Biology notes by Shubham Sir

Biology
 Robert Hooke saw that the cork resembled the structure of a honeycomb consisting of many little
compartments.
 Cork is a substance which comes from the bark of a tree.
 This was in the year 1665 when Hooke made this chance observation through a self-designed
microscope.
 Robert Hooke called these boxes cells.
 This may seem to be a very small and insignificant incident but it is very important in the history of
science.
 This was the very first time that someone had observed that living things appear to consist of separate
units.
 The use of the word 'cell' to describe these units is being used till this day in
biology
 Cells were first discovered by Robert Hooke in 1665.
 He observed the cells in a cork slice with the help of a primitive microscope.
 Leeuwenhoek (1674), with the improved microscope, discovered the free
living cells in pond water for the first time.
 It was Robert Brown in 1831 who discovered the nucleus in the cell.
 Purkinje in 1839 coined the term 'protoplasm for the fluid substance of the cell.
 The cell theory, that all the plants and animals are composed of cells and that the cell is the basic unit of
life, was presented by two biologists, Schleiden (1838) and Schwann (1839).
 The cell theory was further expanded by Virchow (1855) by suggesting that all cells arise from pre-
existing cells.
 With the discovery of the electron microscope in 1940, it was possible to observe and understand the
complex structure of the cell and its various organelles.
 The invention of magnifying lenses led to the discovery of the microscopic world.
 It is now known that a single cell may constitute a whole organism as in Amoeba, Chlamydomonas,
Paramecium and Bacteria. These organisms are called unicellular organisms (uni = single).
 On the other hand, many cells group together in a single body and assume different functions in it to
form various body parts in multicellular organisms (multi = many) such as some fungi, plants and
animals.
 Hanji Can we find out names of some more unicellular
organisms?
 Every multi-cellular organism has come from a single c
 ell.
 Some organisms can also have cells of different kinds.
 The shape and size of cells are related to the specific function they
perform.
 Some cells like Amoeba have changing shapes.
 Pseudopods of amoeba are known to have multiple functions. The two main functions of pseudopods
include locomotion and capturing and engulfing prey.
 In some cases the cell shape could be more or less fixed and peculiar for a particular type of cell; for
example, nerve cells have a typical shape.
 Each living cell has the capacity to perform certain basic functions that are characteristic of all living
forms.
How does a living cell perform these basic functions?
 We know that there is a division of labour in multicellular organisms such as human beings.
Biology notes by Shubham Sir
 This means that different parts of the human body perform different functions.
 The human body has a heart to pump blood, a stomach to digest food and so on.
 Similarly, division of labour is also seen within a single cell.
 In fact, each such cell has got certain specific components within it known as cell organelles.
 Each kind of cell organelle performs a special function, such as making new material in the cell, clearing
up the waste material from the cell and so on.
 A cell is able to live and perform all its functions because of these organelles.
 These organelles together constitute the basic unit called the cell.
 It is interesting that all cells are found to have the same organelles, no matter what their function is or
what organism they are found in.
What is a Cell Made Up of? What is the
Structural Organization of a Cell?
 The cell has special components called organelles.
 If we study a cell under a microscope, we would come across three features in almost every cell; plasma
membrane, nucleus and cytoplasm.
 All activities inside the cell and interactions of the I cell with its environment are possible due to these
features.
PLASMA MEMBRANE /
CELL MEMBRANE
 This is the outermost covering of the cell that separates the contents of the cell from its external
environment.
 The plasma membrane allows or permits the entry and exit of some materials in and out of the cell.
 It also prevents movement of some other materials.
 The cell membrane, therefore, is called a selectively
permeable membrane.

 How does the movement of substances take place into the

cell? How do substances move out of the cell?
 Some substances like carbon dioxide or oxygen can move
across the cell membrane by a process called diffusion.
 There is spontaneous movement of a substance from a
region of high concentration to a region where its
concentration is low.
 Some substance like CO2 (which is cellular waste and
requires to be excreted out by the cell) accumulates in high concentrations inside the cell.
 As soon as there is a difference of concentration of CO₂ inside and outside a cell, CO₂ moves out of the
cell, from a region of high concentration, to a region of low concentration outside the cell by the process
of diffusion.
 Similarly, O₂ enters the cell by the process of diffusion when the level or concentration of O2 inside the
cell decreases.
 Thus, diffusion plays an important role in gaseous exchange between the cells as well as the cell and its
external environment.
 Water also obeys the law of diffusion.
 The movement of water molecules through such a selectively permeable membrane is called osmosis.
 The movement of water across the plasma membrane is also affected by the amount of substance
dissolved in water.
 Thus, osmosis is the net diffusion of water across a selectively permeable membrane toward a higher
solute concentration.
Biology notes by Shubham Sir
 Unicellular freshwater organisms and most plant cells tend to gain water through osmosis.
 Absorption of water by plant roots is also an example of osmosis.
 Thus, diffusion is important in exchange of gases and water in the life of a cell.
 In additions to this, the cell also obtains nutrition from its environment.
 Different molecules move in and out of the cell through a type of transport requiring use of energy.
 The plasma membrane is flexible and is made up of organic molecules called lipids and proteins.
 However, we can observe the structure of the plasma membrane only through an electron microscope.
 The flexibility of the cell membrane also enables the cell to engulf in food and other material from its
external environment. Such processes are known as endocytosis. Amoeba acquires its food through such
processes.
What will happen if we put an animal cell or a
plant cell into a solution of sugar or salt in water?
 One of the following three things could happen:

1. If the medium surrounding the cell has a higher water concentration than the cell, meaning that the
outside solution is very dilute, the cell will gain water by osmosis. Such a solution is known as a
hypotonic solution. Water molecules are free to pass across the cell membrane in both directions, but
more water will come into the cell than will leave. The net (overall) result is that water enters the cell.
The cell is likely to swell up.
2. If the medium has exactly the same water concentration as the cell, there will be no net movement of
water across the cell membrane. Such a solution is known as an isotonic solution. Water crosses the cell
membrane in both directions, but the amount going in is the same as the amount going out, so there is no
overall movement of water. The cell will stay the same size.
3. If the medium has a lower concentration of water
 than the cell, meaning that it is a very concentrated solution, the cell will lose water by osmosis. Such a
solution is known as a hypertonic solution. Again, water crosses the cell membrane in both directions,
but this time more water leaves the cell than enters it. Therefore the cell will shrink.

CELL WALL
 Plant cells, in addition to the plasma membrane, have another rigid outer covering called the cell wall.
 The cell wall lies outside the plasma membrane.
 The plant cell wall is mainly composed of cellulose.
 Cellulose is a complex substance and provides structural strength to plants.
 When a living plant cell loses water through osmosis there is shrinkage or contraction of the contents of
the cell away from the cell wall. This phenomenon is known as plasmolysis.
 It appears that only living cells, and not dead cells, are able to absorb water by osmosis.
 Cell walls permit the cells of plants, fungi and bacteria to withstand very dilute (hypotonic) external
media without bursting.
Biology notes by Shubham Sir
 In such media the cells tend to take up water by osmosis.
 The cell swells, building up pressure against the cell wall.
 The wall exerts an equal pressure against the swollen cell.
 Because of their walls, such cells can withstand much greater changes in the surrounding medium than
animal cells.

NUCLEUS
 The nucleus has a double layered covering called nuclear membrane.
 The nuclear membrane has pores which allow the transfer of material from inside the nucleus to its
outside, that is, to the cytoplasm.
 The nucleus contains chromosomes, which are visible as rod-shaped structures only when the cell is
about to divide.
 Chromosomes contain information for inheritance of characters from parents to next generation in the
form of DNA (Deoxyribo Nucleic Acid) molecules.
 Chromosomes are composed of DNA and protein.
 DNA molecules contain the information necessary for constructing and organizing cells.
 Functional segments of DNA are called genes.
 In a cell which is not dividing, this DNA is present as part of chromatin material
 Chromatin material is visible as entangled mass of thread like structures.

 Whenever the cell is about to divide, the chromatin material gets organized into chromosomes.
 The nucleus plays a central role in cellular reproduction, the process by which a single cell divides and
forms two new cells.
 It also plays a crucial part, along with the environment, in determining the way the cell will develop and
what form it will exhibit at maturity, by directing the chemical activities of the cell.
 In some organisms like bacteria, the nuclear region of the cell may be poorly defined due to the absence
of a nuclear membrane.
 Such an undefined nuclear region containing only nucleic acids is called a nucleoid.

Biology notes by Shubham Sir

 S.No. Prokaryotes Eukaryotes
1. Most prokaryotes are unicellular. Most eukaryotes are multicellular.

2. The nucleus is poorly defined due to The nucleus is well defined and is
the absence of a nuclear membrane. surrounded by a nuclear membrane.

3. Nudeolus is absent. Nucleolus is present.

4. Cell organelles such as plastids, Cell organelles such as plastids,

mitochondria, golgi bodies, etc. are mitochondria, golgi bodies, etc. are
absent. present.

5. Bacteria and blue-green algae are Fungi, plant, and animal cells are
prokaryotic cells eukaryotic cells

 Such organisms, whose cells lack a nuclear membrane, are called prokaryotes (Pro= primitive = or
primary; karyote karyon = nucleus).
 Organisms with cells having a nuclear membrane are called eukaryotes.
 Prokaryotic cells also lack most of the other cytoplasmic organelles present in eukaryotic cells.
 Many of the functions of such organelles are also performed by poorly organized parts of the cytoplasm.
 The chlorophyll in photosynthetic prokaryotic bacteria is associated with membranous vesicles (bag like
structures) but not with plastids as in eukaryotic cells.
CYTOPLASM
 This region takes up very little stain. It is called the cytoplasm.
 The cytoplasm is the fluid content inside the plasma membrane.
 It also contains many specialized cell organelles. Each of these organelles performs a specific function
for the cell.
 Cell organelles are enclosed by membranes.
 In prokaryotes, beside the absence of a defined nuclear region, the membrane-bound cell organelles
are also absent. On the other hand, the eukaryotic cells have nuclear membrane as well as membrane-
enclosed organelles.
 The significance of membranes can be illustrated with the example of viruses. Viruses lack any
membranes and hence do not show characteristics of life until they enter a living body and use its cell
machinery to multiply.

CELL ORGANELLES
 Every cell has a membrane around it to keep its own contents separate from the external environment.
 Large and complex cells, including cells from multicellular organisms, need a lot of chemical activities
to support their complicated structure and function.

Biology notes by Shubham Sir

 To keep these activities of different kinds separate from each other, these cells use membrane-bound
little structures (or 'organelles') within themselves.
 This is one of the features of the eukaryotic cells that distinguish them from prokaryotic cells.
 Some of these organelles are visible only with an electron microscope.
 Some important examples of cell organelles which we will discuss now are; endoplasmic reticulum,
Golgi apparatus, lysosomes, mitochondria and plastids.
 They are important because they carry out some very crucial functions in cells.
ENDOPLASMIC RETICULUM (ER)
 The endoplasmic reticulum (ER) is a large network of membrane-bound tubes and sheets.
 It looks like long tubules or round or oblong bags (vesicles).
 The ER membrane is similar in structure to the plasma membrane.
 ▪There are two types of ER- rough endoplasmic reticulum (RER) and smooth endoplasmic
 reticulum (SER).
 RER looks rough under a microscope because it has particles called ribosomes attached to its surface.
 The ribosomes, which are present in all active cells, are the sites of protein manufacture.
 The manufactured proteins are then sent to various places in the cell depending on need, using the ER.
 The SER helps in the manufacture of fat molecules, or lipids, important for cell function.
 Some of these proteins and lipids help in building the cell membrane.
 This process is known as membrane biogenesis.
 Some other proteins and lipids function as enzymes and hormones.
 Although the ER varies greatly in appearance in different cells, it always forms a network system.
 Thus, one function of the ER is to serve as channels for the transport of materials (especially proteins)
between various regions of the cytoplasm or between the cytoplasm and the nucleus.
 The ER also functions as a cytoplasmic framework providing a surface for some of the biochemical
activities of the cell.
 SER plays a crucial role in detoxifying many poisons and drugs.

GOLGI APPARATUS
 The Golgi apparatus, first described by Camillo Golgi, consists of a system of membrane-bound vesicles
(flattened sacs) arranged approximately parallel to each other in stacks called cisterns. these membranes
often have connections with the membranes of ER and therefore constitute another of a complex cellular
membrane system.
 The material synthesized near the ER is packaged dispatched to various targets inside and outside cell
through the Golgi apparatus. functions include the storage, modification and packaging of products
in vesicles. In some cases, complex sugars may be made from simple sugars in Golgi apparatus.
Golgi apparatus is also involved in the formation

Biology notes by Shubham Sir

 LYSOSOMES (Suicidal bags)
 Structurally, lysosomes are membrane-bound sacs filled with digestive enzymes.
 These enzymes are made by RER. Lysosomes are a kind of waste disposal system of the cell.
 These help to keep the cell clean by digesting any foreign material as well as worn-out cell organelles.
 Foreign materials entering the cell, such as bacteria or food, as well as old organelles end up in the
lysosomes, which break complex substances into simpler substances.
 Lysosomes are able to do this because they contain powerful digestive enzymes capable of breaking
down all organic material.
 During the disturbance in cellular metabolism, for example, when the cell gets damaged, lysosomes may
burst and the enzymes digest their own cell.
 Therefore, lysosomes are also known as 'suicide bars’ of a cell.

MITOCHONDRIA (Powerhouse of Cell)

 Mitochondria are known as powerhouses of the cell.
 Mitochondria have two membrane coverings.
 The outer membrane is porous while the inner membrane is deeply folded. These folds increase surface
area for ATP generating chemical reactions.
 The energy required for various chemical activities needed for life is released by mitochondria in the
form of ATP (Adenosine triphopshate) molecules.
 ATP is known as the energy currency of the cell.
 The body uses energy stored in ATP for making new chemical compounds and for mechanical work.
 Mitochondria are strange organelles in the sense that they have their own DNA and ribosomes.
 Therefore, mitochondria are able to make some of their own proteins.

