Biology - Lecture 1

Topics
1. Cell

2. Tissues

3. Diversity in Living Organisms

4. Parts of Plants
 Introduction of Cells
• While examining a thin slice of cork, 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 primitive microscope.

• Robert Hooke called these boxes cells. Cell is a Latin word for ‘a little room’.
 Introduction of Cells
• Anton Von 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.
 Cell Theory
• In 1838, Matthias Schleiden, a German botanist, examined a large number of plants and observed that all plants are

composed of different kinds of cells which form the tissues of the plant.

• At about the same time, Theodore Schwann (1839), a British Zoologist, studied different types of animal cells and reported

that cells had a thin outer layer which is today known as the ‘plasma membrane’. He also concluded, based on his studies

on plant tissues, that the presence of cell wall is a unique character of the plant cells.

• On the basis of this, Schwann proposed the hypothesis that the bodies of animals and plants are composed of cells and

products of cells.
 Cell Theory
• Schleiden and Schwann together formulated the cell theory. This theory however, did not explain as to how new cells were

formed. Rudolf Virchow (1855) first explained that cells divided and new cells are formed from pre-existing cells (Omnis

cellula-e cellula). He modified the hypothesis of Schleiden and Schwann to give the cell theory a final shape.

• 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.

 Cell Theory
• Cell theory as understood today is:

(i) all living organisms are composed of cells and products of cells.

(ii) all cells arise from pre-existing cells.

 Unicellular Organisms
• The single cellular organisms, such as Amoeba, Chlamydomonas, Paramoecium, and bacteria, are known as unicellular

organisms.

• A single-celled organism performs all the essential functions that a multicellular organism performs. Unlike other

organisms, Amoeba has no definite shape; so, it keeps on changing its shape.

• Amoeba has pseudopodia, which means – pseudo means false and podia means feet.

• Amoeba is a full-fledged organism capable of independent existence.

 Multicellular Organisms
• The organisms consisting of many cells are known as multicellular organisms.

• E.g. human being, animals, birds, etc.

 Characteristics of Cell
• The onion cell which is a typical plant cell, has a distinct cell wall as its outer boundary and just within it is the cell

membrane.

• The cells of the human cheek have an outer membrane as the delimiting structure of the cell.

• Inside each cell is a dense membrane bound structure called nucleus. This nucleus contains the chromosomes which in

turn contain the genetic material, DNA.

 Characteristics of Cell
• Cells that have membrane bound nuclei are called eukaryotic whereas cells that lack a membrane bound nucleus are

prokaryotic.

• In both prokaryotic and eukaryotic cells, a semi-fluid matrix called cytoplasm occupies the volume of the cell.

• The cytoplasm is the main arena of cellular activities in both the plant and animal cells. Various chemical reactions occur in

it to keep the cell in the ‘living state’.

 Characteristics of Cell
• Besides the nucleus, the eukaryotic cells have other membrane bound

distinct structures called organelles like the endoplasmic reticulum (ER),

the golgi complex, lysosomes, mitochondria, microbodies and vacuoles.

The prokaryotic cells lack such membrane bound organelles.

• Ribosomes are non-membrane bound organelles found in all cells – both

eukaryotic as well as prokaryotic.

• Within the cell, ribosomes are found not only in the cytoplasm but also

within the two organelles – chloroplasts (in plants) and mitochondria and

on rough ER.

• Animal cells contain another non-membrane bound organelle called

centrosome which helps in cell division.

 Characteristics of Cell
• Cells differ greatly in size, shape and activities. For example,

Mycoplasmas, the smallest cells, are only 0.3 μm in length while

bacteria could be 3 to 5 μm. The largest isolated single cell is the

egg of an ostrich.

• Among multicellular organisms, human red blood cells are about

7.0 μm in diameter. Nerve cells are some of the longest cells.

• Cells also vary greatly in their shape. They may be disc-like,

polygonal, columnar, cuboid, thread like, or even irregular. The

shape of the cell may vary with the function they perform.
 Prokaryotic Cells
• The cell, which has no nuclear membrane, is known as prokaryotes (i.e. Pro = primitive or primary; karyote ≈ karyon =

nucleus). The prokaryotic cells are represented by bacteria, blue-green algae, mycoplasma and PPLO (Pleuro Pneumonia

Like Organisms).

• They are generally smaller and multiply more rapidly than the eukaryotic cells.

• They may vary greatly in shape and size. The four basic shapes of bacteria are bacillus (rod like), coccus (spherical), vibrio

(comma shaped) and spirillum (spiral).

• All prokaryotes have a cell wall surrounding the cell membrane except in mycoplasma. The fluid matrix filling the cell is the

cytoplasm. There is no well-defined nucleus. The genetic material is basically naked, not enveloped by a nuclear

membrane.
 Prokaryotic Cells
• In addition to the genomic DNA (the single chromosome/circular DNA), many bacteria have small circular DNA outside the

genomic DNA. These smaller DNA are called plasmids. The plasmid DNA confers certain unique phenotypic characters to

such bacteria.

• One such character is resistance to antibiotics. This plasmid DNA is used to monitor bacterial transformation with foreign

DNA.
 Prokaryotic Cells
• Nuclear membrane is found in eukaryotes. No organelles, like the ones in eukaryotes, are found in prokaryotic cells except

for ribosomes.

• Prokaryotes have something unique in the form of inclusions. A specialized differentiated form of cell membrane called

mesosome is the characteristic of prokaryotes. They are essentially infoldings of cell membrane.

• Most prokaryotic cells, particularly the bacterial cells, have a chemically complex cell envelope. The cell envelope consists

of a tightly bound three layered structure i.e., the outermost glycocalyx followed by the cell wall and then the plasma

membrane.
 Eukaryotic Cells
• The eukaryotes include all the protists, plants, animals and fungi. In

eukaryotic cells there is an extensive compartmentalization of cytoplasm

through the presence of membrane bound organelles.

• Eukaryotic cells possess an organised nucleus with a nuclear envelope. In

addition, eukaryotic cells have a variety of complex locomotory and

cytoskeletal structures. Their genetic material is organised into

chromosomes.

• All eukaryotic cells are not identical. Plant and animal cells are different as

the former possess cell walls, plastids and a large central vacuole which are

absent in animal cells.

• On the other hand, animal cells have centrioles which are absent in almost

all plant cells.

