the renal cortex), loop of Henle (in the renal medulla),
and distal convoluted tubule (in the renal cortex).
(i) Proximal convoluted tubules (PCT): it is proximal part of renal tubules next to Bowman’s
capsule. It is lined with microvilli. Useful substances & maximum reabsorption of water, glucose,
amino acids and electrolytes takes place here and the harmful substances are rejected (not absorbed).
Any waste or harmful substance still present is called tubular secretion or augmentation.
(ii) Loop of Henle: It is U shaped middle portion of renal tubules. It is composed of ascending
and descending loop. Ascending loop is thick walled and impermeable to water while descending loop
is thin walled and permeable to water. Counter current mechanism is crucial role of loop of Henle.
(iii) Distal convoluted tubules (DCT): It is the distal part of renal tubules that leads to
collecting ducts. It is similar in structure and function with PCT.
(iv) Collecting tubules: It is not a part of nephron rather it is a part of kidney. The distal
convoluted tubules from several nephrons empty into a collecting tubule. Several collecting tubules
then unite to form a papillary duct that empties urine into a minor calyx and then into major calyx
and finally into renal pelvis. The wastes passed from nephron into the collecting duct (urinary
bladder) contain only urea, uric acid, excess of water and mineral wastes etc called urine.
 28 Biology-X
Glomerulus
(Capillary network) Distal convoluted
tubule (DCT)

Proximal Convoluted
Efferent Tubule (PCT)
arteriole
(Narrow) Collecting
duct

Afferent
arteriole
(Wide)

Bowman’s
capsule Cavity of
Bowman’s capsule

Capillary network
Urine flow

Loop of Henle

GLOMERULAR FILTRATION: The first stage in clearing the blood is filtration, the passage of
a liquid through a filter to remove impurities. Filtration occurs in the glomeruli. Blood pressure
forces plasma, the liquid portion of the blood, through the capillary walls in the glomerulus. The
plasma contains water, glucose, amino acids, and urea. Blood cells and proteins are too large to pass
through the wall, so they stay in the blood. The fluid, now called filtrate, collects in the capsule and
enters the renal tubule.
● REABSORPTION: During reabsorption, needed substances in the filtrate travel back into
the bloodstream. Reabsorption occurs in the renal tubules. There, glucose and other nutrients,
water and essential ions materials pass out of the renal tubules and enter the surrounding
capillaries. Normally 100% of glucose is reabsorbed. (Glucose detected in the urine is a sign of
diabetes mellitus, which is characterized by too much sugar in the blood due to a lack of
insulin). Reabsorption involves both diffusion and active transport, which uses energy in the
form of ATP. The waste-containing fluid that remains after reabsorption is urine.
● TUBULAR SECRETION (AUGMENTATION): Tubular secretion is the passage of certain
substances out of the capillaries directly into the renal tubules. Tubular secretion is another
way of getting waste materials into the urine. For example, drugs such as penicillin and
Phenobarbital are secreted into the renal tubules from the capillaries. Urea and uric acid that
may have been reabsorbed and secreted. Excess potassium ions are also secreted into the
urine. Tubular secretions also maintain the PH of the blood.
● MICTURITION: The word micturition actually means urination. The urge for micturition
occurs when urinary bladder is filled up to 300-400 ml of urine and due to the filling of urinary
bladder stimulates the nerve ending to develop the reflex. However, urine can be retained in
the urinary bladder till it gets filled upto maximum capacity that is 700-800 ml but by this

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 Life Process 29
time the urge of micturition turns into a painful issue. Voluntary micturition can be carried
out by an individual at any time an average person excretes urine upto 1.6-1.8 ltr.
Function of a Nephron: The function of the nephron is to filter the blood passing through it. It
also takes part in the reabsorption of useful substances like glucose, amino acids.
TYPES OF NEPHRON
● Cortical nephron: 80% of the nephrons are short and located within the cortex.

● Juxta medulary nephron: 20% of nephron have long loops of Henle that extend into the
medulla.

Dialysis Or heamodialysis (Artificial Kidney)

Dialysis is a treatment method that replicates the function of the kidneys when they are failing.
In healthy individuals, the kidneys work to filter and remove waste products, excess fluid, salts and
toxins from the blood.
However, in cases of kidney failure, this mechanism fails and individuals need to undergo
dialysis. Dialysis can be used to treat people with chronic or acute kidney disease. Or The procedure
used for cleaning the blood of a person by separating the waste substances from it is called dialysis.

Blood thinner
added to blood Dialysis fluid with Dialysis fluid
treated water waste drain
Blood pump

Dialyser (artificial kidney)

Blood from arm

(arterial side)
Blood back to arm
(venous side)

Bubble trap

EXCRETION IN PLANTS
Like animals, plants also produce their waste products during their life processes. The main
excretory products like carbon-dioxide and oxygen are removed through Stomata of leaves. Plants
also store some of the waste products in their body parts like leaves. Plants get rid of these wastes by
shedding of leaves, peeling of bark and felling of fruits etc. Plants also get rid of wastes by secreting
them in the form of gums and resin. Plants also excrete some waste substances into the around them.
 30 Biology-X

♙ssertion and Reason Based Questions

Directions: In the following questions, A statement of Assertion (A) is followed by a
statement of Reason (R). Mark the correct choice as:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
1. Assertion (A) : Leaves are the major photosynthetic organs of plants.
Reason (R) : They contain chloroplast.
2. Assertion (A) : Raw materials needed for photosynthesis are carbon dioxide,
water and minerals.
Reason (R) : Nutrients provide energy to an organism.
3. Assertion (A) : Photosynthesis is an anabolic process.
Reason (R) : The process of photosynthesis occurs in chlorophyll.
4. Assertion (A) : Nitrogen is a essential element for plant growth and is taken up
by plants in the form of inorganic nitrates or nitrites.
Reason (R) : The soil is nearest and richest source of raw materials like
nitrogen, phosphorus and other minerals for the plants.
5. Assertion (A) : Amoeba follows holozoic made of nutrition.
Reason (R) : It is unicellular and omnivore.
6. Assertion (A) : Herbivores have longer small intestine.
Reason (R) : Digestion of cellulose takes time.
7. Assertion (A) : Digestion breaks large complex molecules to simple smaller
molecules which can be easily absorbed.
Reason (R) : Digestion is necessary for the absorption of all molecules.
8. Assertion (A) : Muscles of stomach wall possess thick layers of muscle fibers.
Reason (R) : These muscles help in mixing the food with the enzymes present
in the alimentary canal.
9. Assertion (A) : The inner walls of the small intestine have finger-like
projections called villi which are rich in blood.
Reason (R) : These villi have a large surface area to help the small intestine
in completing the digestion of food.
10. Assertion (A) : Lipases help in emulsification of fats.
Reason (R) : Lipases hydrolyses fats and oils.
11. Assertion (A) : HCl converts pepsinogen into active enzyme pepsin.
Reason (R) : Pepsin converts protein into proteoses and peptones.
12. Assertion (A) : Amoeba takes in food using finger-like extensions of the cell
surface.
Reason (R) : In all unicellular organisms, the food is taken in by the entire
cell surface

♙nswers
1. (a) 2. (c) 3. (b) 4. (d) 5. (b) 6. (a) 7. (a) 8. (b) 9. (a) 10. (a)

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 Life Process 31

Objective Questions
1. Plants obtain their food from:
(a) Sunlight and (b) Dead and decaying food
(c) Inorganic material (d) Oxygen and water
2. Which of the processes describes autotrophic nutrition?
(a) Photosynthesis (b) Respiration (c) Transpiration (d) Assimilation
3. Enzymes are :
(a) Inorganic catalysts (b) Bio-catalysts
(c) Growth promoters (d) Energy providing materials
4. Heterotrophic nutrition is found in :
(a) Animals and fungi (b) Plants and fungi (c) Plants and animals (d) None of these
5. Potassium hydroxide can absorb :
(a) Water (b) (c) Oxygen (d) Starch
6. Nitrogen is essential for the synthesis of :
(a) Starch (b) Glucose (c) Fats (d) Proteins
7. Iodine gives blue colour with :
(a) Carbon dioxide (b) Starch (c) Alcohol (d) Glucose
8. Guard cells are found in:
(a) Root hairs (b) Stomata of leaf (c) Stem epidermis (d) None of these
9. Which of the following organisms has a parasitic mode of nutrition?
(a) Yeast (b) Plasmodium (c) Euglena (d) Rhizopus
10. The autotrophic mode of nutrition requires :
(a) Carbon dioxide and water (b) Chlorophyll
(c) Water (d) All of the above
11. In the starch test on a leaf, why is it important to boil the leaf in alcohol ?
(a) To dissolve the waxy cuticle
(b) To make the cells more permeable to iodine solution.
(c) To remove the chlorophyll
(d) To stop chemical reactions in the cells
12. Which of the following organisms has a saprophytic mode of nutrition?
(a) Mushroom (b) Tapeworm (c) Leech (d) Ascaris
13. The source of oxygen, which is liberated during photosynthesis is:
(a) Starch (b) Water (c) Carbon dioxide (d) Chlorophyll
14. The reserve food in autotrophs is:
(a) Proteins (b) Fatty acids (c) Glycogen (d) Starch
15. The thread-like structures that develop on a moist slice of bread in are :
(a) Sporangia (b) Filaments (c) Rhizoids (d) Hyphae
16. Most of the photosynthesis (80%) which takes place on this earth is carried out by :
(a) Green plants on land
(b) Algae present in freshwater
(c) Algae found in ocean
(d) Algae present in ocean and freshwater sources
 32 Biology-X
17. One of the events that does not occur during photosynthesis is:
(a) Chlorophyll absorb solar energy
(b) Carbon dioxide is released during the process.
(c) Oxygen is released during the process.
(d) Carbon dioxide is absorbed during the process.
18. The process of taking in by plants and releasing is termed as :
(a) transpiration (b) respiration (c) photosynthesis (d) growth
19. Role of oxygen in photosynthesis is as a :
(a) reactant (b) product (c) by-product (d) catalyst
20. Plants have less energy needs as compared to animals. This is because :
(a) they do not move from one place to another.
(b) most of their tissues contain dead cells.
(c) they do not expend energy
(d) both (a) and (b)
21. Each stack of thylakoids is called?
(a) chloroplast (b) stomata (c) lenticels (d) granum
22. Which of the following maintains the balance of oxygen and carbon dioxide in the air ?
(a) Photosynthesis (b) Respiration (c) Evaporation (d) Combustion
23. Which of the following condition is true for the state of stomata of green leaf shown in the given
diagram?
(a) Large amount of water flows into the guard cells.
(b) Gaseous exchange in occurring in large amount. Stomata
(c) Large amount of water flows out from the guard cells.
(d) Large amount of sugar collects in guard cells. Guard Cells
24. Opening and closing of stomata is due to :
(a) High pressure of gases inside the cells.
(b) Movement of water in and out of the guard cells.
(c) Stimulus of light in the guard cells.
(d) Diffusion of in and out of the guard cells.
25. A student was asked to write a stepwise procedure to demonstrate that carbon dioxide is
necessary for photosynthesis. He wrote the following steps. The wrongly worded step is:

Belljar

Greenplant

KOH
(a) (b)

(a) Both potted plants are kept in dark room for at least three days.
(b) Bottom of the bell jars is sealed to make them air tight.

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 Life Process 33
(c) Both potted plants are kept in sunlight after the starch test.
(d) A leaf from both the plants is taken to test the presence of starch.
(1)
26. In the given diagram of a closed stomata:
(2)
(1), (2), (3) and (4) respectively are :
(3)
(a) nucleus, chloroplast, guard cell, vacuole (4)
(b) nucleus, chloroplast, vacuole, guard cell
(c) Chloroplast, nucleus, vacuole, guard cell
(d) Vacuole, guard cell, nucleus, chloroplast
27. In the following diagram, identify the cells through which massive
amounts of gaseous exchange takes place for photosynthesis :

II

III

IV

(a) I (b) IV (c) III (d) II

28. Amoeba captures its food with the help of :
(a) Food vacuole (b) Nucleus (c) Contractile vacuole (d) Pseudopodia
29. The action of enzyme pepsin can occur in :
(a) Acidic pH (b) Alkaline pH
(c) Both in acidic as well as alkaline pH (d) Neither in acidic nor in alkaline pH
30. Ptyalin acts on :
(a) Glucose (b) Fats (c) Proteins (d) Starch

♙nswers
1. (a) 2. (a) 3. (b) 4. (a) 5. (b) 6. (d) 7. (b) 8. (b) 9. (b) 10. (d)
11. (c) 12. (a) 13. (b) 14. (d) 15. (d) 16. (d) 17. (b) 18. (c) 19. (c) 20 (b)
21. (d) 22. (a) 23. (c) 24. (b) 25. (c) 26. (b) 27. (b) 28. (d) 29. (a) 30. (d)
 34 Biology-X

Textual Questions
Q.1 Why is diffusion insufficient to meet the oxygen requirements of multi-cellular organisms
like humans?
Ans. Unlike the unicellular organisms, the multi-cellular organisms have complex body structures
with specialized cells and tissues to perform various necessary functions of the body. Since
these cells are not in direct contact with surrounding environment so, simple diffusion cannot
meet the oxygen requirement of all these cells.
Q.2 What criteria do we use to decide whether something is alive?
Ans. Any visible movement such as walking, breathing, or growing is generally used to decide
whether something is alive or not. However, a living organism can also have movements,
which are not visible to the naked eye. Therefore, the presence of life processes is a
fundamental criterion that can be used to decide whether something is alive or not.
Q.3 What are outside raw materials used by an organism?
Ans. Various outside raw materials used by an organism are as follows:
Food as source of supplying energy and materials.
Oxygen for breakdown of food to obtain energy.
Water for proper digestion of food and other functions inside the body.
The raw materials required by an organism will vary depending on the complexity of the
organism and its environment.
Q.4 What processes would you consider essential for maintaining life?
Ans. Life processes such as nutrition, respiration, transportation, excretion, etc. are essential for
maintaining life.
Q.5 What are the differences between autotrophic nutrition and heterotrophic nutrition?

Autotrophic Nutrition Heterotrophic Nutrition

Food is synthesized from simple Food is obtained directly or indirectly from
inorganic raw materials such as CO2 and autotrophs. This food is broken down with
water. the help of enzymes.
Chlorophyll is required. Chlorophyll is not required.
Food is generally prepared during day Food can be obtained at all time.
time.
All green plants and some bacteria have All animals and fungi have this type of
this type of nutrition. nutrition.

Q.6 Where do plants get each of the raw materials required for photosynthesis?
Ans. The following raw materials are required for photosynthesis:
Carbon Dioxide: Plants get CO2 from atmosphere through stomata.
Water: Plants absorb water from soil through roots and transport to leaves.
Sunlight: Sunlight, which is absorbed by the chlorophyll and other green parts of the plant.
Q.7 What is the role of the acid in our stomach?
Ans. Following are the roles of acid in our stomach:? The hydrochloric acid present in our stomach
dissolves bits of food and creates an acidic medium. In this acidic medium, enzyme pepsinogen
is converted to pepsin, which is a protein-digesting enzyme.
It also kills many bacteria and other microorganisms that enter along with the food.

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 Life Process 35
Q.8 What is the function of digestive enzymes?
Ans. Digestive enzymes such as amylase, lipase, pepsin, trypsin, etc. help in the breaking down of
complex food particles into simple ones. These simple particles can be easily absorbed by the
blood and thus transported to all the cells of the body.
Q.9 How is the small intestine designed to absorb digested food?
Ans. The small intestine has millions of tiny finger-like projections called villi. These villi increase
the surface area for more efficient food absorption. Within these villi, many blood vessels are
present that absorb the digested food and carry it to the blood stream. From the blood stream,
the absorbed food is delivered to each and every cell of the body.
A villus in the small intestine

Lining
Blood capillary
Lacteal

Q.10 What advantage over an aquatic organism does a terrestrial organism have with regard to
obtaining oxygen for respiration?
Ans. Terrestrial organisms take up oxygen from the atmosphere whereas aquatic animals obtain
oxygen from water. Air contains more O2 as compared to water. Since the content of O2 in air
is high, the terrestrial animals do not have to breathe faster to get more oxygen. Therefore,
unlike aquatic animals, terrestrial animals do not need adaptations for gaseous exchange.
Q.11 What are the different ways in which glucose is oxidized to provide energy in various
organisms?
Ans. At first glucose (6 carbon molecules) is broken in the cytoplasm of cells of all organisms. This
process yields a 3 carbon molecule compound called pyruvate.
Further break down of pyruvate takes place in different manners in different organisms.
Absence of oxygen
Ethanol+CO2
(Yeast) + Energy

Lack of oxygen
Glucose ⎯ I⎯nc⎯yto⎯pla⎯s⎯m→ Pyruvate Lactic acid
(6-carbon molecule) (3−carbon molecule) (In human muscle cells) + Energy

Presence of oxygen
CO2 + water
(In mitochondrial) + Energy
● Anaerobic Respiration: This process takes place in absence of oxygen, e.g. in yeast
during fermentation. In this case pyruvate is converted into ethanol and carbon dioxide.
 36 Biology-X
● Aerobic Respiration: In aerobic respiration, breakdown of pyruvate takes place in presence
of oxygen to give rise 3 molecules of carbon dioxide and water. The release of energy in aerobic
respiration is much more than anaerobic respiration.
● Lack of Oxygen: Sometimes, when there is lack of oxygen, especially during vigorous activity,
in our muscles, pyruvate is converted into lactic acid (3 carbon molecule compounds).
Formation of lactic acid in muscles causes cramp.
Q.12 How is oxygen and carbon dioxide transported in human beings?
Ans. Transport of Oxygen: The respiratory pigments (haemoglobin) present in red blood cells takes
up the oxygen from the air to the lungs. They carry the oxygen to tissues which are deficient in
oxygen.
Transport of carbon dioxide: Carbon Dioxide is more soluble in water. Hence, it is mostly
transported from body tissues in the dissolved form in our blood plasma to lungs where it
diffuses from blood to air in the lungs and then expelled out through nostrils.
Q.13 How are the lungs designed in human beings to maximize the area for exchange of gases?
Ans. Lungs contain millions of alveoli which provide a surface for the exchange of gases. An
extensive network of blood vessels is present in the wall of the alveoli. By lifting our ribs and
flatten the diaphragm, the chest cavity becomes spacious. Air is sucked into the lungs and
alveoli. The oxygen from the breath, diffuses into the blood and CO2 from the blood brought
from the body, diffuses out into the air.
Q.14 What are the components of the transport system in human beings? What are the functions of
these components?
Ans. The main components of the transport system in human beings are the heart, blood, and blood
vessels.
Heart pumps oxygenated blood throughout the body. It receives deoxygenated blood from the
various body parts and sends this impure blood to the lungs for oxygenation.
● Blood helps in the transport of oxygen, nutrients, CO2, and nitrogenous wastes.
● The blood vessels (arteries, veins, and capillaries) carry blood either away from the heart to
various organs or from various organs back to the heart.
Q.15. Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Ans. It is necessary to separate oxygenated and deoxygenated blood to maintain efficient supply of
oxygen into the body. This system is essential in animals that have high energy need. For
example, animals like mammals and birds which constantly use this energy to maintain their
body temperature.
Q.16 What are the components of the transport system in highly organised plants?
Ans. In highly organized plants, there are two different types of conducting tissues-xylem and
phloem. Xylem conducts water and minerals obtained from the soil (via roots) to the rest of the
plant. Phloem transports food materials from the leaves to different parts of the plant body.
Q.17 How are water and minerals transported in plants?
Ans. Water and minerals are transported through xylem cells from soil to the leaves. The xylem
cells of roots stem and leaves are interconnected to form a conducting channel that reaches all
parts of the plant. The root cells take ions from the soil. This creates a difference between the
concentration of ions of roots and soil. Therefore, there is a steady movement of water into
xylem. An osmotic pressure is formed and water and minerals are transported from one cell to
the other cell due to osmosis. The continuous loss of water takes place due to transpiration.
Because of transpiration, a suction pressure is created as a result of which water is forced into
the xylem cells of roots. The effect of root pressure for transportation in plants is more
important in night while during day time transpiration pull becomes the major driving force.

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 Life Process 37
Q.18 How is food transported in plants?
Ans. Phloem transports food materials from the leaves to different parts of the plant. The
transportation of food in phloem is achieved by utilizing energy from ATP which helps in
creating osmotic pressure that transport food from the area of high concentration to low
concentration.
Q.19 Describe the structure and functioning of nephrons.
Ans. Nephrons are the basic filtering units of kidneys. Each kidney possesses large number of
nephrons, approximately 1-1.5 million. The main components of the nephron are glomerulus,
Bowman's capsule, and a long renal tubule.

Functioning of a nephron:
● The blood enters the kidney through the renal artery, which branches into many capillaries
associated with glomerulus.
● The water and solute are transferred to the nephron at Bowman's capsule.
● In the proximal tubule, some substances such as amino acids, glucose, and salts are selectively
reabsorbed and unwanted molecules are added in the urine.
● The filtrate then moves down into the loop of Henle, where more water is absorbed.
● From here, the filtrate moves upwards into the distal tubule and finally to the collecting duct.
Collecting duct collects urine from many nephrons.
● The urine formed in each kidney enters a long tube called ureter. From ureter, it gets
transported to the urinary bladder and then into the urethra.
Q.20 What are the methods used by plants to get rid of excretory products?
Ans. Plants can get rid of excess of water by transpiration. Waste materials may be stored in the
cell vacuoles or as gum and resin, especially in old xylem. It is also stored in the leaves that
later fall off.
Q.21 How is the amount of urine produced regulated?
Ans. The amount of urine produced depends on the amount of excess water and dissolved wastes
present in the body. Some other factors such as habitat of an organism and hormone such as
Anti-diuretic hormone (ADH) also regulates the amount of urine produced.
Q.22 The kidneys in human beings are a part of the system for
(a) nutrition. (c) excretion.
(b) respiration. (d) transportation.
● (c) excretion
 38 Biology-X
Q.23 The xylem in plants are responsible for
(a) transport of water.
(b) transport of food.
(c) transport of amino acids.
(d) transport of oxygen.
● (a) transport of water.

Q.24 The autotrophic mode of nutrition requires

(a) carbon dioxide and water.
(b) chlorophyll.
(c) sunlight.
(d) all of the above.
● (d) all of the above.

Q.25. The breakdown of pyruvate to give carbon dioxide, water and energy takes place in
(a) cytoplasm.
(b) mitochondria.
(c) chloroplast.
(d) nucleus.
● (b) mitochondria.

Q.26 How are fats digested in our bodies? Where does this process take place?
Ans. Fats are present in the form of large globules in the small intestine. The small intestine
receives the secretions from the liver and the pancreas. The bile salts (from the liver) break
down the large fat globules into smaller globules so that the pancreatic enzyme lipase can
easily act on them. This is referred to as emulsification of fats. This process takes place in the
small intestine.
Q.27 What is the role of saliva in the digestion of food?
Ans. The role of saliva in the digestion of food:
● It moistens the food for easy swallowing.