Biology notes by Shubham Sir

 PLASTIDS
 Plastids are present only in plant cells.
 There are two types of plastids - chromoplasts (coloured plastids) and leucoplasts (white or colourless
plastids).
 Chromoplasts containing the pigment chlorophyll are chloroplasts. known as Chloroplasts.
 Chloroplasts are important for photosynthesis in plants.
 Chloroplasts also contain various yellow or orange pigments in addition to chlorophyll.
 Leucoplasts are primarily organelles in which materials such as starch, oils and protein granules are
stored.
 The internal organisation of the Chloroplast consists of numerous membrane layers embedded in a
material called the stroma.
 These are similar to mitochondria in external structure.
 Like the mitochondria, plastids also have their own DNA and ribosomes.

VACUOLES
 Vacuoles are storage sacs for solid or liquid contents.
 Vacuoles are small sized in animal cells while plant cells have very large vacuoles.
 The central vacuole of some plant cells may occupy 50-90% of the cell volume.
 In plant cells vacuoles are full of cell sap and provide turgidity and rigidity to the cell.
 Many substances of importance in the life of the plant cell are stored in vacuoles.
 These include amino acids, sugars, various organic acids and some proteins.
 "In single-celled organisms like Amoeba, the food vacuole contains the food items that the Amoeba has
consumed.
 In some unicellular organisms, specialized vacuoles also play important roles in expelling excess water
and some wastes from the cell.
 Each cell thus acquires its structure and ability to function because of the organisation of its membrane
and organelles in specific ways.
 The cell thus has a basic structural organisation.
 This helps the cells to perform functions like respiration, obtaining nutrition, and clearing of waste
material, or forming new proteins.
 Thus, the cell is the fundamental structural unit of living organisms.
 It is also the basic functional unit of life.

Biology notes by Shubham Sir

 The process of cell division by which most of the cells divide for growth is called mitosis.
 In this process, each cell called mother cell divides to form two identical daughter cells.
 The daughter cells have the same number of chromosomes as mother cell.
 It helps in growth and repair of tissues in organisms.
 Specific cells of reproductive organs or tissues in animals and plants divide to form gametes, which
after fertilization give rise to offspring. They divide by a different process called meiosis which involves
two consecutive divisions.
 When a cell divides by meiosis it produces four new cells instead of just two.
 The new cells only have half the number of chromosomes than that of the mother cells.

 All living organisms are made of cells.

 In unicellular organisms, a single cell performs all basic functions.
 For example, in Amoeba, a single cell carries out movement, intake of food, gaseous exchange and
excretion.
 But in multicellular organisms there are millions of cells.
 Most of these cells are specialized to carry out specific functions.
 Each specialized function is taken up by a different group of cells.
 Since these cells carry out only a particular function, they do it very efficiently.
 In human beings, muscle cells contract and relax to cause movement, nerve cells carry messages, blood
flows to transport oxygen, food, hormones and waste material and so on.
Cell
↓
Tissue
↓
Organ
↓
Organ System
↓
Body
 In plants, vascular tissues conduct food and water from one part of the plant to other parts.
 So, multi-cellular organisms show division of labour.
 Cells specialising in one function are often grouped together in the body.
 This means that a particular function is carried out by a cluster of cells at a definite place in the body.
 This cluster of cells, called a tissue, is arranged and designed so as to give the highest possible efficiency
 of function.
 Blood, phloem and muscle are all examples of tissues.
 A group of cells that are similar in structure and/or work together to achieve a particular function forms
a tissue.
Are Plant And Animal Tissues are Same?
 There are noticeable differences between the two.
Biology notes by Shubham Sir
 Plants are stationary or fixed - they don't move.
 Since they have to be upright, they have a large quantity of supportive tissue.
 The supportive tissue generally has dead cells.
 Animals on the other hand move around in search of food, mates and shelter.
 They consume more energy as compared to plants.
 Most of the tissues they contain are living.
 Another difference between animals and plants is in the pattern of growth.
 The growth in plants is limited to certain regions, while this is not so in animals.
 There are some tissues in plants that divide throughout their life.
 These tissues are localised in certain regions.
Types of Plant Tissue:

MERISTEMATIC TISSUE
 The growth of plants occurs only in certain specific regions.
 This is because the dividing tissue, also known as meristematic tissue, is located only at these points.
 Depending on the region where they are present, meristematic tissues are classified as
▪ Apical,
▪ Lateral
▪Intercalary.
 New cells produced by meristem are initially like those of meristem itself, but as they grow and mature,
their characteristics slowly change and they become differentiated as components of other tissues.
 Apical meristem is present at the growing tips of stems and roots and increases the length of the stem
and the root.
 The girth of the stem or root increases due to lateral meristem (cambium).
 Intercalary meristem seen in some plants is located near the node.
 Cells of meristematic tissue are very active, they have dense cytoplasm, thin cellulose walls and
prominent nuclei.
 They lack vacuoles.

Biology notes by Shubham Sir

 PERMANENT TISSUE
 What happens to the cells formed by meristematic tissue?
 They take up a specific role and lose the ability to divide.
 As a result, they form a permanent tissue.
 This process of taking up a permanent shape, size, and a function is called differentiation.
 Differentiation leads to the development of various types of permanent tissues.
SIMPLE PERMANENT TISSUE
1.Parenchyma
2.Collenchyma
3. Sclerenchyma

 A few layers of cells beneath the epidermis are generally simple permanent tissue.
1.Parenchyma:
 It is the most common simple permanent tissue. It consists of relatively unspecialised cells with thin cell
walls. They are living cells.
 They are usually loosely arranged, thus large spaces between cells (intercellular spaces) are found in this
tissue. This tissue generally stores food.
 In some situations, it contains chlorophyll and performs photosynthesis, and then it is called
chlorenchyma
 It is made up of Palisade and Spongy mesophyll tissues.

Biology notes by Shubham Sir

 Palisade mesophyll consists of tightly packed columnar cells, the structure of spongy mesophyll is not
well characterized and often treated as a random assemblage of irregularly shaped cells.
 In aquatic plants, large air cavities are present in parenchymn to help them float Such a parenchyma
type is called aerenchyma.
 The parenchyma (Found in: Stem, Roots, Leaves, Flowers and Fruits. Thus, the parenchyma tissue is
found in the soft parts of the plant such as cortex of roots, ground tissues in stems and mesophyll of
leaves.
 It is also distributed in pith, medullary rays and packing tissue in xylem and phloem.
2.Collenchyma:
 The flexibility in plant is due to Collenchyma.
 It allows bending of various parts of a plant like tendrils and stems of climbers without breaking.
 It also provides mechanical support.
 We can find this tissue in leaf stalks below the epidermis.
 The cells of this tissue are living, elongated and irregularly thickened at the corners.
 .There is very little intercellular space.
 The cells of collenchyma are located below the epidermis (i.e., hypodermis) of dicotyledon stem and
petiole (leaf stalk) (i.e., in outer region of cortex).
 These cells also occur in the midribs of dicot leaves.
 Collenchyma is absent in monocot stems, roots and leaves.
Sclerenchyma:
 It is the tissue which makes the plant hard and stiff We have seen the husk of a coconut.
 It is made of sclerenchymatous tissue.
 The cells of this tissue are dead (V.IMP)
 They are long and narrow as the walls are thickened due to lignin.
 Often these walls are so thick that there is no internal space inside the cell.
 This tissue is present in stems, around vascular bundles, in the veins of leaves and in the hard covering
of seeds and nuts. It provides strength to the plant parts.
 Sclerenchyma are found in stems (around the vascular bundle), roots, veins of leaves, hard coverings of
seeds and nuts. Sclereids form the gritty part of most of the ripe fruits and contribute hardness to the seed
coat and nutshells. Husk of coconut is made of sclerenchymatous tissue.
Epidermis
 The epidermis is usually made of a single layer of cells. In some plants living in very dry habitats, the
epidermis may be thicker since protection against water loss is critical.
 The entire surface of a plant has an outer covering epidermis.
 It protects all the parts of the plant.
 Epidermal cells on the aerial parts of the plant often secrete a waxy, water resistant layer on their outer
surface. This aids in protection against loss of water, mechanical injury and invasion by parasitic fungi
 Since it has a protective role to play, cells of epidermal tissue form a continuous layer without
intercellular spaces. Most epidermal cells are relatively flat. Often their outer and side walls are thicker
than the inner wall.

Biology notes by Shubham Sir

 We can observe small pores here and there in the epidermis of the leaf.
 These pores are called stomata.
 Stomata are enclosed by two kidney-shaped cells called guard cells.
 Stomata are necessary for exchanging gases with the atmosphere.
 Transpiration (loss of water in the form of water vapour) also takes place through stomata.
 Epidermal cells of the roots, whose function is water absorption, commonly bear long hairlike parts that
greatly increase the total absorptive surface area.
 In some plants like desert plants, epidermis has a thick waxy coating of cutin (chemical substance with
waterproof quality) on its outer surface.
 Is the outer layer of a branch of a tree different from the outer layer of a young stem?
 As plants grow older, the outer protective tissue undergoes certain changes.
 A strip of secondary meristem located in the cortex forms layers of cells which constitute the cork.
 Cells of cork are dead and compactly arranged without intercellular spaces.
 They also have a substance called suberin in their walls that makes them impervious to gases and water

 Epidermal cells of the roots, whose function is water absorption, commonly bear long hair like parts that
greatly increase the total absorptive surface area.
 In some plants like desert plants, epidermis has a thick waxy coating of cut in (chemical substance with
waterproof quality) on its outer surface.
 As plants grow older, the outer protective tissue undergoes certain changes.
 A strip of secondary meristem located in the cortex forms layers of cells which constitute the cork.
Biology notes by Shubham Sir
 Cells of cork are dead and compactly arranged without intercellular spaces.
 They also have a substance called suberin in their walls that makes them impervious to gases and water.
COMPLEX PERMANENT TISSUE
 Complex tissues are made of more than one type of cells. All these cells coordinate to perform a
common function.
Permanent Tissue: Xylem & Phloem
 They are both conducting tissues and constitute a vascular bundle.
 Vascular tissue is a distinctive feature of the complex plants, one that has made possible their survival in
the terrestrial environment.
Xylem:
Consists of Tracheids, Vessels, Xylem Parenchyma and Xylem Fibres.
 Tracheids and vessels have thick walls, and many are dead cells when mature.
 Tracheids and vessels are tubular structures.
 This allows them to transport water and minerals vertically.
 The parenchyma stores food.
 Xylem fibres are mainly supportive in function.

Phloem:
It is made up of five types of cells. Sieve cells, Steve Tubes, Companion Cells, Phloem Fibres and the
Phloem Parenchyma.
(Question will be asked that sieve cells, sieve tubes, companion cells are part of Xylem, Phloem etc).
Trick: Sieve Cells, Sieve Tubes, (Phloem initial is P next alphabet is S).
 Sieve tubes are tubular cells with perforated walls.
 Phloem transports food from leaves to other parts of the plant.
 Except phloem fibres, other phloem cells are living cells.

Animal Tissues
 When we breathe we can actually feel the movement of our chest.
 How do these body parts move? For this we have specialised cells called muscle cells.
 The contraction and relaxation of these cells result in movement.
 During breathing we inhale oxygen. Where does this oxygen go?
Biology notes by Shubham Sir
 It is absorbed in the lungs and then is transported to all the body cells through blood.
 Why would cells need oxygen?
 The functions of mitochondria we studied earlier provide a clue to this question.
 Blood flows and carries various substances from one part of the body to the other.
 For example, it carries oxygen and food to all cells.
 It also collects wastes from all parts of the body and carries them to the liver and kidney for disposal.
 Blood and muscles are both examples of tissues found in our body
 On the basis of the functions they perform we can think of different types of animal tissues, such as
epithelial tissue, connective tissue, muscular tissue and nervous tissue.
 Blood is a type of connective tissue, and muscle forms muscular tissue.
Type of Animal Tissues
1. EPITHELIAL TISSUE
Squamous
Cuboidal
Columnar (Ciliated)
Stratified Squamous

2.CONNECTIVE TISSUE
3.MUSCULAR TISSUE
4.NERVOUS TISSUE

1. EPITHELIAL TISSUE
 The covering or protective tissues in the animal body are epithelial tissues.
 Epithelium covers most organs and cavities within the body. It also forms a barrier to keep different
body systems separate.
 The skin, the lining of the mouth, the lining of blood vessels, lung alveoli and kidney tubules are all
made of epithelial tissue.
 Epithelial tissue cells are tightly packed and form a continuous sheet.
 They have only a small amount of cementing material between them and almost no intercellular spaces.
 Obviously, anything entering or leaving the body must cross at least one layer of epithelium.
 As a result, the permeability of the cells of various epithelia play an important role in regulating the
exchange of materials between the body and the external environment and also between different parts
of the body.
 Regardless of the type, all epithelium is usually separated from the underlying tissue by an extracellular
fibrous basement membrane.
 Different epithelia how differing structures that correlate with their unique functions.
 For example, in cells lining blood vessels or lung alveoli, where transportation of substances occurs
through a selectively permeable surface, there is a simple flat kind of epithelium.
 This is called the simple squamous epithelium (squama means scale of skin).
 Simple squamous epithelial cells are extremely thin and flat and form a delicate lining.
 The oesophagus and the lining of the mouth are also covered with squamous epithelium.
 The skin, which protects the body, is also made of squamous epithelium.