 Structural Organization of Cell
Following are the three basic features that every cell possesses −

1. Plasma Membrane/Cell Membrane

2. Nucleus

3. Cytoplasm
 Plasma Membrane/Cell Membrane
• Plasma membrane is the outermost covering layer of the cell and is mainly composed of lipids and proteins.

• In addition to phospholipids, membrane also contains cholesterol.

• Later, biochemical investigation clearly revealed that the cell membranes also possess protein and carbohydrate. The ratio

of protein and lipid varies considerably in different cell types.

• The fluid nature of the membrane is also important from the point of view of functions like cell growth, formation of

intercellular junctions, secretion, endocytosis, cell division etc.

 Plasma Membrane/Cell Membrane
• One of the most important functions of the plasma membrane is the transport of the molecules across it. The membrane

is selectively permeable to some molecules present on either side of it.

• Many molecules can move briefly across the membrane without any requirement of energy and this is called the passive

transport.

• Neutral solutes may move across the membrane by the process of simple diffusion along the concentration gradient, i.e.,

from higher concentration to the lower. Water may also move across this membrane from higher to lower concentration.

Movement of water by diffusion is called osmosis.

 Plasma Membrane/Cell Membrane
Cell Wall

• A non-living rigid structure called the cell wall forms an outer covering for

the plasma membrane of fungi and plants (absent in animal cell).

• Cell wall not only gives shape to the cell and protects the cell from

mechanical damage and infection, it also helps in cell-to-cell interaction

and provides barrier to undesirable macromolecules.

• Algae have cell wall, made of cellulose, galactans, mannans and minerals

like calcium carbonate, while in other plants it consists of cellulose,

hemicellulose, pectins and proteins.

• The cell wall of a young plant cell, the primary wall is capable of growth,

which gradually diminishes as the cell matures and the secondary wall is

formed on the inner (towards membrane) side of the cell.

 Nucleus
• Nucleus or nuculeus is a Latin term and its meaning is kernel or seed. The nucleus has a double layered covering, which is

known as nuclear membrane.

• It has some pores, which allow certain materials come inside (in nucleus) and go outside (in the cytoplasm).

• The interphase nucleus (nucleus of a cell when it is not dividing) has highly extended and elaborate nucleoprotein fibres

called chromatin, nuclear matrix and one or more spherical bodies called nucleoli.
 Nucleus
• Nuclear envelope, which consists of two parallel membranes with a space

between (10 to 50 nm) called the perinuclear space, forms a barrier between

the materials present inside the nucleus and that of the cytoplasm.

• The outer membrane usually remains continuous with the endoplasmic

reticulum and also bears ribosomes on it. At a number of places the nuclear

envelope is interrupted by minute pores, which are formed by the fusion of its

two membranes.

• These nuclear pores are the passages through which movement of RNA and

protein molecules takes place in both directions between the nucleus and the

cytoplasm.
 Nucleus
• The most significant feature of nucleus is – it contains chromosomes. They are rod-shaped structures and it is visible only

when the cell is about to divide.

• Chromatin contains DNA and some basic proteins called histones, some non-histone proteins and also RNA.

• A single human cell has approximately two metre long thread of DNA distributed among its forty six (twenty three pairs)

chromosomes.
 Cytoplasm
• Cells consist of cytoplasm inside the cell membrane, which contains many biomolecules including proteins and nucleic

acids.

• There are many structures found in the cytoplasm known as cell organelles.
 Endomembrane System
• While each of the membranous organelles is distinct in terms of its structure and function, many of these are considered

together as an endomembrane system because their functions are coordinated.

• The endomembrane system include endoplasmic reticulum (ER), golgi complex, lysosomes and vacuoles.

• Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components,

these are not considered as part of the endomembrane system.

 Endoplasmic Reticulum
• The endoplasmic reticulum (ER) is a large network of membrane-

bound tubes and sheets.

• The ER often shows ribosomes attached to their outer surface. The

endoplasmic reticulum bearing ribosomes on their surface is called

rough endoplasmic reticulum (RER). In the absence of ribosomes they

appear smooth and are called smooth endoplasmic reticulum (SER).

• RER is frequently observed in the cells actively involved in protein

synthesis and secretion. They are extensive and continuous with the

outer membrane of the nucleus.

• The smooth endoplasmic reticulum is the major site for synthesis of

lipid. In animal cells lipid-like steroidal hormones or fat molecules are

synthesised in SER.
 Endoplasmic Reticulum
• One of the significant functions of ER is to serve as channels for the transportation of materials (especially proteins) in

various regions of the cytoplasm and also between the cytoplasm and the nucleus.
 Golgi Apparatus
• Camillo Golgi (1898) first observed densely stained reticular structures near

the nucleus. These were later named Golgi bodies after him.

• They consist of many flat, disc-shaped sacs or cisternae of 0.5μm to 1.0μm

diameter. These are stacked parallel to each other. Varied number of

cisternae are present in a Golgi complex.

• The significant functions of Golgi Apparatus are the storage, modification,

and packaging of products in vesicles.

• A number of proteins synthesised by ribosomes on the endoplasmic

reticulum are modified in the cisternae of the golgi apparatus.

• Golgi apparatus is the important site of formation of glycoproteins and

glycolipids.

• The Golgi apparatus also helps in the formation of lysosomes.

 Lysosomes
• Lysosomes are a sort of waste disposal system of the cell.

• Lysosomes help in keeping the cell clean by digesting the foreign material as

well as worn-out cell organelles.

• Lysosomes contain powerful digestive enzymes capable of breaking down all

sorts of organic materials.

• The isolated lysosomal vesicles have been found to be very rich in almost all

types of hydrolytic enzymes (hydrolases – lipases, proteases, carbohydrases)

optimally active at the acidic pH. These enzymes are capable of digesting

carbohydrates, proteins, lipids and nucleic acids

• Lysosome has a typical feature i.e. when the cell gets damaged lysosome most

likely bursts and the released enzymes digest their own cell. Because of this

reason, lysosome is also known as the ‘suicide bags’ of a cell.

 Vacuoles
• Vacuoles are commonly the storage sacs that contain solid or liquid materials.

• In animal cell, vacuoles are small; whereas in plant cell, vacuoles are of large size. In plant cells the vacuoles can occupy up

to 90 per cent of the volume of the cell.

• Plant cells vacuoles are filled with cell sap and provide turgidity and rigidity to the cell.