● It contains a digestive enzyme called salivary amylase, which breaks down starch into sugar.

Q.28 What are the necessary conditions for autotrophic nutrition and what are its by-products?
Ans. Autotrophic nutrition takes place through the process of photosynthesis. Carbon dioxide,
water, chlorophyll pigment, and sunlight are the necessary conditions required for
autotrophic nutrition. Carbohydrates (food) and O2 are the by-products of photosynthesis.
Q.29 What are the differences between aerobic and anaerobic respiration? Name some organisms
that use the anaerobic mode of respiration.

Aerobic respiration Anaerobic respiration

It occurs in the presence of O2. It occurs in the absence of O2.
It involves the exchange of gases Exchange of gases is absent.
between the organism and the outside
environment.
It occurs in cytoplasm and It occurs only in cytoplasm.
mitochondria.
It always releases CO2 and H 2O. End products vary.
It always releases CO2 and H 2O. End products vary.

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Q.30 How are the alveoli designed to maximize the exchange of gases?
Ans. Alveoli provide a surface for the exchange of gases. An extensive network of blood vessels is
present in the wall of the alveoli. By lifting our ribs and flatten the diaphragm, the chest
cavity becomes spacious. Air is sucked into the lungs and alveoli. The oxygen from the breath,
diffuses into the blood and CO2 from the blood brought from the body, diffuses out into the air.
Q.31 What would be the consequences of a deficiency of haemoglobin in our bodies?
Ans. Haemoglobin is the respiratory pigment that transports oxygen to the body cells for cellular
respiration. Therefore, deficiency of haemoglobin in blood can affect the oxygen supplying
capacity of blood. This can lead to deficiency of oxygen in the body cells. It can also lead to a
disease called anaemia.
Q.32 Describe double circulation in human beings. Why is it necessary?
Ans. During a single cycle blood goes twice in the heart which is known as double circulation. It is
necessary in human being to separate oxygenated and de-oxygenated blood because this
makes their circulatory system is more efficient and helps in maintaining constant body
temperature.
Q.33 What are the differences between the transport of materials in xylem and phloem?
Ans.

Aerobic respiration Anaerobic respiration

Xylem tissue helps in the transport of Phloem tissue helps in the transport of
water and minerals. food.
Water is transported upwards from Food is transported in both upward and
roots to all other plant parts. downward directions.
Transport in xylem occurs with the Transport of food in phloem requires
help of simple physical forces such as energy in the form of ATP.
transpiration pull.

Q.34 Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to
their structure and functioning.

Alveoli Nephrons
Structure Structure
Alveoli are tiny balloon-like structures Nephrons are tubular structu res
present inside the lungs. present inside the kidneys.
The walls of thealveoli are one cell Nephrons are made of glomerulus,
thick and it constains an extensive bowman’s capsule, and a long renal
network of blood capillaries. tube.
Function Function
The exchange of O 2 and CO2 takes The blood enters the kidneys through
place between the blood of the the renal artery. The blood is entered
capillaries that surround the alveoli here and the nitrogenous waste in the
and the gases present in the alveoli. form of urine is collected by collecting
Alveoli are the site of gaseous duct.
exchange. Nephrons are the basic filtration unit.
 40 Biology-X

2
All the living organisms respond to the stimuli which occur in the environment around them.
Response to any stimuli is the characteristic feature of a living thing.
STIMULI: The changes in the environment to which the organisms respond &react are called
stimuli.
Living organisms shows response to stimuli like heat, cold, sound, smell, touch, water etc.
The response of organism to a stimuli is usually in the form of some movement of their body part.
e.g If a man touches a very hot utensil accidently, he quickly pulls his hand away from the hot utensil.
Here hotness is the Stimulus & the man reacts by moving his hand away from the hot utensil.
The response to a stimuli is a characteristic property of the living organisms.
CO-ORDINATION: The working together of the various organs of an organism in a systemic
manner so as to produce a proper response to the stimulus is called co-ordination.
SENSE ORGANS: We receive a variety of information from the environment around us through
these sense organs. e.g Eyes, Ears, Nose, Tongue & Skin are some examples of sense organs. Sense
organs contain Receptors.
RECEPTOR: A receptor is a cell or a group of cells in sense organ which is sensitive to a
particular type of stimulus such as light, heat, pressure etc.
A receptor detect stimulus. e.g eyes contain receptors called photoreceptors which detect light.
Ears contain receptors called Phonoreceptors which detect sound. Nose contains receptors called
Olfactory receptors which detect smell. Tongue contains receptors called Gustatory receptors which
detect taste. Skin contains receptors called Thermoreceptors which detect heat or cold.
EFFECTOR ORGAN: An effector is a part of the body which can response to a stimulus
according to the instructions sent from the nervous system. The effectors are mainly muscles of our
body. All our muscles response to stimuli sent from the nervous system.
HARMONE: The term hormone was introduced by William M. Baylis and Ernest H Starling in
1902. Harmones are the organic substances produced in less quantities by specific endocrine glands
or Special secretory living tissues and are secreted into the blood stream (animals) to control the
biological activities in the target cells. The tissues or organs secreting hormones are called endocrine
tissues and endocrine organs. Hormones have low molecular weight and are effective in low
concentration. Harmones are regarded as the chemical messengers involved in the coordination of
the body functions. In plants, harmones are also called as Phytoharmones (Phyto=plant).

CO-ORDINATION IN ANIMALS
The control & co-ordination in animals takes place through Nervous system as well as Endocrine
system. Nervous system is made up of nerve cells called Neurons where as endocrine system is made
up of endocrine glands.

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CO-ORDINATION IN HUMAN BEINGS

There are two systems of control & co-ordination in human beings & they are:-
(1) NERVOUS SYSTEM
(2) ENDOCRINE SYSTEM
In human beings Nervous system & Endocrine system work together to control & co-ordinate all
our activities such as physical actions , Thinking & also emotional behaviour.
(1) NERVOUS SYSTEM: The function of nervous system is to co-ordinate the activities of our
body. It is the nervous system of our body which make together working of other body systems. The
nervous system also co-ordinates things like heart beat & breathing. The nervous system receives
information from the surroundings, process it, interprets it & then responds accordingly.
Brain

Spinal cord

Nerves

Diagram Showing Human Nervous System

NEURON
(THE BASIC UNIT OF NERVOUS SYSTEM)
Neuron or nerve cell is the basic structural & functional unit of nervous system. Nervous system
is made up of special cells called Neurons. Human neural system has about 100 billion neurons.
Majority of neurons occur in brain. Fully formed neurons never divide. Neuron is the largest cell in
the Human body. The function of the neuron is to carry the message in the body in the form of
electrical impulses.
A neuron has three components or parts and are
(A) Cell body
(B) Dendrites
(C) Axon
(i) Cell body/Perikaryon/cyton/soma: It varies in size & varies in shape. Like a typical cell it
consists of cytoplasm called as neuroplasm, nucleus and cell membrane. The cytoplasm has cell
organelles, neurofibrils (thread like for the transmission of impulses) and Nissil’s granules. The
Nissl’s granules probably synthesize proteins for the cell.
 42 Biology-X
(ii) Dendrites/Dendrons/Neuritis: Dendrites are basically the processes of neurons. The
dendrites are usually shorter, tapering and much branched processes. They may be one to several.
Cytoplasm of dendrites contain neurofibrils and Nissl’s granules. They conduct nerve impulse from
receptors & passes towards the cyton hence called afferent processes ( = receiving processes).
(iii) Axon: Axon is a single, long process of uniform thickness. The part of cyton from where the
axon arises is called Axon Hillock. Most sensitive part of neuron is axon hillock. The cytoplasm of
axon contains neurofibrils, neurotubules but doesn’t have Nissl’s granules. The cell membrane of
axon is called axolemma and its cytoplasm as axoplasm. Axon is covered with sheaths & sheaths may
be myelinated or non-myelinated. Myelinated sheaths conduct impulse more efficiently than
non-myelinated sheaths. At intervals, axon possesses un-myelinated areas called Node of Ranvier.
In Axon Schwann cells are present for the formation of myelin sheath. The axon ends in a group of
branches called terminal arborizations. Terminal arborizations at its ending forms a swelling called
synaptic knob. Synaptic knob comes very close to Dendron of next neuron but leaving a little gap
between each other and this gap is called as synapse. At the synapse, the synaptic knob secretes a
neurotransmitter chemical which initiates electrical impulse on denron of next neuron. The axon
conducts nerve impulse away from the cell body, therefore, called an efferent process.

Neurons are of three types and are:

(i) Sensory Neurons
(ii) Motor Neurons
(iii) Relay Neurons
(i) Sensory Neurons/Receptor neurons/Afferent neurons: They passes electrical impulses
from receptors towards the spinal cord and then brain.
(ii) Motor Neurons/Effector neurons/Efferent neurons: They transmit electrical impulses
from the Brain towards the muscles (effectors).
(iii) Relay Neurons/Connector neurons/Association Neurons: They occur in the brain and
spinal cord and they serve between Sensory neurons and Motor Neurons.

REFLEX ACTION AND REFLEX ARC

REFLEX ACTION: The simplest form of response in the nervous system is the reflex action.
Reflex action is a rapid, automatic and involuntary response to a stimulus, which is not under the
voluntary action of brain. Reflex action is one which we perform automatically. E.g moving our hand
immediately away on touching a hot plate.
REFLEX ARC: The pathway taken by electrical impulse in a reflex action is called the reflex arc.

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 Control and Co-Ordination 43
Spinal cord
(CNS) Message to brain

Sensory neuron Relay neuron

Motor
neuron
Receptors = Heat/Pain
receptors in skin
Effector = Muscle in arm

Diagram Showing Reflex Action & Reflex ARC

CENTRAL NERVOUS SYSTEM (CNS)

The central nervous system consists of Brain and Spinal Cord. The job of the central nervous
system is to collect all the information from all the receptors in our body. This information is added
together before messages are sent out to the effectors. In this way the best action can be taken in a
particular set of circumstances.

THE HUMAN BRAIN (ENCEPHALON)

Brain is the anterior most part of the central nervous system (CNS) which is lodged in the cranial
cavity of cranium (brain box) of the skull. The human brain weighs from 1200-1400 grams. The
human neural system has about 100 billion neurons and majority, 98%, of them occur in brain.
The brain is covered by three membranes called meninges.. The innermost membrane is the
piameter, the middle membrane is arachnoid membrane and the outermost membrane is called
durameter. Between the piameter and arachnoid membrane is a space known as sub-arachnoid
space. The space between the arachnoid and durameter is called subdural space. The sub-arachnoid
space is filled with cerebro-spinal fluid (CSF). This fluid serves as a pad to cushion the central
nervous system from shocks.
The human brain is divided into three parts.

1. Fore Brain
It is also called Prosencephalon and is the main thinking part of the brain. It is formed of three
parts:- olfactory lobes, cerebrum and diencephalons.
(i) Olfactory lobes: The anterior part of the brain is formed by a pair of short club-shaped
structures, the olfactory lobes. Each lobe consists of two parts, an anterior olfactory bulb and a
posterior olfactory tract. Olfactory lobes are concerned with the sense of smell.
(ii) Cerebrum: It is the largest part of the brain (80%). It consists of right and left hemispheres
connected by corpus callosum. The roof of each cerebral hemisphere is highly folded to form gyri &
sulci. The peripheral part of cerebrum is formed of grey matter (neurons & non-medilated nerve
fibres) & is called as cerebral cotex. The central part of cerebrum is formed of white matter
(medullated nerve fibres) & is called as cerebral medulla. Each cerebral hemisphere of cerebrum is
divided into four lobes by three deep fissures & are:-
(a) Frontal lobe: inner monitoring of complex thoughts and actions, creative idea, speech, facial
muscular activities as well ability to abstract etc.
 44 Biology-X
(b) Parietal lobe: perception of touch, pain, heat and cold. It is the region of conscious
association.
(c) Temporal lobe: It is concerned with language comprehension, smell, memory or it is the
region for auditory reception.
(d) Occipital lobe: decoding of visual information, shape and color. It is the region of visual
reception (sight).
(iii) Diencephalon: It is completely covered by cerebrum & appears at the upper end of the
brain stem, situated between the cerebrum and the brain stem. It is formed of two main parts
thalamus, subthalamus, hypothalamus, and epithalamus.

2. Mid Brain
It is also called Mesencephalon and has two parts corpora quadrigemina (optic lobe) and crura
cerebri (cerebral peduncles).
(i) Corpora quadrigemia / Optic lobe /Colliculi: The mid brain is concerned with sense of
sight and concerned with sense of hearing.
(ii) Cerebral peduncles/Crura Cerebri: These are two bundles of fibres which lie on the lower
surface of mid brain & it coordinates hind brain with fore brain.

3. Hind Brain
It is also called Rhombencephalon and consists of cerebellum, pons varolii and medulla oblongata.
(i) Cerebellum: The second largest part of the brain is the cerebellum (little cerebrum). It
consists of lateral cerebellar hemispheres and central worm-shaped part called vermis.
The cerebellum controls rapid muscular activities, such as running, cycling, typing and even
talking, Posture of the body.
All activities of the cerebellum are involuntary, but may involve learning in their early stages.
(ii) Pons varoli / Pons: It is situated in front of the cerebellum below the mid brain and above
the medulla oblongata. It acts as a coordination centre between cerebellum & cerebrum.
(iii) Medulla oblongata: It is the posterior part of the brain & continues with the spinal cord. It
rises from pons varoli and is continuous with the spinal cord. It receives and integrates signals from
spinal cord and sends it to cerebellum. It controls involuntary functions of visceral organs. It controls
reflex actions too like coughing, sneezing, blood pressure & peristalsis etc.

Functions of a brain
(i) It receives messages and then accordingly sends instructions to different parts of body.
(ii) It correlates the stimuli from different sense organs and coordinates the body activities
effectively.
(iii) Olfactory lobes of brain are concerned with the sense of smell.
(iv) Optic lobes deal with the sense of sight. Cerebrum is the seat of thinking ability, memory,
emotions and experience.
(v) Medulla oblongata controls heart beating, respiration, swallowing, digestion, peristaltic
movements etc.
(vi) Cerebellum maintains equal and body movements.

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Frontal lobe
Parietal lobe

Occipital lobe

Cerebellum

Temporal lobe
Brain stem

Corpus
callosum
Lateral ventricle

Skull

Meninges

Cerebrum

3rd ventricle

Thalamus
Diencephalon
Hypothalamus

Midbrain Pituitarygland
th
4 ventricle
Pons
Brain
Cerebellum
stem
Medulla
Oblongala

Spinal cord

Vertebra
The Human Brain

SPINAL CORD / CORD

It is a posterior part of CNS which runs mid-dorsally within the vertebral column in a cavity
called nueral canal. It is a cylindrical structure and is about 45cm long. It begins in continuation with
the medulla oblongata of brain and extends down wards upto early part of lumbar region. At the
lower end spinal cord forms a tapering end called conus medullaris or filum terminale. It is
surrounded by the three protective membranes (meninges) as found in brain, viz. inner pia mater,
the middle arachnoid membrane and the outer dura mater. The sub arachnoid space is filled with
CSF. There is an additional space between dura mater & vertebral column called the epidural. The
epidural space contains fatty and connective tissues and veins.
Functions of spinal cord:
(i) it conducts stimuli from sensory organs and passes to brain & passes motor impulses to
effector organs.
(ii) It is the centre of reflex actions.
 46 Biology-X

PERIPHERAL NEURAL SYSTEM (PNS)

It connects CNS with different parts of body.
● Voluntary peripheral nervous system is concerned with the actions which are under the
control of will. The nerves of voluntary peripheral nervous system arise directly from CNS
connecting different body parts for voluntary control of brain.
● Involuntary peripheral nervous system (it is also called autonomic nervous system. It is not
under the control cranial and spinal nerves.
The spinal nerves are the nerves arising from spinal cord and the nerves arising from brain are
called cranial nerves. The cranial nerves are 12 pairs and spinal nerves are 31 pairs. The spinal
nerves are collectively called cauda equine or horse’s tail.
The visceral nerves are those nerves which control the activities of internal organs such as heart,
kidney, lungs, urinary bladder etc. So, it forms the autonomic nervous system. Cranial nerves I, II
and VIII are sensory nerves; cranial III, IV, VI, XI and XII are motor nerves and cranial nerves V,
VII, IX and X are mixed nerves (containing both sensory and motor nerve fibres). All spinal nerves
are mixed nerves

(2) ENDOCRINE SYSTEM

A group of endocrine glands which produces various harmones is called an Endocrine system. The
endocrine system is also called as Hormonal system. The term hormone was introduced by William
M. Baylis and Ernest H Starling in 1902. The tissues or organs secreting hormones are called
endocrine tissues and endocrine organs. Hormones have low molecular weight and are effective in
low concentration. The secretion of hormones is controlled by the anterior lobe of pituitary gland
located at the base of brain. Hormones are chemical messengers secreted by ductless endocrine
glands that regulate biological processes in living organisms.
Hormones are released in blood and action on specific organ that becomes its target organ/target
cell/ target site.
The endocrine system in our body consists of a number of glands which store and release chemical
messengers called harmones. There are a large number of endocrine glands in the human body and are:-
PINEAL GLAND
HYPOTHALAMUS GLAND
PITUITARY GLAND
THYROID GLAND
PARATHYROID GLAND
THYMUS GLAND
PANCREAS
ADRENAL GLAND
TESTES (MALES)
OVARIES (FEMALES)
Different endocrine glands make different types of harmones. The working of endocrine glands is
controlled by our nervous system. The harmones produced in our body act as messengers between the
nervous system and the organs of our body.
PINEAL GLAND: Pineal gland is present in brain,& has no known function.
HYPOTHALAMUS: Hypothalamus gland is present in brain .Hypothalamus works in response
to the stimulus of central nervous system. Hypothalamus releases certain hormones, these hormones
stimulate or inhibit the release of hormones from pituitary gland. Hormones from hypothalamus

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 Control and Co-Ordination 47
stimulate pituitary gland to secrete the hormone they synthesize. Hypothalamus secrete following
hormones:
(i) Thyrotropin releasing hormone (TRH)
(ii) Corticotropin releasing hormone (CRH)
(iii) Gonadotropin releasing hormone (GnRH)
(iv) Growth hormone releasing hormone (GRH)
(v) Growth hormone release inhibiting hormone (GRIH)
(vi) Prolactin release inhibiting hormone (PRIH)
PITUITARY GLAND or HYPOPHYSIS: Pituitary gland is present just below the
Hypothalamus. Pitutary gland has two parts : Anterior pituitary gland (Adenohypophysis) and
Posterior pituitary gland (Neurohypophysis). These two parts are connected by a bridge called Pars
Intermedia.
I. Anterior pituitary gland or adenohypophysis truly known as Master endocrine gland. It
releases following hormones:
a. Growth hormone (GH)
b. Prolactin (PRL)
c. Thyriod stimulating hormone (TSH)
d. Follicle stimulating hormone (FSH)
e. Luteinizing hormone (LH)
f. Human chorionic gonadotropin (hCG).
g. Interstetial cells stimulating hormone (ICSH)
II. Posterior pituitary gland or Neurohypophysis it releases only two hormones and
are as:
(a) Oxytocin (birth hormone/ lactating hormone)
(b) Antidiuretic hormone (ADH also called Vasopressin)
a Oxytocin: This hormone releases when breast nipple is stimulated and uterine and vegina
distention occurs. So, this hormone contracts breasts to ejects milk and it also causes the contraction
of pregnant uterus and induces labor pain.
(b) Antidiuretic hormone: it controls water balance in the body . it stimulates distilled
convoluted tubules of kidneys to absorb water thus, increases blood pressure. In the absence of this
hormone, the urine output would be 20 leters/day (polyuria).
THYROID GLAND: Thyroid gland is attached to the wind pipe. It produces the following
harmones and are:
(a) Thyroxine (T4): which is made upof iodine.The function of Thyroxine harmone is to control the
rate of metabolism of carbohydrates, fats & proteins in the body. Deficiency of Iodine in our food leads
to deficiency of Thyroxine harmone which ultimately causes a disease known as Goitre. So, it is
advised to use iodised salt.
(b) Tri-idothyronine (T3 )
(c) Calcitonin: It is secreted when calcium level is high in the blood (hyper calcemia).
It lowers Ca level by suppressing release of calcium ions from the bones.
PARATHYROID GLAND: Parathyroid glands are four in number and are embedded in Thyroid
gland. They produces a harmone called Paratharmone or parathyroid hormone (PTH) or collip’s
hormone. It increases calcium level in blood by separating calcium from bones.
THYMUS GLAND: Thymus gland lies in the lower part of the neck. It secretes a harmone called
Thymosine harmone, which develops our immune system.
 48 Biology-X
PANCREAS: The pancreas is present just below the stomach. It secrets the following harmones
and are:
(a) Insulin: The function of insulin harmone is to lower the blood sugar level in the body, if
glucose level is raised. Deficiency of Insulin harmone in the blood causes a disease known as
Diabetes. Patients with diabetes are treated by giving insulin so as to maintain the blood sugar level.
(b) Glucagon: this hormone changes excess glucose to glycogen.
(c) Gastrin: Gastrin stimulates secretion of gastric acid (HCl) in stomach.
(d) Somatostatin: Somatostatin inhibits glucagons and somatotropin releases and suppresses
the release of other hormones from pancreas.
(e) Pancreatic polypeptide: It increases glycogenolysis (glycogen? glucose) and regulates
gastrointestinal activity.
ADRENAL GLAND: Adrenal glands also called as suprarenal glands are present on the top of
both kidneys. Adrenal glands secretes following hormones and are:
(a) Adrenaline harmone or Epinephrine: Adrenaline harmone is also called as emergency
harmone because this harmone is released more during any emergency and increases heart beat,
respiration rate, carbohydrate metabolism, so prepares body for emergency condition. Which needs
more energy for fight, flight or fright, so also called as 3F hormone.
(b) Cortisol
(c) Androgen
(d) Aldosterone.
TESTES: Testes are the glands which are present only in males. Testes secrete male sex
harmone called Testosterone. The function of testosterone harmone is to develop the male sex organs
or secondary sexual characters and it also increases blood glucose level as it converts glycogen into
glucose.
OVARIES: Ovaries are the glands which are present only in females. Ovaries secrete female sex
harmones and are:
(a) Oestrogen: The function of Oestrogen harmone is to develop female sex organs or secondary
sexual characters like development of reproductive system, breast development etc.
(b) Progestrone: The function of Progestrone harmone is to stop the Ovulation maintains
pregnancy during gestation period and is also called as hormone of pragnency.
(c) Relaxin: This hormone is released only at the time of delivery, and it widens the pelvis and
helps in easy child birth.