Biology notes by Shubham Sir

 Skin epithelial cells are arranged in many layers to prevent wear and tear. Since they are arranged in a
pattern of layers, the epithelium is called stratified squamous epithelium.
 Where absorption and secretion occur, as in the inner lining of the intestine, tall epithelial cells are
present.
This columnar (meaning 'pillar-like') epithelium facilitates movement across the epithelial barrier.
 In the respiratory tract, the columnar epithelial tissue also has cilia, which are hair-like projections on the
outer surfaces of epithelial cells. These cilia can move, and their movement pushes the mucus forward to
clear it. This type of epithelium is thus ciliated columnar epithelium.
 Cuboidal epithelium (with cube-shaped cells) forms the lining of kidney tubules and ducts of salivary
glands, where it provides mechanical support.
 Epithelial cells often acquire additional specialization as gland cells, which can secrete substances at the
epithelial surface. Sometimes a portion of the epithelial tissue folds inward, and a multicellular gland is
formed. This is glandular epithelium

CONNECTIVE TISSUE
(Blood, Bone, Ligament, Tendon, Cartilage, Adipose Tissue) All Are Examples Of Connective Tissues,
 Blood is a type of connective tissue.
 Why would it be called 'connective' tissue?
 Now, let us look at this type of tissue in some more detail.
 The cells of connective tissue are loosely spaced and embedded in an intercellular matrix.
 The matrix may be jelly like, fluid, dense or rigid.
 The nature of matrix differs in concordance with the function of the particular connective tissue.
 Blood has a fluid (liquid) matrix called plasma, in which red blood corpuscles (RBCs), white blood
corpuscles (WBCs) and platelets are suspended.
Biology notes by Shubham Sir
 The plasma contains proteins, salts and hormones.
 Blood flows and transports gases, digested food, hormones and waste materials to different parts of the
body.
 Bone is another example of a connective tissue.
 It forms the framework that supports the body.
 It also anchors the muscles and supports the main organs of the body.
 It is a strong and non-flexible tissue.
 Bone cells are embedded in a hard matrix that is composed of calcium and phosphorus compounds.
 Two bones can be connected to each other by another type of connective tissue called the ligament.
 This tissue is very elastic.
 It has considerable strength.
 Ligaments contain very little matrix and connect bones with bones.

 Tendons connect muscles to bones and are another type of connective tissue.
 Tendons are fibrous tissue with great strength but limited flexibility.
 Another type of connective tissue, cartilage, has widely spaced cells.
 The solid matrix is composed of proteins and sugars.
 Cartilage smoothens bone surfaces at joints and is also present in the nose, ear, trachea and larynx.
 We can fold the cartilage of the ears, but we cannot bend the bones in our arms.
 Think of how the two tissues are different!
 Areolar connective tissue is found between the skin and muscles, around blood vessels and nerves and in
the bone marrow.
 It fills the space inside the organs, supports internal organs and helps in repair of tissues.
 Where are fats stored in our body?

Biology notes by Shubham Sir

 Fat storing adipose tissue is found below the skin and between internal organs
 The cells of this tissue are filled with fat globules.
 Storage of fats also lets it act as an insulator.

MUSCULAR TISSUE
 Muscular tissue consists of elongated cells, also called muscle fibres.
 This tissue is responsible for movement in our body. Muscles contain special proteins called
contractile proteins, which contract and relax to cause movement.
 We can move some muscles by conscious will. Muscles present in our limbs move when we want them
to, and stop when we so decide. Such muscles are called voluntary muscles.
 These muscles are also called skeletal muscles as they are mostly attached to bones and help in body
movement. Under the microscope, these muscles show alternate light and dark bands or striations when
stained appropriately. As a result, they are also called striated muscles.

NERVOUS TISSUE
 All cells possess the ability to respond to stimuli.
 However, cells of the nervous tissue are highly specialised for being stimulated and then transmitting the
stimulus very rapidly from one place to another within the body.
 The brain, spinal cord and nerves are all composed of the nervous tissue. The cells of this tissue are
called nerve cells or neurons.
Biology notes by Shubham Sir
 A neuron consists of a cell body with a nucleus and cytoplasm, from which long thin hair-like parts
arise, Usually each neuron has a single long part (process). called the axon, and many short, branched
parts (processes) called dendrites.
 An individual nerve cell may be up to a metre long.
 Many nerve fibres bound together by connective tissue make up a nerve.
 The signal that passes along the nerve fibre is called a nerve impulse.
 Nerve impulses allow us to move our muscles when we want to.
 The functional combination of nerve and muscle tissue is fundamental to most animals.
 This combination enables animals to move rapidly in response to stimuli.
 Nerves include non-neuronal Schwann cells that coat the axon in Myelin (a sheath made by fat and
protein molecules).

Biology notes by Shubham Sir

 IMPROVEMENT IN FOOD RESOURCES
 We know that all living organisms need food.
 Food supplies proteins, carbohydrates, fats, vitamins and minerals, all of which we require for body
development, growth and health.
 Both plants and animals are major sources of food for us.
 We obtain most of this food from agriculture and animal husbandry.

 Our population is more than one billion people, and it is still growing.
 As food for this growing population, we will soon need more than a quarter of a billion tonnes of grain
every year.
 This can be done by farming on more land.
 But India is already intensively cultivated.
 Efforts to meet the food demand by increasing food production have led to some successes so far.
 We have had the green revolution, which contributed to increased food-grain production.
 We have also had the white revolution, which has led to better and more efficient use as well as
availability of milk.
 However, these revolutions mean that our natural our natural resources are getting used more
intensively.
 As a result, there are more chances of causing damage to our natural resources to the point of destroying
their balance completely.
 Therefore, it is important that we should increase food production without degrading our environment
and disturbing the balances maintaining it.

M.S. Swaminathan Green Revolution. White Revoluation

 Hence, there is a need for sustainable practices in agriculture and animal husbandry.
 Also, simply increasing grain production for storage in warehouses cannot solve the problem of
malnutrition and hunger.
 Food security depends on both availability of food and access to it.
 The majority of our population depends on agriculture for their livelihood.
 Increasing the incomes of people working in agriculture is therefore necessary to combat the problem of
hunger.
IMPROVEMENT IN CROP YIELDS
 Cereals such as wheat, rice, maize, millets and sorghum provide us carbohydrate for energy
Biology notes by Shubham Sir
 requirement.
 Pulses like gram (chana), pea (matar), black gram (urad), green gram (moong), pigeon pea (arhar), lentil
(masoor), provide us with protein.
 And oil seeds including soyabean, ground nut, sesame, castor, mustard, linseed and sunflower provide us
with necessary fats.
 Vegetables, spices and fruits provide a range of vitamins and minerals in addition to small amounts of
proteins, carbohydrates and fats.
 In addition to these food crops, fodder crops like berseem, oats or sudan grass are raised as food for the
livestock.
 Different crops require different climatic conditions, temperature and photoperiods for their growth and
completion of their life cycle.
 Photoperiods are related to the duration of sunlight.
 Growth of plants and flowering are dependent on sunlight.
 As we all know, plants manufacture their food in sunlight by the process of photosynthesis.
 There are some crops, which are grown in rainy season, called the kharif season from the month of
 June to October, and some of the crops are grown in the winter season, called the rabi season from
November to April.
 Paddy, soyabean, pigeon pea, maize, cotton, green gram and black gram are kharif crops, whereas wheat,
gram, peas, mustard, linseed are rabi crops.

CROP VARIETY IMPROVEMENT

 This approach depends on finding a crop variety that can give a good yield.
 Varieties or strains of crops can be selected by breeding for various useful characteristics such as disease
resistance, response to fertilizers, product quality and high yields.
 One way of incorporating desirable characters into crop varieties is by hybridization.
 Hybridization refers to crossing between genetically dissimilar plants.
 This crossing may be inter-varietal (between different varieties), inter-specific (between two different
species of the same genus) or inter-generic (between different genera).
 Another way of improving the crop is by introducing a gene that would provide the desired
characteristic.
 This results in genetically modified crops.
 For new varieties of crops to be accepted, it is necessary that the variety produces high yields under
different conditions that are found in different areas.
 Farmers would need to be provided with good quality seeds of a particular variety, that is, the seeds
should all be of the same variety and germinate under the same conditions.
 Cultivation practices and crop yield are related to weather, soil quality and availability of water.
 Since weather conditions such as drought and flood situations are unpredictable, varieties that can be
grown in diverse climatic conditions are useful.

Biology notes by Shubham Sir

 Similarly, varieties tolerant to high soil salinity have been developed.

MICRO & MACRONUTRIENTS (V.IMP)

DIRECT QUESTIONS WERE ASKED ON

MACRO AND MICRO NUTRIENTS....
 Using biological waste material is also a way of recycling farm waste.
 Based on the kind of biological material used, manure can be classified as:
 Compost and vermi-compost: The process in
 which farm waste material like livestock excreta
 (cow dung etc.), vegetable waste, animal refuse,
 domestic waste, sewage waste, straw, eradicated weeds etc. is decomposed in pits is known as
composting. The compost is rich in organic matter and nutrients. Compost is also prepared by using
earthworms to hasten the process of decomposition of plant and animal refuse. This is called
vermicompost.
 Green manure: Prior to the sowing of the crop seeds, some plants like sun hemp or guar are grown and
then mulched by ploughing them into the soil. These green plants thus turn into green manure
 which helps in enriching the soil in nitrogen and phosphorus.
FERTILIZERS:
 Fertilizers are commercially produced plant nutrients.
 Fertilizers supply nitrogen, phosphorus and potassium.

Biology notes by Shubham Sir

 They are used to ensure good vegetative growth (leaves, branches and flowers), giving rise to healthy
plants.
 Fertilizers are a factor in the higher yields of high- cost farming.
 Fertilizers should be applied carefully in terms of proper dose, time, and observing pre and post-
application precautions for their complete utilization.
 For example, sometimes fertilizers get washed away due to excessive irrigation and are not fully
absorbed by the plants.

CROPPING PATTERNS
 Different ways of growing crops can be used to give maximum benefit.
 Mixed cropping is growing two or more crops simultaneously on the same piece of land. This reduces
risk and gives some insurance against failure of one of the crops.
 Inter-cropping is growing two or more crops simultaneously on the same field in a definite pattern.

 The crops are selected such that their nutrient requirements are different.
 This ensures maximum utilisation of the nutrients supplied, and also prevents pests and diseases from
spreading to all the plants belonging to one crop in a field.
 This way, both crops can give better returns.
Biology notes by Shubham Sir
 The growing of different crops on a piece of land in a pre-planned succession is known as crop rotation.
 Depending upon the duration, crop rotation is done for different crop combinations.

 The availability of moisture and irrigation facilities decide the choice of the crop to be cultivated after
one harvest.
 If crop rotation is done properly then two or three crops can be grown in a year with good harvests.
CROP PROTECTION MANAGEMENT
 Field crops are infested by a large number of weeds, insect pests and diseases.
 If weeds and pests are not controlled at the appropriate time then they can damage the crops so much
that most of the crop is lost.
 Weeds are unwanted plants in the cultivated field, for example, Xanthium (gokhroo), Parthenium (gajar
ghas), Cyperinus rotundus (motha).
 They compete for food, space and light.
 Weeds take up nutrients and reduce the growth of the crop.
 Therefore, removal of weeds from cultivated fields during the early stages of crop growth is essential for
a good harvest.
 Generally insect pests attack the plants in three ways:
 hey cut the root, stem and leaf,
 they suck the cell sap from various parts of the plant, and
 They bore into stem and fruits.
 They thus affect the health of the crop and reduce yields.
 Diseases in plants are caused by pathogens such as bacteria, fungi and viruses.
 These pathogens can be present in and transmitted through the soil, water and air.

 Weeds, insects and diseases can be controlled by various methods.

 One of the most commonly used methods is the use of pesticides, which include herbicides,
insecticides and fungicides.
 These chemicals are sprayed on crop plants or used for treating seeds and soil.

Biology notes by Shubham Sir

 However, excessive use of these chemicals creates problems, since they can be poisonous to many plant
and animal species and cause environmental pollution.
 Weed control methods also include mechanical
 removal.
 Preventive methods such as proper seed bed preparation, timely sowing of crops, intercropping and
crop rotation also help in weed control.
 Some other preventive measures against pests are the use of resistant varieties, and summer ploughing,
in which fields are ploughed deep in summers to destroy weeds and pests.

Nutritional values of animal products

Animal Per cent (%) Nutrients

Products
Fat Protein Sugar Minerals Water Vitamins
Milk (Cow) 3.60 4.00 4.50 0.70 87.20 B1,B2,B12,D,E
Egg 12.00 13.00 “ 1.00 74.00 B2,D
Meat 3.60 21.10 “ 1.10 74.20 B2, B12
Fish 2.50 19.00 “ 1.30 77.20 Niacin, D,A
*Present is very small amounts.

Biology notes by Shubham Sir

 DIVERSITY IN LIVING
ORGANISMS
 Attempts at classifying living things into groups have been made since time immemorial.
 Greek thinker Aristotle classified animals according to whether they lived on land, in water or in the air.
 This is a very simple way of looking at life, but misleading too.
 For example, animals that live in the sea include corals, whales, octopuses, starfish and sharks. see that
these are very different
 We can immediately from each other in numerous ways.
 In fact, habitat is the only point they share in common.
 This is not an appropriate way of making groups of organisms to study and think about.
Classification and Evolution
 All living things are identified and categorized on the basis of their body design in form and function.
 Some characteristics are likely to make more wide- ranging changes in body design than others.
 There is a role of time in this as well.
 So, once a certain body design comes into existence, it will shape the effects of all other subsequent
design changes, simply because it already exists.
 In other words, characteristics that came into existence earlier are likely to be more basic than
characteristics that have come into existence later.
 This means that the classification of life forms will be closely related to their evolution.
What is evolution?
 Most life forms that we see today have arisen by an accumulation of changes in body design that allow
the organism possessing them to survive better.
 Charles Darwin first described this idea of evolution in 1859 in his book, The Origin of Species.

Biodiversity
 Biodiversity means the diversity of life forms.
 It is a word commonly used to refer to the variety of life forms found in a particular region.
 Diverse life forms share the environment, and are affected by each other too.
 As a result, a stable community of different species comes into existence.
 Humans have played their own part in recent times in changing the balance of such communities.

Biology notes by Shubham Sir

 Of course, the diversity in such communities is affected by particular characteristics of land, water,
climate and so on.
 Rough estimates state that there are about ten million species on the planet, although we actually know
only one or two millions of them.
 The warm and humid tropical regions of the earth, between the Tropic of Cancer and the Tropic of
Capricorn, are rich in diversity of plant and animal life. This is called the region of megadiversity.
 Of the biodiversity on the planet, more than half is concentrated in a few countries - Brazil, Colombia,
Ecuador, Peru, Mexico, Zaire, Madagascar, Australia, China, India, Indonesia and Malaysia.