• It also contains water, sap, excretory product and other materials not useful for the cell
 Mitochondria
• Mitochondria are the sites of aerobic respiration. They produce cellular energy in the form of ATP (Adenosine

Triphosphate) molecules, hence they are called ‘power houses’ of the cell.

• ATP is popular as the energy currency of the cell.

• Mitochondria have their own DNA and ribosomes; hence, they are capable to make some of their own proteins.
 Plastids
• Plastids are present only in the plant cells. They bear some specific
pigments, thus imparting specific colours to the plants.

• Plastid is categorized as – Chromoplasts (it is coloured plastids) and

Leucoplasts (It is either white or colourless plastids).

• Plastids contain chlorophyll pigment, which are known as

Chloroplasts. Chloroplasts play important role in the photosynthesis
in plants. Chloroplasts also contain various types of yellow or orange
pigments.

• Leucoplasts are the organelles in which some important materials

such as starch, oils, and protein granules get stored.

• Plastids look like mitochondria (in terms of external structure). Like

the mitochondria, plastids also possess their own DNA and
ribosomes.
 Ribosome
• Ribosomes are the granular structures first observed under the electron microscope as dense particles by George Palade

(1953). They are composed of ribonucleic acid (RNA) and proteins and are not surrounded by any membrane.

• The ribosomes, normally, present in all active cells. Ribosome are the sites of protein manufacturing.
 Cytoskeleton
• An elaborate network of filamentous proteinaceous structures consisting of microtubules, microfilaments and

intermediate filaments present in the cytoplasm is collectively referred to as the cytoskeleton.

• The cytoskeleton in a cell are involved in many functions such as mechanical support, motility, maintenance of the shape

of the cell.
 Cilia and Flagella
• Cilia and flagella are hair-like outgrowths of the cell membrane. Cilia are small structures which work like oars, causing the

movement of either the cell or the surrounding fluid.

• Flagella are comparatively longer and responsible for cell movement. The prokaryotic bacteria also possess flagella but

these are structurally different from that of the eukaryotic flagella.

 Centrosome and Centrioles
• Centrosome is an organelle usually containing two cylindrical structures called centrioles.

• They are surrounded by amorphous pericentriolar materials.

• Both the centrioles in a centrosome lie perpendicular to each other in which each has an organisation like the cartwheel.
 Cell Cycle
• Cell division is a very important process in all living organisms. During the division of a cell, DNA replication and cell growth

also take place.

• All these processes, i.e., cell division, DNA replication, and cell growth, hence, have to take place in a coordinated way to

ensure correct division and formation of progeny cells containing intact genomes.

• The sequence of events by which a cell duplicates its genome, synthesises the other constituents of the cell and eventually

divides into two daughter cells is termed cell cycle.

• Although cell growth (in terms of cytoplasmic increase) is a continuous process, DNA synthesis occurs only during one

specific stage in the cell cycle.

• The replicated chromosomes (DNA) are then distributed to daughter nuclei by a complex series of events during cell

division.
 Cell Division - Mitosis
• The process by which new cells are made is called cell division. There are two main types of cell division: mitosis and

meiosis.

• 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.
 Cell Division - Mitosis
• Mitosis accomplishes not only the segregation of duplicated chromosomes into daughter nuclei (karyokinesis), but the cell

itself is divided into two daughter cells by the separation of cytoplasm called cytokinesis at the end of which cell division

gets completed.

• Mitosis usually results in the production of diploid daughter cells with identical genetic complement. The growth of

multicellular organisms is due to mitosis.

• Cell growth results in disturbing the ratio between the nucleus and the cytoplasm. It therefore becomes essential for the

cell to divide to restore the nucleo-cytoplasmic ratio.

• A very significant contribution of mitosis is cell repair. The cells of the upper layer of the epidermis, cells of the lining of the

gut, and blood cells are being constantly replaced.

• Mitotic divisions in the meristematic tissues – the apical and the lateral cambium, result in a continuous growth of plants

throughout their life.

 Cell Division
• Specific cells of reproductive organs or tissues in animals and plants

divide to form gametes, which after fertilisation 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.

• Meiosis involves two sequential cycles of nuclear and cell division

called meiosis I and meiosis II but only a single cycle of DNA replication.

• We come across meiosis during gametogenesis in plants and animals.

 Tissues
• 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 specialised to carry out specific functions. Each specialised 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.

• 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.

 Tissues
• A group of cells that are similar in structure and work together to accomplish a particular function is known as tissue.

• Tissues are categorized as − Plant Tissue & Animal Tissue. There are noticeable differences between the two.

• 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.

• Based on the dividing capacity of the tissues, various plant tissues can be classified as growing or meristematic tissue and

permanent tissue. Cell growth in animals is more uniform. So, there is no such demarcation of dividing and nondividing

regions in animals.
 Plant Tissues
• Meristematic Tissues

• Permanent Tissues

1. Simple Permanent Tissues

I. Parenchyma

II. Collenchyma

III. Sclerenchyma

IV. Epidermis

2. Complex Permanent Tissue

I. Xylem

II. Phloem
 Meristematic Tissue
• Meristematic tissue mainly consists of actively dividing cells, and helps in increasing the length and thickening the stems of
the plant.

• Meristematic tissue, commonly, present in the primary growth regions of a plant, for example, in the tips of stems or
roots.

• Depending on the region (where the meristematic tissues are found); meristematic tissues are classified as apical, lateral,
and intercalary.
 Meristematic Tissue
• 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. Lateral
Meristem is found in stem or root region and helps in their growth. Intercalary
meristem is found at the base of the leaves or internodes (on twigs) and helps
in growth.

• Cells of meristematic tissue are very active, they have dense cytoplasm, thin
cellulose walls and prominent nuclei. They lack vacuoles.
 Permanent Tissue
• The cells formed by meristematic tissue 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.

• Permanent Tissue is further categorized as − Simple Permanent Tissue and Complex Permanent Tissue
 Simple Permanent Tissue
Simple Permanent Tissue further categorized as −

I. Parenchyma

II. Collenchyma

III. Sclerenchyma

IV. Epidermis

• Parenchyma 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.

• Sometimes, parenchyma tissue contains chlorophyll and performs photosynthesis, in such a condition, it is known as
chlorenchyma. The collenchyma tissue provides flexibility to plant and also provides mechanical support (to plant).
 Simple Permanent Tissue
• The large air cavities, which are present in parenchyma of aquatic plants, give buoyancy to the plants and also help them
float, are known as aerenchyma.