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CO-ORDINATION IN PLANTS
Animals have a nervous system for controlling the activities of the body, but plants don’t have
nervous system. Plants can respond things like Light, Gravity, Chemicals, Water & Touch by the
action of hormones in them. Plants cant response quickly to any stimuli because they don’t have
Nervous system like in animals. Plants movements are very slow. Plant movements are largely
brought about by some definite internal and external stimuli. They are caused due the pigment
known as phytochrome. The function of control & co-ordination in plants is performed by the
chemical substances called harmones. Plant harmones are also called as Phytoharmones. (Phyto =
plant)
There are Five major plant harmones and are:-
(A) AUXIN
(B) GIBBERELLIN
(C) CYTOKININ
(D) ETHYLENE
(E) ABSCISIC ACID
1. Auxin: The existence of first growth hormone came from the work of Darwin (1881). Darwin
and his son while working on canary grass observed auxins responsible for phototropism of plant
shoot/ stem.
Functions
● Auxins are well known to promote elongation of stem, longitudinal growth & also Promote root
growth only at low concentration.
● Auxin promotes apical dominance & are well known to induce parthenocarpy.

● Auxins generally inhibit the flowering but in pine apple, spraying of certain auxins initiates
uniform flowering in the whole crop.
● Auxin regulates some of the important plant growth movements’ viz. phototropism and
geotropism.
2. Gibberellins: Gibberellins were discovered by a Japanese plant pathologist Kurosawa in
1926, while working in the rice fields, Kurosawa observed that some rice seedlings grew much taller
than the others and such plants were found to be infected by a fungus “Gibberella Fujikuroi”. The
disease was known as “Bakanae disease” (Bakanae in Japanese means foolish). The seedlings grew
foolishly so tall that they ultimately resulted into death of the plants.
Later Yabuta and Sumiki isolated the crystalline form of fungi and named it gibberellic acid.
Functions
● Gibberellins produce extra ordinary elongation of stems and leaf sheaths in intact plants.

● One of the most striking effect of the gibberellins is the reversal of dwarfism in many
genetically dwarf plants.
● Induces parthenocarpy.

● some of the light sensitive seeds (barley etc) can germinate with the treatment of gibberellic
acid.
● They also have been shown to break the dormancy.

3. Cytokinins: The cytokinins are plant growth substances which act primarily on cell division
and have little or no effect on extension growth. It was first isolated by Miller, Skoog and their
collaborators at Wisconsin university, USA in 1995 while working on tobacco pith culture and wanted
to grow it indefinitely.
 50 Biology-X
Functions
● Promotes cell division hence Causes the enlargement of cells.

● Counteraction of apical dominance i.e. cytokinins promote the growth of lateral buds even if
the apical bud is intact.
● Cytokinins can break dormancy of many seeds and also promotes their germination.

● Delay senescence.

4. Ethylene: Ethylene (CH2=CH2) is a natural product for ripening of fruits (Gane, 1934).
Functions
● Prevents elongation of stem and roots in longitudinal direction.

● Inhibits the growth of lateral buds thus causes apical dominance.

● Fruit growth and ripening is stimulated by ethylene in some plants.

● Breaks seed dormancy.

● Inhibits auxin synthesis and transport.

5. Abscisic Acid: (ABA) Carns and Addicott (1963), while working on the physiological studies of
the shedding of cotton balls, found that the chemical substance Abscisin II is responsible for their
shedding.
Functions
● Abscisic acid acts as a growth inhibitor and induces bud dormancy in a variety of plants.

● ABA also inhibits gibberellin stimulated growth.

● ABA inhibits seed development and germination.

● ABA is responsible for abscission.

● ABA stimulates positive geotropic responses by acting as inhibitor.

● Causes closure of stomata.

● ABA promotes senescence in leaves by causing loss of chlorophyll.

● It initiates resistance of plants to cold.

PLANT MOVEMENTS
Plants movements are very slow. Plant movements are largely brought about by some definite
internal and external stimuli. They are caused due to the pigment known as phytochrome. Plants
show two types of movements and are:
1. Trophic movement.
2. Nastic movement.

TROPISMS OR TROPHIC MOVEMENTS

A growth movement of a plant in responsible to an external stimulus in which the direction of
stimulus determines the direction of response is called Tropism. Tropism is of two types and are:-
If the growth of a plant part is towards the stimulus it is called positive tropism.
If the growth of a plant part is away from the stimulus ,then it is called as Negative tropism.
There is generally five stimuli in the environment. These five stimuli give us five types of
tropisms and are:-
(1) Stimulus by light is called Phototropism.
(2) Stimulus by gravity is called Geotropism.
(3) Stimulus by water is called Hydrotropism.
(4) Stimulus by Chemical is called Chemotropism.

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 Control and Co-Ordination 51
(5) Stimulus by Touch is called Thigmotropism.
(1) STIMULUS BY LIGHT: The movement of a plant part in response to light is called
phototropism. If a plant part move towards the light it is called positive Phototropism and if the plant
part moves away from the light then it is called as negative phototropism.
(2) STIMULUS BY GRAVITY: The movement of a plant part in response to Gravity is called
Geotropism. If a plant part moves towards gravity it is called positive geotropism & if the plant part
moves away from the gravity then it is called negative geotropism.
(3) STIMULUS BY WATER: The movement of a plant part in response to water is called
hydrotropism. If the plant part moves towards water it is called positive hydrotropism & if the plant
part moves away from the water then it is called negative hydrotropism.
(4) STIMULUS BY CHEMICALS: The movement of a plant part in response to a chemical
stimuli is called chemotropism. If the plant part moves towards chemicals it is called positive
chemotropism & if the plant part moves away from the chemicals then it is called negative
chemotropism.
(5) STIMULUS BY TOUCH: If the plant part moves in response to the touch of an object is
called Thigmotropism. If the plant party moves towards the external touch it is called positive
thigmotropism & if the plant part moves away from the touch then it is called negative
thigmotropism.

NASTICS OR NASTIC MOVEMENTS

These are non-directional induced variation movements that occur due to turgor changes. These
reveal immediate response to stimulus but do not involve growth. Nastic movements include:
(i) Seismonastic movement/ Thigmonastic/ Haptonastic movements: It is the shock
movement in response to the stimulus of touch or it is a nastic movement due to touch. It is best seen
in tentacles of drosera, leaf of Mimosa Pudica (touch me not).
(ii) Nyctinastic movements: It is the movement of plant organs in response to day and light. It
is also known as sleep movement. If the movement is induced by changes in light intensity, it is called
photonastic e.g. dandelion and if by changes in temperature, it is called thermonastic movement.

♙ssertion and Reason Based Questions

Directions: In the following questions, A statement of Assertion (A) is followed by a
statement of Reason (R). Mark the correct choice as:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
1. Assertion (A) : Auxin is the most important plant hormone.
Reason (R) : It promotes cell enlargement and cell division.
2. Assertion (A) : Ethylene is a growth inhibiting hormone.
Reason (R) : It is a liquid hormone.
3. Assertion (A) : Abscisic acid is a growth promoting hormone.
Reason (R) : It promotes all those activities, which are against the normal
growth.
4. Assertion (A) : When the response of a plant part to light is called phototropism.
 52 Biology-X
Reason (R) : The roots of plant always move towards water.
5. Assertion(A) : Movement of leaves of sensitive plant is different from
movement of a shoot towards light.
Reason (R) : Sensitive plant shows seismonastic movements which are due to
turgidity of cells whereas the movement of shoot is a tropic
movement.
6. Assertion (A) : Nastic movement (response) is fast.
Reason (R) : This movement is exhibited by all parts of the plant.
7. Assertion (A) : A neuron transmits message in both directions.
Reason (R) : Neuron is specialised for conducting information via electrical
impulses from one part of body to another.
8. Assertion (A) : Adrenative makes the heartbeat faster, resulting in supply of
more oxygen to our muscles.
Reason (R) : Adrenative is secreted directly into the blood and carried to
different parts of the body.
9. Assertion (A) : Cerebellum controls the coordination of body movement and
posture.
Reason (R) : Medulla oblongata controls and regulates the centre for
coughing, sneezing and vomiting.
10. Assertion (A) : Amount and timing of hormones released are regulated by
feedback mechanism.
Reason (R) : Hypersecretion or hyposecretion of any hormone can lead to
different disorders.

♙nswers
1. (b) 2. (c) 3. (d) 4. (b) 5. (a) 6. (c) 7. (d) 8. (a) 9. (b) 10. (c)

Objective Questions
1. Name the chemicals that are mainly involved in the chemical coordination activity:
(a) Enzymes (b) Hormones (c) Carbohydrates (d) Vitamins
2. Plant hormone which responsible for the ripening of fruits, is:
(a) Auxin (b) Ethylene (c) Abscisic acid (d) Cytokinin
3. The movement of the plant when the stimulus has a fixed direction, is called:
(a) nastic movement (b) tropic movement (c) thigmonasty (d) none of these
4. Which hormone is mainly found in the root tips?
(a) Gibberellin (b) Auxin (c) Cytokinin (d) Abscisic acid
5. Name the plant hormone, which is responsible for leaf falling and stomatal closure:
(a) Auxin (b) Gibberellin (c) Cytokinin (d) Abscisic acid
6. The primary effect of gibberellin is:
(a) Fruit ripening (b) Leaf fall
(c) lengthening of stem (d) Formation of buds
7. Pineapple can be made to flower in off season by :
(a) Zeatin (b) Ethylene (c) Temperature (d) Short days

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 Control and Co-Ordination 53
8. Which of the following is a plant hormone?
(a) Insulin (b) Thyroxin (c) Oestrogen (d) Cytokinin
9. Auxins help cell to grow longer when growing plants detect :
(a) smell (b) light (c) temperature (d) chemicals
10. In plants the role of cytokinin is:
(a) promote cell division (b) wilting of leaves
(c) promote the opening stomatal pore (d) help in the growth of stem
11. Ethylene synthesis in plants is induced by environmental stresses and:
(a) gibberellins (b) cytokinins (c) auxins (d) abscisic acid
12. Directional movement of a plant in response to contact is called:
(a) hydrotropism (b) thigmotropism (c) phototropism (d) chemotropism
13. Mimosa pudica shows an example of :
(a) phototropism (b) chemotropism
(c) geotropism (d) nastic movement
14. Name the plant hormone which can increase the height of the plant:
(a) Auxin (b) Gibberellin
(c) Cytokinin (d) Abscisic acid
15. Sensory neuron is present between:
(a) CNS and muscles (b) Sense organ and CNS
(c) CNS and ANS (d) Sense organs and muscles
16. Which part of the brain is responsible for balancing the body?
(a) Cerebrum (b) Cerebellum
(c) Medulla oblongata (d) Diencephalon
17. How many cranial nerves are found in human body?
(a) 13 pairs (b) 10 pairs (c) 8 pairs (d) 12 pairs
18. Which gland of human body is called master gland?
(a) Thyroid gland (b) Liver (c) Pituitary gland (d) Pancreas
19. The centre of memory and intelligence in human brain, is:
(a) Medulla oblongata (b) Cerebral hemispheres (Cerebrum)
(c) Cerebellum (d) Diencephalon
20. The gap between two successive neurons is called:
(a) ganglia (b) axon (c) synapse (d) dendrite
21. Name the organ that controls the reflex actions:
(a) Brain (b) Spinal cord (c) Pituitary gland (d) Hypothalamus
22. Insulin is secreted from:
(a) Pancreas (b) Thyroid (c) Parathyroid (d) Pituitary
23. Which of the following hormones is not secreted from pituitary gland?
(a) TSH (b) Oxytocin (c) Growth hormone (d) Testosterone
24. Brain box is also called :
(a) Skull (b) Head (c) Cranium (d) Meninges
25. Spinal cord is the posterior elongation of:
(a) Cerebrum (b) Cerebellum (c) Medulla oblongata (d) Diencephalon
 54 Biology-X
26. Which hormone is called birth hormone?
(a) TSH (b) Oxytocin (c) Insulin (d) Progesterone
27. Secondary sexual characters in male arise due to the effect of:
(a) TSH (b) Oxytocin (c) Progesterone (d) Testosterone
28. In comparison with other cells, nerve cells show a higher degree of:
(a) Metabolism (b) Growth (c) Contractility (d) Irritability
29. The photoreceptor cells of the eye are located in:
(a) Sclera (b) Iris (c) Retina (d) Optic nerve
30. The peripheral nervous system consists of:
(a) Nerves within the spinal cord (b) Only sensory nerves
(c) Only motor nerves (d) Both motor and sensory nerves

♙nswers
1. (b) 2. (b) 3. (b) 4. (b) 5. (d) 6. (c) 7. (b) 8. (d) 9. (b) 10. (a)
11. (c) 12. (b) 13. (d) 14. (b) 15. (b) 16. (b) 17. (d) 18. (c) 19. (b) 20 (c)
21. (b) 22. (a) 23. (d) 24. (c) 25. (c) 26. (b) 27. (d) 28. (d) 29. (c) 30. (d)

Textual Questions
Q.1 What is the difference between a reflex action and walking?
Ans. A reflex action is voluntary action which is rapid and automatic response to stimuli while
walking is a voluntary action which requires our thinking and is in our control.
Q.2 What happens at the synapse between two neurons?
Ans. A synapse is a gap between the two neurons. At synapse the electrical signals converted into
chemicals that can easily cross over the gap and pass on to the next neurons where it again is
converted into electrical signals.
Q.3 What part of the brain maintains posture and equilibrium of our body?
Ans. Cerebellum.
Q.4 How do we detect the smell of an agarbati?
Ans. When the smell of agarbati reaches to our nose then the Olfactory receptors present in our
nose detects it sends this information to fourbrain in the form of electrical signals.Fourbrain
interprets this information as the smell of agarbati where it is already stored.
Q.5 What is the role of brain in reflex action?
Ans. Brain has no direct involument in reflex action. It is mainly controlled by spinal cord as these
actions not requires thinking and are very quick actions.
Q.6 What are plant harmones?
Ans. Plant harmones are the chemicals which are secreted within the plant and are also known as
phytoharmones. Plant harmones regulate the growth and development of the plant. E.g of the
plant harmones are Auxin, Giberellin, Cytokinin, abscisic acid.
Q.7 How is the movement of leaves of the sensitive plant different from the movement of a shoot
towards light?

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 Control and Co-Ordination 55
Ans. The movements of the leaves of the sensitive plant are touch sensitive and independent of
growth while the movement of the shoot towards light is growth related and known as
phototropism.
Q.8 Give an example of a plant harmone that promotes growth?
Ans. Auxin.
Q.9 How do auxins promote the growth of a tendril around a support?
Ans. When tendrils come in contact with any support the part of the tendril in contact with the
object does not grow as rapidly as the part of the tendril away from the object. This is called by
the action of auxin harmone.Less auxin occurs on the side of contact as compared to the free
side as a result ,auxin promotes growth on the free side and the tendrils coil around the
support.
Q.11 How does chemical co-ordination take place in animals?
Ans. Chemical co-ordination takes place in animals with the help of harmones. Harmones are
chemicals that are secreted by the endocrine glands. Harmones regulate the overall growth
and development of animals.
Q.12 Why is the use of iodised salt advisable?
Ans. Iodine stimulates the thyroid gland to produce thyroxine harmone.Thyroxine harmone
regulates carbohydrate , fat & protein metabolism in our body. Defeicency of this harmone
results in the enlargement of the thyroid gland. This can lead to Goitre , therefore iodised salt
is advised for normal functioning of thyroid gland.
Q.13 How does our body respond when adrenaline is secreted into the blood?
Ans. When some one is in danger or any emergency then adrenal glands secrete adrenaline
harmone. It is secreted directly into the blood and is transported to different parts of the body.
It speeds up the heart beat and hence supplies more oxygen to the muscles. This results in
increasing breathing rate and blood pressure which enable them to fight with such urgent
situation.
Q.14 Why are some patients of diabeties treated by giving injection of insulin?
Ans. Diabetes is caused due to less or no secretion of insulin harmone by pancreas, In such a person
blood sugar level is high . Insulin maintains the blood sugar level. Thus patients suffering
from diabetes are given insulin injection to control their blood sugar level.
Q.15 How do Auxins promote the growth of a tendril around a support?
Ans. When tendrils come in contact with any support, the part of the tendril in contact with the
object does not grow as rapidly as the part of the tendril away from the object. This is caused
by the action of auxin harmone. Less auxin occurs on the side of contact as compared to the
free side as a result , auxin promotes growth on the free side and the tendrils coil around the
support.
Q.16 (i) Which of the following is a plant harmone?
Ans. Cytokinin
(ii) The gap between two neurons is called as?
Ans. Synapse
(iii) The brain is responsible for?
Ans. All of the above.
Q.17 What is the function of receptors in our body? Think of situations where receptors don’t work
properly. What problems are likely to arise?
Ans. Functions of receptors are:
(a) They sense the external stimuli such as heat or pain.
(b) They also trigger an impulse in the sensory neuron which sends message to
 56 Biology-X
the spinal cord.
When the receptors are damaged, the external stimuli transferring signals to the brain are
not felt. For e.g in the case of damaged receptors, if we accidently touch any hot object then
our hands might get burnt as damaged receptors can’t perceive the external stimuli of heat
and pain.
Q.18 Draw the structure of a neuron and explain its function?

Functions of the three parts of the neuron are

(i) Axon: It conducts messages away from the cell body.
(ii) Dendrite: It receives information from axon of another neuron and conducts the messages
towards the cell body.
(iii) Cell body: It contains nucleus, Mitochondria, and other organells. It is mainly concerned
with the maintenance and growth.
Q.19 How does Phototropism occur in plants?
Ans. The growth movements in plants in response to light stimulus is known as phototropism. The
shoots show positive phototropism and the roots show negative phototropism, This means
that the shoots bend towards the source of light where as the roots bend away from the light
source. E.g the flower head of sunflower is positively phototropic and hence it moves from east
to west along with the sun.
Q.20 Which signals will get disrupted in case of a spinal cord injury?
Ans. In case of a spinal cord injury, the signals coming from the nerves as well as the signals
coming to the receptors will be disrupted. As both these signals meet in a bundle in spinal cord
so there is any spinal cord injury then both these signals are disrupted.
Q.21 How does chemical co-ordination occur in plants?
Ans. Chemical co-ordination occurs in plants with the help of plant harmones. Different plant
harmones help to co-ordinate growth , development , responses to the environment . they are
synthesized at places away from where they act and diffuse to the area for action, e.g Auxin
promotes cell growth , Giberellin promote stem growth, Cytokinin promote cell division and
Abscisic acid inhibits growth and its effects include wilting of leaves.
Q.22 What is the need for a system of control and co-ordination in an organism?
Ans. There are various organs in an organism. These organs must be carefully controlled and
co-ordinated for the survival of an organism. In the body of an organism various harmones are
secreted from the glands of the endocrine system. These harmones are responsible for the
overall growth and development of an organism, and all others like voluntary and involuntary
actions are controlled by central nervous system.

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 Control and Co-Ordination 57
Q.23 How are involuntary actions and reflex actions different from each other?
Ans. Involuntary action is the set of muscle movement which don’t require thinking. But it is
controlled by brain for example beating of heart beat. Reflex action is rapid is rapid and
spontaneous action in response to any stimulus. E.g closing of eyes immediately when bright
light is focused.
Q.24 Compare and contrast nervous and hormonal mechanisms for control and co-ordination in
animals?

Nervous System Mechanism Harmonal System Mechanism

It consists of nerve impulses between It consists of endocrine system which
CNS and brain secretes harmones
The axons and dendrites transmit the The information is transmitted through
information through a co-ordinated blood
effort
The flow of information is rapid and The information travels slowly and the
the response is quick response is slow
Nerve impulses are not specific in Each harmone has specific action
their action
Effects are short lived It has prolonged effects

Q.25 What is the difference between the manner in which movement takes place in a sensitive
plant and the movement of our legs?

Movement in Sensitive Plant Movement in Our Legs

The movement in a sensitive plant is Movement in our legs is a voluntary
response to stimulus which is action
involuntary action
No special tissue is there for the A complete system CNS is there for the
transfer of message transfer of information
Plant cells don’t have specialized Animal cells have specialized protein
protein for the movements which help muscles to contract
 58 Biology-X

CHAPTER

3
Reproduction
Reproduction is one of the most important and fundamental properties of living organisms by
which every kind of living organisms multiplies to form new individuals of its own kind. In this
process one generation of living organisms gives rise to the next generation. It is a function essential
for the life of the species. Reproduction is of two types. i.e asexual and sexual reproduction.

Do Organisms Create Exact Copies of Themselves

Organisms look similar because their body designs are similar. If body designs are to be similar,
the blue prints for these designs should be similar. Thus, reproduction involves making copies of the
blueprints of body design. The chromosomes in the nucleus of a cell contain information for
inheritance of features from parents to next generation in the form of DNA (Deoxy-ribo Nucleic Acid)
molecules. The DNA in the cell nucleus is the information source for making proteins. If the
information is changed, different proteins will be made. Different proteins will eventually lead to
altered body designs. A basic even in reproduction is the creation of a DNA copy. Cells use chemical
reactions to build copies of their DNA. The process of copying DNA will have some variations each
time. The DNA (de-oxy ribonucleic acid) copies generated will be similar but may not be identical to
the original.
Variations: The differences shown by the individuals of species, and also by the off springs of the
same parents are referred to as variations.

The Importance of Variation

The consistency of DNA copying during reproduction is important, which leads to the stability of
population species. Changes in ecological system, which are beyond our control like varying
temperature, varying water levels and natural calamities, can wipe out the population species. So if
there is some variations are present in some individuals of the population species then there is a
chance for the survival of these species over time.

Asexual Reproduction
Asexual reproduction also called as apomixis is that type of reproduction in which production of
new individuals from a single parent without the involvement of sex cells is called asexual
reproduction. It does not involve the fusion of gametes or sex cells. There are many types of asexual
reproduction, all producing individuals that are genetically identical to their parent.
Modes or types of Asexual Reproduction
(i) Fission: Fission occurs in lower plants and animals such as the bacteria, blue-green algae and
protozoa. In this process, the cell divides after the genetic material has divided. If the cell divides into
two it is called binary fission. The DNA or the nucleus of a mature cell divides first and then the cell
divides into two daughter cells of almost the same size. It is seen in bacteria and protozoans like

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 How Do Organisms Reproduce 59
amoeba and paramecium. If the parent cell divides into many daughter cells simultaneously during
unfavorable conditions like deficiency of food or water or extremes of temperature, then it is called
multiple fission. It is seen in the life cycle of the Amoeba, plasmodium (the malarial parasite). The
nucleus divides many times (karyokinesis) and then the cytoplasm divides (cytokinesis) and
surrounds the nuclei.
Cytoplasm
Nucleus

Daughter

Daughter

Binary fission in Amoeba

(ii) Budding: It is that type of asexual reproduction In which the parent cell or body gives out or
inside a outgrowth called the bud. Each bud grows and develops the parental characters and then
generally separates from the parent to lead an independent life. The nucleus divides and one of the
daughter nuclei passes into the daughter cell. The bud grows in size while being attached to the
parent body. It then gets separated from the body of the parent . It then falls off and germinates into a
new individual. It is seen in multicellular animals. e.g. In case of hydra & yeast.
On the basis of position of bud formation , budding is of two types:
● External budding

● Internal budding

● External budding: External budding is also called as exogenous budding. In this type of
budding buds are formed on the outer surface of the parental body. E.g: Hydra.