The Hierarchy of Classification Groups

 Biologists, such as Ernst Haeckel (1894), Robert Whittaker (1969) and Carl Woese (1977) have tried to
classify all living organisms into broad categories, called kingdoms.
 The classification Whittaker proposed has five kingdoms:
 Monera, Protista, Fungi, Plantae and Animalia, and is widely used.
 These groups are formed on the basis of their cell structure, mode and source of nutrition and body
organisation.
 The modification Who introduced by dividing the Monera into Archaebacteria (or Archaea) and
Eubacteria (or Bacteria) is also in use.

 Thus, by separating organisms on the basis of a hierarchy of characteristics into smaller and smaller
groups, we arrive at the basic unit of classification, which is a 'species'.
 So what organisms can be said to belong to the same species?
 Broadly, a species includes all organisms that are similar enough to breed and perpetuate.

Biology notes by Shubham Sir

 The important characteristics of the five kingdoms of Whittaker are as follows:
1.Monera
2.Protista
3.Fungi
4.Plantae
5.Animalia

1.MONERA

 These organisms do not have a defined nucleus or organelles, nor do any of them show multi-cellular
body designs.
 On the other hand, they show diversity based on many other characteristics.
 Some of them have cell walls while some do not.
 Of course, having or not having a cell wall has very different effects on body design here from having or
not having a cell wall in multicellular organisms.

Biology notes by Shubham Sir

 The mode of nutrition of organisms in this group can be either by synthesising their own food
(autotrophic) or getting it from the environment (heterotrophic).
 This group includes bacteria, blue-green algae or cyanobacteria, and mycoplasma.

2.PROTISTA

 This group includes many kinds of unicellular eukaryotic organisms.

 Some of these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.
 Their mode of nutrition can be autotrophic or heterotrophic.
 Examples are unicellular Algae, Euglena, Diatoms and Protozoans.

Biology notes by Shubham Sir

3.FUNGI

 These are heterotrophic eukaryotic organisms.

 Some of them use decaying organic material as food and are therefore called saprotrophs.
 Others require a living protoplasm of a host organism for food.
 They are called parasites.
 Many of them have the capacity to become multicellular organisms at certain stages in their lives.
 They have cell-walls made of a tough complex sugar called chitin.
 Examples are yeasts, molds and mushrooms.
 Some fungal species live in permanent mutually dependent relationships with blue-green algae (or
cyanobacteria).
 Such relationships are called symbiotic.
 These symbiotic life forms are called lichens.
 We have all seen lichens as the slow-growing large coloured patches on the bark of trees.

4.Plantae
 These are multicellular cukaryotes with cell walls.
 They are autotrophs and use chlorophyll for photosynthesis.
 Thus, all plants are included in this group.
 Since plants and animals are most visible forms of the diversity of life around us

Biology notes by Shubham Sir

 The first level of classification among plants depends on whether the plant body has well differentiated,
distinct parts.
 The next level of classification is based on whether the differentiated plant body has special tissues for
the transport of water and other substances.
 Further classification looks at the ability to bear seeds and whether the seeds are enclosed within fruits.
THALLOPHYTA
 Plants that do not have well-differentiated body design fall in this group.
 The plants in this group are commonly called algae.
 These plants are predominantly aquatic.
 Examples are Spirogyra, Ulothrix, Cladophora, Ulva and Chara

Biology notes by Shubham Sir

BRYOPHYTA
 These are called the amphibians of the plant kingdom.
 The plant body is commonly differentiated to form stem and leaf-like structures.
 However, there is no specialised tissue for the conduction of water and other bundles) from one part of
the substances(Vascular plant body to another.
 Examples are moss (Funaria) and Marchantia

PTERIDOPHYTA
 In this group, the plant body is differentiated into roots, stem and leaves and has specialised tissue for the
conduction of water and other substances from one part of the plant body to another.
 Some examples are Marsilea, ferns and horse-tails.
 The reproductive organs of plants in all these three groups are very inconspicuous, and they are therefore
called 'cryptogams', or 'those with hidden reproductive organs'.
 On the other hand, plants with well differentiated reproductive parts that ultimately make seeds are
called phanerogams.
 Seeds are the result of sexual reproduction process.
 They consist of the embryo along with stored food, which assists for the initial growth of the embryo
during germination.
 This group is further classified, based on whether two groups: gymnosperms and angiosperms

Biology notes by Shubham Sir

GYMNOSPERMS
 This term is derived from two Greek words: gymno-means naked and sperma- means seed.
 The plants of this group bear naked seeds and are usually perennial, evergreen and woody.
 Examples are pines and deodar

ANGIOSPERMS
 This word is made from two Greek words: angio means covered and sperma- means seed.
 These are also called flowering plants.
 The seeds develop inside an ovary which is modified to become a fruit.
 Plant embryos in seeds have structures called cotyledons.
 Cotyledons are called 'seed leaves' because in many instances they emerge and become green when the
seed germinates.
 The angiosperms are divided into two groups on the basis of the number of cotyledons present in the
seed.
 Plants with seeds having a single cotyledon are called monocotyledonous or monocots.
 Wheat, corn, millet, lilies, sugarcane, banana, onions, ginger, palm, and bamboo.
 Plants with seeds having two cotyledons are called dicots
 Wheat, corn, millet, lilies, sugarcane, banana, onions, ginger, palm, and bamboo.

Biology notes by Shubham Sir

5.Animalia

 These are organisms which are eukaryotic, multicellular and heterotrophic.

 Their cells do not have cell-walls. Most animals are mobile.
 They are further classified based on the extent and type of the body design differentiation found.

Biology notes by Shubham Sir

PORIFERA
 The word Porifera means organisms with holes.
 These are non-motile animals attached to some solid support.
 There are holes or 'pores, all over the body.
 These lead to a canal system that helps in circulating water throughout the body to bring in food and
oxygen.
 Covered with a hard outside layer or exo-skeleton.
 The body design involves very minimal differentiation and division into tissues.
 They are commonly called sponges, and are mainly found in marine habitats.

Biology notes by Shubham Sir

 Parifera
COELENTERATA (CNIDARIA)
 These are animals living in water.
 They show more body design differentiation.
 There is a cavity in the body but there is no body cavity (Coelen) between epidermis(outer) and
gastrodermis(inner), therefore they are Acoelomates
 The body is made of two layers of cells: one makes up cells on the outside of the body(ectoderm), and
the other makes the inner lining of the body(endoderm) i.e Diploblastic
 Some of these species live in colonies (corals), while others have a solitary like-span (Hydra). Jellyfish
and sea anemones are common examples.
 They show Radial symmetry

PLATYHELMINTHES

 The body of animals in this group is far more complexly designed than in the two other groups we have
considered so far.
 The body is bilaterally symmetrical, meaning that the left and the right halves of the body have the same
design,

Biology notes by Shubham Sir

 There are three layers of cells from which differentiated tissues can be made, which is why such animals
are called triploblastic. (Ectoderm, Mesoderm and Endoderm)
 This allows outside and inside body linings as well as some organs to be made.
 However, there is no true internal body cavity or coelom, in which well developed organs can be
accommodated. Acoelomates
 They are BTA (Bilaterally Symmetrical, Triplobalastic, Acoelomates).
 The body is flattened dorsoventrally (meaning from top to bottom), which is why these animals are
called flatworms.
 They are either free-living or parasitic.
 Some examples are free-living animals like planarians, or parasitic animals like liverflukes

NEMATODA

 The nematode body is also bilaterally symmetrical and triploblastic.

 However, the body is cylindrical rather than flattened.
 There are tissues, but no real organs, although a sort of body cavity or a pseudocoelom, is present.
 They are BTP ( bilaterally symmetrical, triploblastic and pseudocoelom)
 These are very familiar as parasitic worms causing diseases, such as the worms causing elephantiasis
(filarial worms) or the worms in the intestines (roundworm or pinworms).

ANNELIDA

 Annelid animals are also bilaterally symmetrical and triploblastic, but in addition they have a true body
cavity (Coelomate). This allows true organs to be packaged in the body structure.
 They are BTC (bilaterally symmetrical, triploblastic, and Coelomate)
 This differentiation occurs in a segmental fashion, with the segments lined up one after the other from
head to tail.

Biology notes by Shubham Sir

 These animals are found in a variety of habitats-fresh water, marine water as well as land.
 Earthworms and leeches are familiar examples

ARTHROPODA (*Keede-Makode)

 This is probably the largest group of animals.

 These animals are bilaterally symmetrical, triploblastic and segmented.
 There is an open circulatory system, and so the blood does not flow in well defined blood vessels.
 The coelomic cavity is blood-filled i.e, coelomate.
 They are BTS (bilaterally symmetrical, triploblastic and segmented)
 They have jointed legs (the word 'arthropod' means 'jointed legs').
 Some familiar examples are prawns, butterflies, houseflies, spiders, scorpions and crabs

MOLLUSCA

 In the animals of this group, there is bilateral symmetry and triploblastic.

 Coelomate, however coelomic cavity is reduced in this group.
 They are BTC (bilaterally symmetrical, triploblastic, and Coelomate)
 There is little segmentation. de e parte a ti y
 They have an open circulatory system and kidney- like organs for excretion.
 There is a foot that is used for moving around.
 Examples are snails and mussels

Biology notes by Shubham Sir

ECHINODERMATA

 In Greek, echinos means hedgehog (spiny mammal), and derma means skin.
 Thus, these are spiny skinned organisms.
 These are exclusively free-living marine animals.
 They are triploblastic and have a coelomic cavity.
 They show Radial Symmetry.
 They Shows (Radial Symmetry, triploblastic and coelomic cavity)
 They also have a peculiar water-driven tube system that they use for moving around.
 They have hard calcium carbonate structures that they use as a skeleton.
 Examples are sea-stars and sea urchins

PROTOCHORDATA

 These animals are bilaterally symmetrical, triploblastic and have a coelom. i.e.,
 In addition, they shốw a new feature of body design, namely a notochord, at least at sornestages during
their lives.
 The notochord is a long rod-like support structure (chord=string) that runs along the back of the animal
separating the nervous tissue from the gut.
 It provides a place for muscles to attach for ease of movement.
 Protochordates may not have a proper notochord present at all stages in their lives or for the entire length
of the animal.
 Protochordates are marine animals.
 Examples are Balanoglossus, Herdmania and

Biology notes by Shubham Sir

 Amphioxus scaleless.
 They are ectoparasites or borers of other vertebrates.
 Petromyzon (Lamprey) and Myxine (Hagfish) are examples.

VERTEBRATA

 These animals have a true vertebral column and internal skeleton, allowing a completely different
distribution of muscle attachment points to be used for movement
 Vertebrates are bilaterally symmetrical, triploblastic, coelomic and segmented, with complex
differentiation of body tissues and organs
 BTC
 All chordates possess the following features:
(i) have a notochord
(ii) have a dorsal nerve cord
(iii) are triploblastic
(iv) have paired gill pouches
(v) are coelomate.

Vertebrates: are grouped into six classes:

1.Cyclostomata,
2. Pisces,
3. Amphibia,
4. Reptilia,
5. Aves,
6. Mammalia.

CYCLO STOMATA
Biology notes by Shubham Sir
 Cyclostomes are jawless vertebrates.
 They are characterised by having an elongated eel-like body, circular mouth, slimy skin and are
scaleless. They are ectoparasites or borers of other verterbrates.
 Petromyzon (Lamprey) and Myxine (Hagfish) are examples.

PISCES

 These are fish.

 They are exclusively aquatic animals.
 Their skin is covered with scales/ plates.
 They obtain Oxygen dissolved in water by using gills.
 The body is streamlined, and a muscular tail is used for movement.
 They are cold-bloodel and their heatts have only
 bvo chanmbers, unlike the four that humans have.
 They lay eggs.
 We can think of many kinds of fish. some with skeletons made entirely of cartilage, such as sharks, and
sonme with a skeleton made of both bone and cartilage, such as tuna or rohu.

Biology notes by Shubham Sir

AMPHIBIA

 These animals differ from the fish in the lack of scales, in having mucus glands in the skin, and a three-
chambered heart.
 Respiration is through either gills or lungs.
 They lay eggs.
 These animals are found both in water and on land.
 Frogs, toads and salamanders are some examples

REPTILIA

 These animals are cold-blooded, have scales and breathe through lungs.
 While most of them have a three-chambered heart, crocodiles have four heart chambers.
 They lay eggs with tough coverings and do not need to lay their eggs in water, unlike amphibians.
 Snakes, turtles, Izards and crocodiles fall in this category.

AVES

 These are warm-blooded animals and have a four chambered heart

Biology notes by Shubham Sir

 They lay eggs.
 There is an outside covering of feathers, and two forelimbs are modified for flight.
 They breathe through lungs.
 All birds fall in this category.

MAMMALIA
 Mammals are warm-blooded animals with for chambered hearts
 They have mammary glands for the production milk to nourish their young.

 Their skin has hairs as well as Sweat and oil gland
 Most mammals familiar to us produce live ones.
 However, a few of them, like the platypus and the echidna lay eggs, and some, like kangaroos give
birth to very poorly developed young ones.

Human

Biology notes by Shubham Sir

 Vertebrate Comparison Chart

Body temp Heart Outer Resp.O2 Fert. Site Embryo

chambers Cover And CO2 Dev.
Fish Cold 2 Scales Gills External in In water soft
water eggs
Amphibian Cold (ectoth 3 Molts skin Skin and External in In water soft
ermk.) with mucous Lungs water eggs
Reptile Cold 3 except Dry skin Lungs Internal External
alligators and with scales leathery eggs
crocs 4 hatch
Bird Warm (endot 4 Skin with Lungs Internal External hard
hermic) feathers shell hatch
Ammonal warm 4 skin Lungs Internal Internal born

Biology notes by Shubham Sir

 HEALTH & DISEASE

Health:
Health is a state of complete physical, mental and social well-being
Disease:
when the body is not at ease i.e. comfortable then it is said to have a disease.
When there is a disease, the functioning or appearance of one or more systems of the body changes

Acute Diseases:
Acute diseases are those that last fora very short time. These diseases can be fatal and are usually caused
by an extermal agent. E.g. common cold, lu, pneumonia, malaria, etc.