• The flexibility in plants is due to another permanent tissue, 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.
 Simple Permanent Tissue
• The Sclerenchyma tissue makes the plant hard and stiff. For example, the husk of a coconut is made up of
sclerenchymatous tissue.

• The cells of Sclerenchyma tissue normally are dead. 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.
 Simple Permanent Tissue
• The outermost layer of cells is known as epidermis. The epidermis is usually made up of a single layer of cells. The entire
surface of a plant has the outer covering of epidermis, which protects all the parts of the plant.

• In some plants living in very dry habitats, the epidermis may be thicker since protection against water loss is critical.

• 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.
 Simple Permanent Tissue
• 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. They 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.

• 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.
 Complex Permanent Tissue
• The different types of tissues we have discussed until now are all made of one type of cells, which look like each other.
Such tissues are called simple permanent tissue.

• Yet another type of permanent tissue is complex tissue. Complex tissues are made of more than one type of cells. All these
cells coordinate to perform a common function.

• Xylem and phloem are examples of such complex tissues. 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
• 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
• Phloem is made up of five types of cells: sieve cells, sieve tubes, companion cells, phloem fibres and the phloem
parenchyma.

• 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 Tissue
• The tissue found in animals have comparatively some different properties than the plant tissue.
 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 and almost no intercellular spaces.
 Connective Tissue
• 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.

• Connective tissues are further divided as − Fibrous connective

tissue, Skeletal connective tissue and Fluid connective tissue

• Blood has a fluid (liquid) matrix called plasma, in which red blood

corpuscles (RBCs), white blood corpuscles (WBCs) and platelets are

suspended. The plasma contains proteins, salts and hormones.

Blood flows and transports gases, digested food, hormones and

waste materials to different parts of the body.

 Connective Tissue
• 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 nonflexible 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
 Connective Tissue
• 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.

• 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.

• 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 largely consists of elongated cells, and also known as muscle fibers. The muscular tissue is accountable for
the movements in our body.

• The muscular tissue contains special proteins known as contractile proteins; and this protein helps in contraction and
relaxation and supports free 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. The cells of this tissue are long, cylindrical, unbranched and multinucleate
(having many nuclei).
 Muscular Tissue
• The movement of food in the alimentary canal or the contraction and relaxation of blood vessels are involuntary
movements. We cannot really start them or stop them simply by wanting to do so.

• Smooth muscles or involuntary muscles control such movements. They are also found in the iris of the eye, in ureters and
in the bronchi of the lungs. The cells are long with pointed ends (spindle-shaped) and uninucleate (having a single
nucleus). They are also called unstriated muscles.
 Muscular Tissue
• The muscles of the heart show rhythmic contraction and relaxation throughout life.

• These involuntary muscles are called cardiac muscles.

• Heart muscle cells are cylindrical, branched and uninucleate.

 Nervous Tissue
• The brain, spinal cord, and nerves all are composed of the nervous tissue.

• Cells of the nervous tissue are extremely particular and sensitive for being stimulated and then transmitting the stimulus
swiftly from one place to another within the body.

• The cells of nervous tissue are known as nerve cells or neurons.

• Nerve impulses allow us to move our muscles whenever we want to do so.

 Diversity in Living Organisms
• Some biologists, namely Ernst Haeckel (1894), Robert Whittaker
(1959), and Carl Woese (1977) have attempted to classify all living
organisms into broad categories and named them ‘Kingdoms.’

• R.H. Whittaker (1969) proposed a Five Kingdom Classification. The

kingdoms defined by him were named Monera, Protista, Fungi,
Plantae and Animalia.

• The main criteria for classification used by him include cell

structure, body organisation, mode of nutrition, reproduction and
phylogenetic relationships.
Diversity in Living Organisms
 Monera
• Bacteria are the sole members of the Kingdom Monera.

• The organisms of Monera kingdom do not have a defined nucleus or organelles, neither do any of them show multi-
cellular body designs.

• 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).

• Bacteria are grouped under four categories based on their shape: the spherical Coccus (pl.: cocci), the rod-shaped Bacillus
(pl.: bacilli), the comma-shaped Vibrium (pl.: vibrio) and the spiral Spirillum (pl.: spirilla)

• The examples of this monera kingdom are bacteria, anabaena, blue-green algae or cyanobacteria, and mycoplasma.
 Protista
• The organisms of Protista kingdom include many kinds of unicellular eukaryotic organisms.

• Members of Protista are primarily aquatic. This kingdom forms a link with the others dealing with plants, animals and
fungi.

• Being eukaryotes, the protistan cell body contains a well defined nucleus and other membrane-bound organelles. Some of
these organisms use appendages, such as hair-like cilia or whip-like flagella for moving around.

• Protists reproduce asexually and sexually by a process involving cell fusion and zygote formation. Their mode of nutrition
can be autotrophic or heterotrophic.
 Fungi
• The fungi constitute a unique kingdom of heterotrophic eukaryotic organisms. They show a great diversity in morphology
and habitat.

• You must have seen fungi on a moist bread and rotten fruits. The common mushroom you eat and toadstools are also
fungi. White spots seen on mustard leaves are due to a parasitic fungus.

• Some unicellular fungi, e.g., yeast are used to make bread and beer. Other fungi cause diseases in plants and animals;
wheat rust-causing Puccinia is an important example. Some are the source of antibiotics, e.g., Penicillium. Fungi are
cosmopolitan and occur in air, water, soil and on animals and plants. They prefer to grow in warm and humid places.
 Fungi
• With the exception of yeasts which are unicellular, fungi are filamentous. Their bodies consist of long, slender thread-like
structures called hyphae. The network of hyphae is known as mycelium.

• The cell walls of fungi are composed of tough complex sugar called chitin and polysaccharides.

• Most fungi are heterotrophic and absorb soluble organic matter from dead substrates and hence are called saprophytes.
Those that depend on living plants and animals are called parasites. They can also live as symbionts – in association with
algae as lichens and with roots of higher plants as mycorrhiza.

• Many of them have the capacity to become multicellular organisms at certain stages in their lives. Reproduction in fungi
can take place by vegetative means – fragmentation, fission and budding.
 Plantae
• Kingdom Plantae includes all multicellular eukaryotic chlorophyll-containing organisms with cell walls commonly called
plants. A few members are partially heterotrophic such as the insectivorous plants or parasites.