Developing New bud

bud

Parent
Hydra

New Hydra

(a) (b) (c) (d)

Internal budding: Internal budding is also called as

Microplye
endogenous budding. In this type of budding a number of
internal buds called gemmules are formed inside the Outer Covering
parent. So, it is also called as gemmulation. The Spicules
gemmules are made up of number of cells called
archeocytes. These gemmules are resistant to unfavorable Archaeocytes
conditions. When favorable conditions exists outside the inner Covering

parental body then these archeocyte cell comes out of the

gemmule and develop into a young organism. E.g:
sponges.
(iii) Spore Formation or sporulation: In spore formation the parent plant produces hundreds
of spores which are reproductive units, when the sporangium of the fungus plant bursts , then the
 60 Biology-X
spores spread into air. When these air borne spores land on food under favorable conditions they
germinate and produces new fungs plants. For example, fungi such as (Rhizopus & Mucor), Bacteria,
non flowering plants like ferns and mosses.
Sporangiospores
Sporangium
Columella

Sporangiophore

Aseptatehyphae

Rhizoides

(iv) Fragmentation: It takes place in some lower plants and animals such as some worms. The
mature organism breaks up into two or more pieces or fragments. The fragments then grow into
complete organisms. For example: flatworm Microstomum, Spirogyra & Sea-Anemones Can
reproduce by the method of fragmentation.
Mouth Intenstine
Mouth Mouth Mouth
Eyes

Fragmentation in Microstomum (a flatworm)

(v) Regeneration: Regeneration is one of the methods of asexual reproduction in lower or less
evolved animals. When the parent body breaks into pieces, each piece can grow into a new organism.
It is the ability of an organism to regenerate its lost part of the body which has been removed. For
example: Planaria & Hydra.

Parent
Planaria Fragments
of Planaria

Daughter
Planaria
Regenerationin Planaria

(vi) Vegetative propagation: It is also a common method of asexual reproduction in seedless

plants and others. Here any part (vegetative) of the plant like roots, stem and leaves can give rise to
the new plant. It may occur by methods like cutting, grafting, layering, adventitious bud formation.
Methods of vegetative reproduction: Vegetative propagation or vegetative reproduction may
be accomplished by natural (natural vegetative propagation) as well as artificial (artificial vegetative
propagation) means. Since plants resulting from vegetative propagation are produced asexually from
a single parent plant, they are genetic clones of the parent plant. This can have advantages and

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 How Do Organisms Reproduce 61
disadvantages. One advantage of vegetative propagation is that plants with traits that are favorable
for a particular environment are repeatedly reproduced. A major disadvantage of vegetative
propagation is that this process does not allow for genetic variation. The plants are genetically
identical and are all susceptible to the same plant viruses and diseases that can destroy entire crops.
NATURAL VEGETATIVE PROPOGATION: Natural vegetative propagation involves the
development of a new plant from parts of a single mature plant. The new plants grow and develop
naturally without human intervention. Natural vegetative propagation can take Place from the
stems, roots, or leaves of a parent plant to form new plant.
ARTIFICIAL VEGETATIVE PROPAGATION: Artificial vegetative propagation is a type of
plant reproduction that is accomplished through artificial means involving human intervention. The
most common types of artificial vegetative reproductive techniques involve cutting, layering,
grafting, suckering, and tissue culture. These methods are employed by many farmers and
horticulturists to produce healthier crops with more desirable qualities. Artificial vegetative
propagation is of many type:
(i) Cutting: It is also a common method of vegetative propagation. Mostly stem cuttings are used
for it. Small pieces of stem are cut and their free ends are cut obliquely to form cuttings. These
cuttings are placed slightly vertically in the soil. One or two buds on these cuttings develop into shoot
system and root system develops from underground part of cutting.
(ii) Grafting: Grafting is the method in which the cut stems of two Scion

different plants one with roots and another without roots are joined
together in such away that the two stems join and grow as a single plant.
The plant part which contributes its root system is called as stock and the
plant part which contributes its shoot system is called as scion.
A twig from a mature plant of desired variety (scion) with some buds is
inserted into the stock. In due course of time, the scion joins with stock and
develops into an aerial shoot that bears leaves, flowers etc. it is common
method used in the production of apples, pears, plums, peaches, mangoes
etc.
(iii) Layering: This method involves bending plant branches or stems Rootstock

so that they touch the ground. The portions of branches or stems in contact with the ground are then
covered with soil but the free end of the branch is kept uncovered is called Mound Layering.
Adventitious roots develop in the parts covered by soil and the attached shoot (branch or stem) with
new roots is known as a layer. Latter in due course of time it is detached from the main branch of
parent plant and gives rise to a complete plant. This type of layering also occurs naturally. In another
technique called air layering, branches are scraped and covered with plastic to reduce moisture loss.
Adventitious roots develop where the branches were scrapped and the branches are removed from
the tree and planted. The branches develop into new plants over time.
 62 Biology-X

Tissue culture or Micropropagation

This technique involves the culturing of plant cells that may be taken from different parts of a
parent plant. The tissue is placed in a sterilized container and nurtured in a special medium until a
mass of cells known as a callus is formed. The callus is then cultured in a hormone-ladened medium
and eventually develops into plantlets. Plantlets can then be planted and develop into fully grown
plants. e.g. chrysanthemum asparagus etc.
Unisexual: the organism that bears only one of the two sexes either male or female is called as
unisexual.
Bisexual or Hermaphrodite: both types of sex organs are present in the same individual, that
individual is known as bisexual or hermaphrodite. e.g. earthworm, hydra, tapeworm etc.
Pollination: The transfer of pollen grains from the anther to the stigma is called pollination. It
is of two types
Self pollination: self pollination involves the transfer of pollen grains from the anther of a
flower to the stigma of the same flower or to the stigma of another flower borne on the same plant.
Cross pollination: Cross pollination involves the transfer of pollen grains from the flower of one
plant to the stigma of the flower of another plant of the same species.
Agents for pollination/ Pollinators: pollination can take place by insects (Entomophily), by
wind (Anemophily), by water (hydrophily), by bats (Zoophily), by ants (Necrocoleopterophily).
Isogamy: When male and female gametes are structurally and functionally similar. E.g:In
Protozoans.
Heterogamy: When male and female gametes are structurally and functionally different.e.g:In
humans.
Self fertilization: Self-fertilization fusion of male and female gametes (sex cells) produced by
the same individual. Self-fertilization occurs in bisexual organisms, including most flowering plants,
numerous protozoans, and many invertebrates.
Cross fertilization: fertilization in which the gametes are produced by separate individuals or
sometimes by individuals of different kinds.
Hypoandrous condition: The condition in which andocium is short in size than gynoecium.
Hypogynous condition: The condition in which gynoecium is short in size than andocium
Polyandrous condition: The condition in which multiple andocium are present in a single
flower.
Polygynous condition: The condition in which multiple gynoecium are present in a single
flower.
Sexual dimorphism: Sexual dimorphism is the condition where the two sexes of the same
species exhibit different characteristics beyond the differences in their sexual organs. The condition
occurs in many animals and some plants. Differences may include secondary sex characteristics, size,
weight, color, markings, and may also include behavioral and cognitive differences. These differences
may be subtle or exaggerated, and may be subjected to sexual selection. The opposite of dimorphism
is monomorphism.
Copulation & insemination: copulation involves sexual intercourse during which male inserts
penis in vegina called copulation or Coitus and releases 3.5 ml of seminal fluid called insemination.

SEXUAL REPRODUCTION
Sexual reproduction is also called as Amphimixis is that type of reproduction which involves the
formation of gametes from male and female parents and their fusion. It requires two individuals of
opposite sexes. Male produces the male gamete called as sperm while as female produces female

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gametes called as ovum. Hence gametes have half the number of chromosomes as compared to the
parents. Their fusion during fertilization restores the diploid number of chromosomes in the next
generation.

Sexual Reproduction in Flowering Plants (ANGIOSPERMS)

The plants that sexually reproduce have the reproductive structures called the flowers. The
flower is a condensed shoot with the nodes present very close to each other. The different parts of the
plant are attached to the nodes. A flower is brightly coloured, reproductive part of a plant.
Flowers are not seen all the times because flowering in a plant occurs at a particular season of the
year and is controlled by photoperiod (daily duration of light) & temperature. Term photoperiodism
was introduced by Garner & Allard in 1920. Some plants need longer light days for flowering called
long day plants (LDP) e.g Wheat, Radish & Oat etc while as some plants need shorter light days for
flowering called Short day plants (SDP) e.g: Tobacco, Rice, Dahlia etc.
The stalk of flower is called Pedicel. Swollen flat tip of pedicel forms the thalamus, The four types
of floral leaves are sepals, petals, stamen & carpels appear from thalamus. Sepals and petals (calyx
and corolla) are reffered as non-essential parts of a flower because they are not involved in sexual
reproduction. Where as stamen and carpel (androecium and gynoecium) are reffered as essential
parts of a flower because they are involved in sexual reproduction. All the structures present at one
node are collectively called the whorl.
Parts of a Flower: The important parts of a flower taking part in the sexual reproduction are:
1. Sepals or Calyx is the outermost and most often green in colour. The individual units of calyx
are called the sepals. It protects the inner whorls at bud stage.
2. Petals or Corolla is the next inner whorl and is often coloured brightly. The individual units of
corolla are called petals. They serve to attract bees, birds, etc which are the agents of pollination.
3. Stamens or Androceium is the male reproductive part of the flower. The individual units of
androecium are called the stamens. Each stamen has a thread-like filament at the free end of which
is attached the anther. The anther contains yellow powder like structures called pollen grains which
are male sex cells of a flower.
4. Carpel or Gynoecium or pistil is the female reproductive part of the flower. The individual units
are called the carpels or pistils. A flower may have one or many carpels. Each carpel is made up of the
basal ovary, middle style and the upper stigma. The ovary is the chamber where there are many
ovules that are attached to an axis. Each ovule is a female sex cell of a flower. The stigma is a sticky
structure that receives the pollen grains. The style is hollow and provides a passage for the male
gametes to reach the female gametes.
Bisexual flower: Flowers that contain both male part and female part are called as bisexual
flower or hermaphrodite flowers e.g: Mustard & pea.
Unisexual flower: Flowers that contain only one single sex i.e either male part or female part
are called unisexual flowers e.g: Papaya & water melon.
Monoecious plant: Plants that bear flowers of both sexes are called Monoecious plants. E.g:
Maize & castor bean.
Diecious plant: Plants that bear only one type of unisexual flowers Are called as diecious plants
e.g: Date palm & Mulberry.
Neuter flower: Insome plants flowers lack both stamen and pistil, such flowers are called as
neuter flower e.g: Mango bear some neuter flowers.
 64 Biology-X

Pollen grain
Stigma
Pollen tube

Style

Overy wall
Three Antipodal cells

Two Polar
nuclei Two Synergid cells

Female
gametophyte

One Egg cell

Sperm cell

Tube nucleus

Pollination
Transfer of pollen grains from the anther to the stigma is called pollination.
TYPES OF POLLINATION
1. SELF POILLINATION
2. CROSS POLLINATION
(1) SELF POLLINATION (Autogamy): Self pollination involves the transfer of pollen grains
from the anther of a flower to the stigma of the same flower or to the stigma of another flower borne
on the same plant i.e. genetically similar flower. It is of two types
(a) Autogamy; (GK. Autos = self, gamos = marriage): It is a kind of self pollination in which the
pollen from the anthers of a flower is transferred to the stigma of the same flower.
(b) Geitonogamy; (GK. Geiton = neighbour, gamos = marriage): It is a kind of self pollination in
which the pollen from the anthers of one flower is transferred to the stigma of another flower borne
on the same plant.

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(2) CROSS POLLINATION (Allogamy): If the pollen grains are transferred from anther to the
stigma of another flower of the same species, the pollination is called cross-pollination or allogamy.
Cross pollination is brought about by various agencies or agents like by wind also called Anemophily,
by water also called Hydrophily, by bees also called Entomophily, by birds also called Ornithophily,
bats and other animals including man.
The anthers on maturity burst open with force and this is called dehiscence. This releases the
pollen grains with force which are then carried by wind and water to other plants. In other plants, the
flowers are brightly coloured and scented to attract the birds, bees, etc. The insect or the bird enters
the flower to suck the nectar produced by glands at the base of the flower. The pollen grains present
on the dehisced or open anther, stick to the legs or abdomen. When the same insect visits other
flowers the pollen grains are transferred to the stigma of those flowers.
Structure of pollen grain (Microsporangia): The study of pollen is called palynology. A
microscopic structure, The pollen grains are produced within the anther of the flower. The pollen
grains do not remain united at maturity, and are dissociated into single pollen grain called monad.
Pollen consists of one or more vegetative cells and a reproductive cell. A pollen grain itself is not the
male gamete. The wall of the pollen grain always consists of two layers: the inner intine wall and the
outer exine wall. Pollen itself is not the male gamete. A pollen grain contains vegetative cell or
non-reproductive cell and a generative cell or reproductive cell. In flowering plants the vegetative cell
forms the pollen tube where as the generative cell divides to form the two sperm cells

Vacuole
Tube Cell
Exine

Tube
Intine Nucleus

Germ Pore Generative

Cell

Section of a mature 2 celled pollen grain of an angiosperm

Structure of OVULE OR (Megasporangia): In seed

plants, the ovule is the structure that gives rise to and
contains the female reproductive cells. It consists of three
parts: The integuments, forming its outer layers, the nucellus
and the Embryo sac or female gametophyte in its center. The
female gametophyte specifically termed a megagametophyte.
The basal portion of the nucellus from where the integuments
appear is called Chalaza and the end is called as chalazal end.
A small opening is left at the apex of integuments is known as
micropyle. Egg cell is embedded in the centre of the ovule. Egg
cell contains eight cells nine nucleus. Three cells present at
chalazal side are called antipodal cells, two cells at micropilar end are called Synergids between
synergids is present Egg cell. And the large sized cell in centre with two polar nuclei is called as
central cell.
Fertilization: On reaching the stigma, the pollen grains put out a tube called pollen tube. This is
called germination of the pollen grain. The tip of the pollen tube contains the male nuclei. The tube
grows and enters the ovule through micropilar end where pollen tube bursts at the tip releasing the
male gametes. One of the male gametes fuses with the egg cell of ovule. The fusion of the male gamete
with the female gamete or egg cell is called fertilization. This results in the formation of zygote that is
 66 Biology-X
diploid. The zygote develops into the embryo. The other male gamete fuses with the polar nuclei
present inside the embryo sac, & result in the formation of a triploid nucleus called the primary
endosperm nucleus (PEN). And the central cell after fertilization forms primary endosperm cell
(PEC). Since the process of fertilization involves two fusions, one fertilization with egg cell and
another fertilization with polar nuclei so, it is called double fertilization. The divisions of the
endosperm nucleus result in the formation of the endosperm that provides food to the growing
embryo. The ovule then becomes the seed and the ovary changes into fruit.
Pollen grain
Stigma

Male germ-cell

Pollen tube

Ovary

Female
germ-cell

STRUCTURE OF SEED: Seeds are matured ovules. Seed contains an embryo and reserved
food. Reserved food is used by developing embryo at the time of seed formation. A mature see d is
made up of two important parts.
(a) seed coat
(b) Embryo.
(a) Seed coat: seed coat is hard layer which protects the internasal parts of seed.
(b) Embryo: Embryo is further made upof four sub parts.
● Radicle

● Plumule

● Cotyledon

● Endosperm

● Radicle: it forms young root after germination of seed.

● Plumule: it forms young shoot after germination of seed.

● Cotyledon: cotyledons are the embryonic leaf of a plant.

● Endosperm: it is a tissue inside the seed of most of the flowering plants.it provides nutrition

to growing seed in the form of starch. Seeds may be endospermic (contains endosperm) or
non-endospermic (have no endosperm).seeds with single cotyledon are called as
monocotyledons (maize) and seeds with two cotyledons are called as dicotyledons (apple).

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Seed coat Plumule (shoot)

Epicotyl Endosperm
Hypocotyl Hypocotyl

Seed coat Radicle (root)

Cotyledons
Epicotyl Cotyledon
Cotyledon
Seed coat Radicle

Dicotyledon Monocotyledon

SEXUAL REPRODUCTION IN ANIMALS

Sexual reproduction mostly occurs in higher multicellular plants and animals. However, it is also
seen in lower organisms like the bacteria, Spirogyra (an alga) and Paramecium (a protozoan).
The organisms that follow sexual reproduction have the specific reproductive organs. The
reproductive organs produce the haploid sex cells called the gametes by the process of meiosis. There
are two types of gametes - male and female. Male gametes are called sperm cells and the female
gametes are called ova or eggs. The eggs are bigger as they contain the reserve food for the growing
embryo. The male reproductive organs produce the sperm cells and the female reproductive organs
produce the eggs. The sperm cells are generally motile and travel to the eggs and fuse with them.
This results in the formation of diploid zygote that has the characteristics of both the male and the
female parents. The zygote then grows into an embryo by mitotic divisions. The embryo by further
growth and differentiation results in the formation of young adult.

Some important terms

● Puberty: Puberty is the period during which growing boys or girls undergo the process of
sexual maturation. Puberty involves a series of physical stages or steps that lead to the
achievement of fertility and the development of the so-called secondary sex characteristics,
rapid growth, the physical features associated with adult males and females (such as the
growth of pubic hair). The time when puberty begins varies greatly among individuals;
however, puberty usually occurs in girls between the ages of 10 and 14 and between the ages of
12 and 16 in boys. Central precocious puberty (CPP) is puberty that occurs earlier than normal
due to release of hormones from the hypothalamus of the brain.
Signs and Symptoms of Central Precocious Puberty
● breast development,

● enlargement of the testes and penis.

● presence of pubic hair, axillary hair, and facial hair. initiation of menstrual periods,

● increasing in sweat production,

● development of body odor,

● lowering of the pitch of voice, rapid height acquisition ("growth spurt"), and

● increase in size and strength of muscles.

Gametogenesis: the process of formation of sex cells or gametes, or germ cells, inside gonads of
an organism. The formation of female sex cell or egg cells, or ova, is technically called oogenesis, and
the formation of male sex cells or sperm cells, or spermatozoa, is called spermatogenesis.
Fertilization: Fertilization also known as generative fertilisation, insemination, fecundation,
syngamy and impregnation is the fusion of male gamete with female gametes to form a new
individual or organism or offspring. Fertilization is of two types:
 68 Biology-X
● Internal fertilization: If the fusion of male and female gametes takes place inside the body is
called as internal fertilization.
● External fertilization: When fusion of gametes (sperm and ovum) takes place outside the
body is called as external fertilization.
Male reproductive system: Male reproductive system contains following organs:
(a) Two testes or Spermaries
(b) Epididymis
(c) Vas deferns (sperm duct)
(d) Ejaculatory duct
(e) Urethra
(f) Penis
(g) Male reproductive glands.
(a) Testes or Spermaries: Testes are the primary reproductive organs in males. They are one
pair, soft, oval shaped & Pinkish coloured having a length of 4-5cm. testes are extra abdominal
means they are present outside the body in a sac like structure Called Scrotum. Scrotum is only
meant for keeping testicular temperature 20C lower than body temperature for normal
spermatogenesis. Origin of testes is lower back of abdomen just below the kidneys & when the foetus
attains the age of seven months, testes decends downwards into scrotum through anguinal canals,
sometimes testes fail to decend into scrotum such medical abnormality is known as Cryptochidism.
Each testes is covered by three coverings collectively called as Tunicae. internally each testes
contains 250 compartments called testicular lobules & each testicular lobule contains about three
seminiferous tubules. Each seminiferous tebule is internally lined by two types of cells i.e
spermatogonia cells or male germ cell & sertoli cells or nourish cells. Spermatogonia cells or male
germ cells synthesize sperm cells where as sertoli cells provide nourishment to sperm cells. So, sertoli
cells are also called as nourish cells or supporting cells or sustanticular cells & were discovered by
Enricho Sertoli. In a testis all these seminiferous tubules combine to form epididymis.
(b) Epididymis: They are paired, highly coiled ducts having length of 6m. Each epididymis
arises from the superior side of testis. it is involved in storage of sperms for few days & provides
nutrition to sperms.
(c) Vas deferns or sperm duct: They are also paired uncoiled ducts having a length of 30cm.
each vas deferns arises from epididymis, enters the abdomen, passes over the urinary bladder & joins
the ducts of seminal vesicles to form ejaculatory duct.
(d) Ejaculatory duct: They are also paired. Each ejaculatory duct is 2cm long. Ejaculatory duct
transports semen (sperm + seminal fluid = semen). Both ejaculatory duct enters into the prostrate
gland & forms a single duct called prostratic urethra.
(e) Urethra: It is a single about 20cm long duct arises from the mid of prostrate gland where both
prostatic urethra & duct of urinary bladder combines. Urethra carries both sperms & urine & is
commonly called urinogenital canal. It passes through penis & opens at penial tip. The opening of
urethra at penile tip is called urethral meatus.
(f) Penis: It is an erectile, copulatory organ. Penis posses a sharp tip called Glans penis which is
covered by loose foreskin called Prepuce. Which is removed in some religions by a method called
Circumcision. Penis is meant for transfer of sperms into female genital tract.
(g) Male reproductive glands: In man there are three types of reproductive glands and are:
(i) Seminal vesicles
(ii) Prostrate gland
(iii) Cowpers gland or balbourethral gland.

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(i) Seminal vesicles: They are two in number. They are present between urinary bladder &
rectum. Seminal vesicles produce seminal fluid called mucoid which constiyute 70% of total semen.
(ii) Prostrate gland: It is a single brownish yellow in colour present just below the urinary
bladder. Prostrate gland gives its secretion called prostrate fluid into prostratic urethra. Its secretion
constitutes 20% of total semen & is alkaline which nutrilises acidic PH of urethra & female genital
track.
(iii) Cowpers gland or Balbourethral gland: They are two in number, white colour, pea seed
shaped. Its secretion is called cowper’s fluid (pre-ejaculate fluid) Which helps in lubrication of
urinogenital track. So, that smooth passage of semen occurs. Its contribution is 5% of total semen.
Seminal vesicle

Ureter
Bladder

Prostate gland

Penis
Urethra
Vas
deferens

Testis
Scrotum

STRUCTURE OF SPERM
At the time of ejaculation nearly 3-4 ml of semen is transferred to female body. 3-4ml of semen
contains 300 million Sperms. Sperm is a tadpole like structure with a long tail, haploid having a
length of 60 micron. Sperm is divided into four parts and are:
(a) Head: head is a broad part of sperm contains nucleus, acrosome, antifertilizin receptors &
head cap. Sperm nucleus contains single (haploid) set of chrosomes. Acrosome surrounds nucleus
while as antifertilizin receptors are present on plasma membrane of sperm surrounded by head cap
or cholesterol for protection of antifertilizin receptors.
(b) Neck: it is a small part of sperm which contains two centrioles i.e proximal centriole &
distilled centriole.
(c) Middle piece: Middle piece contains about 40 mitochondria binded with each other forms
Neberkern. These mitochondria provides energy to sperm for mortality.
(d) Tail: It is the longest part of the sperm. It is only meant for mortality by whiplash movement.
 70 Biology-X

Female Reproductive System

Female reproductive system consists of following organs
(a) Two ovaries
(b) Two fallopian tubes
(c) Uterus
(d) Vegina
(e) Vulva or external Genitalia
(f) Reproductive glands
(a) Ovaries: Ovaries are the primary reproductive organs, two in number, almond shaped, white
in colour present in pelvic cavity just below the fallopian tubes.ovary is concerned with secretion of
estrogen, progesterone & relaxin hormones & also takes part in the formation of female sex cell. Each
ovary is filled with large number of primary follicles, even during foetal age. After attaining puberty
every 28 days a primary follicle is converted into graffian follicle & later on graffian follicle is
converted into secondary oocyte or egg or ovum.
(b) Fallopian tube: it is also called as oviduct or Salpanges or fertilization canal. They are two in
number, ciliated & lie above & behind the urinary bladder. Cilia present inside fallopian tubes are
important for transportation of ovum towards fertilization site. fallopian tube is devided into four
parts & are:
● Infendibulum

● Ampula

● Isthamus

● Uterine part.