Chronic Diseases
Chronic diseases are those that last for a long time. They take a lot of time to heal and can be caused by
any external or internal factor. E.g. elephantiasis, asthma, tuberculosis, diabetes, cancer, etc.

Infectious Diseases(Communicable diseases)

Diseases that are caused by pathogens and can spread to other individuals in the population are called
infectious díseases. E.g. conmon cold, smallpox oalaria, HIV etc

Non-infectious diseases(Non-Communicable diseases)

Diseases that cannot spread from one individual to another are called non-infectious diseases. Usually,
these ses are not caused by a pathogen. E-g- diabetes and high blood pressure.

Infectious Agents Diseases

Viruses Common cold, infuenza, measles, chickeń pox, AIDS, Hepatitis-B etc.
Bacteria Cholera, typhoid, TB, tetanus, anthrax, food poisoning etc.
Fungi Skin infections
Protozoan Malaria, kala-azar, amoebic dysentery. sleeping sickiess
Worms Intestinal infections, elephantiasis

Pathogens
 Pathogens arc external agents that cause diseases in other organisms. This pathogen includes harmful
microbes or microorganisms such as bacteria, viruses, fungi or protozoa.

Vector

 Vector are those organisms that carry a pathogen from the host to the recipient. Mosquitoes, rats and
mice are some of common vectors that carry infectious diseases.

Bacteria

Bacteria are microorganisms that are seen in almost all environmental conditions. Not all bacteria are
harmful to pathogens. Some bacteria are also beneficial to human beings. Bacteria are beneficial for,
digestion, extracting antibiotics from them,
nitrogen fixation, etc. A few of the common diseases caused by bacteria are cholera, pneumonia,
tuberculosis, etc.
Biology notes by Shubham Sir
S.No. Disease Pathogen Main Symptoms
1 Cholera Comma shaped -Mbrio Severe diarrhoea and
(Haiza) coma (Vcholerac) vomiting
2 Pneunonia Diplococcus or Sudden chill, chest pain,
Streptococcus difficulty in in breathing
pneumonioe
3 Typhoid Rod like motile Constant fever
Salmonella typhi
4 Tubercuslosis Mcobacterium Cough, bloody sputum.
tuberculosis (rod chest pain, loss of weight
shaped)..

Virus
A virus is a microorganism that is always pathogenic in nature. They do not have molecular machinery
to replicate without a host. Therefore, they enter the host cell and replicate and, in the process, destroy
the host cell. A few of the common diseases spread by the viruses are cold, influenza, dengue fever
AIDS, etc.
S.No. Disease Pathogen Main Symptoms
1. Infiuenza Myrovius Nasal discharge, sheezing.
(Flu) Infuenzae coughing. fever, body ache

Fungi
Fungi are a group of organisms which are eukaryotic in nature and saprophytic in nutrition. They could
be either unicellular or multicellular organisms. Many common skin infections, such as ringworm, nail
infection etc., are examples of fungal diseases.

Parasites
A parasite is an organism that lives in another organism, called the host, and often harms it. It is
dependent on its host for survival -it has to be in the host to live, grow and multiply.

AIDS
AIDS stands for acquired immunodeficiency syndrome. It is caused by the Human Immunodeficiency
virus. AIDs systematically destroys the immune system of the patient, leaving them vulnerable to the
easiest of diseases.

Immunisation
Immunisation is the process whereby a person is made immune or resistant to an infectious disease.
Vaccines àre the common means to immunise people. The process of immunisation is based on the cells
of the immune system retaining the memory of a pathogen. The vaccine contains the inactivated or
weakened pathogen or its antigen (protein).
Factopedia
Traditional Indian and Chinese medicinal systems sometimes deliberately rubbed the skin crusts from
smallpox victims into the skin of healthy people. They thus hoped to induce a mild form of smallpox that
would create resistance against the disease. Famously, two centuries ago, an English physician named

Biology notes by Shubham Sir

Edward Jenner, realised that milkmaids who had had cowpox did not catch smallpox even during
epidemics. Cowpox is a very mild diseasse.
Jenner tried deliberately giving cowpox to people (as he can be seen doing in the picture), and found that
they were now resistant to smallpox. This was because the smallpox virus is closely related to the
cowpox virus. ‘Cow' is vacca' in Latin, and cowpox is vaccinla' (EPFO 2020)
From these roots, the word 'vaccination' has come into our usage.

Factopedia
Then two Australians made a discovery that a bacterium, Helicobacter pylori (CDS /NDA), was
responsible for peptic ulcers. Robin Warren (born 1937), a pathologist from Perth, Australia, saw these
small curved bacteria in the lower part of the stomach in many patients. He noticed that signs of
inflammation were always present around these bacteria. Barry Marshall (born 1951), a young clinical
fellow, became interested in Warren's findings and succeeded in cultivating the bacteria from these
sources.

Name of the Causing ngentl Vector/ mode of Symptoms Effects

disease pathogen infection
Typhoid Salmonellatyphi By contaminated Continued high Can be diagnosed
(Bacteria) food and water fever, headache, by Widal test
stomachache, Intestinal
constipation and perforation in
loss of appetite severe cases
Pneumonia Streptococcus By inhaling Fever, chills, Respiration
pneumoniae, droplets or cough and problems due to
Hemophilus aerosols released headache fluid that gets
influenzae by an infected filled in the alveoli
(Bacteria) person or using
infected utensils

Common cold Rhinoviruses By cough, sneezes Nasal congestion Nose and

and contaminated and discharge, sore Respiratory
objects throat, cough, passage
headache
Malaria Plasmodium Female anopheles High fever with The parasite
falciparum, mosquito is a chills multiplies in liver
P. vivax vector Spread by cells, attacks rbcs
(Protozoan) mosquito bite and rupture
Amoebic Entamoeba Housefly are a Constipation, Infection in the
Dysentery histolytica carrier Spread by abdominal pain, large intestine
(Protozoan) contaminated food mucous and blood
by the faecal in the stool
matter
Ascariasis Ascaris Contaminated muscular pain, Blockage of
(Helimenthes) water, vegetables, internal bleeding intestinal passage
fruits Parasites encaenia, fever
eggs are exerted
our in faeces of the
infected person,
which
contaminates soil
Filarlasis/ Wuchereià Bloodsucking Inflammation of Lymphatic
Elephantiasis bụncroft black flies and he lower limb and vessels, especially
W.malayi female mosquito genital organs of the lower limbs,
Biology notes by Shubham Sir
 (Helminthes) act as a vector got blocked
Ringworms Microsporum, Spread from the Dry scaly lesions, Effects skin, nail
Trichophyton, soil, towel, clothes itchy skin in he scalp
Epidermophyton or comb of an groin or between
(Fungi) infected person the toes

 Leishmania, the protozoan organism that causes kala-azar

 Staphylococci, the bacteria which can cause acne
 Trypanosoma, the protozoan organism responsible for sleeping sickness. (UPSC’s Fav)
 Adult roundworm (Ascaris lumbricoides) from the small intestine.

Biology notes by Shubham Sir

 LIFE PROCESSES
Life processes

 Constantly exhibit the functions of maintenance and repair in living organisms

 Some Examples- Digestion, Respiration, Circulation ete.

Nutritien

 Pocess ofobtaining nutrients from the environment ie. intake of food and then its digestion in the body.
 Two types - Autotrophic (selsuficient for food) and Heterotrophie (dependent on others for food).

Autotrophie Nutrition :

Autotrophic nutrition is present in plants, algae and some bacteria. Organisams produce their own food u
using light energy or chemical energy by photosynthesis or chemosynthesis, respectively.
6CO2 + 12H2O → C6H12O6 + 6O2 + 6H2O
 This material is taken in the form of carbon dioxide and water which is converted into carbohydrates in
the presence of sunlight and chlorophyll Carbohydrates are utilised for providing energy to the plant.
The
carbohydrates which are not used immediately are stored in the form of starch, which serves as the
internal energy reserve to be used as and when required by the plant.
The following events occur during this process
(1) Absorption of light energy by chlorophyll.
(2) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen &
oxygen.
(3) Reduction of carbon dioxide to carbohydrates
Stomata which are tiny pores present on the surface of the leaves, Massive amounts of gaseous
exchange takes place in the leaves through these pores for the purpose of photosynthesis. But it is
important to note here that exchange of gases occurs across the surface of stems, roots and leaves as
well. Since large amounts of water can also be lost through these stomata, the plant closes these pores
when it does not need carbon dioxide for photosynthesis. The opening and closing of the pore is a
function of the guard cells. The guard cells swell when water flows into them, causing the stomatal pore
to open. Similarly the pore closes if the guard cells shrink.

Heterotrophic Nutrition
Heterotrophic nutrition is present in bacteria, fungi and animals. They derive energy from organic
compounds. Such as animals eating plants or other animals for food. Heterotrophic nutrition has
subtypes such as holozoic, saprophytic and parasitic nutrition.

Saprophytic Nutrition
Some organisms feed on dead and decaying organic matter. This mode of nutrition is called saprophytic
nutrition.
 The food is partially digested outside the body and then it is absorbed.
 E.g. Fungi are saprophytes.

Biology notes by Shubham Sir

Parasitic Nutrition

Some organisms feed at the expense of another organism and in turn cause harm. This is called the parasitic
mode of nutrition.

 These parasites live on the body or in the body of a host organism and derive the nutrients directly from
the body of the host.
 Eg. Leech is an ectoparasite while Ascaris is an endoparasite. Cuscuta is a parasitic plant.

HOLOZOIC NUTRITION

Holozoic nutrition is a type of heterotrophic nutrition that is characterized by the internalization (ingestion)
and internal processing of liquids or solid food particles.

Nutrition In Human

The human digestive system comprises of the alimentary canal and associated digestive glands.

 Alimentary Canal: It comprises of mouth, esophagus, stomach, small intestine and large intestine.
 Associated Glands: Main associated glands are
 Salivary gland
 Gastric Glands
 Liver
 Pancreas

Mouth or Buccal Cavity:

 The mouth has teeth and tongue. Salivary glands are also present in the mouth.
 The tongue has gustatory receptors which perceive the sense of taste.
 e tongue helps in turning over the food so that saliya can be properly mixed in it.
 Teeth help in breaking down the food int0 smaller particles so that, swallowing of food becomes easier.
 There are four types of teeth in hurnan beings. The incisor teeth are used for cutting the food.
 The canine teeth are used for tearing the food and for cracking hard substances.
 The premolars are used for the coarse grinding of food. The molars are used for fine grinding of food.

Saliary glands secrete saliva: Saliya makes the food slippery which makes it easy to swallow the food.
Saliva also contains the enzyme salivary amylase or ptyalin Salivarý anykse digests starch and converts it
into sucrose, (maltose).

Stomach
 Stomach is a bag-like organ. Highly muscular walls of the stomach help in churning the food.
 The walls of the stomach secrete hydrochloric acid. Hydrochloric acid kills the germs which may be
present in food.
Biology notes by Shubham Sir
 Moreover, it makes the medium inside the stomach as acidic. The acidic medium is necessary for gastric
enzymes to work
 The enzyme pepsin, secreted in the stomach does partial digestion of protein.
 The mucus, secreted by the walls of the stomach saves the inner lining of the stomach from getting
damaged from hydrochloric acid.

Small Intestine: It is a highly coiled tube-like structure. The small intestine is longer than the large
intestine but its lumen is smaller than that of the large intestine. The small intestine is divided into three
parts, like duodenum, jejunum and ileum.

Liver: Liver is the largest organ in the human body. The liver manufactures bile, which gets stored in the
gall bladder. From the gall bladder, bile is released as and when required.

Digestive Glands
 Several glands produce digestive juices that help in digestion of the food.
 Salivary glands, Gastric glands, Liver, Gallbladder, Pancreas are few to name.
 Salivary glands secrete saliya which initiates digestion in the mouth itself.
 Gastric glands present in the wall of the stomach secrete hydrochloric acid and enzyme pepsin.
 The liver secretes bile which is stored in the gallbladder. Bile helps in digestion of fats.
 The pancreas secretes many digestive enzymes and its secretion is called as pancreatic juice.
 Enzymes like trypsin, chymotrypsin, lipase, amylase are present in the pancreatic juice.

Pancreas
 The pancreas is a long, flat gland present behind the stomach in humans.
 It is one of the major digestive glands and is of mixed nature i.e, endocrine as well as exocrine,
 As an endocrine organ, it secretes two hormones called insulin and glucagon which maintain the blood
sugar level.
 As an exocrine gland, it secretes pancreatic juice which is nothing but a mixture of many digestive
enzymes.
 The digestive enzymes secreted by the pancreas include trypsin and chymotrypsin and proteases which
digest proteins.
 It also includes amylase which digests the starch content of the food.
 Pancreatic lipases are the pancreatic enzymes that help in digestion of fats.