• Bladderwort and Venus fly trap are examples of insectivorous plants and Cuscuta is a parasite. The plant cells have an
eukaryotic structure with prominent chloroplasts and cell wall mainly made of cellulose.
 Plantae
• Based on distinct body structure, components, etc. plantae kingdom is further classified as :

I. Thallophyta

II. Bryophyta

III. Pteridophyta

IV. Gymnosperms

V. Angiosperms
 Thallophyta
• The plants of thallophyta do not have well-differentiated body design.

• The plants in thallophyta are known as algae and they are predominantly aquatic.

• Some of the significant examples of thallophyta are Spirogyra, Ulothrix, Cladophora, Chara, etc.
 Bryophyta
• The plants of amphibian group are categorized as bryophyta.

• Though not distinctly developed, but the plant body can be differentiated to form stem and leaf-like structures.

• The examples of bryophyta are moss (Funaria) and Marchantia.

 Pteridophyta
• Plants of pteridophyta have defined roots, stem, and leaves.

• Pteridophyta plants have specialized tissue that transports water and other materials from one part to another part of the
plant.

• Examples of pteridophyta are Marsilea, ferns, and horse-tails.

• The commonality among the thallophytes, the bryophytes, and the pteridophytes are – all of them have naked embryos,
which are known as spores.

• The reproductive organs of plants of these groups are known as ‘cryptogamae,’ which means ‘hidden reproductive organs’.
 Gymnosperm
• The gymnosperms (gymnos : naked, sperma : seeds) are plants in which the ovules are not enclosed by any ovary wall and
remain exposed, both before and after fertilisation.

• The seeds that develop post-fertilisation, are not covered, i.e., are naked.

• Gymnosperms include medium-sized trees or tall trees and shrubs. These plants are normally perennial, evergreen, and
woody.

• One of the gymnosperms, the giant redwood tree Sequoia is one of the tallest tree species. The roots are generally tap
roots.

• Examples of gymnosperm are pines such as deodar, cycas, etc.

 Angiosperm
• The plants of angiosperm bear covered seeds. Plants of angiospherms are
also known as 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. Plants with seeds having two cotyledons are called dicots.
 Animalia Kingdom
• This kingdom is characterised by heterotrophic eukaryotic organisms that are multicellular and their cells lack cell walls.
They directly or indirectly depend on plants for food.

• They digest their food in an internal cavity and store food reserves as glycogen or fat.

• Their mode of nutrition is holozoic – by ingestion of food. They follow a definite growth pattern and grow into adults that
have a definite shape and size. Higher forms show elaborate sensory and neuromotor mechanism. Most of them are
capable of locomotion.

• The sexual reproduction is by copulation of male and female followed by embryological development. S
 Animalia Kingdom
• Based on the extent and type of the body design differentiation, Animalia kingdom classified as −

I. Porifera

II. Coelenterata

III. Platyhelminthes

IV. Nematoda

V. Annelida

VI. Arthropoda

VII. Mollusca

VIII. Echinodermata

IX. Protochordata

X. Vertebrata = Pisces, Amphibia, Reptilia, Aves, Mammalia

 Porifera
• The literal meaning of ‘porifera’ is the organisms with holes.

• The organisms of porifera are non-motile and attached to some solid support.

• .They are commonly called sponges, and are mainly found in marine habitats.

• The examples of this group are Sycon, Spongilla, Euplectelia, etc.

 Coelenterata (Cnidaria)
• Organisms of coelenterata group live in water. The organisms of this group have cavity in their bodies.

• Some of these species live in colonies (corals), while others have a solitary like–span (Hydra). Jellyfish and sea anemones
are the common example of coelenterate.

• The name cnidaria is derived from the cnidoblasts or cnidocytes (which contain the stinging capsules or nematocysts)
present on the tentacles and the body. Cnidoblasts are used for anchorage, defense and for the capture of prey.
 Platyhelminthes
• The organisms of this group do not have true internal body cavity ; so, they neither have well-developed organs.

• The bodies of organisms of this group are flattened from top to bottom; therefore, they are also known as flatworms. They
are either free-living or parasitic.

• Planareia, liverfluke, tape worm, etc., are the typical examples of this group.
 Nematoda
• The organisms of nematode have cylindrical body.

• The organisms have tissue, but as such no well-developed body (i.e. no real organ).

• The filarial worms (causing elephantiasis disease), roundworm in the intestines, etc., are the common examples of
nematodes.
 Annelida
• The organisms of annelida group live almost everywhere including fresh water, marine water as well as on land.

• Earthworms, nereis, and leeches are the familiar examples of annelida.

 Arthropoda
• Arthropoda, probably, is the largest group of animals.

• The animals of this group don’t have well defined blood vessels rather there is an open circulatory system.

• The literal meaning of arthropod is jointed legs; so, they have jointed legs.

• Prawns, butterflies, houseflies, spiders, scorpions, etc. are the typical examples of arthropod.

• Economically important insects – Apis (Honey bee), Bombyx (Silkworm), Laccifer (Lac insect)

• Vectors – Anopheles, Culex and Aedes (Mosquitoes)

• Gregarious pest – Locusta (Locust)

• Living fossil – Limulus (King crab).

 Mollusca
• The organisms of mollusca are invertebrate.

• Most of the organisms of Mollusca group live in water.

• Snails and mussels are the typical example of Mollusca.

 Echinodermata
• The organisms of Echinodermata have spiny skinned.

• Echinodermata are free-living marine organisms.

• The examples of echinodermata are starfish, sea urchins, feather star, etc.
 Protochordata
• The organisms of protochordata are normally marine. E.g. Balanoglossus, Herdemania, and Amphioxus.

• The organisms of protochordata show a typical feature of body design, called as notochord; however, it does not present
there throughout the life.
 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 further classified as −

I. Cyclostomata

II. Pisces

III. Amphibia

IV. Reptilia

V. Aves

VI. Mammalia
 Cyclostomata
• Cyclostomes are jawless vertebrates.

• They are characterised by having an elongated eel-like body, circular

mouth, slimy skin and are scaleless.
 Pisces
• The organisms of this group are typically different types of fishes. Fishes can live only in water. The skin of fish is covered
with scales/plates.