Infendibulum is funnel shaped and its free ends bear finger like projections called Fimbrae.
Between these fimbrae is present a hole called Ostium, which is important for passage of ovum.
(c) Uterus: Uterus is also called as wamb or metra. It is a pear shaped organ and lies between
urinary bladder and rectum. Wall of uterus is made up of three layers from outside to inside they are :
(1) Endometrium
(2) Myometrium
(3) Perimetrium
Endometrium is highly vasscularized and glandular in nature . Endometrium regenerates after
puberty after every menstrual cycle . Uterus is divided into three parts :
(1) Fundus
(2) Corpus or body
(3) Cervix.
Fundus is dome shaped present above the corpus. Where as corpus is the main part of uterus
which nourishes the developing foetus and cervix is the below and narrow of uterus which contains
mucus gland which secrets mucus.
(d) Vegina: It is a tube like structure and acts as female copulatory organ ,because it receives
semen at the time of matting . Opening of vegina is called veginal orifice. At the end of vegina is
present a cavity or space called vestibule. Vegina acts as birth canal also.
(e) Vulva or external genitalia: External genitalia or vulva includes those organs which are
present outside the vegina and they include vestibule, labia minora, labia majora , clitoris, perineum
and mons pubis.

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Vestibule is a cavity or space outside the vegina surrounded by labia minora. In vestibule both
urethral opening and veginal opening are present. Urethral opening is present above and veginal
opening is present below side.
Labia minora is also called as lesser lips surrounded by labia majora which bear pubic hairs.
Clitoris is a small finger like projection present above between two labia. Clitoris is a sexual
pleasure zone in females.
Perinium is the area between libia majora and anus whereas mons pubis is the area above labia
majora were pubis hairs are present.
(f) Reproductive glands: In human females, there are three types of reproductive glands and
are:
(i) Bartholins glands
(ii) Skenes glands
(iii) Mammary glands
● Bartholis glands are one pair present around veginal canal .They secret mucus which
lubricates vestibule and veginal opening at the time of matting.
● Skenes glands are numerous in number and are located around urethral opening.They also
produce mucus for lubrication.
● Mammary glands are two in number commonly called breasts present on thorasic region. Each

breast has an erectile nipple at centre which carries milk from the number of ducts. Mammary
glands are present in both males and females are characteristic feature of mammals but are
developed only in females due to the presence of oestrogen , projestrone and prolactin
hormones.

Ovid uct or
Fallo pian
tube
Ovary

Uterus

Cervix

Vagina

● Structure of female sex cell or Ovum: Female sex cell or ovum is a female haploid, non
motile , without any shell. Inside ovum is present cytoplasm called as ooplasm covered by
plasma membrane called as oolema. Ooplasm of ovum contains cuticle granules which prevent
polyspermae. Ovum contains haploid nucleus called germinal vesicle and inside nucleus is
present nucleolus called as germinal spot. Oolema of ovum is further surrounded by two layers
that are zona pellucida and corona radiata.Zona pellucida is the covering present above the
ooleum. Surface of Zona pellucida contains receptors called fertilizin receptors which are
important for species specific fertilization. Space between Oolema and Zona pellucida is called
perivittaline space. Above Zona pellucida are present corona radiata cells. Corona radiata cells
are binded with each other by hyaluronic acid.
 72 Biology-X

Corona Radiata

Follicile Cells

Cytoplasm

Nucleus

Plasma Membrane

Zona Pellucida

Fertilization in Human Beings

Fertilization means the fusion of male and female haploid gametes to form diploid zygote. This
process happens at Ampula isthamus junction (AI Junction).
Female sex cell takes 12 hours to reach at A.I junction from ovary after ovulation & remains or
waits at A.I junction for sperm for next 12 hours. If female is inseminated, nearly 4ml of semen is
deposited in vegina which contains 300 million sperms. But only 500 sperms reach towards A.I
junction. Rest sperms fail to reach because of acidic medium of uterus. Life span of sperm is 72 hours.
Once sperm reaches to A.I junction head cap or cholesterol is removed from sperm. Thus antifertilizin
receptors are exposed. Now sperm binds with cells of corona radiata & releases hyaluronidase
enzyme which digests hyaluronic acid present between corona radiate cells. After that sperm
penetrates inside & binds with zona pellucida layer were antifertilizin receptors of sperm binds with
fertilizing receptors of ovum & compatibility reaction occurs, which is important for species specific
fertilization.
Once compatibility reaction is completed zona lysin is released by sperm which digests zona
pellucid layer & sperm now binds with oolema. Once sperm binds with oolema depolarization wave is
produced within oolema. Once depolarization wave occurs corticle granules present in ooplasm comes
out & they digests remaining fertilizin receptors present on zona pellucida & hence polyspermae is
prevented.
Sperm binded to oolema enters into the ovum & tail is left out side. Now haploid nucleus of sperm
fuses with haploid nucleus (germinal vesicle) of ovum & diploid zygote is formed.

Development of Embryo or Embroyonic Development

Embryonic development means a series of phases which transforms a one celled zygote to a
multicellular & fully formed embryo till birth by the process of cleavage.First division of zygote
occurs after 30 hours of fertilization & forms two blastomer cells. Second division occurs after 60
hours after fertilization which results in formation of four blastomer cells. third division occurs after
72 hours after fertilization which results in formation of 8 blastomer cells. Fourtrh division occurs
after 90 hours after fertilization which results in the formation of 16 blastomer cells. At 16 blastomer
cell stage embryo resembles like mulberry therefore it is also called as Marula. End product of
cleavage is morula. Morula moves towards uterus & it undergoes 5th & 6th division & forms 64
blastomer cells. At 64 blastomer cell stage each blastomer take uterine milk from uterine glands &
this structure is called blastocyst. Blastocyst is still surrounded by zona pellucida because to prevent
ectopic pregnancy. Blastomer cells cause a hole in zona pellucida through which blastomer cells
comeout in the form of letter ‘’8’’. Some times letter ‘’8’’ structure cuts in centre & forms two spherical
mass of blastomer cells & results in the formation of monozygotic twin. At 7th day of fertilization
blastocyst gets embedded in the endometrium & forms villi which drags food from endometrium.
With time villi are converted into placenta. Placenta is a temporary but a mechanical connection
between foetus & mother. placenta helps in transportation of nutrition, respiration & excretion etc

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between mother and foetus. Blastocyst embedded in uterus is now converted into gastrula which is
characterized by three germ layers i.e ectoderm, mesoderm & endoderm. Each germ layer forms
specific organs by the process of organogenesis.
Now the foetus so formed remains inside mothers womb till its birth & the period is called
gestation or pregnancy. Gestation period varies in different organisms. Gestation is of 15 days in rat
& 30 days in rabbit & 280 days in humans while as it is of 670 days in elephant.
When gestation is completed the foetus moves towards cervix for coming out by the process called
parturition. Prior to parturition female experiences mild uterine contractions called Braxtons hicks
reflex. Due to Braxtons hicks reflex, some hormones are released from adrenal gland which dilates
cervix & foetal head comes into cervix (10cm wide) due to expansion of cervix, nerve impulses
originates which stimulates hypothalamus to secrete oxytocin hormone. Oxytocin hormone binds
with uterus & cause strong uterine contractions which results in labour pain. Labour pain lasts for 12
hours. Where as relaxin hormone secreted by ovary causes widening of pelvis & vagina for easy child
birth. By the strong contractions of uterus neonate is expelled out & takes about 20 minutes to one
hour. After birth placenta is clamped & is cut & the neonate start its own breathing.

What Happens When the Egg is not Fertilized/Menstrual Cycle

Menstrual cycle or periods or menstrual flow or vaginal bleeding is a regular, repeated biological
process that occurs in the females of humans & apes from menarche to menopause. Menarche means
start of menstrual cycle & it occurs when a girl attains puberty age (11-13 years) while as menopause
means the cessation of menstrual cycle permanently & it occurs when a female reaches at the age of
45 – 50 years. in humans menstrual cycle lasts for 28 days & is characterized by vaginal discharge of
endometrial lining along with some blood & mucus. Menstrual cycle is devided into three phases.
(a) Bleeding phase
(b) Follicular phase
(c) Secretory phase
(a) Bleeding phase: This phase is also called as menstrual phase or catamenia. This phase losts
for four days. During this phase there is vaginal discharge of endometrial lining, some blood &
mucus. Nearly 100 ml of blood is lost during this phase.
(b) Follicular phase or proliferative phase: This phase lasts for 10 days starting from the
stoppage of bleeding phase. During this phase damaged endometrium is renewed by oestrogen
produced by ovary which increases the thinkness of endometrium. FSH secreted by pituitary gland
stimulates primary follicle of ovary to transform into graafian follicle lateron graffian follicle is
converted into secondary oocyte or ovum. This secondary oocyte or ovum comes out from ovary
towards fallopian tube at 14th day by the process of ovulation.
(c) Secretory phase or Luteal phase: This phase lasts for next 14 days. This phase is
characterized by secretion of projestrone hormone (hormone of pregnancy).which stimulates further
enlargement of endometrium & secretion of uterine milk from uterine glands. So uterus prepares
itself for implantation. If fertilization doesn’t occur levels of projestrone downs results in disrupture
of endometrium followed by again vaginal bleeding after 28th day. Menstrual cycle is also called as
funeral of unfertilized egg.

Birth Control Measures

World’s population is 7 billion on 31st October 2011. India's population upto 2011 was 1210
million. The high growth rate of human population is called population explosion. To mitigate the ill
effects of increasing population, there is an urgent need of population control. The possible way is to
reduce the rate through family planning program and practicing birth control or contraceptive
measures. Some birth control measures are as:
 74 Biology-X
● Barrier Method: In barrier method ovum and sperm do not meet due to physical barriers and
hence fertilization doesn’t occur e.g: Condoms, Femidoms, Diaphragm, cervical caps, Vault
caps.
● Mechanical Method or Intra Uterine devices (IUD’s): these are the plastic or metal

objects which are inserted in the uterus to prevent reaching the sperms to ovum, so prevent
fertilization. Examples: Copper-T, Copper-7, Multiload 375.
● Chemical method: These are the chemicals which are inserted in the vagina before
intercourse which kills the sperms hence prevent fertilization. Example: Sponge, Delfen.
● Oral contraceptive Pills: these are the drugs which kill the sperms or changes the hormonal

balance e.g: spermicidal tablets, Mala-D, Mala-N, Saheli Tablet & unwanted-72, i-pill (i-pill is
also called as morning after pill).
● Surgical method: these are the permanent methods of contraception. E.g:

● Castration: removal of testes in males.

● Ovarictomy: removal of ovaries in females.

● Vesectomy: cutting of vas deferns.

● Tubectomy: cutting of fallopian tubes.

● Tubal ligation: Blocking of fallopian tubes.

● Medical termination of pregnancy (MTP) or Abortion.

● Natural method: They are of various types like,

● Periodic Abstinence/Rhythm method: Couples avoid from coitus from day 10 to day 17 of
the menstrual cycle.
● Coitus Interruptus: withdrawal of penis out from the vagina before insemination.

● Lactational Amenorrhea method: copulation during when menstrual cycle doesn’t occur i.e
after childbirth upto six months.
Reproductive health: According to WHO (World health organization) health is a state of
complete physical, mental and social well being and not merely the absence of diseases. General body
growth is continuous while the reproductive organs are growing gradually. Therefore it does not
necessarily mean that the body or mind is ready for sexual acts and bringing up of child. In this
situation making a choice can become very difficult. Diseases can be transmitted from one person to
another in a variety of ways. The sexual act is very intimate connection of bodies. So many diseases
can be sexually transmitted and those diseases which are caused due to sexual intercourse are called
as sexual transmitted diseases (STD's) or also called as veneral diseases (VD's).These include
bacterial infection such as Gonorrhea, warts, syphilis & AIDS (acquired immuno deficiency
syndrome). AIDS is caused by a retrovirus called Human immuno Virus (HIV) which was first
reported in Hatai (USA) in 1981. While in India it was first reported in some prostitutes of Chennai in
1986. According to UNAIDS estimation there are about 5.1 billion HIV positive individuals at the end
of 2004. India is considered as the world capital of AIDS. HIV kills the helper-T cells thus, decreasing
the number of antibodies in the body fluid. This weakens the humoral immune system of man and
increases the chances of bacterial and viral infection. Such clinically unhealthy persons are referred
as opportunistic. It is possible to prevent from these diseases through some contraceptive methods
like using of condoms in males and in females some ways to avoid pregnancy which fall in a number
of category to make barrier mechanically which does not allow sperm to reach to the uterus.

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 How Do Organisms Reproduce 75

♙ssertion and Reason Based Questions

Directions: In the following questions, A statement of Assertion (A) is followed by a
statement of Reason (R). Mark the correct choice as:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
1. Assertion (A) : Amoeba reproduces by binary fission.
Reason (R) : All unicellular organisms reproduce asexually.
2. Assertion (A) : Plants are vegetatively propagated even though they bear seeds.
Reason (R) : Potatoes reproduces through tubers, apples by cutting etc.
3. Assertion (A) : Characteristics of parental plants can be preserved through
asexual reproduction.
Reason (R) : Vegetative reproduction involves only mitosis.
4. Assertion (A) : Regeneration is getting a full organism back from its body parts.
Reason (R) : Hydra and Planaria show regeneration.
5. Assertion (A) : Plasmodium reproduces by multiple fission.
Reason (R) : Multiple fission is a type of asexual reproduction.
6. Assertion (A) : An embryo is formed from fertilized egg.
Reason (R) : A monocot embryo comprises embryonal axis with two
cotyledons.
7. Assertion (A) : DNA copying is necessary during reproduction.
Reason (R) : DNA copying leads to the transmission of characters from
parents to offspring.
8. Assertion (A) : Unisexual plants have separate male and female flowers.
Reason (R) : Papaya, pumpkin, cucumber and water melon are example of
unisexual plants.
9. Assertion (A) : Double fertilisation is unique to angiosperms.
Reason (R) : Triple fusion occurs in asexual reproduction.
10. Assertion (A) : Fertilization results in formation of zygote.
Reason (R) : Zygote divides several times to form an embryo.
11. Assertion (A) : Sexual reproduction increases genetic diversities and plays a
role in origin of new species.
Reason (R) : Sexual reproduction involves formation of gametes and fusion of
gametes.
12. Assertion (A) : In human male, testes are extra-abdominal organs which are
present inside scrotum.
Reason (R) : Scrotum has a relatively lower temperature needed for the
production and storage of sperms.
13. Assertion (A) : At puberty, in boys, voice begins to crack and thick hair grows on
face.
Reason (R) : At puberty, there is decreased secretion of testosterone in boys.
14. Assertion (A) : A bisexual flower produces ova as well as the pollen.
Reason (R) : Ova and pollen are produced in the carpel.
 76 Biology-X
15. Assertion (A) : In human beings the female produces two type of gametes.
Reason (R) : Female has two X chromosomes.
16. Assertion (A) : Testes in human males are located outside the abdominal cavity
in scrotum.
Reason (R) : Scrotum provides a lower temperature than the normal body
temperature.
17. Assertion (A) : Surgical methods are most effective methods of contraception.
Reason (R) : Surgical method blocks gametes transport and hence prevent
fertilisation.

♙nswers
1. (a) 2. (b) 3. (a) 4. (b) 5. (b) 6. (c) 7. (a) 8. (b) 9. (c) 10. (b)
11. (a) 12. (a) 13. (c) 14. (c) 15. (d) 16. (a) 17. (a)

Objective Questions
1. Asexual reproduction produces offspring that are :
(a) genetically identical to their parents (b) genetically identical to their sibling
(c) both (a) and (b) (d) none of the above
2. The development of offspring from any part of animal body is called :
(a) asexual reproduction (b) sexual reproduction
(c) vegetative reproduction (d) all of these
3. Main method of reproduction in Amoeba is:
(a) Multiple fission (b) Budding
(c) Sexual reproduction by gamete formation (d) Binary fission
4. Asexual reproduction by budding takes place in :
(a) Amoeba (b) Yeast (c) Spirogyra (d) Moss
5. Multiplication in yeast occurs by :
(a) binary fission (b) budding (c) spore formation (d) fragmentation
6. In sweet potato vegetative propagation takes place by :
(a) Root (b) Stem (c) Leaves (d) All of these
7. Regeneration can be seen in :
(a) Hydra (b) Star fish (c) Planaria (d) all of these
8. Vegetative buds on leaves are found in :
(a) Cuscuta (b) Bryophyllum (c) Silaginella (d) Discorea
9. Plasmodium divides by :
(a) binary fission (b) multiple fission
(c) budding (d) spore formation
10. Which one of these multiplies by bulbil ?
(a) Agave (b) Ginger (c) Onion (d) Potato
11. Which one of these does not reproduce by roots ?
(a) Sweet potato (b) Dahlia (c) Asparagus (d) Ginger

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 How Do Organisms Reproduce 77
12. Grafting is a/an .......... method of reproduction in many plants.
(a) Sexual (b) Asexual
(c) Trans sexual method (d) None of these
13. Conidia are a type of:
(a) Asexual spores in many fungi (b) Sexual spores in animals
(c) Sexual spores in green plants (d) Asexual spores in only flowering plants
14. The reproduction in Rhizopus takes place by :
(a) budding (b) leaf (c) spores (d) cutting
15. Which of the following is not a vegetative reproductive organ ?
(a) root (b) stem (c) leaf (d) seed
16. Choose the correct order of the stages of binary fission in Leishmania.

(I) (II) (III) (IV) (V)

(a) I, II, III, IV, V (b) I, III, II, V, IV (c) I, III, V, II, IV (d) I, II, III, V, IV
17. In horticulture, the most common practice of growing plants is :
(a) cutting of stem (b) cutting of root (c) grafting (d) tissue culture
18. Choose the correct statement(s) on budding in Hydra from the following :
I. A parent cell divides into two or more daughter cells and here the parent identity is lost.
II. In this, the elongated nucleus divides to form two or more daughter nuclei.
III. A bud arises from a particular region on a parent body.
IV. After detaching from the parent body, the bud grows into a new independent individual.
(a) I only (b) III only (c) II and III (d) III and IV
19. The male organ in flower is :
(a) carpel (b) sepal (c) petal (d) stamen
20. Self fertilization is also called:
(a) Geitonogamy (b) Allogamy
(c) Autogamy (d) All of these
21. The part that does not belong to carpel is :
(a) stigma (b) style (c) ovary (d) filament
22. Pollen grains are produced by:
(a) corolla (b) anther (c) ovary (d) ovule
23. Seminiferous tubules are composed of:
(a) Spermatogonia (b) Glandular epithelium
(c) Sensory epithelium (d) Germinal epithelium
 78 Biology-X
24. Outer thick and rough wall of pollen grain is called:
(a) Germ wall (b) Exine (c) Intine (d) Pollen sac
25. The anther contains:
(a) Sepals (b) Ovules (c) Carpel (d) Pollen grains
26. The stamen contains:
(a) stigma (b) pollen grain (c) sepal (d) ovule
27. Seeds are called products of sexual reproduction because they :
(a) give rise to new plants (b) are formed by fusion of gametes
(c) are formed by the fusion of pollen tubes (d) can survive for a longer period
28. Fertilisation is the process of :
(a) transfer of male gamete to female gamete
(b) fusion of nuclei of male and female gametes
(c) adhesion of male and female reproductive organs
(d) the formation of gametes by a reproductive organ
29. Consider the following three flowers namely X, Y and Z.
Which flower(s) would develop into a fruit ?

Flower ‘X’ Flower ‘Y’ Flower ‘Z’

(a) ‘X’ only (b) ‘Z’ only (c) ‘X’ and ‘Y’ only (d) ‘Y’ and ‘Z’
30. Like animals, plants produce :
(a) many more sperm than eggs (b) a few more sperm than eggs
(c) equal numbers of sperm and eggs (d) fewer sperm than eggs

♙nswers
1. (c) 2. (a) 3. (d) 4. (b) 5. (b) 6. (a) 7. (d) 8. (b) 9. (b) 10. (a)
11. (d) 12. (b) 13. (a) 14. (c) 15. (c) 16. (b) 17. (b) 18. (d) 19. (d) 20 (a,c)
21. (d) 22. (b) 23. (d) 24. (b) 25. (d) 26. (b) 27. (b) 28. (b) 29. (b) 30. (a)

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 How Do Organisms Reproduce 79

Textual Questions
Q.1 What is the importance of DNA copying in reproduction?
Ans. DNA is the genetic material present in the cells of all organisms. The genetic information
from generation to generation is carried by DNA .It is therefore possible for the organism to
produce organism of its own type due to DNA copying only. For the inheritance of traits of the
parent, DNA copying is a must.DNA copying also brings about variation ,which forms the
basis for the origin of new species.
Q.2 Why is variation beneficial to the species but not necessarily for the individual?
Ans. Variations are beneficial to the species than individual because sometimes for a species, the
environmental conditions change so drastically that their survival becomes difficult. For
example, if the temperature of water increases suddenly, then most of the bacteria living in
that water would die. Only few variants that are resistant to heat would be able to survive.
However, if these variants were not there, then the entire species of bacteria would have been
destroyed. Thus, these variants help in the survival of the species. However, all variations are
not necessarily beneficial for the individual organisms.
Q.3 How does binary fission differ from multiple fission?
Ans. In binary fission a single cell divides into two equal halves. Amoeba and Bacteria divide by
binary fission. Binary fission occurs during favorable conditions.e.g: bacteria, blue-green
algae and protozoa.
In multiple fission, a single cell divides into many daughter cells simultaneously. Plasmodium
divide by multiple fission. It is seen in bacteria and protozoans like amoeba and paramecium.
If the parent cell divides into many daughter cells simultaneously during unfavorable
conditions like deficiency of food or water or extremes of temperature, then it is called
multiple fission.
Q.4 How will an organism be benefited if it reproduces through spores?
Ans. Advantages of spore formation:
● Large numbers of spores are produced in one sporangium.

● Spores are distributed easily by air to far-off places to avoid competition at one place.

● Spores are covered by thick walls to prevent dehydration under unfavourable conditions.