Digestive Juices
 Pancreatic juice, bile and intestinal juice (succus entericus) are collectively called digestive iuie
 A common duct from digestive glands pours the secretions into the duodenum.
 Chyme enters the small intestine where complete digestion takes place due to the action of varies
enzymes.
 In the duodenum, the acidity of chyme is turned to alkalinity by the action of bile coming from the liver.
This is necessary for pancreatic enzyme action.
 Bile also emulsifies the fats into smaller globules.
 Pancreatic and intestinal amylases break down carbohydrates into glucose.
 Trypsin and chymotrypsin are the proteases responsible for the breakdown of proteins finally into
acids.
 Lipase is the enzyme which acts on the emulsified fats and breaks them down into glycerol and fatty
acids.
Biology notes by Shubham Sir
RESPIRATION
 Diverse organisrns do thís in different ways some use oxygen to break-down glucose completely into
carbon dioxide and water, some use other pathways that do not involve oxygen

Pyruvate is Converted in 3 Ways: UPSC'S Fav Tapic (5 Times Question Asked)

Location Oxygen (Present/Absent ) Result

In Yeast Absence of Oxygen Ethanol + CO2+ Energy
In Muscle Cells (Human) Lack of Oxygen Lactic Acid + Energy
In Mitochondria Presence of Oxygen CO2+ Water + Energy

 In all cases, the first step is the break-down of glucose, a six-carbon molecule, into a three-carbon
molecule called pyruvate.
 This process takes place in the cytoplasm.
 Further, the pyruvate may be converted into ethanol and carbon dioxide.
 This process takes place in yeast during fermentation. Since this process takes place in the absence of air
(oxygen), it is called anaerobic respiration.
 Breakdown of pyruvate using oxygen takes place in the mitochondria.
 This process breaks up the three- carbon pyruvate molecule to give three molecules of carbon dioxide.
 The other product is water
 Since this process takes place in the presence of air (oxygen), itis called aerobic respiration.
 The release of energy in this aerobic process is a lot greater than in the anaerobic process.
 Sometimes, when there is a lack of oxygen in our muscle cells, another pathway for the break-down of
pyruvate is taken.
 Here the pyruvate is converted into lactic acid which is also a three-carbon molecule.
 This build-up of lactic acid in our muscles during sudden activity causes cramps.
 The energy released during cellular respiration is immediately used to synthesise a molecule called ATP
which is used to fuel all other activities in the cell.
 In these processes, ATP is broken down giving rise to a fixed amount of energy which can drive the
endothermic reactions taking place in the cell.
 Since the amount of dissolved oxygen is fairly low compared to the amount of oxygen in the air, the rate
of breathing in aquatic organisms is much faster than that seen in terrestrial organisms.
 Fishes take in water through their mouths and force it past the gills where the dissolved oxygen is taken
up by blood.
 In human beings, air is taken into the body through the nostrils.
 The air passing through the nostrils is filtered by fie hairs that line the passage.
Biology notes by Shubham Sir
 The passage is also lined with mucus which helps in this process.
 From here, the air passes through the throat and into the lung
 Rings of cartilage are present in the throat.
 These ensure that the air-passage does not collapse.
 Within the lungs, the passage divides into Smaller and Smaller tubes which finally terminate in balloon-
like structures which are called alveoli (singular-alveolus).
 The alveoli provide a surface where the exchange of gases can take place. (UPSC CDS)
 The walls of the alveoli contain an extensive network of blood- vessels.
 As we have seen in earlier years, when we breathe in we lift our ribs and flatten our diaphragm, and the
chest cavity becomes larger as a result.
 Because of this, air is sucked into the fungus and fills the expanded alveoli.
 The blood brings carbon dioxide from the rest of the body for release into the alveoli, and the oxygen in
the alveolar air is taken up by blood in the alveolar blood vessels to be transported to all the cells in the
body.
 During the breathing cycle, when air is taken in and let out, the lungs always contain a residual volume
of air so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.
 When the body size of animals is large, the diffusion pressure alone cannot take care of oxygen delivery
to all parts
 Instead, respiratory pigments take up oxygen from the air in the lungs and carry it to tissues which are
deficient in oxygen before releasing it.
 In human beings, the respiratory pigment is hemoglobin which has a very high affinity for oxygen.
 This pigment Is present in the red blood corpuscles.
 Carbon dioxide is more soluble in water than oxygen is and hence is mostly transported in the dissolved
form in our blood.

TRANSPORTATION

Transportation in Human Beings

 Blood consists of a fluid medium called plasma in which the cells are suspended.
 Plasma transports food, carbon dioxide and nitrogenous wastes in dissolved form.
 Oxygen is carried by the red blood corpuscles.
 Many other substances like salts, are also transported by the blood. We thus need a pumping organ to
push blood around the body, a network of tubes to reach all the tissues and a system in place to ensure
that this network can be repaired if damaged.

Our pump ---- the heart

Biology notes by Shubham Sir

 The heart is a muscular organ which is as big as our fist.
 Because both oxygen and carbon dioxide have to be transported by the blood, the heart has different
chambers to prevent the oxygen-rich blood from mixing with the blood containing carbon dioxide
 The carbon dioxide-rich blood has to reach the lungs for the carbon dioxide to be removed, and the
Oxygenated blood from the lungs has to be brought back to the heart.
 This oxygen-rich blood is then pumped to the rest of the body.
 Oxygen-rich blood from the lungs comes to the thin-walled
upper chamber of the heart on the left, the left atrium.
 The left atrium relaxes when it is collecting this blood.
 It then contracts, while the next chamber, the left ventricle,
relaxes, so that the blood is transferred to it.

 When the muscular left ventricle contracts in its turn, the

blood is pumped out to the body.
 De-oxygenated blood comes from the body to the upper
chamber on the right, the right atrium, as it relaxes
 As the right atrium contracts, the corresponding lower
chamber, the right ventricle, dilates.
 This transfers blood to the right ventricle, which in tum
Pumps it to the lungs for oxygenation.
 Since ventricles have to pump blood into various organs
they have thicker muscular walls than the atria do.
 Valves ensure that blood does not flow backwards when
the atria or ventricles contract.

Oxygen enters the blood in the lungs

 The separation of the right side and the left side of the heart is useful to keep oxygenated and
deoxygenated blood from mixing.
 Such separation allows a highly efficient' supply of oxygen to the body.
 This is useful in animals that have high energy needs, such as birds and mammals, which constantly use
energy to maintain their body temperature.
 In animals that do not use energy for this purpose, the body temperature depends on the temperature in
the environment..
 Such animals, like amphibians or many reptiles have three chambered hearts, and tolerate some mixing
 of the oxygenated and de-oxygenated blood streams.
 Fishes, on the other hand, have only two chambers to their hearts, and the blood is pumped to the gills, a
oxygenated there, and passes directly to the rest of the body.
 Thus, blood goes only once through the heart in the fish during one cycle of passage through the o
 On the other hand, it goes through the during each cycle in other vertebrates. This is known as double
circulation.

The tubes - blood vessels

 Arteries are the vessels which carry blood away from the heart to various organs of the body.
 Since the blood emerges from the heart under high pressure, the arteries have thick, elastic walls.
 Veins collect the blood from different organs and bring it back to the heart. They do not need thick walls
Biology notes by Shubham Sir
 because the blood is no longer under pressure, instead they have valves that ensure that the blood flows
only in one direction.
 The smallest vessels have walls which are one-cell thick and are called capillaries.
 Exchange of material between the blood and surrounding cells takes place across this thin wall.
 The capillaries then join together to form veins that convey the blood away from the organ or tissue.

Maintenance by platelets
The blood has platelet cells which circulate around the body and plug these leaks by helping to clot the
blood at these points of injury.

Lymph

 There is another type of fluid also involved in transportation.

 This is called lymph or tissue fluid,
 Through the pores present in the walls of capillaries some amount of plasma, proteins and blood cells
escape into intercellular spaces in the tissues to form the tissue fluid or lymph.
 It is similar to the plasma of blood d but colourless and contains Jess protein.
 Lymph drains into lymphatic capillaries from the intercellular spaces, which join to form large lymph
vessels that finally open into larger veins.
 Lymph carries digested and absorbed fat from intestine and drains excess fluid from extra cellular space
back into the blood.

Transportation in Plants
 Plant transport systems will move energy stores from leaves and aw materials from roots.
 These two pathways are constructed as independently organised conducting tubes.
 One, the xylem moves water and minerals obtained from the soil.
 The other. phloem transports products of photosynthesis from the leaves where they are synthesised to
other parts of the plant.

Transport of water
 In xylem tissue, vessels and tracheid of the roots. stems and leaves are interconnected to form a
Continuous system of water-conducting channels reaching all parts of the plant.
 At the roots, cells in contact with the soil actively take up ions.

Biology notes by Shubham Sir

 this Creates a difference in the concentration of these ions between the root and the soil. Water,
therefore, moves into the root from the soil to eliminate this difference.
 This means that there is steady movement of water into root xylem, creating a column of water that is
steadily pushed upwards.

Transport of food and other substances

 This transport of soluble products of photosynthesis is called translocation and it occurs in the part of the
vascular tissue known as phloem
 Besides the products of 1 photosynthesis, the phloem transports amino acids and other substances.
 These substances are especially delivered to the storage organs of roots, fruits and seeds and to growing
organs.

EXCRETION
 The biological process involved in the removal of these harmful mnetabolic wastes from the body is
called excretion. Many unicellular organisms remove these wastes by simple diffusion from the body
surface into the surrounding water.

Excretion in Human Beings

 The excretory system of human beings includes a par of kidneys, a pair of ureters, a urinary bladder and
a urethra.

 Kidneys are located-in the abdomen, one on either side of the backbone,
 Urine produced in the kidney passes though the ureters into the urinary bladder where it is stored until is
is released through the urethra.
 The purpose of making urine is to filter out waste product from the blood.
 Just as CO2 is removed from the blood in the lungs, nitrogenous waste such as urea or uric acid are
removed from blood in the kidneys
 It is then no surprise that the basic filtration unit in the kidneys, like in the lungs, is a cluster of very thin-
walled blood capillaries.
 Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called
Bowman's capsule that collects the filtrate.
 Each kidney has large numbers of these filtration units called nephrons packed close together.
 Some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water,
are selectively re-absorbed as the urine flows along the tube.
 The urine forming in each kidney eventually enters a long tube, the ureter, which connects the kidneys
with the urinary bladder. Urine is stored in the urinary bladder until the pressure of the expanded bladder
leads the urge to pass it out through the urethra. The bladder is muscular, so it is under nervous control.
 As a result, we can usually control the urge to urinate.
Biology notes by Shubham Sir
Artiffcal kidney (Hemodialys)
Kidneys are vital organs for survival. Several factors like infections, injury or restricted blood low to
kidneys reduce the actively of kidneys. This leads to accumulation of poisonous wastes in the body.
which can even lead to death. In case of kidney failure. an artificial kidney can be used. An artificial
kidney is a device to remove nitrogenous waste products from the blood through dialysis.

Artificial kidney contains a number of tubes with a semi permeable lining, suspended
In a tank filled with dialyzing fluid.
This fluid has the same osmotic pressure as blood, except that is devoid of nitrogenous wastes. The
patient's blood s passed through these tubes. During this passage, the waste products from t the blood
pass into dialyzing fluid by diffusion. The purified blood is pumped back into the patient. This is similar
to the function of the kidney. but it is different since there is no re-absorption involved, Normally, in a
healthy adult, the Initial filtrate in the kidney is about 180 L daily. However the volume actually
excreted is only a liter or two a day, because the remaining filtrate is re- absorbed in the kidney tubules.

Excretion in Plants
 Plants use completely different strategies for Creation than those of animals:
 Oxygen itself can be thought of as a waste product generated during photosynthesis.
 They can get rid of excess water by transpiration.
 For other wastes, plants use the fact that many of their reissues consist of dead cells, and that they can
even lase some parts such as leaves.
 Many plant waste products are stored in cellular vacuoles.
 Waste products may be stored in leaves that fall off.
 Other waste products are stored as resins and gums, especially in old xylem. Plants also excrete Some
waste substances into the soil around them.

Biology notes by Shubham Sir

 HUMAN BLOOD
 The quantity of blood in the human's body is 7% of the total weight.
 Blood is fluid connective tissue and composed of blood corpuscles, plasma and platelets
 It is slightly alkaline in nature (pH.74)2
 Its volume in an adult is 5.8 L.
 People who live at high altitudes have more blood than those who live in low regions. This extra blood
supplies additional oxygen to body cells.
 During blood clotting fibrinogen changes into fibrin by thrombin which is in the presence of Ca?
 Female contains half liter of blood less in comparison to male.

BLOOD CONSISTS OF TWO PARTS

 Plasma; and (B) Blood corpuscles.
 Plasma: This is the liquid part of blood.
 60% of the blood is plasma.
 takes place through plasma.
 Its 90% part is water, 7% protein, 0.9% salt and 0. 1% is glucose.
 Function of plasma: Transportation of digested food, hormones, excretory product, etc. from the body
 Blood corpuscles: This is the remaining 40% part of the blood.
 Serum: When Fibrinogen and protein is extracted out of plasma the remaining plasma is called Serum.
 Red Blood Corpuscles (RBC): Red Blood Corpuscles (RBC) in mammal is biconcave.
 There is no nucleus in it. Exception-Camel and Lama.
 RBC is formed in Bone marrow. Its life span is from 20 days to 120 days.
 Its destruction takes place in liver and spleen. Therefore, liver is the grave of RBC
 It contains hemoglobin, in which hame iron containing compound found and due to this the colour of
blood is red.
 The main function of RBC is to carry oxygen to all cells of the body bring back the carbon dioxide.
 White Blood Corpuscles (WBC) or Leucocytes
 Its formation takes place in Bone marrow, lymph node and sometimes in liver and spleen
 Its life span is from 1 to 2 days. Nucleus is present in the White Blood Corpuscles.
 WBC's main function is to protect the body from the disease, The ratio of RBC and WBC is 600 : 1
 Blood Platelets or Thrombocytes: It is found only in the blood of human and other mammals
 There is no nucleus in it its formation takes place in Bone marrow. Its life span is from 3 to 5 days.
 It dies in the Spleen. Its main function is to help in clotting of blood.

FUNCTIONS OF BLOOD
 To control the temperature of the body and to protect the body from diseases.
 Clotting of blood.
 Transportation of O2 CO2, digested food, conduction of hormones, etc.
 To help in establishing coordination among different pars.
 The main reason behind the difference in blood of human is the glycoprotein which is found in Red
Blood Corpuscles called antigens. Antigens are of two types: Antigen A And Antigen B.

Biology notes by Shubham Sir

Blood Group Antigen Antibody Donor Groups
A A Anti-b A and O
B B Anti-a B and O
AB Both A and B None A, B and A B
O None Both anti-a and anti-b O

Biology notes by Shubham Sir

 CONTROL & COORDINATION
Your nervous system uses specialized cells called neurons to send signals, or messages, all over your
body.
These electrical signals travel between your brain, skin, organs, glands and muscles.
Parts of the Nervous System
The main parts of the nervous system are:
Central Nervous System (CNS): Your brain and spinal cord make up your CNS. Your brain uses your
nerves to send messages to the rest of your body. Each nerve has a protective outer layer called myelin.
Myelin insulates the nerve and I helps the messages get through.