• Fish use oxygen dissolved in water by using gills. The tail of fish helps in their movements.

• Fishes are cold-blooded organisms and their hearts have only two chambers. Fishes lay eggs.
 Amphibia
• The organisms of amphibia have mucus glands in the skin, and they have three-chambered heart.

• Amphibian can live in water as well as on land.

• The organisms of amphibian respire through either gills or lungs.

• The organisms of amphibia lay eggs.

 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, lizards
and crocodiles fall in this category.
 Aves
• These are warm-blooded animals and have a four-chambered heart. 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
• The organisms of Mammalia group are warm-blooded and they have four-chambered hearts.

• Mammalia are typically characterized for their mammary glands.

• Mammary glands produce milk to nourish the young one.

• Most of the mammals produce live baby; however, a few of mammals, such as, the platypus and the echidna lay eggs.

• Mammals’ skin has hairs along with sweat and oil glands.
 Parts Of Plants
The main parts of a plant include:

• Roots

• Stem

• Leaves

• Flowers

• Fruit
 Root System
• Roots are the important underground part of all vascular plants.

• This part of the plant is mainly responsible for anchoring it down into the ground and absorbing the essential mineral
elements, nutrients, and water from the soil. It is also used to store food.

• However, not all plants have their roots underground, some plants have their roots growing above the ground. These are
called aerial roots.

• Alike underground roots, these aerial roots are also responsible for absorbing nutrients, anchoring and affixing the plant
by supporting them to the structures such as nearby walls, rocks, trellises, etc.

• Few examples of plants with the aerial roots are – Bonsai, Banyan Tree, Mangroves, etc.
 Root System
Tap Root System

• Taproots have a main central root upon which, small, lateral roots called root hairs
are attached. Mustard, carrot, beetroot, parsley, china rose are examples of taproot
systems.

Fibrous Root System

• Fibrous roots, on the other hand, are bushy roots in which thin, moderately
branching roots grow from the stem. Rice, wheat, maize, marigold, banana and all
monocotyledons are some examples of the fibrous root system.
 Root System
• In some plants, like grass, Monstera and the banyan tree, roots arise from parts of the plant other than the radicle and are
called adventitious roots
 Functions of Roots
• Anchoring: Roots are the reason plants remain attached to the ground. They support the plant body, ensuring that it
stands erect.

• Absorption: Primary function of the roots is to absorb water and dissolved minerals from the soil. This is crucial as it helps
in the process of photosynthesis.

• Storage: Plants prepare food and store in the form of starch in the leaves, shoots and roots. Prominent examples include
carrots, radish, beetroot, etc.

• Reproduction: Even though roots are not the reproductive part of plants, they are vegetative parts. In some plants, the
roots are a means of reproduction. This type of reproduction is called vegetative propagation.

• Ecological Function: They check soil erosion, provide sustenance and also habitat to various organisms
 Shoot System - Stem
• The stem is the part of the plant which is found above the ground. The bark of trees
are brown in colour and younger stems are green in colour.

• It forms the basis of the shoot system and bears leaves, fruits and flowers. The
region where the leaves arise is known as the node and the region between the
nodes is known as the internode.

• Stems arise vertically upwards to the ground. Initially, stems are usually weak and
cannot stand straight.

• It eventually grows to become the toughest part of the plant called the trunk.

• The trunk is covered by a thick outer covering known as the bark.

• Overall stem provides a definite framework and structure to a plant, which later
develops into a tree.
 Shoot System - Leaves
• Leaves are the most important part of a plant. They contain chlorophyll
that helps the plants to prepare their food using sunlight, carbon
dioxide and water.

• A leaf consists of three main parts - petiole, leaf base and lamina.

• The petiole keeps the leaf blade exposed to wind and cools the leaf.

• The leaf base is a protruding part of a leaf.

• The lamina of the leaf contains veins and veinlets that provide rigidity
to the leaf blade and help in the transport of mineral nutrients.
 Shoot System - Leaves
• Primarily, leaves have three main functions:

1. Photosynthesis: Green leaves prepare food for plants by using water and carbon dioxide in the presence of sunlight. This
process is called photosynthesis.

2. Transpiration: Other than photosynthesis, leaves play a crucial role in the removal of excess of water from plants through
tiny pores called stomata. This is the process of transpiration.

3. Reproduction: Leaves of some plants helps in reproduction also.

 Shoot System - Flowers
The vegetative part of a flower consists of the following:

• Petals: This is a bright-coloured part that attracts bees, insects, and

birds. The colour of petals varies from plant to plant; some are
bright while some are pale coloured. Thus, petals help us to
differentiate one flower from another.

• Sepals: Sepal is the green-coloured part beneath the petals to

protect rising buds. Some flowers have fused petals-sepals while a
few have separated petals-sepals.
 Shoot System - Flowers
Reproductive Parts of a Flower

• A flower includes reproductive parts – the stamen and pistil. A

flower may have only female parts, only male parts, or both.

• Stamen: This is the male reproductive organ and is also known as

Androecium. It consists of two parts namely: anther and filaments.

• The anther is a yellowish, sac-like structure, involved in producing

and storing the pollens.

• The filament is a slender, threadlike object, which functions by

supporting the anther.
 Shoot System - Flowers
Reproductive Parts of a Flower

• Pistil: This is the innermost part and the female reproductive organ
of a flower which comprises three parts -stigma, style and ovary.
This is collectively known as the pistil.

• Stigma: It is the topmost part or receptive tip of carpels in the

gynoecium of a flower.

• Style: It is the long tube-like slender stalk that connects the stigma
and the ovary.

• Ovary: It is the ductless reproductive gland that holds a lot of

ovules. It is the part of the plant where the seed formation takes
place.
 Shoot System - Fruits
• Fruits are seed-bearing structures. It develops from a ripe ovary.

• They are a rich source of vitamins, minerals and fibres.

• The fruit is the characteristic feature of flowering plants, which is a ripened or mature ovary and the seed is what the
ovules develop into after fertilization.

• The fruit that develops without fertilization of the ovary is known as parthenocarpic.
 Shoot System - Seeds
• A seed is a basic part of a plant, which is found enclosed within the fruit. It is made up of a seed coat and an embryo.

• During the development of the fruit, the wall of the ovary becomes the pericarp.