Q.5 Can you think of reasons why more complex organisms cannot give rise to new individuals
through regeneration?
Ans. Higher complex organisms cannot give rise to new individuals through regeneration because
complex organisms have organ-system level of organization. All the organ systems of their
body work together as an interconnected unit. They can regenerate their lost body parts such
as skin, muscles, blood, etc. However, they cannot give rise to new individuals through
regeneration.
Q.6 Why is vegetative propagation practiced for growing some types of plants?
Ans. Vegetative propagation is practiced for growing some types of plants because of following
advantages:
● It is used to grow a plant in which viable seeds are not formed or very few seeds are produced
such as Orange, Banana, Pineapple.
● It helps to introduce plants in new areas where the seed germination fails to produce mature
plant due to change in environmental factors and the soil.? It is more rapid, easier and cheaper
method.
● By this method a good quality of a race or variety can be preserved.
 80 Biology-X
Q.7 Why is DNA copying an essential part of the process of reproduction?
Ans. DNA copying is an essential part of reproduction as it passes genetic information from
parents to offspring. It determines the body design of an individual. The reproducing cells
produce a copy of their DNA through some chemical reactions and result in two copies of DNA.
The copying of DNA always takes place along with the creation of additional cellular
structure. This process is then followed by division of a cell to form two cells.

Q.8 How is the process of pollination different from fertilization?

Ans. Pollination is the process of transfer of pollens from anther to stigma. It occurs with the help
of certain pollinators or pollen agents such as air, water, birds, or some insects.
where as Fertilization is the fusion of the male and female gametes. It occurs inside the ovule
in plants and inside the fallopian tube in humans and it leads to the formation of zygote which
continuously divides and transforms into embryo.
Q.9 What is the role of the seminal vesicles and the prostate gland?
Ans. The secretions from seminal vesicles and prostate glands lubricate the sperms and provide a
fluid medium for easy transport of sperms. Their secretion also provides nutrient in the form
of fructose, calcium, and some enzymes.
Q.10 What are the changes seen in girls at the time of puberty?
Ans. The changes seen in girls at the time of puberty are:
● Increase in breast size and darkening of skin of the nipples present at the tips of the breasts.

● Appearance of hair in the genital area.

● Appearance of hair in other areas of skin like underarms, face, hands, and legs.

● Increase in the size of uterus and ovary.

● Beginning of menstrual cycle.

● More secretion of oil from the skin, which results in the appearance of pimples.

Q.11 How does the embryo get nourishment inside the mother's body?
Ans. After fertilization the lining of uterus thickens and is richly supplied with blood to nourish the
growing embryo. The embryo gets nutrition from the mother’s blood with he help of a special
tissue called placenta. It is embedded in the uterine wall. Placenta contains Villi on the
embryo’s side of the tissue and blood spaces on mother’s side surrounding the villi. This
provides a large surface from mother to the embryo and waste products from embryo to
mother.
Q.12 If a woman is using a copper-T, will it help in protecting her from sexually transmitted
diseases?
Ans. No, because copper-T is meant for prevent contact between body fluids like sperms with ovum.
Thus ,it will not protect her from sexually transmitted diseases.
Q.13 Asexual reproduction takes place through budding in
(a) amoeba (b) yeast (c) plasmodium (d) leishmania
● (b) yeast

Q.14 Which of the following is not a part of the female reproductive system in human beings?
(a) Ovary (b) Uterus (c) Vas deferens (d) Fallopian tube
● (c) Vas deferens

Q.15 The anther contains

(a) sepals (b) ovules (c) carpel (d) pollen grains
● (d) pollen grains

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 How Do Organisms Reproduce 81
Q.16 What are the advantages of sexual reproduction over asexual reproduction?
Ans. Advantages of sexual reproduction:
● In sexual reproduction, more variations are produced. Thus, it ensures survival of species in a
population.
● The new formed individual has characteristics of both the parents.
● Variations are more viable in sexual mode than in asexual one. This is because in asexual
reproduction, DNA has to function inside the inherited cellular apparatus.
Q.17 What are the functions performed by the testis in human beings?
Ans. Functions of testes:
● Produce sperms, which contain haploid set of chromosomes of father.
● Produce a hormone called testosterone, which brings about secondary sexual characters in
boys.
Q.18 Why does menstruation occur?
Ans. Menstruation is a process in which blood and mucous flows out every month through the
vagina. This process occurs every month because one egg is released from the ovary every
month and at the same time, the uterus (womb) prepares itself to receive the fertilized egg.
Thus, the inner lining of the uterus gets thickened and is supplied with blood to nourish the
embryo. If the egg does not get fertilized, then the lining of the uterus breaks down slowly and
gets released in the form of blood and mucous from the vagina.
Q.19 Draw a labelled diagram of the longitudinal section of a flower.
Ans.

Q.20 What are the different methods of contraception?

Ans. The contraceptive methods can be broadly divided into the following types:
● Natural method: It involves avoiding the chances of meeting of sperms and ovum. In this

method, the sexual act is avoided from day 10th to 17th of the menstrual cycle because during
this period, ovulation is expected and therefore, the chances of fertilization are very high.
● Barrier method: In this method, the fertilization of ovum and sperm is prevented with the

help of barriers. Barriers are available for both males and females. Condoms are barriers
made of thin rubber that are used to cover penis in males and vagina in females.
● Oral contraceptives: In this method, tablets or drugs are taken orally. These contain small
doses of hormones that prevent the release of eggs and thus fertilization cannot occur.
● Implants and surgical methods: Contraceptive devices such as the loop or Copper-T are

placed in uterus to prevent pregnancy. Some surgical methods can also be used to block the
gamete transfer. It includes the blocking of vas deferens to prevent the transfer of sperms
known as vasectomy. Similarly, fallopian tubes of the female can be blocked so that the egg
will not reach the uterus known as tubectomy.
 82 Biology-X
Q.21 How are the modes for reproduction different in unicellular and Multicellular organisms?
Ans. In unicellular organisms, reproduction occurs by the division of the entire cell. The modes of
reproduction in unicellular organisms can be fission, budding, etc. whereas in multicellular
organisms, specialized reproductive organs are present. Therefore, they can reproduce by
complex reproductive methods such as vegetative propagation, spore formation, etc. In more
complex multicellular organisms such as human beings and plants, the mode of reproduction
is sexual reproduction.
Q.22 How does reproduction help in providing stability to populations of species?
Ans. Reproduction is the process of producing new individuals of the same species by existing
organisms of a species, so, it helps in providing stability to population of species by giving
birth to new individuals as the rate of birth must be at par with the rate of death to provide
stability to population of a species.
Q.23 What could be the reasons for adopting contraceptive methods?
Ans. Contraceptive methods are mainly adopted because of the following reasons:
● To prevent unwanted pregnancies.

● To control population rise or birth rate.

● To prevent the transfer of sexually transmitted diseases.

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 Heridity and Evolution 83

Heridity and Evolution

4
GENETICS
The science concerned with with precise understanding the biological properties which are
transmitted from parent to offspring is called genetics. The term genetics was coined by Willium
Bateson in 1905. The process of transmission of characters from one generation to another is known
as inheritance or heredity.
● TRAIT: Character of any living organism like height, complexion, shape of hair, color of eyes,
and shape of nose and chin etc are called traits or characters. They are of two types and are:-
● INHERITED TRAITS: Inherited traits are those traits which are obtained from the parents
and pass from generation to generation.
● ACQUIRED TRAITS: The acquired traits are those traits which are developed during the life
of an organism and these die with the death of an organism.
● HEREDITY: Transmission of characters from parents to their offsprings is called Heredity.
● VARIATION: The differences in the characters or traits among the individuals of same
species is called variation. E.g some people are tall and some are dwarf, In some individuals
Earlobe is free and in others earlobe is attached. Variation is necessary for Evolution. The
great advantage of variation to a species is that it increases the chance of its survival in a
changing environment.
● CHROMOSOME: Chromosome is a thread like structure formed of DNA which carries the
genes and is present in the nucleus of a cell .In human beings they are 46 in number.
● Gene or criston: Essential fragment of DNA of a chromosome is called a gene. A gene
controls a specific character of an organism. Genes are bridges of heredity which carry
characters from parents to their offsprings during reproduction.
● ALLELE: Alternative forms of gene; denoted by the same letter of groups; e.g. W and w;
alleles govern the contrasting forms of the same trait.
● Dominant and recessive allele: Dominant allele is that allele which shows expression itself
and this allele is referred to as the dominant allele. Recessive allele is that allele which
remains silent or don’t shows its expression and is called as recessive allele.
● Phenotype: The observable characteristics of an organism; may refer to a single character or
a group of characters, e.g. round and wrinkled (pea seed).
● Genotype: The genetic make-up of an organism; may refer to one or more genes; e.g. RR, Rr
and rr.
● Homozygous: An individual that has two copies of the same alleles, e.g. RR or rr.
● Heterozygous: An individual that has two different alleles of a gene, e.g. Rr.
 84 Biology-X

Accumulationof Variations During Reproduction

Asexual reproduction involves single parent. When a single individual reproduces asexually, the
resultant two individuals again after some time reproduce to form four individuals. In this way, large
number of individual are formed after many generations. All these individuals would be similar.
However, there would be only very minor differences between them. These minor differences arise
due to inaccuracies in DNA copying. Asexual reproduction generates little diversity.
Sexual reproduction, on the other hand, generates even greater diversity. This is so because
sexual reproduction involves two parents (father and mother) and every offspring receives some
characters of their parents (father and mother), they show distinct differences (variations) among
themselves as well as from their parents.

Gregor John Medel

Was born in 1822 to a family of poor farmers in Silisian (Austria).He finished his high school at
the age of eighteen. He got his early education in a monastery in Bruno (Austria). At very early age he
was ordinate a priest of Saint Thomas at Bruno. A few years after, he was sent to the university of
Vienna (Austria) for special training in Physics, Mathematics and Natural science. After completing
his special training, he returned back to Bruno in 1854, where he continued to work as a priest and to
teach in a high school. In 1857 he began his famous experiments on peas in the Monastery garden.
This was not an accident but was the result of his careful thoughts and calculations due to his
knowledge of science and mathematics. Mendel presented data of his experiments in a paper entitled
''Experiments in plant Hybridization''. He was read before Brunn Natural History Society in1865
and his experiment was published in Annual proceedings of Brunn Natural History Society in 1866.
But this work of Mendel did not attract the slightest attention. Mendel disappointed for no respond to
his good thoughts and finally died in 1884 without even knowing that future generations would refer
him as the father of genetics.

Rules for Inheritance of Characters: Mendels Contribution

Every inherited trait can be affected by both maternal and paternal DNA, since both the parents
contribute equal amounts of genetic material. Mendel gave rules for transfer of characters from
parents to their offsprings.

MENDEL’S EXPERIMENT
Mendel had conducted breeding experiments on garden pea. Mendel choose garden pea (Pisum
sativum) because the pea plant is small, Self pollinated, easy to grow, cross bred artificially and have
contrasting characters. This plant, being bisexual, is self-fertilizing in nature but can be easily cross
pollinated experimentally like emasculation and bagging. It reproduces a large number of offspring
and completes its life cycle in one season.
Mendel selected seven visible characters, each with two contrasting traits.

S.No. Character Contrasting Traits

Dominant Recessive
1. Plant size or height Tall Dwarf
2. Position of flower on the stem Axial Terminal
3. Colour of unripe pod Green Yellow

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 Heridity and Evolution 85
4. Shape of pod Inflated Constricted
5. Shape of seed Round Wrinkled
6. Color of seed Yellow Green
7. Color of flower Violet White

From his studies on pea plants, Mendel proposed the following three laws (Principals) of
genetics:
(1) LAW OF DOMINANCE: In a hybrid or heterozygous individual two dissimilar unit factors
are present for one character. Out of two factors (genes) only one is able to express itself and it
prevents expression of the other. The one which expresses itself is called dominant gene or factor and
the one which remains unexpressed is called recessive factor or gene. For example, in hybrid tall (Tt)
only unit factor (gene) of tallness expresses itself, hence it is called dominant. The unit factor (gene)
for dwarfness fails to express itself, hence it is called recessive.
1. Law of Dominance
2. Law of Segregation and
3. Law of independent Assortment.
Mendel’s Experimental Technique: Mendel conducted breeding experiments in three steps:
(i) Selection of pure parent plant (plants producing similar traits in every generation).
(ii) Production of first generation of plants by crossbreeding (hybridization).
(iii) Raising second and subsequent generations by self fertilization of hybrids.
(2) LAW OF SEGREGATION / MONOHYBRID CROSS/ IST LAW OF INHERITANCE: A
breeding experiment dealing with a single character is called a monohybrid cross. In this experiment,
Mendel crossed round seeds with another having winkled seeds. The seeds resulting in F1 generation
were all round and the seeds produced by selfing of F1 plants, were three seeds round shaped and
one seed of wrinkled shaped. On the basis of these findings Mendel proposed the law of segregation
which states that the two alleles separate and pass into different gametes, producing two different
types of gametes in equal frequencies; this is known as segregation. This law is also called “Principle
of purity of gametes”.
The Phenotypic ratio of F2 generation is 3:1 and the genotypic ratio of F2 generation is 1:2:1. The
result of monohybrid cross enabled to formulate his first law of inheritance which is called the law of
segregation. According to the law of segregation'' The characters or traits of an organism are
determined by internal factors which occur in pairs, only one in a pair of such factor can be in a single
gamete.

Mendel’s monohybrids cross

The phenotypic ratio came out to be 3:1 (as 3 out of 4 were Tall and 1 out of 4 was Dwarf).
The genotypic ratio came out to be 1:2:1 (as 1 was pure tall, 2 were mixed tall & 1 was pure
dwarf).
(3) LAW OF INDEPENDENT ASSORTMENT / DIHYBRID CROSS/ 2nd LAW OF
INHERITANCE:
This law states that the unit factor (allele) of each character is assorted or distributed into the
gametes independently of the unit factors (genes) of only other character and gets randomly
rearranged in the offspring.
Based on dihybrid cross Mendel proposed law of independent assortment. A breeding experiment
dealing with two characters at the same time is called a dihybrid cross.
 86 Biology-X
Let us consider a cross in which plants producing round and yellow seeds were crossed with
plants producing wrinkled and green seeds. The F 1 generations were all yellow and round seeded,
suggesting that yellow is dominant over green and round seed is dominant over wrinkled seed. When
these F1 are selfed, Mendel postulated that the segregation of one pair of unit factors will occur
independently of the other pair or they will assort independently. Accordingly, the gametes must
carry all possible combinations of the unit factors in equal frequency. In this example gametes with
random distribution of unit factors will give following combinations;
(i) Yellow & Round
(ii) Yellow & Wrinkled
(iii) Green & Round
(iv) Green & Wrinkled.
These combinations will result in a phenotypic ratio of 9:3:3:1 and this ratio are same for all
dihybrid crosses. Now according to Mendel's second law of inheritance '' In the inheritance of more
than one pair of characters in a cross simultaneously, the factors responsible each pair of character
are distributed independently to the gametes.

Mendel’s Dihybrids cross.

Now in table, Fusion of gametes of F1 generation & formation of F2 generation

Ry Ry rY rY

Ry RyRY Round Yellow RYRY Round Yellow Ryry Round Yellow RyrY Round Yellow
Ry RYRY Round Yellow RyRy Round Green Ryry Round Yellow Ryry Round Green
rY Ryry Round Yellow ryRy Round Yellow rYrY Wrinkled Yellow rYrY Wrinkled
yellow
Ry ryRY Round Yellow ryRy Round Green rYrY Wrinkled yellow ryry Wrinkled Green

In F2 generation the Phenotypic ratio is as, 9:3:3:1

Round & Yellow = 9
Round & Green = 3
Wrinkle & Yellow = 3
Wrinkled & Green = 1
In F2 generation the Genotypic ratio is as, 1:2:1:2:4:2:1:2:1
RRYY : RrYY : rrYY : RRYy : RrYy : rrYy : RRyy : Rryy: rryy
1: 2: 1: 2: 4 : 2: 1: 2: 1
Gene: This sequence of bonding of nitrogenous bases constitute gene i.e. the segment of DNA is
known as gene and this sequence contains a code for protein synthesis and every protein controls a
specific characteristic of an organism. Thus gene is known as the unit of inheritance. These
sequences when inherited, actually inherits trait and thus traits are expressed in organisms.

How are Characteristics Transmitted to Progeny

Genes are responsible for characteristic features of an organism. The characteristics or traits of
parents are transmitted to their progeny or offsprings through genes on their chromosomes during
the process of sexual reproduction. Gene work in pairs (one is Dominant & another is recessive).
There is a pair of allele which form a gene & gene controls a character of an organism. Each parent
posses a pair of allele for each character but a parent passes only one allele for each characteristic to

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 Heridity and Evolution 87
its progeny through sex cells. Thus mother passes its one allele only to its children and father also
simultaneously. When male sex cell fusses with female sex cell they make a new cell called zygote
which contains full gene with both alleles. This zygote grows and develops to form a baby having
characteristics of both the parents because the characters were present in alleles which a baby
received from its parents. A gene is responsible for a particular character and is always present on
the corresponding position on a chromosome known as gene locus.

HOW BLOOD GROUPS ARE INHERITED

A person has one of the four blood groups: A, B, AB or O. This blood group system is controlled by
a allele which has three different forms denoted by the symbol I A , I B & I O . The allele I A & I B show
no dominance over each other, that is, they are co-dominant. However, alleles I A & I B both are
dominant over the allele IO. In other words, the blood allele IO is recessive in relation to genes I A &
IB.
Although there are three alleles for blood, but any one person can have only two of them. So, the
blood group of a person depends on which two forms of the alleles he posseses.
● If both the alleles of a gene in a person are I A & I A , Then the blood group of the person is A.
And if the alleles of a gene in a person are I A & I O even then the blood group is A. Because
allele A is always dominant over allele O.
● If both the alleles of a gene in a person are I B & I B , then the blood group of the person is B.
And if the alleles of a gene in a person are I B & I O , then the blood group of the person is B.
Because allele B is always dominant over allele O.
● If the alleles of a gene in a person are I A & I B , then the blood group of a person is AB, Because
A allele and B allele are both dominant over each other (co-dominance).
● If the alleles of a gene in a person are I O & I O , then the blood group of a person is O.

Chromosomal bais of Sex Determination

It refers to the condition where the genes involved in the sex determination are located on specific
chromosomes known as the sex chromosomes. The sex is determined by the last pair of chromosomes
which is known as sex chromosome, for example in human beings there are 23 pair of chromosomes.
Out of 23 pair 22 pairs are autosomal chromosomes and are same in both male and female while as
the last pair i.e. 23rd pair is different in male and female and thus this pair determines sex, thus
known as sex chromosome.
The difference in chromosomes which determines the sex may be of three types.
1. Difference in number.
2. Difference in shape.
3. Difference in size of the sex chromosome.
1. Difference in Number: (Higher concept)
2. Difference in Shape: (Higher concept)
3. Difference in Size:
Human cells contain 23 pairs of chromosomes (i.e. 46 in whole) of chromosomes. Out of these, 22
pairs are alike and are Autosomes while 23rd pair is composed of sex chromosomes. In female this
pair of sex chromosomes contains two similar chromosomes while in male one of the chromosomes is
similar in size as of female and the other is smaller in size. The smaller chromosome is labeled as Y
and the chromosome similar to each of the female sex chromosome is labeled as X. Therefore females
are homozygous XX while males are heterozygous XY.
 88 Biology-X

♙ssertion and Reason Based Questions

Directions: In the following questions, A statement of Assertion (A) is followed by a
statement of Reason (R). Mark the correct choice as:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
1. Assertion (A) : A geneticist crossed a pea plant having violet flowers with a pea
plant having white flowers, he got all violet flowers in first
generation.
Reason (R) : White colour gene is not passed on to next generation.
2. Assertion (A) : Mendel choose a number of varieties of garden pea as plant
material for his experiments.
Reason (R) : Garden pea has well defined characters and is bisexual.
3. Assertion (A) : In humans, males play an important role in determining the sex
of the child.
Reason (R) : Males have two X chromosomes.
4. Assertion (A) : Learning a skill such as dance and music is an acquired trait.
Reason (R) : Acquired traits develop in the life time of an individual and do
not pass to the progeny.
5. Assertion (A) : Traits like eye colour or height are inherited traits.
Reason (R) : Inherited traits are not transferred from parents to young ones.
6. Assertion (A) : Acquired trait cannot be passed on from one generation to next
generation.
Reason (R) : Acquired trait cannot change the DNA of the germ cells.
7. Assertion (A) : The sex of a child in human beings will be determined by the
type of chromosome he/she inherits from the father.
Reason (R) : A child who inherits ‘X’ chromosome from his father would be a
girl (XX), while a child who inherits a ‘Y’ chromosome from the
father would be a boy (XY).
8. Assertion (A) : Height in pea plants is controlled by efficiency of enzymes and is
thus genetically controlled.
Reason (R) : Cellular DNA is the information source for making proteins in
the cell.
9. Assertion (A) : In humans, if gene (B) is responsible for black eye and gene (b) is
responsible for brown eyes, then the colour of eyes of the progeny
having gene combination Bb, bb or BB will be black only.
Reason (R) : The black colour of the eyes is a dominant trait.
10. Assertion (A) : Gene inherited from the parents decide the sex of a child.
Reason (R) : X chromosome in a male child is inherited from his father.