Peripheral Nervous System: : Your peripheral nervous system consists of many nerves that branch out
from your CNS all over your body. This system relays information from your brain and spinal cord to
your organs, arms, legs, fingers and toes. Your peripheral nervous system contains your:
 Somatic nervous system: which guides your voluntary movements.
 Autonomic nervous system, which controls the activities you do without thinking about them.

Central Nervous System

Central I Nervous System (CNS) is often called the central processing unit of the body. It consists of the
brain and the spinal cord.

Brain
The brain is one oft the important, largest and central organ of the human nervous system. It is the control
unit of the nervous system, which helps us in discovering new things remembering and understanding,
making decisions, and a lot more. It is enclosed within the skull, which provides frontal, lateral and dorsal
protection. The human brain is composed of three major parts

1. Forebrain: The anterior part of the brain, consists of Cerebrum, Hypothalamus and Thalamus.
2. Midbrain: The smaller and central part of the brainstem, consists of Tectum and Tegmentum.
3. Hindbrain: The central region of the brain, composed of Cerebellum, Medulla and Pons.

Spinal Cord
The spinal cord is a cylindrical bundle of nerve fibers and associated tissues enclosed within the spine and
connect all parts of the body to the brain It begins in continuation with the medulla and extends downwards.
It is enclosed in a bony cage called vertebral column and surrounded by membranes called meninges. The
spinal cord is concerned with spinal reflex actions and the conduction of nerve impulses to and from the
brain.

Neuron
A Neuron is a structured and functional unit of the nervous system and unlike other cells, neurons are
irregular in shape and able to conduct electrochemical signals. Thẹ different parts of a neuron are discussed
below.

 Dendrite stretches cut from the cell body of a person, and it is the shortest fiber in the cell body.
 Axon is the longest thread on the cell body of a neuron and has an insulating and protective sheath of
myelin around it.
 Cell body consists of cytoplasm and nucleus.
Biology notes by Shubham Sir
 Synapse is the microscopic gap between a pair of adjacent neurons over which nerve impulses pass,
when moving from one neuron to the other.

Nerves
Nerves are thread-like structures that emerge from the brain and spinal cord. It is responsible for carrying
messages to all the parts of the body. There are three types of nerves. Sensory nerves send messages from all
lie senses to the brain.

1. Motor nerves Carry messages from the brain to all the muscles.
2. Mixed nerves carry both sensory and motor nerves.

REFLEX ACTION: A reflex, or reflex action, is an involuntary and nearly instantaneous movement in
response to a stimulus. A reflex is made possible by neural pathways called reflex arcs which can act on an
impulse before that impulse reaches the brain.

Examples include When light acts as a stimulus, the pupil of the eye changes in size. Coughing or sneezing
Because of irritants in the nasal passages. Knees jerk in response to a blow or someone stamping the leg.

REFLEX ARC: Reflex arc is the nerve pathway involved in a reflex action, including at its simplest a
sensory nerve and a motor nerve with a synapse between.

Reflex arc consist of

I) Receptor or Sensory Organ,

2) Sensory Neurine,
3) Reflex Centre (Brain or Spinal Cord),
4) Motor Neurone and
5) Effector(muscle or gland).

Biology notes by Shubham Sir

 COORDINATION IN PLANTS
 Animals have a nervous system for controlling and coordinating the activities of the body. But plants
neither a nervous system nor muscles.
 So, how do they respond to stimuli?
 When we touch the leaves of a chhui-mui (the sensitive' or 'touch-me-not' plant of the Mimosa famil they
begin to fold up and droop.
 When a seed germinates, the root goes down, the stem comes up into the air. What happens?
 Firstly, the leaves of the sensitive plant move very quickly in response to touch.
 There is no growth involved in this movement.
 On the other hand, the directional movement of a seedling is caused by growth.
 If it is prevented from growing, will not show any movement.
 So plants show two different types of movement-one dependent on growth and the other independer
growth.

Immediate Response to Stimulus

 Let us think about the first kind Iof movement, such as that of the sensitive plant.
 Since no growth is involved, the plant must actually move its leaves in response to touch.
 But there is S no nervous tissue, nor any muscle tissue.
 How does the plant detect the touch, and how do the leaves move in response?

 If we think about where exactly the plant is touched, and what part of the plant actually moves, it is
apparent that movement happens at a point different from the point of touch.
 So, information that a touch has occurred must be communicated.
 The plants also use electrical-chemical means to convey this information from cell to cell, but un in
animals, there is no specialized tissue in plants for the conduction of information.
 Finally, again as in animals, some cells must change shape in order for movement to happen.
 Instead of the specialized proteins found in animal muscle cells, plant cells change shape by changing
amount of water in them, resulting in swelling or shrinking, and therefore in changing shapes.

Movement Due to Growth

 Some plants like the pea plant climb up other plants or fences by means of tendrils.
 These tendrils are sensitive to touch. When they come in contact with any support, the part of the tender
contact with the object does not grow as rapidly as the part of the tendril away from the object.
 This causes the tendril to circle around the object and thus cling to it.

Biology notes by Shubham Sir

 More commonly, plants respond to stimuli slowly by growing in a particular direction,
 Because is growth is directional, it appears as if the plant is moving

Fgure 7.6 Plant showng geotroptsm

What is phototropism?

 It is the way in which plants or other living organisms react to light.

 Positive phototropism is the term for a response that points in the direction of the light.
 Negative phototropism is the term for a response that is directed away from the light.
 Examples of such phenomena include sunflowers turning in the direction of the sun and plants growing
in that direction.

What is geotropism?

 Geotropism refers to the growth of a plant's components in reaction to gravity.

 Positive geotropism is the term used when the response is towards
 Negative geotropism is the term used when the response is away from gravity.
 The growth of plant stems in the opposite direction of gravity (negative geotropism) and the expansion
of plant roots in the direction of gravity (positive geotropism).

What is hydrotropism?

 It denotes the response of plant roots to

moisture while growing
 Positive hydrotropism occurs when roots
grow towards the moisture.
 Negative hydrotropism occurs when roots
react by moving away from moisture.
 The expansion of plant roots toward
increasing humidity is one example.

What is chemotropism?

 It refers to a plant's reaction to a chemical

Biology notes by Shubham Sir
 stimulation.
 Positive chemotropism is the term used to
describe growth that is directed toward the
stimulus, such as the formation of pollen
tubes.
 Negative chemotropism occurs when
growth occurs away from the chemical
stimulus, such as when roots grow farthest
from dangerous chemicals.

Biology notes by Shubham Sir

 Plant hormone
Plant hormone Physiological effect
Auxin  Synthesized in the young tip of roots and shoots. It diffuses towards the shady
side of plant which stimulates the cells to grow longer, resulting in bending of
shoot towards light.
 Promotes cell elongation and division
 Plays important role in formation of roots and seedless fruits.
Gibberellin  Help in growth of stem and flower.
 Help in germination of seed.
Cytokines  Promote cell division and delay leaf ageing.
 Also stimulate leaf expansion.
Abscises Acid  Growth inhibitor
 Reverses the growth promoting effects of axons and gibberellins.
Ethylene  Promotes transverse growth.
 Essential for fruit ripening. Promotes senescence and abscission of leaves.

Hormones In Human Beings

 This is done in many animals,
including human beings, using a
hormone called adrenaline that is
secreted from the adrenal glands.
In which heartbeat is increased due
to fear, excitement like, if a
barking dog running behind you,
Adrenaline is secreted directly
into the blood and carried to
different parts of the body and
you will Run like Anything to
save you.
 The target organs or the specific
tissues on which it acts include
the heart.

UPSC Questions :

 First of all you should remember the

names of plant hormones & Animal
Hormone (50% Work Done).
 2nd They will ask Specific functions of
hormone like, Adrenaline, Thyroid,
etc....

Biology notes by Shubham Sir

Biology notes by Shubham Sir
 Reproduction
 Reproducing organisms create new individuals that look very much like themselves.

DO ORGANISMS CREATE EXACT COPIES OFTHEMSELVES?

 Organisms look similar because their body designs are similar.

 If body designs are to be similar, the blueprints for these designs should be similar.
 Thus, reproduction at its most basic level will involve making copies of the blueprints of body design.
 We know that chromosomes in the nucleus of a cell contain information for inheritance of features from
parents to next generation in the form of DNA (Deoxyribo Nucleic Acid) molecules.
 The DNA in the cell nucleus is the information source for making proteins.
 Therefore, a basic event in reproduction is the creation of a DNA copy.
 Cells use chemical reactions to build copies of their DNA.
 .No bio-chemical reaction is absolutely reliable.
 Therefore, it is only to be expected that thé process of copying the DNA will have some variations each
As a result, the DNA copies generated will be similar, but may not be identical to the original.

Asexual Reproduction Sexual Reproduction

1 involves only a single parent 1. Involves two parents (male & female).
2 The entire reproduction process ales lese fame and 2.The process takes longer time and more energy.
energy 3.Population increases relatively slower.
3 Population can increase at faster rate. 4.It involves more variation.
4. It involves less variation. 5.Species can adapt to an environment which
5. The spies is very vulnerable to hang environment changes.
6 This does not leads to evolution 6.This leads to evolution.
7. Eg. Amoeba 7.Eg. Humans

MODES OF REPRODUCTION USED BY SINGLE ORGANISMS

Fission
 For unicellular organisms, cell division, or fission, leads to the creation of new individuals.
 Many different patterns of fission have been observed
 Many bacteria and protozoa simply split into two equal halves during cell division.
 In organisms such as Amoeba, the splitting of the two cells during division can take place in any plane.

 However, some unicellular organisms show somewhat more organization of their bodies, such as is seen
in Leishmania (which cause kala-azar), which have a whip-like structure at one end of the cell.
 in such organisms, binary fission occurs in a definite orientation in relation to these structures.
 Other single-celled organisms, such as the malarial parasite, Plasmodium, divide into many daughter
cells simultaneously by multiple fission.

Biology notes by Shubham Sir

Fragmentation
 In multi-cellular organisms with relatively simple body organization, simple reproductive methods can
still work.
 Spirogyra, for example, simply breaks up into smaller pieces upon maturation.
 These pieces or fragments grow Into new Individuals.
 This is not true for all multi-cellular organisms.
 They cannot simply divide cell-by-cell.
 Specialized cells are organised as tissues, and tissues are organised into organs, which then have to be
placed at definite positions in the body.
 The reason is that many multi-cellular organisms, as we have seen, are not Simply a random collection
of cells.
 In such a carefully organised situation, cell-by-cell division would be impractical.
 Multi-cellular organisms, therefore, need to use more complex ways of reproduction.
 A basic strategy used in multi-cellular organisms is that different cell types perform different specialised
functions.
 Following this general pattern, reproduction in such organisms is also the function of a specific cell type.

Regeneration
 Many fully differentiated organisms have the ability to give rise to new individual organisms from their
body parts.
 That is, if the individual is somehow cut or broken up into many pieces, many of these pieces grow into
separate individuals.
 For example, simple animals Ike Hydra and Planarian can be cut into any number of pieces and
each piece grows into a complete organism.
 This is known as regeneration.
 Regeneration is carrted out by specialsed cells.
 These cells proliferate and make large numbers of cells,
 From this mass of cells, different cells undergo changes to become various cell types and tissues.
 These changes take place in an organised sequence referred to as development.

Biology notes by Shubham Sir

 However, regeneration is not the same as reproduction, since most organisms would not normally
depend on being cut up to be able to reproduce.
Budding

 Organisms such as Hydra use regenerative cells for reproduction in

the process of budding.
 In Hydra, a bud develops as an outgrowth due to repeated cell
division at one specific site.
 These buds develop into tiny individuals and when fully mature,
detach from the parent body and become new independent
individuals.

Vegetative Propagation
 There are many plants in which parts like the root, stem and leaves develop into new plants under
appropriate conditions.
 Unlike in most animals, plants can indeed use such a mode for reproduction.
 This property of vegetative propagation is used in methods such as layering or grafting to grow many
plants like sugarcane, roses, or grapes for agricultural purposes.
 Plants raised by vegetative propagation can bear flowers and fruits earlier than those produced from
seeds.
 Such methods also make possible the propagation of plants such as banana, orange, rose and jasmine that
have lost the capacity to produce seeds.
 Another advantage of vegetative propagation is that all plants produced are genetically similar enough to
the parent plant to have all its characteristics.
 Similarly buds produced in the notches along the leaf margin of Bryophyllum fall on the soil and
develop into new plants.

Tissue culture

 In tissue culture, new plants are grown by removing tissue or separating cells
from the growing tip of a plant. The cells are then placed I are artificial medium
where they divide rapidly to form small group of cells or callus. The callus is
transferred to another medium containing hormones for growth and
differentiation The plantlets are then placed in the soil o that they can grow into mature plants. Using
tissue culture, many plants can be grown from one parent in disease-free conditions. This technique is
commonly used for ornamental plants,

Spore Formation
 Even in many simple multi-cellular organisms, specific reproductive parts can be identified.
 The thread-like structures that developed on the bread are the hyphae of the bread mould (Rhizopus)
 They are not reproductive parts.
 On the other hand, the tiny blob-on-a-stick structures are involved in reproduction.
 The blobs are sporangia, which contain cells, Or 8pores, that can eventually develop into new Rhizopus
Biology notes by Shubham Sir
 individuals.
 The spores are covered by thick walls that protect them until they come into contact with another moist
surface and can begin to grow.
 All the modes of reproduction that we have discussed so far allow new generations to be created from a
single individual.
 This is known as asexual reproduction:
Vegetative propagation – Advantages/Disadvantages
Advantages Disadvantages
1. True to type-each is a clone of the 1.Lite chances of a new variety arising.
parent. Only way for Some Monocultures are susceptible to
varieties. diseases.
2. Uniformity- each it the exactly the 2.Cost- requires skilled labour and
same. aftercare.
3.The anly yay to reproduce sterile 3.Time taking each plant has to be
varieties such as Vițis vinifera. individually propagated.
4. Speed to maturity is much quiker
SEXUAL
REPRODUCTION
 We are also familiar with modes of reproduction that depend on the involvement of two individuals
before a new generation can be created.
 Bulls alone cannot produce new calves, nor can hens alone produce new chicks.
 In such cases, both sexes, males and females, are needed to produce new generations.
 What is the significance of this sexual mode of reproduction?
 Are there any limitations of the asexual mode of reproduction, which we have been discussing
above?