• In some plants, the ovary wall dries out completely, while in some it remains fleshy.
Biology - Lecture 2
 Topics
1. Genetics

2. Nutrition in Human Beings

 Genetics
• Genetics is termed as the study to understand the functioning of inheritance of traits from parents to offspring.

• The groundwork on which heredity stands is known as inheritance. It is defined as the procedure by which characteristics
are handed down from one generation to the other.

• Gregor Johann Mendel is known as the “Father of Modern Genetics” for his discoveries on the basic principles of heredity.

• Variation, as the name suggests is the amount of dissimilarity that exists between children and their parentages.
 Genes
• Genes are functional units of heredity as they are made of DNA.

• The chromosome is made of DNA containing many genes.

• Every gene comprises of the particular set of instructions for a particular function or protein-coding.

• For example, the globin gene was instructed to produce haemoglobin. Haemoglobin is a protein that helps to carry oxygen
in the blood.
 Reasons For Hereditary
• Genes come in pairs in the same way as the chromosomes.

• Each parent of a human being carries two copies of their genes and each parent passes one copy of genes to their child.

• This is the reason why the child has many characteristics of both the parents like hair colour, same eyes etc.
 Function of Genes
• Genes control the functions of DNA and RNA.

• Proteins are the most important materials in the human body which not only help by being the building blocks for
muscles, connecting tissue and skin but also takes care of the production of the enzyme.

• These enzymes play an important role in conducting various chemical processes and reactions within the body.

• Therefore, protein synthesis is responsible for all activities carried on by the body and are mainly controlled by the genes.

• Genes consist of a particular set of instructions or specific functions.

 Mendel's Laws of Inheritance
• The whole process of heredity is dependent upon inheritance and this understanding of
inheritance was made possible by a scientist named Gregor Mendel, who formulated certain
laws to understand inheritance known as Mendel’s laws of inheritance.

• Between 1856-1863, Mendel conducted the hybridization experiments on the garden peas.

• During Mendel’s investigations into inheritance patterns it was for the first time that statistical
analysis and mathematical logic were applied to problems in biology.

• His experiments had a large sampling size, which gave greater credibility to the data that he
collected. Also, the confirmation of his inferences from experiments on successive generations
of his test plants, proved that his results pointed to general rules of inheritance rather than
being unsubstantiated ideas.

• During that period, he chose some distinct characteristics of the peas and conducted some
cross-pollination/ artificial pollination on the pea lines that showed stable trait inheritance and
underwent continuous self-pollination.

• Such pea lines are called true-breeding pea lines.

 Mendel's Laws of Inheritance
He selected a pea plant for his experiments for the following reasons:

I. The pea plant can be easily grown and maintained.

II. They are naturally self-pollinating but can also be cross-pollinated.

III. It is an annual plant, therefore, many generations can be studied within a

short period of time.

IV. It has several contrasting characters.

• Mendel conducted 2 main experiments to determine the laws of inheritance:

Monohybrid Cross & Dihybrid Cross

• While experimenting, Mendel found that certain factors were always being
transferred down to the offspring in a stable way.

• Those factors are now called genes i.e. genes can be called the units of
inheritance.
 Monohybrid Cross
• In this experiment, Mendel took two pea plants of opposite traits (one
short and one tall) and crossed them. He found the first generation
offspring were tall and called it F1 or Filial 1 Progeny.

• Mendel observed that all the F1 progeny plants were tall, like one of its
parents; none were dwarf. He made similar observations for the other
pairs of traits – he found that the F1 always resembled either one of the
parents, and that the trait of the other parent was not seen in them.

• Then he self pollinated the F1 progeny and obtained both tall and short
plants in the ratio 3:1.

• The tall and dwarf traits were identical to their parental type and did
not show any blending, that is all the offspring were either tall or dwarf,
none were of in-between height.
 Monohybrid Cross
• Mendel even conducted this experiment with other contrasting traits like green peas vs yellow peas, round vs wrinkled,
etc. In all the cases, he found that the results were similar.

• Based on these observations, Mendel proposed that something was being stably passed down, unchanged, from parent to
offspring through the gametes, over successive generations. He called these things as ‘factors’. Now we call them as genes.

• Genes, therefore, are the units of inheritance. They contain the information that is required to express a particular trait in
an organism. Genes which code for a pair of contrasting traits are known as alleles, i.e., they are slightly different forms of
the same gene.

• If we use alphabetical symbols for each gene, then the capital letter is used for the trait expressed at the F1 stage and the
small alphabet for the other trait. For example, in case of the character of height, T is used for the Tall trait and t for the
‘dwarf’, and T and t are alleles of each other.

• Hence, in plants the pair of alleles for height would be TT, Tt or tt.

• Mendel also proposed that in a true breeding, tall or dwarf pea variety the allelic pair of genes for height are identical or
homozygous, TT and tt, respectively. TT and tt are called the genotype of the plant while the descriptive terms tall and
dwarf are the phenotype.
 Monohybrid Cross
• As Mendel found the phenotype of the F1 heterozygote Tt to be exactly like the TT parent in appearance, he proposed
that in a pair of dissimilar factors, one dominates the other (as in the F1 ) and hence is called the dominant factor while
the other factor is recessive . In this case T (for tallness) is dominant over t (for dwarfness), that is recessive.

• From the observation that the recessive parental trait is expressed without any blending in the F2 generation, we can infer
that, when the tall and dwarf plant produce gametes, by the process of meiosis, the alleles of the parental pair separate or
segregate from each other and only one allele is transmitted to a gamete.

• This segregation of alleles is a random process and so there is a 50 per cent chance of a gamete containing either allele, as
has been verified by the results of the crossings. In this way the gametes of the tall TT plants have the allele T and the
gametes of the dwarf tt plants have the allele t.

• During fertilisation the two alleles, T from one parent say, through the pollen, and t from the other parent, then through
the egg, are united to produce zygotes that have one T allele and one t allele. In other words the hybrids have Tt. Since
these hybrids contain alleles which express contrasting traits, the plants are heterozygous.

• When the alleles are the same, they are known as homozygous alleles and when the alleles are different they are known
as heterozygous alleles.
 Laws of Inheritance
• Based on his observations on monohybrid crosses Mendel proposed two general rules to consolidate his understanding of
inheritance in monohybrid crosses.