♙nswers
1. (c) 2. (a) 3. (c) 4. (a) 5. (c) 6. (a) 7. (a) 8. (a) 9. (d) 10. (c)

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 Heridity and Evolution 89

Objective Questions
1. Mendel worked on :
(a) edible pea (b) wild pea (c) garden pea (d) none of these
2. Mendel choose pea plants because:
(a) they were cheap
(b) they were having seven pairs of contrasting characters
(c) they were easily available
(d) of great economic importance
3. Genetics is the study of :
(a) Inheritance (b) Cell structure
(c) Only plants (d) Only animals
4. Factors that determine traits are called :
(a) autosomes (b) genes
(c) chromosomes (d) loci
5. A character that is able to express itself is called :
(a) co-dominant (b) recessive
(c) dominant (d) none of these
6. What will be ratio if plants with YYRR and yyrr are crossed?
(a) 3 : 1 (b) 1 : 2 : 1
(c) 9 : 3 : 3 : 1 (d) 1 : 1 : 1 : 1
7. A ratio of 3 : 1 in generation is obtained if the cross is made with:
(a) One character (b) Two character
(c) Three character (d) Many character
8. If Y sperm of a person is fertilised with ovum of a woman, the offspring would be:
(a) Male (b) Female
(c) Neither male nor female (d) Die
9. X chromosome of a boy comes from his :
(a) Mother (b) Father
(c) Either mother or father (d) Neither mother nor father
10. The alternative form of a character that appears in heterozygous state is :
(a) Recessive
(b) Dominant
(c) Neither recessive nor dominant
(d) Some time recessive sometimes dominant
11. How much amount of DNA is contributed by both parents to generate a progeny?
(a) Equal (b) More by father and less by mother
(c) More by mother and less by father (d) Random i.e., not fixed
12. According to Mendel, each character is governed by how much alleles (gene copies)?
(a) 1 (b) 2
(c) 3 (d) 4
 90 Biology-X
13. What is the phenotypic ratio of F2 generation in Mendel’s monohybrid crosses?
(a) 1 : 1 (b) 2 : 1 : 1 (c) 3 : 1 (d) 1 : 1 : 1 : 1
14. A cross between pea plant with white flowers (vv) and pea plant with violet flowers (VV)
resulted in progeny in which ratio of violet (VV) and white (vv) flowers will be:
(a) 1 : 1 (b) 2 : 1 (c) 3 : 1 (d) 1 : 3
15. What is the genotypic ratio of generation in Mendel’s monohybrid crosses?
(a) 1 : 1 (b) 1 : 2 : 1 (c) 3 : 1 : 1 (d) 1 : 1 : 1
16. When two different traits (characters) such as seed shape and seed colour are considered in a
cross, the phenotypic ratio of progeny will be:
(a) 1 : 1 : 1 : 1 (b) 9 : 3 : 4 (c) 9 : 3 : 3 : 1 (d) 4 : 6 : 6
17. Chemically a gene is made up of :
(a) RNA (b) DNA (c) Protein (d) Carbohydrate
18. Sex of the child is determined by :
(a) Mother (b) Father
(c) Both mother and father (d) None of these
19. Which pair of sex chromosomes will determine a male ?
(a) XO (b) XX (c) XY (d) YY
20. Mendel’s concept of segregation implies that the two members of an allelic pair of genes :
(a) are distributed to separate gametes (b) may contaminent one another
(c) are segregated in pairs (d) are linked
21. If two parents have the genotypes AAaa, the probability of having an aa genotype in the F
generation is :
(a) 25% (b) 50%
(c) 75% (d) None of these
22. Sex-linked disorders such as colour blindness and haemophilia are :
(a) caused by genes on the X-chromosome (b) caused by genes on the autosome
(c) caused by genes on the Y-chromosome (d) expressed only in men
23. The genotype of offspring formed from will be :
(a) TT tt (b) Tt and tt (c) Only tt (d) Only TT
24. Which of the following is heterozygous ?
(a) TTRR (b) ttrr (c) TT (d) Tt
25. In an experiment with pea plants, a pure tall plant (TT) is crossed with a pure short plant (tt).
The ratio of pure tall plant to pure short plants in generation will be :
(a) 1 : 3 (b) 3 : 1 (c) 1 : 1 (d) 2 : 1
26. From heredity point of view which marriage is not suitable :
(a) Man and woman (b) Both
(c) Both (d) Man and Woman
27. Plants having similar genotypes produced by plant breeding are called :
(a) Clone (b) Haploid
(c) Autopolyploid (d) Genome
28. In humans, each female gamete will have :
(a) an X chromosome only (b) a Y chromosome only
(c) both X and Y chromosomes (d) none of these

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 Heridity and Evolution 91
29. If a tall pea plant is crossed with a pure dwarf pea plant then, what percentage of and
generation respectively will be tall ?
(a) 25%, 25% (b) 50%, 50%
(c) 100%, 75% (d) 75%, 100%
30. The number of chromosomes in parents and offsprings of a particular species undergoing
sexual reproduction remain constant due to:
(a) doubling of chromosomes after zygote formation
(b) halving of chromosomes after zygote formation
(c) doubling of chromosomes before gamete formation
(d) halving of chromosomes at the time of gamete formation

♙nswers
1. (c) 2. (b) 3. (a) 4. (b) 5. (c) 6. (c) 7. (a) 8. (a) 9. (a) 10. (b)
11. (a) 12. (b) 13. (c) 14. (c) 15. (b) 16. (c) 17. (b) 18. (b) 19. (c) 20 (a)
21. (d) 22. (a) 23. (b) 24. (d) 25. (c) 26. (d) 27. (a) 28. (a) 29. (c) 30. (d)

Textual Questions
Q.1 If a trait A exists in 10% of a population of an asexually reproducing species and a trait B
exists in 60% of the same population, which trait is likely to have arisen earlier?
Ans. In asexually reproducing population, there is no reshuffling of traits. New traits do develop
due to small inaccuracies produced during DNA copying. They will be in smaller proportion
than the traits already present. Therefore, trait B which exists in 60% of population must
have arisen earlier than the trait A which occurs in 10% of the population.
Q.2 How does the creation of variations in a species promote survival?
Ans. Variations occur due to sexual reproduction and also due to inaccurate copying of DNA.
Depending on the nature of variations, different individuals would have different kinds of
advantages. For example, bacteria variants which can withstand heat have better chances to
survive in a heat wave non-variant bacteria having no capacity to tolerate heat wave. Thus,
variations in a population of a species help in survival of a species.
Q.3 How do Mendel's experiments show that traits may be dominant or recessive?
Ans. The trait which appears in all the members of F1 generation and also in 75% numbers of F2
generation obtained by self fertilization of F1 generation is dominant character.
The trait which does not appear in F generation but after self-fertilization of F1 generation,
reappears in 25% of F2 generation is known as recessive.
Q.4 How do Mendel's experiments show that traits are inherited independently?
Ans. Mendel crossed pure breeding tall plants having round seeds with pure breeding short plants
having wrinkled seeds. The plants of F 1 generation were all tall with round seeds indicating
that the traits of tallness and round seeds were dominant. Self breeding of F 1 yielded plants
with characters of 9 tall round seeded, 3 tall wrinkled seeded , 3 short round seeded and one
short wrinkled seeded. Tall wrinkled seeded and short round seeded plants are new
combinations which can develop only when the traits are inherited independently.
 92 Biology-X
Q.5 A man with blood group A marries a woman with blood group O and their daughter has blood
group O. Is this information enough to tell you which of the traits - blood group A or O - is
dominant? Why or why not?
Ans. No. The information is not enough to tell whether the trait of the blood group A (IA) or blood
group O (I0) is dominant. Either can be possible. Each individual carries two alleles. A
recessive character appears only when the two alleles are similar.
Possibility1. Blood Group A is dominant and O Recessive. The trait of blood group O can
appear only when both the recessive alleles occur together as in mother and daughter (I0I0). A
group father should carry both the alleles of A and O (IA I0).
Possibility2. Blood Group O is Dominant and A Recessive:- In this case the father should
carry the alleles of A (IAIA) while the mother can be homozygous or heterozygous (I 0I0, I0
IA). The daughter will have one dominant alleles of O (I0IA).
As both the possibility can occur, the given information is unable to tell whether alleles for
blood group A or O is dominant.
Q.6 How is the sex of the child determined in human beings?
Ans. In human beings, the females have two X chromosomes and the males have one X and one Y
chromosome. Therefore, the females are XX and the males are XY.
The gametes, as we know, receive half of the chromosomes. The male gametes have 22
autosomes and either X or Y sex chromosome.
Type of male gametes: 22+X OR 22+ Y.
However, since the females have XX sex chromosomes, their gametes can only have X sex
chromosome.
Type of female gamete: 22+X

Male Female

Gametes

Zygote

Offsprtings

Female Male

Thus, the mother provides only X chromosomes. The sex of the baby is determined by the type
of male gamete (X or Y) that fuses with the X chromosome of the female.

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 Heridity and Evolution 93
Q.7 What are the different ways in which individuals with a particular trait may increase in a
population?
Ans. Individuals with a particular trait may increase in a population as a result of the following:
● Natural selection: When that trait offers some survival advantage.
● Genetic drift: When some genes governing that trait become common in a population.
● When that trait gets acquired during the individual's lifetime.

Q.8 Why are traits acquired during the life-time of an individual not inherited?
Ans. Acquired traits are structural, functional and behavioral changes that an individual develops
during its life time due to a particular environment, disease, trauma, use and disuse,
conditioning or learning. The traits are not passed on to DNA of germ cells. They remain
restricted to somatic cells. They are destroyed with the death of the individual. Therefore,
intelligence, experiences and structural acquired changes cannot pass to the progeny.
Weismann (1892) cut the tails of mice for 21 generations but a tail still developed in 22nd
generation.
Q.9 Why are the small numbers of surviving tigers a cause of worry from the point of view of
genetics?
Ans. The small number of members in a population of tigers do not allow large number of variation
to occur which are essential to survival of the species. A deadly disease or calamity may cause
death of all the tigers. The small number of tiger also indicates that existing tiger variants are
not well adopted to the existing environment and may extinct soon.
Q.10 What factors could lead to the rise of a new species?
Ans. (i) Absence of gene flow amongst subpopulations due to the presence of physical barriers, long
distance, differences in habitats, environmental and climatic conditions.
(ii) Accumulation of different variations in the different sub-populations of the species.
(iii) Natural selections of particular traits in a particular environment.
(iv) Genetic Drift: Separation of a small population, changes in its allele frequency, new
mutations and adaptations to new habitat.
(v) Reproductive Isolation:. Accumulation of different variations and genetic drift result in
absence of interbreeding in the previous subpopulations of a species. This results in the
formation of a new species.
Q.11 Will geographical isolation be a major factor in the speciation of a self-pollinating plant
species? Why or why not?
Ans. Geographical isolation can prevent the transfer of pollens among different plants. However,
since the plants are self-pollinating, which means that the pollens are transferred from the
anther of one flower to the stigma of the same flower or of another flower of the same plant,
geographical isolation cannot prevent speciation in this case.
Q.12 Will geographical isolation be a major factor in the speciation of an organism that reproduces
asexually? Why or why not?
Ans. No, because geographical isolation does not affect much in asexually reproducing organisms.
Asexually reproducing organisms pass on the parent DNA to offsprings that leaves no chance
of speciation. However, geographical isolation works as a major factor in cross pollinated
species. As it would result in pollinated species. As it would result in accumulation of
variation in the two geographically separated population.
 94 Biology-X
Q.13 Give an example of characteristics being used to determine how close two species are in
evolutionary terms.
Ans. Feathers in some ancient reptiles like dinosaurs, as fossils indicate, evolved to provide
insulation in cold weather. However, they cannot fly with these feathers later on birds
adapted the feathers to flight. This means that birds are very closely related to reptiles, since
dinosaurs were reptile.
Q.14 Can the wing of a butterfly and the wing of a bat be considered homologous organs? Why or
why not?
Ans. The wing of a butterfly and the wing of a bat are similar in function. They help the butterfly
and the bat in flying. Since they perform similar function, they are analogous organs and not
homologous.
Q.15 What are fossils? What do they tell us about the process of evolution?
Ans. Fossils are the remains of organisms that once existed on earth.
They tell us about the development of the structures from simple structured to complex
structured organisms. They tell us about the phases of evolutions through which they must
have undergone in order to sustain themselves in the competitive environment.
Q.16 Why are human beings who look so different from each other in terms of size, colour and looks
said to belong to the same species?
Ans. A species is a group of organisms that are capable of interbreeding to produce a fertile
offspring. Skin colour, looks, and size are all variety of features present in human beings.
These features are genetic but also environmentally controlled. Various human races are
formed based on these features. All human races have more than enough similarities to be
classified as same species. Therefore, all human beings are a single species as humans of
different colour, size, and looks are capable of reproduction and can produce a fertile offspring.
Q.17 In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have
a 'better' body design? Why or why not?
Ans. Evolution cannot always be equated with progress or better body designs. Evolution simply
creates more complex body designs. However, this does not mean that the simple body designs
are inefficient. In fact, bacteria having a simple body design are still the most cosmopolitan
organisms found on earth. They can survive hot springs, deep sea, and even freezing
environment.
Therefore, bacteria, spiders, fish, and chimpanzees are all different branches of evolution.
Q.18 A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with
short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of
them were short. This suggests that the genetic make-up of the tall parent can be depicted as
(a) TTWW (b) TTww (c) TtWW (d) TtWw
● (c) TtWW
Q.19 An example of homologous organs is
(a) our arm and a dog's fore-leg.
(b) our teeth and an elephant's tusks.
(c) potato and runners of grass.
(d) all of the above.
● (b) our teeth and an elephant's tusks.

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 Heridity and Evolution 95
Q.20 In evolutionary terms, we have more in common with
(a) a Chinese school-boy.
(b) a chimpanzee.
(c) a spider.
(d) a bacterium.
● (a) a Chinese school-boy.
Q.21 A study found that children with light-coloured eyes are likely to have parents with
light-coloured eyes. On this basis, can we say anything about whether the light eye colour
trait is dominant or recessive? Why or why not?
Ans. This information is not sufficient. For considering a trait as dominant or recessive, we need
data of at least three generations. This data is about only two generations.
Q.22 How are the areas of study - evolution and classification - interlinked?
Ans. Classification involves grouping of organism into a formal system based on similarities in
internal and external structure or evolutionary history.
Two species are more closely related if they have more characteristics in common. And if two
species are more closely related, then it means they have a more recent ancestor.
For example, in a family, a brother and sister are closely related and they have a recent
common ancestor i.e., their parents. A brother and his cousin are also related but less than
the sister and her brother. This is because the brother and his cousin have a common ancestor
i.e., their grandparents in the second generation whereas the parents were from the first
generation. With subsequent generations, the variations make organisms more different than
their ancestors. This discussion clearly proves that we classify organisms according to their
resemblance which is similar to creating an evolutionary tree.
Q.23 Explain the terms analogous and homologous organs with examples.
Ans. Homologous organs: are those organs which have the same basic structural design and
origin but have different functions.
For Example: The forelimbs of humans and the wings of birds look different externally but
their skeletal structure is similar.
Analogous organs: are those organs which have the different basic structural design and
origin but have similar functions. For Example: The wings of birds and insects.
Q.24 Outline a project which aims to find the dominant coat colour in dogs.
Ans. Dogs have a variety of genes that govern coat colour. There are at least eleven identified gene
series (A, B, C, D, E, F, G, M, P, S, T) that influence coat colour in dog.
A dog inherits one gene from each of its parents. The dominant gene gets expressed in the
phenotype. For example, in the B series, a dog can be genetically black or brown.
Let us assume that one parent is homozygous black (BB), while the other parent is
homozygous brown (bb)

BB
B B
bb
B Bb Bb
B Bb Bb

In this case, all the offsprings will be heterozygous (Bb).

 96 Biology-X
Since black (B) is dominant, all the offsprings will be black. However, they will have both B
and b alleles.
If such heterozygous pups are crossed, they will produce 25% homozygous black (BB), 50%
heterozygous black (Bb), and 25% homozygous brown (bb) offsprings.

B B
B BB Bb
b Bb Bb

Q.25 Explain the importance of fossils in deciding evolutionary relationships.

Ans. Fossil provide us evidence about
● The organisms that lived long ago such as the time period during which they lived, their
structure etc.
● Evolutionary development of species i.e., line of their development.
● Connecting links between two groups. For example, feathers present in some dinosaurs means
that birds are very closely related to reptiles.
● Which organisms evolved earlier and which later.
● Development of complex body designs from the simple body designs.
Q.26 What evidence do we have for the origin of life from inanimate matter?
Ans. The evidence for the origin of life from inanimate matter, was provided through an
experiment, conducted in 1953, by Stanley L. Miller and Harold C. Urey. In experiment, they
assembled an atmosphere containing molecules like ammonia, methane and hydrogen
sulphide, but no oxygen, over water. This was similar to atmosphere that thought to exist on
early earth . This was maintained at a temperature just below 100°C and sparks were passed
through the mixture of gases to simulate lightning. At the end of a week, 15% of the carbon
from methane, had been converted to simple compounds of carbon including amino acids
which make up protein molecules and support the life in basic form. Thus, amply suggesting
that life arose afresh on earth.
Q.27 Explain how sexual reproduction gives rise to more viable variations than asexual
reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Ans. Sexual reproduction causes more viable variations due to the following reasons:
● Error in copying of DNA, which are not highly significant.
● Random segregation of paternal and maternal chromosome at the time of gamete formation.
● Exchange of genetic material between homologous chromosomes during formation of gametes.
● Accumulation of variations occured due to sexual reproduction over generation after

generation and selection by nature created wide diversity.

In case of asexual reproduction, only the very small changes due to inaccuracies in DNA
copying pass on the progeny. Thus, offsprings of asexual reproduction are more or less
genetically similar to their parents. So, it can be concluded that evolution in sexually
reproducing organisms proceeds at a faster pace than in asexually reproducing organisms.
Q.28 How is the equal genetic contribution of male and female parents ensured in the progeny?
Ans. In human beings, equal genetic contribution of male and female parents is ensured in the
progeny through inheritance of equal number of chromosomes from both parents. There are
23 pairs of chromosomes All human chromosomes are not paired. Out of these 23 pairs, the
first 22 pairs are known as autosomes and the remaining one pair is known as sex

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 Heridity and Evolution 97
chromosomes represented as X and Y. Females have a perfect pair of two X sex chromosomes
and males have a mismatched pair of one X and one Y sex chromosome.
During the course of reproduction, as fertilization process takes place, the male gamete
(haploid) fuses with the female gamete(haploid) resulting in formation of the diploid zygote.
The zygote in the progeny receive an equal contribution of genetic material from the parents.
Out of 23 pairs of chromosomes in progeny, male parent contributes 22 autosomes and one X
or Y chromosome and female parent contributes 22 autosomes and one X chromosome
Q.29. Only variations that confer an advantage to an individual organism will survive in a
population. Do you agree with this statement? Why or why not?
Ans. We agree with the statement that Only variations that confer an advantage to an individual
organism will survive in a population. All the variations do not have an equal chance of
surviving in the environment in which they find themselves. The chances of surviving depend
on the nature of variations. Different individual would have different kind of advantages. A
bacteria that can withstand heat will survive better in a heat wave. Selection of variants by
environmental factors forms the basis for revolutionary process.
 98 Biology-X

Our Environment
5
ENVIRONMENT
Environment is defined as the surroundings in which the organism lives. The environment may
be the physical environment, the chemical environment or the biological environment. Thus, the
environment has two components-Abiotic and Biotic. The Abiotic environment includes the air
(atmosphere), water (hydrosphere) and land (lithosphere). The biotic environment includes the
plants, animals and the microbes.
Organisms are dependent on the environment to fulfil their needs; man is also constantly
interacting with the environment in order to fulfil his needs. These needs include the basic needs of
oxygen, food and shelter in addition to the social needs like entertainment, medicines, etc. The things
that man requires for his survival and comfort are called the resources. The environment is a
reservoir of resources. Maintaining the natural resources of the environment and their careful use is
called conservation. The conservation of environment involves the conservation of the natural
resources.
A healthy environment is an absolute necessity for the well-being of all organisms, including
man. All our needs, big and small are being met by the environment. However, man having reached
the pinnacle of evolution is trying to bring about changes in the environment to suit his convenience.
Unfortunately, this convenience is temporary. In the long run, man is losing out on a healthy
environment.
What happens when we add our waste to the environment: Accumulation of wastes due to
its improper disposal is a major problem in our country. Population has been growing at a rapid rate.
With this increase, there has also been an increase in the amount of wastes being produced especially
in the cities. Every person, on an average generates about 400 to 500 grams of wastes per day. At this
rate, in a city of about 10 lakh people around 500 tonnes of wastes is being produced every day.
In the absence of proper waste management, this waste lies littered on our streets, road corners
and improperly disposed of in vacant land. All of these are serious health hazards apart from being
eyesores. If they are not cleared regularly at the earliest, they invite host of problems like increasing
numbers of insect vectors like flies, mosquitoes, etc., scavengers such as stray dogs, pigs and rats
which spread dangerous diseases. It also generates bad odour and causes pollution. This in turn gives
rise to epidemic diseases in and around our surroundings.

ECOSYSTEM
The environment in which the man and other organisms live is called the biosphere. The
biosphere is made up of different regions that have different types of flora (plants) and fauna
(animals).
An ecosystem is a complete community of living organisms and the non-living materials of their
surroundings.

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 Our Environment 99
Components of ecosystem: The various components of an ecosystem are categorised into two
main types. i.e. Abiotic (non living) and biotic (living) components.
(i) Abiotic components: These components consists of air, water, soil, minerals and climatic
conditions like light, temperature, pressure, humidity etc. It also includes organic compounds like
carbohydrates, proteins, lipids etc. along with inorganic substances like carbon dioxide, nitrogen,
oxygen, sulphur.
(ii) Biotic components: The living organisms present in an ecosystem form the biotic
components; it includes the green plants called as producers or autotrophs, animals called consumers
(Herbivores, carnivores and omnivores) and micro organisms (decomposers or saprotrophs).
(a) Producers: Those organisms which can synthesise their own food through photosynthesis by
using carbon dioxide, water and sunlight are called as producers or autotrophs. e.g. green plants.
(b) Consumers: Those organisms which depend on autotrophs or producers for their food
directly or indirectly are called as consumers. These organisms are of three types.
(i) Herbivores: The animals which consume plants directly as their food are known as
herbivores. e.g. cow, deer goat etc.
(ii) Carnivores: The animals which consume other animals as their food are known as
carnivores. e.g. lions, tigers, snake etc.
(iii) Omnivores: The animals which consume both plants as well as animals as their food are
known as omnivores. e.g. man, dog, cat, bear etc.
(c) Decomposers (reducers or saprotrophs): The non-green micro organisms like bacteria
fungi etc. Which depend upon dead and decaying plants animals for their food are called as
decomposers. They decompose the dead bodies of plants and animals into simpler substances and
release the essential elements into the nutrient pool.
Importance of decomposers: The decomposers help in decomposing the dead bodies of plants
and animals and hence act as cleansing agents of the environment. They also help in putting back
various elements of which dead plants and animals were made into the soil, water and air which are
being reused by the producers (plants). This shows that decomposers help in recycling off materials in
the biosphere so that the process of life may go on like an unending chain.