Sexual Reproduction in Flowering Plants

 The reproductive parts of angiosperms are located in the flower.
 The different parts of a lower- sepals, petals, stamens and pistil.
 Stamens and pistil are the reproductive parts of a flower which contain the germ-cells.
 What possible functions could the petals and sepals serve?
 The flower may be unisexual (papaya, watermelon) when it contains either stamens or pistil or bisexual
(Hibiscus, mustard) when it contains both stamens and pistil.
 Stamen is the male reproductive part and it produces pollen grains that are yellowish in colour.

 Pistil is present in the center of a flower and is the female reproductive part It is made of three parts
 The swollen bottom part is the ovary, middles elongated part is the style/and the terminal part which may
be sticky is the stigma.
Biology notes by Shubham Sir
 The ovary contains ovules and each ovule has an egg cell.
 The male germ-cell produced by pollen grain fuses with the female gamete present in the ovule.
 This fusion of the germ-cells or fertilization gives us the zygote which is capable of growing into a new
plant.
 Thus the pollen needs to be transferred from the stamen to the stigma.
 If this transfer of pollen occurs in the same flower, it is referred to as self-pollination.
 On the other hand, if the pollen is transferred from one flower to another, it is known as crosspollination
 This transfer of pollen from one flower to another is achieved by agents like wind, water or animals.
 After the pollen lands on a suitable stigma, it has to Teach the female germ-cells which are in the ovary
 For this, a tube grows out of the pollen grain and travels through he style to reach the ovary
 After fertilization, the zygote divides several times to form an embryo within the ovule.
 The ovule develops a tough coat and is gradually converted into a seed.
 The ovary grows rapidly and ripens to form a fruit.

 Meanwhile, the petals, sepals, stamens, style and stigma may shrivel and fall off.
 Have your ever observed any flower part still persisting in the fruit?
 Try and work out the advantages of seed-formation for the plant.
 The seed contains the future or embryo which develops into a seedling under appropriate conditions.
 This process is known as germination.

Biology notes by Shubham Sir

 Reproduction in Human Beings
 Human beings also develop special tissues for this purpose.
 However, while the body of the individual organism is growing to its adult size, the resources of the
body are mainly directed at achieving this growth.
 While that is happening, the maturation 1 of the reproductive tissue is not likely to be a major priority.
 Thus, as the rate of general body growth begins to slow down, reproductive tissues begin to mature.
 This period during adolescence is called puberty.
 So how do all the changes that we have talked about link to the reproductive process?
 We must remember that the sexual mode of reproduction means that germ-cells from two individuals
have to join together.
 This can happen by the external release of germ-cells from the bodies of individuals, as happens in
flowering plants.

Male Reproductive System

 The male reproductive system consists of portions which produce the germ-cells and other portions that
 deliver the germ-cells to the site of fertilization.
 The formation of germ-cells or sperms takes place in the testes.
 These are located outside the abdominal cavity in scrotum because sperm formation requires a
lower temperature than the normal body temperature.
 We have discussed the role of the testes in the secretion of the hormone, testosterone, in the previous
chapter.
 In addition to regulating the formation of sperms, testosterone brings about changes in appearance seen
in boys at the time of puberty.
 The sperms formed are delivered through the vas deferens wheel waits with a tube coming from
the urinary bladder.

 The urethra thus forms a common passage for both the

sperms and urine.
 Along the path the vas deferens, glands like the prostate
and the seminal vesicles add their secretions so that the
sperms are now in fluid which makes their transport easier
and this fluid also provides nutrition,
 The sperms are tiny bodies that consist of mainly genetic
material and a long tail that helps to move towards the
female germ-cell.

Female Reproductive System

 The female germ cells or eggs are made in the ovaries.
 They are also responsible for the predication of some hormones.
 When a girl is born, the varies already contain thousands of immature eggs. puberty, some of these start
maturing.
 One egg is produced every month by one of the ovaries.
 The egg is carried from the ovary to the womb through a thin oviduct or fallopian tube.
 The two oviducts unite into an elastic bag-like structure known as the uterus.
Biology notes by Shubham Sir
 The uterus opens into the vagina through the cervix.
 The sperms enter through the vaginal passage during sexual intercourse.
 They travel upwards and reach the oviduct where they may encounter the egg.
 The fertilized CER (Zygote) starts dividing and form a ball of cells or embryo.
 The embryo is implanted in the lining of the uterus where they continue to grow and develop organs to
become foetus.
 We have seen in earlier sections that the mother's body is designed to undertake the development of the
child.
 Hence his uterus prepares itself every month to receive and nurture the growing embryo.
 The lining thickens and is richly supplied with blood to nourish the growing embryo.
 The embryo gets mutilation from the mother's blood with the help of a special tissue called placenta,
 This is a disc which is embedded in the uterine wall.
 It contains villi on the embryo's side of the tissue.
 On the mother's side are blood spaces, which surround the villi.
 This provides a large surface area for glucose and oxygen to pass from the mother to the embryo.
 The developing embryo will also generate waste substances which can be removed by transferring them
into the mother's blood through the placenta.
 The development of the child inside the mother's body takes approximately nine
 The child is born as a result of rhythmic contractions of the muscles in the uterus.

What happens when the Egg is not Fertilised?

 If the egg is not fertilized, it lives for about one day.
 Thus its lining becomes thick and spongy
 Since the ovary releases one egg every month, the uterus also prepares itself every month to receive a
fertilized egg
 This would be required for nourishing the embryo if fertilization had taken place
 Now, however, this lining is not needed any longer.
 So, the lining slowly breaks and comes out, through the vagina as brood and mucous.
 This cycle takes place roughly every month and is known as menstruation,
 It usually lasts for about two to eight days

Reproductive Health
 As we have seen, process of sexual maturation is gradual, and takes place while general body growth is
still going on.
 Therefore, some degree of sexual maturation does not necessarily mean that the body or the mind is
ready for sexual acts or for having and bringing up children.
 How do we decide if the body or the mind is ready for this major responsibility?

Biology notes by Shubham Sir

 All of us are under many different kinds of pressures about these issues.
 There can be pressure from our friends for participating in many activities, whether we really want to or
not.
 There can be pressure from families to get married and start having children.
 There can be pressure from government agencies to avoid having children. In this situation, making
choices can become very difficult
 We must also consider e possible health consequences of having sex.
 We have discussed in Class IX that diseases can be transmitted from person to person in a variety of
ways.
 Since the sexual act is a very intimate connection of bodies, it is not surprising that many diseases can be
sexually transmitted.
 These include bacterial infections such as gonorrhea and syphilis, and viral infections such as
warts and HIV- AIDS.
 Is it possible to prevent the transmission of such diseases during the sexual act?
 Using a covering, called a condom, for the penis during sex helps to prevent transmission of many of
these infections to some extent.
 The sexual act always has the potential to lead to pregnancy.
 Pregnancy will make major demands on the body and the mind of the woman, and if she is not ready for
it, her health will be adversely affected.
 Therefore, many ways have been devised to avoid pregnancy.
 These contraceptive methods fall in a number of categories.
 One category is the creation of a mechanical barrier so that sperm does not reach the egg-
 Condoms on the penis or similar coverings wom in the vagina can serve this purpose.
 Another category of contraceptives acts by changing the hormonal balance of the body so that eggs are
not released and fertilization cannot occur.

 These drugs commonly need to be taken orally as pills

 However since they change hormonal balances, they can cause side-effects too.
 Other contraceptive devices such as the loop or the copper-T are placed in the uterus to prevent
pregnancy.
 Again they can cause side effects due to irritation of the uterus.
 If the vas deferens in the male is blocked, sperm transfer will be prevented.
 If the fallopian tube in the female is blocked, the egg will not be able to reach the uterus.
 In both cases fertilization will not take place.
 Surgical methods can be used to create such blocks.

 While surgical methods are safe in the long run, surgery itself can cause infections
and other problems if not performed properly.
 Surgery can also be used for removal of unwanted pregnancies.
 These may be misused by people who do not want a particular child, as happens in
illegal sex-selective abortion of female foetuses.
 For a healthy society, the female-male sex ratio must be maintained. Because of
reckless female foeticides, child sex ratio is declining at an alarming rate in some
sections of our society, although prenatal sex determination has been prohibited by
law.

Biology notes by Shubham Sir

ACCUMULATION OF VARIATION DURING REPRODUCTION
 Inheritance from the previous generation provides both a common basic body design, and subtle changes
in it, for the next generation.
 Now think about what would happen when this hew generation, in s turn, produces.
 The second generation will have differences that they inherit from the fist generation, as well as newly
created differences.
 If one bacterium divides, and then the resultant we bacteria divided again, the four individual bacteria
generated would be very similar,
 There would be only very minor differences between them, generated due to small insecurities in DNA
copying.
 However, if sexual reproduction is involved, even greater diversity will be generated, as We will see
when we discuss the rules of inheritance.

HEREDITY
 The most obvious outcome of the reproductive process still remains the generation of individuals of
similar design.
 The rules of heredity determine the process by which traits and characteristics are reliably inherited.
 Let us take a closer look at these rules,

Inherited Traits
 What exactly do we mean, by similarities and differences?
 We know that a child bear all the basic feature of a human being.
 However, it does not look exactly like its parents, and human populations show a great deal of variation.

Rules for the Inheritance of Traits- Mendel's Contributions

 The rules for inheritance of such traits in human beings are related to the fact that
both the father and the mother contribute practically equal amounts of genetic
material to the child.
 This means that each trait can be influenced by both paternal and maternal DNA.
 Thus, for each trait there will be two versions in each child.
 What will, then, the trait seen in the child be?
 Mendel worked out the main rules of such inheritance, and it is interesting to
look at some of his experiments from more than a century ago.
 Mendel used a number of contrasting visible characters of garden peas-
round/wrinkled seeds, tall/short plants, white/violets flowers and so on.
 He took pea plants with different characteristics -a tail plant and a short plant,
produced progeny by crossing them, and calculated the percentages of tall or short
progeny.
 In the first place, there were no halfway characteristics In this first generation, or F1 progeny -no
'medium-height' plants.

 All plants were tall.

 This meant that only one of the parental traits was seen, not some mixture of the two.

Biology notes by Shubham Sir

 So the next question was, were the tall plants in the Fl generation exactly the
same as the tall plants of the parent generation?
 Mendelian experiments test this by getting both the parental plants and these e
F1
tall plants to reproduce by self-pollination.
 The progeny of the parental plants are, of course, all tall.
 However, the second-generation, or F2, progeny of the FI tall plants are not all
tall.
 Instead, one quarter of them are short.
 This indicates that both the tallness and shortness traits were inherited in the Fl
plants
but only the tallness trait was expressed.
 This led Mendel to propose that two copies of factor (now called genes) controlling
traits are present in sexually reproducing organısm.
 These two may be identical, or may be different, depending on the parentage.
 A pattern of inheritance can be worked out with this assumption.

 In this explanation, both TT and Tt are tall plants, while only tt is a short plant.
 In other words, a single copy of T is enough to make the plant tall, while both copies have to be t for the
plant to be short. Traits like Tare called dominant traits, while those that behave like ‘t' are called
recessive traits.
 What happens when pea plants showing two different characteristics, rather than just one, are bred with
each other?
 What do the progeny of a tall plant with round seeds and a short
plant with wrinkled-seeds look like?

 They are all tall and have round seeds.

 Tallness and round seeds are thus dominant traits.
 But what happens when these F1 progeny are used to generate F2
progeny by self-pollination?
 A Mendelian experiment will find that some F2 progeny are tall
plants with round seeds, and some were short plants with wrinkled
seeds.
 However, there would also be some F2 progeny that showed new
combinations.
 Some of them would be tall, but have wrinkled seeds, while others
would be short, but have round seeds.

Biology notes by Shubham Sir

 You can see as to how new combinations of traits are formed in F2 offspring when factors controlling
for seed shape and seed colour recombine to form zygote leading to form F2 offspring.
 Thus, the tall/short trait and the round seed/wrinkled seed trait are independently inherited.

How do these Traits get expressed?

 How does the mechanism of heredity work?
 Cellular DNA is the information source for making proteins in the cell.
 A section of DNA that provides information for one protein is called the gene for that protein.
 How do proteins control the characteristics that we are discussing here? Let us take the example of
tallness as a characteristic.
 We know that plants have hormones that can trigger growth.
 Plant height can thus depend on the amount of a particular plant hormone.
 The amount of the plant hormone made will depend on the efficiency of the process for making it.
 How do germ-cells make a single set of genes from the normal two copies that all other cells in the body
have?
 This is because the two characteristics 'R' and 'y' would then be linked to each other and cannot be
independently inherited.
 This is explained by the fact that each gene set is present, not as a single long thread of DNA, but as
separate independent pieces, each called a chromosome.
 Thus, each cell will have two copies of each chromosome, one each from the male and female parents.
 "Every germ cell will take one chromosome from each pair and these may be of either maternal or
paternal origin.

Sex Determination
Biology notes by Shubham Sir
 We have discussed the idea that the two sexes participating in sexual reproduction must be somewhat
different from each other for a number of reasons.
 How is the sex of a newborn individual determined?
 Different species use very different strategies for this.
 Some rely entirely on environmental cues.
 Thus, in some animals like a few reptiles, the temperature at which fertilized eggs are kept determines
whether the animals developing in the eggs will be male or female.
 In other animals, such as snails, individuals can change sex, indicating that sex is not genetically
determined.
 However, In human beings, the sex of the individual is largely genetically determined.
 In other words, the genes inherited from our parents decide whether we will be boys or girls.
 But so far, we have assumed that similar gene sets are inherited from both parents.
 If that is the case, how can genetic inheritance determine sex?
 The explanation lies in the fact that all human chromosomes are not paired
 Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs.
 But one pair, called the sex chromosomes, is odd In not always being perfect pair, Women have a perfect
pair of Sex chromosomes, both called X.

Biology notes by Shubham Sir