FOOD CHAINS
A food chain is a series of steps by which energy is obtained, used, and transformed by living
things. For example; sunlight helps plants to grow, the plants are eaten by cattle, and lions eat the
cattle and so on. We know that green plants manufacture their own food with the help of sun's energy
and from common elements derived from air, water and soil. These green plants are, therefore, called
the autotrophs. The autotrophs are the chief source of potential energy for the living world. Hence
they are called the producers. When the producers are eaten by some animal, the energy of the
producers is passed on to the animal which is called consumer. The primary consumer is eaten by
another animal which is called the secondary consumer which may be eaten by a tertiary consumer
and so on. This pathway of energy transfer from one organism to another constitutes a food chain. For
example, in a forest community, grass is eaten by a deer which, in turn, is eaten by a lion. This flow of
energy from grass (producer) to deer (primary consumer) and then to lion (secondary consumer) is
called a food chain. The shorter the food chain, the greater is the available energy. Food chains are of
three types:
 100 Biology-X
(i) Grass land food chain
Food chain that operates in grass lands (meadows) is termed as grass lands food chain e.g.
Green plants ⎯ ⎯⎯→ insects (grasshopper) ⎯ ⎯⎯→ frog
  
(producers) (pry. consumer) (top order consumers)
(ii) Forest food chain
Food chain that operates in forests is termed as forest food chain e.g.
Green plants ⎯ ⎯⎯→ deer ⎯ ⎯⎯→ lion
  
(producers) (pry. consumers) (top order consumers)
(iii) Aquatic food chain
Food chain that operates in water is called aquatic food chain e.g.
Algae ⎯ ⎯⎯→ Zooplanktons ⎯ ⎯⎯→ small fish ⎯ ⎯⎯→ large fish
   
(producers) (pry. Consumers) (sec. consumer) (top order consumers)

Length of Food Chain

A food chain may end at the
(i) primary consumer (herbivore) level, e.g. plants- elephant;
(ii) secondary consumer (primary carnivore) level, for instance, plants? rabbit? bear,
(iii) tertiary consumer (secondary carnivore) level, such as plants? rabbit? wild cat? tiger, or (iv)
quaternary consumer (tertiary carnivore) level, say plants? rabbit? cat? wolf? tiger.
There is perhaps no living thing that does not serve as a trophic level in some food chain. Some
animals may form a link in more than one food chain.
Food chains may be longer or shorter than those cited above, but usually there are only four or
five successive trophic levels.
A food chain always begins with the producers, i.e., green plants. Next in the chain is always the
plant eater or the herbivore which is called the primary consumer. The primary consumers are eaten
by flesh eaters - the secondary and tertiary consumers. Certain food chains may be very long and may
extend to fourth, fifth or even higher order consumers. In aquatic ecosystems of the biosphere, like
fresh water ponds, lakes or sea, the food chain starts with microscopic free floating plants
(phytoplankton).
Algae ⎯⎯→ small animals ⎯⎯→ Fish ⎯⎯→ Big Fish
(Phytoplanktons) (Zoo plankton)

Trophic Levels
Each link in a food chain is known as a trophic level. For example, in each food chain, plants
always form the first trophic level. The plant eating animals called herbivores like insects, rodents,
rabbits, deer, cattle, etc. form the second trophic level. The animals like frog, small fish, small birds
which feed on the second trophic level organism form the third trophic level. These are eaten by still
longer carnivores like lion or tiger, which constitute the fourth trophic level.

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Increasing Levels
of food chain
Significance of Food Chains: The study of food chains helps in understanding some of the
important aspects of the ecosystem in particular and environment in general.
● The food relationship among the different organisms in an ecosystem.

● The food chains are the living components of the biosphere.

● These are the vehicles of transfer of energy from one level to another.

● Through the food chains, transfer of materials and nutrients also takes place.

Food Webs: The network of food chains which become interconnected at various trophic levels so
as to form a number of feeding connections amongst different organisms of a biotic community is
called as a food web.

A Food Web in a Grassland Ecosystem with Five Possible Food Chains

 102 Biology-X
Characteristics of food webs
(i) Food webs are never straight like food chains. It is formed by the interlinking of various food
chains.
(ii) It provides the alternative pathways of food availability for different organisms with respect to
their food habits.
(iii) Greater alternatives available in a food web make the ecosystem more stable.
(iv) Food webs also help in checking the overpopulations of highly productive species of plants and
animals.
(v) Food webs also help in ecosystem development.

Ecological Pyramids
Ecological pyramid is a graphical representation of a specific parameter (aspect) of a food chain,
such as the number of individuals in the trophic levels. The ecological pyramids are also called
Eltonian pyramids because these were first developed by an eminent British animal ecologist,
Charles Elton, in 1927.

Energy Flow
All living beings require a constant supply of energy for the various functions they perform. The
energy is obtained from the sun. This energy is introduced into the biosphere by green plants by a
process known as photosynthesis. Plants are able to trap this light energy and by the process of
photosynthesis convert it into chemical energy. Thus the initial point of entry of energy in the
ecosystem is through the green plants (autotrophs or producers). It has been estimated that on an
average, about one per cent of total sun's energy reaching the earth is trapped by green plants during
the process of food manufacture (i.e., photosynthesis). The energy thus trapped by plants is stored as
carbohydrates. Some of the energy trapped by plants is used by them in performing their metabolic
activities like respiration, growth, etc., and some energy is released in the atmosphere as heat. When
the plants are eaten by herbivorous animals, the energy stored in plants gets transferred to the
consumer animals. These animals utilize this energy for their own metabolic activities. Here again
some of the energy is released as heat. When primary consumers are eaten by secondary consumers,
the same process is repeated at every step of the food chain. Here it must be remembered, that energy
released as heat is considered as energy lost.
So we can conclude that
● Conversion of energy takes place from one form to another. The light energy gets converted

into chemical energy by plants during photosynthesis.

● Plants act as converters of energy. They do not produce energy.

● The energy lost as heat is quite substantial, if taken together from various trophic levels

● During the transfer of energy through successive trophic levels in an ecosystem, there is a lost

of energy at each trophic level. In other words, the level following the previous one always
receives less amount of energy.
● The flow of energy is unidirectional. It enters into the living system from non-living
environment
The energy lost at heat cannot be utilised
The 10 Per Cent Law of Flow of Energy: This law was given by Lindeman in 1942. It is also
termed as second law of thermodynamics or law of entropy. It states that about 90% of the energy is
used up at each level and only 10% of it is transferred to the next trophic level. As a result, at the last
trophic level (decomposer), no energy is left for recycling. This is how the flow of energy is
unidirectional. Fast decreasing energy level at each step sets the limit of trophic levels only to 4-5 at

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 Our Environment 103
the maximum. Therefore, the plants (producers) receive the maximum energy and as you go further
down the trophic levels, the energy in the food goes on decreasing.
Sun ⎯⎯→ producer ⎯⎯→ Herbivores ⎯⎯→ Carnivores
10,000j (1000j) (100j) (10j)

Impact of Man's Activities on Environment

Human beings are the integral part of the environment and the human activities make changes
in the environment which in turn affect the human beings in various aspects. Environment is
affected by the human activities in a number of ways but depletion of ozone layer and the waste
disposal are the two main problems which influenced the whole living community.

Depletion of Ozone Layer

Ozone is a form of oxygen. It is a tri-atomic molecule made up of three atoms of oxygen, O3. Very
little quantity of ozone is present in the lower part of atmosphere, called troposphere. However, good
amount of ozone is present in the upper part of atmosphere called stratosphere.
The rich zone of ozone in stratosphere is called ozone layer or ozonosphere. Ozone present in
ozonosphere has a concentration of about 10ppm. It is protective in nature because it filters U.V-B
radiations. It is, however, under severe stress due to ozone depleting substances (ODS) being
released by high flying jets and rockets.
Ozone depleting substances are those chemicals which react with ozone and change the same into
oxygen. The important ones are chlorofluorocarbons, halons, nitrogen-oxides, chlorine, methyl
chloroform and carbon tetrachloride. The maximum depletion has been caused by chlorofluorocarbon
(14%) though halons are 10 times more powerful in depleting ozone. Nitrogen-oxides (depletion 3.5%)
directly react with ozone converting it into oxygen.
NO2 + O3 ⎯⎯→ 2O2NO
Chlorofluorocarbons undergo photo dissociation to produce chlorine. Chlorine catalyses
conversion of ozone into oxygen. It is estimated that one chlorine molecule can convert one lakh
molecules of ozone into oxygen.
CFCl3 ⎯⎯→CFCl2 + Cl
CFCl2 ⎯⎯→ CF2Cl + Cl
Cl + 2O3 ⎯⎯→ Cl + 3O2
Due to distribution of ozone in the ozonosphere, its concentration has fallen down all over in the
ozonosphere. There is 8% thinning of ozone in stratosphere above 300-500 North. This thinning of
ozone was noticed in 1980s.
Over Antarctica chlorine continues to accumulate during the winter. In early spring
(August-September) it causes severe depletion of ozone so that a large area of stratosphere comes to
have very low ozone concentration. This area is called ozone hole and was discovered in 1985 by
Farman and his co-workers.

Effects of Ozone Layer Depletion

(i) Skin Cancers: There is an increase in incidence of skin cancers. 1% fall in ozone conc.
Increases U.V B load of earth by 2% that causes addition of 50,000 cases of skin cancer. In Australia
every second middle aged person suffers from skin cancer while in old persons the incidence is nearly
100%.
(ii) Blinding: Many land animals would lose their eye sight and become blind. 1% fall in ozone
conc. In stratosphere will blind another 1 lakh persons.
 104 Biology-X
(iii) Immune System: it is partially suppressed. Incidence of herpes and other immune system
related diseases are likely to increase.
(iv) Larval stages: More larval stages and young ones of aquatic animals will die.
(v) Terrestrial plants: productivity will decrease by 10-25%.
(vi) Aquatic ecosystem: productivity is going to decrease by 6-22%.
(vii) Global warming: Decreased photosynthesis would result in increase in the conc. Of CO2.
This will result in global warming.

Waste Managment
We are an integral part of the environment. Our activities change the environment around us.
Changes in the environment affect us. Environmental problems like depletion of the ozone layer and
waste disposal are issues that have to be dealt with serious concern. In our daily activities, we
generate a lot of materials that are thrown away. These accumulated wastes can be classified as
biodegradable and non-biodegradable. Substances that are broken down by biological processes are
said to be biodegradable. Substances that are not broken down by biological processes are said to be
non-biodegradable.
Disposal literally means ‘to get rid of ‘ so, to get rid of waste, we have many methods. These
methods depend upon the nature of wise and are as under:-
(1) Land fills: It is the method in which solid wastes are buried in low lying areas to level uneven
surface of land.
(2) Recycling of wastes: Most of the solid wastes can be recycled by sending them to respective
recycling units. For instance, paper is sent to plastic processing factories where these are melted and
remoulded.
(3) Preparation of compost: Household waste such as peeling of fruits and vegetables, left –
over food, fallen dead leaves of kitchen garden plants etc can be converted into compost and used as
manure.
(4) Incineration of burning at high temperature: Incineration is the process of burning of
substances at high temperature (usually more than 10000c) and ultimately converting them into
ashes. It is carried out in an incinerator examples are: household waste, chemical waste, hospital
waste etc.
(5) Production of biogas and manure: Biodegradable wastes can be used in biogas plants to
generate biogas and manure. Biogas is a cheap source of fuel, and manure, a cheap fertilizer.

Biological Magnification or Bioampliphication

Extensive usage of several pesticides and other chemicals to protect our crops from diseases and
pests has resulted in the entry of these harmful chemicals into our bodies through the food chain.
These chemicals are either washed down into the soil or into the water bodies. From the soil, these
are absorbed by the plants along with water and minerals, and from the water bodies these are taken
up by aquatic plants and animals. This is one of the ways in which they enter the food chain. As these
chemicals are not degradable, they get accumulated progressively at each trophic level. As human
beings occupy the top level in any food chain, the maximum concentration of these chemicals gets
accumulated in our bodies. This phenomenon is known as biological magnification. This is the reason
why our food grains such as wheat and rice, vegetables and fruits, and even meat, contain varying
amounts of pesticide residues. They cannot always be removed by washing or other means.

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♙ssertion and Reason Based Questions

Directions: In the following questions, A statement of Assertion (A) is followed by a
statement of Reason (R). Mark the correct choice as:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is NOT the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
1. Assertion (A) : Biodegradable waste material which can be broken down to
non-poisonous or harmless substances by the action of certain
micro-organism like bacteria and fungi.
Reason (R) : The enzyme released by micro-organism help to degraded into
simple compounds.
2. Assertion (A) : Polythene bags and plastic containers are non-biodegradable
substances.
Reason (R) : They can be degraded by micro-organisms in natural simple
harmless substances.
3. Assertion (A) : The natural ecosystem is a community of living and non-living
organism.
Reason (R) : Where each component interacts together as a unit through
biological, physical and chemical process.
4. Assertion (A) : Aquariums are known as the man-made ecosystems.
Reason (R) : Aquariums are created and maintained by humans.
5. Assertion (A) : Producer are the organisms, which produces food in the
ecosystem, by carrying out photosynthesis.
Reason (R) : They occupy the first trophic level in an ecosystem.
6. Assertion (A) : Biological magnification is the process in which harmful
chemicals enter a food chain and get accumulated progressively
at each trophic level.
Reason (R) : Biological magnification affects organisms belonging to different
trophic levels particularly the tertiary consumers.
7. Assertion (A) : Sun is not the ultimate source of energy in an ecosystem.
Reason (R) : The green plants in a terrestial ecosystem capture about 1% of
the sunlight.
8. Assertion (A) : The energy which passes to the herbivores does not come back to
autotrophs.
Reason (R) : The flow of energy in a food chain is unidirectional.
9. Assertion (A) : Ozone is formed by two atoms of oxygen.
Reason (R) : It forms a protective layer in upper atmosphere, which protects
ecosystem by absorbing all harmful UV radiations.
10. Assertion (A) : Ozone layer is getting depleted at the higher levels of the
atmosphere.
Reason (R) : Chlorofluorocarbons affect the ozone layer which are used as
refrigerants and in fire extinguishers.
 106 Biology-X

♙nswers
1. (a) 2. (c) 3. (a) 4. (a) 5. (b) 6. (b) 7. (d) 8. (a) 9. (d) 10. (a)

Objective Questions
1. An ecosystem includes :
(a) only biotic factors (b) abiotic factors only (c) both these factors (d) none of these
2. Flow of energy in an ecosystem is always:
(a) unidirectional (b) bidirectional (c) multidirectional (d) random
3. Flow of energy occurs always:
(a) from primary consumers to producers (b) tertiary consumers to producers
(c) producers to consumers (d) decomposers to consumers
4. Interconnecting food chains establish a :
(a) Food link (b) Food web
(c) Community (d) Ecosystem
5. Which one is not a biodegradable waste?
(a) Polybags (b) Sewage
(c) Paper napkins (d) Animal excreta
6. In making a food chain in an ecosystem, which trophic level is kept at first place?
(a) Herbivores (b) Carnivores
(c) Decomposers (d) Producers
7. In an ecosystem, the 10% of energy available for transfer from one trophic level to the next is in
the form of :
(a) Heat energy (b) Light energy
(c) Chemical energy (d) Mechanical energy
8. Which of the following is not a biotic component of an ecosystem?
(a) Rainfall (b) Plants
(c) Animals (d) Human beings
9. Food web is constituted by:
(a) relationship between the organisms and the environment
(b) relationship between plants and animals
(c) various interlinked food chain in an ecosystem
(d) relationship between animals and environment
10. Which of the following constitute a food-chain?
(a) Grass, wheat and mango (b) Grass, goat and human
(c) Goat, cow and elephant (d) Grass, fish and goat.
11. Which of the following limits the number of trophic levels in a food chain?
(a) Decrease in energy at higher levels (b) Deficient food supply
(c) Polluted air (d) Water
12. The biotic components in an environment are :
(a) air and water (b) plants and animals
(c) plants and water (d) animals and air

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13. Which of the following is non-biodegradable ?
(a) Paper (b) Cotton (c) DDT (d) None of these
14. In a lake polluted with pesticides, which of the following will contain the maximum amount of
pesticides in their body ?
(a) Small fishes (b) Microorganisms
(c) Small fishes (d) Water birds
15. In an ecosystem the activities of living organisms are influenced by the factors like :
(a) air (b) water
(c) temperature (d) all of these
16. In a food chain, producers belong to which trophic level ?
(a) First (b) Second
(c) Fourth (d) Third
17. In which year did UNEP signed the agreement to stop CFC production ?
(a) 1986 (b) 1985 (c) 1987 (d) 1978
18. Biomagnification occurs due to the excessive use of :
(a) water (b) manure
(c) pesticides (d) all of these
19. A lion is a:
(a) tertiary consumer (b) secondary consumer (c) herbivore (d) parasite
20. How much energy is transferred to the next trophic level in a food chain ?
(a) 100% (b) 10% (c) 20% (d) 1%
21. Which of these form the second trophic level in a food chain ?
(a) Herbivores (b) Plants
(c) Carnivores (d) Top carnivores
22. In an ecosystem, the biotic component is :
(a) temperature (b) moisture
(c) plant (d) oxygen
23. Example of an artificial ecosystem is/are :
(a) crop-fields (b) gardens
(c) aquarium (d) all of these
24. An area of ecosystem where an organism lives :
(a) habitat (b) atmosphere
(c) environment (d) none of these
25. Chloro-fluoro carbons cause damage to:
(a) Green plants (b) Ozone layer
(c) Pond ecosystem (d) Polar ice
26. Ozone layer helps us by absorbing :
(a) X-rays (b) Infrared rays
(c) Ultraviolet rays (d) Electromagnetic waves
27. Which of the following material can be biomagnified in an ecosystem?
(a) Sewage waste (b) Pesticide residues
(c) Plastic bags (d) Aluminium canes
 108 Biology-X
28. Concentration of harmful chemicals in a food chain is maximum in the :
(a) first level (b) second level
(c) third level (d) top level
29. Oldest form of garbage disposal :
(a) incineration (b) recycling
(c) landfills (d) composting
30. Which method of waste disposal may cause air pollution ?
(a) Composting (b) Land filling
(c) Recycling (d) Burning

♙nswers
1. (c) 2. (a) 3. (c) 4. (b) 5. (a) 6. (d) 7. (c) 8. (a) 9. (c) 10. (b)
11. (a) 12. (b) 13. (c) 14. (d) 15. (d) 16. (a) 17. (c) 18. (c) 19. (a) 20 (b)
21. (a) 22. (c) 23. (d) 24. (a) 25. (b) 26. (c) 27. (b) 28. (d) 29. (c) 30. (d)

Textual Questions
Q.1 Why are some substances biodegradable and some non-biodegradable?
Ans. Substances which are of organic origin are biodegradable, while those of inorganic origin are
non-biodegradable. Organic substances can be utilized by decomposers as food, while other
substances cannot be utilized by decomposers as food. Due to this, some substances are
biodegradable while some others are non-biodegradable.
Q.2 Give any two ways in which biodegradable substances would affect the environment.
Ans. Biodegradable substances can affect the environment in following ways:
(a) By recycling the raw materials in nature.
(b) By improving the humus content in soil.
Q.3 Give any two ways in which non-biodegradable substances would affect the environment.
Ans. Non-biodegradable substances would affect the environment in following two ways:
(a) By increasing the burden on the environment because they would accumulate.
(b) By producing harmful polluting gases, if they are burnt.
Q.4 What are trophic levels? Give an example of a food chain and state the different trophic levels
in it.
Ans. A particular level in a food chain is called trophic level. Following example shows trophic
levels in a food chain:
Producer ? Primary Consumer ? Secondary Consumer ? Tertiary Consumer
Grass ? Grasshopper ? Frog ? Snake
Q.5 What is the role of decomposers in the ecosystem?
Ans. Decomposers decompose dead remains of plants and animals. By doing so, they serve two
purposes. One; they reduce the burden on the environment by clearing dead remains. Two;
they channelize the raw materials back to the environment.

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Q.6 What is ozone and how does it affect any ecosystem?
Ans. Ozone is a form of oxygen. Ozone is a triatomic molecule while oxygen is a diatomic molecule.
Ozone forms the ozone layer in our atmosphere. Ozone plays an important role in the
ecosystem. The ozone layer wards off harmful ultraviolet radiations from the sun and thus
protects the living beings.
Q.7 How can you help in reducing the problem of waste disposal? Give any two methods.
Ans The problem of waste disposal can be reduced in many ways. Two methods are given below:
(a) By using more of biodegradable substances and reducing the use of non-biodegradable
substances. For example; instead of plastic bags, one should carry jute bags or cloth bags for
shopping.
(b) By proper segregation of waste before disposing.
Q.8 Which of the following groups contain only biodegradable items?
(a) Grass, flowers and leather
(b) Grass, wood and plastic
(c) Fruit-peels, cake and lime-juice
(d) Cake, wood and grass
Ans. Both c & d.
Q.9 Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Ans. (b) Grass, goat and human
Q.10 Which of the following are environment-friendly practices?
(a) Carrying cloth-bags to put purchases in while shopping
(b) Switching off unnecessary lights and fans
(c) Walking to school instead of getting your mother to drop you on her scooter
(d) All of the above
Ans. All of the above
Q.11 What will happen if we kill all the organisms in one trophic level?
Ans. If all the organisms in one trophic level are killed, it will disturb the whole ecosystem. Let us
take a hypothetical example to understand this. If all the deer are killed in a jungle, the lions
would be left with no food. This would endanger the existence of lions. Once the lions and deer
would be finished, it would result in population explosion of green plants. If all the lions die in
a jungle, it would create another problem. Since no lion would be left to kill the deer, the
population of deer would increase substantially. This will finish off all the green plants and
finally even the deer would be left with no food for them.
Q.12 Will the impact of removing all the organisms in a trophic level be different for different
trophic levels? Can the organisms of any trophic level be removed without causing any
damage to the ecosystem?
Ans. The impact of removing all the organisms in a trophic level shall be similar for different
trophic levels; although their manifestations can be different. Organisms of any trophic level
cannot be removed without causing any damage to the ecosystem. The examples of lions and
deer in the previous answer illustrate this.
Q.13 What is biological magnification? Will the levels of this magnification be different at different
levels of the ecosystem?
 110 Biology-X
Ans. The accumulation of a particular substance through different trophic levels is called biological
magnification. Let us take example of lead poisoning which may affect plants because of water
pollution. The level of lead would be at a particular level in plants. When an herbivore would
eat these plants, the level of lead shall be more in the body of herbivore because it would eat a
large number of plants. When this herbivore would be eaten by a carnivore, the level shall rise
further because the carnivore would eat a large number of herbivores. Hence, the level of this
magnification will increase as we move to higher trophic levels.
Q.14 What are the problems caused by the non-biodegradable wastes that we generate?
Ans. Non-biodegradable waste creates many problems. Biodegradable waste keeps on
accumulating in the environment because it does not decompose. Hypothetically, a time may
come when the whole earth would be filled with non-biodegradable waste. If we try to destroy
such waste by way of burning, it would create many polluting gases.
Q.15 If all the waste we generate is biodegradable, will this have no impact on the environment?
Ans. If all the waste we generate is biodegradable, this would also have an impact on the
environment but most of the impacts would be positive. After decomposition, the
biodegradable substance produces different raw materials which are sent back to the
ecosystem. The solid remains would add to the humus content of soil.
There can be some negative impacts; like obnoxious smell which is created during the process
of decomposition. There can also be a possibility of sparking an epidemic if the waste is
dumped near a residential area or is allowed to contaminate the water bodies. So, it is not the
biodegradable waste which is going to create the problem, rather the way we dispose it.
Q.16 Why is damage to the ozone layer a cause for concern? What steps are being taken to limit this
damage?
Ans. Ozone layer works like a protective shield for living beings. The ozone layers wards off
harmful ultraviolet radiations from the sun. Damage to the ozone layer can result in
increased level of ultraviolet radiations in our atmosphere. This would be very dangerous for
all life forms.
In 1987, the UNEP (United Nations Environment Programme) succeeded in forging an
agreement among different nations to freeze the CFC production at 1986 level. Later, an
agreement was signed among different nations to phase out CFCs. It is important to note that
CFC is used in refrigerators and aerosol spray. India is also a signatory of that agreement and
thanks to the efforts by the United Nations and different environmentalists, the CFC
emission has been put under some control.

SKIE CLASSES SRINAGAR CLASS 10TH BIOLOGY #8899880136