• Today these rules are called the Principles or Laws of Inheritance: the First Law or Law of Dominance and the Second Law
or Law of Segregation.
 Law Of Dominance
• “When parents with pure, contrasting traits are crossed together, only one form of trait appears in the next generation.
The hybrid off springs will exhibit only the dominant trait in the phenotype.”

• In this law, each character is controlled by distinct units called factors, which occur in pairs. If the pairs are heterozygous,
one will always dominate the other.

• Law of dominance explains that in a monohybrid cross between a pair of contrasting traits, only one parental character
will be expressed in the F1 generation and both parental characters will be expressed in the F2 generation in the ratio 3:1.

• The one which is expressed in the F1 generation is called the dominant trait and the one which is suppressed is called a
recessive trait.

• In simple words, the law of dominance states that recessive traits are always dominated or masked by the dominant trait.
 Law Of Dominance
• The trait which is expressed in the phenotype is called the dominant
trait while the one that is not is called the recessive trait.

• He then continued his experiment with self-pollination of F1 progeny

plants.

• This resulted in both tall and short plants in the ratio of 3:1 which
gave rise to the law of segregation.
 Law of Segregation
• “During the formation of gamete, each gene separates from each other so that
each gamete carries only one allele for each gene.”

• This law is based on the fact that the alleles do not show any blending and that
both the characters are recovered as such in the F2 generation though one of
these is not seen at the F1 stage. Though the parents contain two alleles during
gamete formation, the factors or alleles of a pair segregate from each other
such that a gamete receives only one of the two factors.

• Of course, a homozygous parent produces all gametes that are similar while a
heterozygous one produces two kinds of gametes each having one allele with
equal proportion.

• This law explains that the pair of alleles segregate from each other during
meiosis cell division (gamete formation) so that only one allele will be present in
each gamete.

• Thus, the law of segregation is based on the fact that each gamete contains only
one allele.
 Dihybrid Cross & Law of Independent Assortment
• In a dihybrid cross experiment, Mendel considered two traits, each having
two alleles. He crossed wrinkled-green seed and round-yellow seeds and
observed that all the first generation progeny (F1 progeny) were round-
yellow. This meant that dominant traits were the round shape and yellow
colour.

• He then self-pollinated the F1 progeny and obtained 4 different traits:

round-yellow, round-green, wrinkled-yellow, and wrinkled-green seeds in
the ratio 9:3:3:1.

• Based upon such observations on dihybrid crosses (crosses between

plants differing in two traits) Mendel proposed a second set of
generalisations that we call Mendel’s Law of Independent Assortment.
The law states that ‘when two pairs of traits are combined in a hybrid,
segregation of one pair of characters is independent of the other pair of
characters’.
 Pleiotropy
• We have so far seen the effect of a gene on a single phenotype or
trait.

• There are however instances where a single gene can exhibit multiple
phenotypic expression. Such a gene is called a pleiotropic gene.

• The underlying mechanism of pleiotropy in most cases is the effect of

a gene on metabolic pathways which contribute towards different
phenotypes.

• An example of this is the disease phenylketonuria, which occurs in

humans. The disease is caused by mutation in the gene that codes for
the enzyme phenyl alanine hydroxylase (single gene mutation). This
manifests itself through phenotypic expression characterised by
mental retardation and a reduction in hair and skin pigmentation.
 Determination Of Sex
• There are two different types of sexes, that participate in sexual reproduction. So it is natural to find it confounding as
from which sex the baby inherits, that results in the sex of the child.

• In human beings, the sex of an individual is genetically determined. In other words, the genes which are inherited from
their parents decide the sex of the child.

• Humans have 23 pairs of chromosomes. Out of these 23 pairs, 22 pairs are Autosomes and only one pair is the ‘Sex
Chromosome’, which actively takes part in the process of sex determination

• Both males and females carry two sets of sex chromosome.

 Determination Of Sex
• During spermatogenesis among males, two types of gametes are produced. 50 per
cent of the total sperm produced carry the X-chromosome and the rest 50 per cent
has Y-chromosome besides the autosomes in in which both are active.

• Females, however, produce only one type of ovum with an X-chromosome in which
one is active. All children will inherit an X chromosome from their mother, despite
whether they are a boy or girl.

• There is an equal probability of fertilisation of the ovum with the sperm carrying either
X or Y chromosome.

• In case the ovum fertilises with a sperm carrying X-chromosome the zygote develops
into a female (XX) and the fertilisation of ovum with Y-chromosome carrying sperm
results into a male offspring.

• Thus, it is evident that it is the genetic makeup of the sperm that determines the sex of
the child. It is also evident that in each pregnancy there is always 50 per cent
probability of either a male or a female child.
 Chromosomes
• Chromosomes are the genetic material present in all cells.

• They are present in the nucleus of a eukaryotic cell. They are a thread-like structure.

• Each chromosome of a eukaryotic cell contains DNA and associated proteins.

• They are responsible for the hereditary traits and passed from parents to offspring from one generation to another.

• DNA codes for specific proteins and are responsible for variations in a species and among various organisms.
 Properties of Chromosomes
• Cells must continuously repair, grow and regenerate to replace the old cells.

• Cell division is important for the growth and development of an organism.

• Chromosomes ensure that DNA is divided equally between the daughter cells during cell division.

• Even a small irregularity in the process may lead to various diseases and deformities.

• Uncontrolled cell division results in tumour cells and causes cancer.

• Chromosomal aberration like changes in structure or number can cause genetic disorders, e.g. Down’s syndrome, Turner’s
syndrome, etc.

• Defective chromosomes may even lead to a certain type of leukaemia in humans.

 Mutation
• Mutation is a phenomenon which results in alteration of DNA sequences and consequently results in changes in the
genotype and the phenotype of an organism. In addition to recombination, mutation is another phenomenon that leads to
variation in DNA.

• One DNA helix runs continuously from one end to the other in each chromatid, in a highly supercoiled form.

• Therefore loss (deletions) or gain (insertion/duplication) of a segment of DNA, result in alteration in chromosomes. Since
genes are known to be located on chromosomes, alteration in chromosomes results in abnormalities or aberrations.
 Mutation
• Chromosomal aberrations are commonly observed in cancer cells.

• In addition to the above, mutation also arise due to change in a single base pair of DNA. This is known as point mutation.

• A classical example of such a mutation is sickle cell anemia. Deletions and insertions of base pairs of DNA, causes frame-
shift mutations.
 Genetic Disorders
• Genetic disorders are due to alterations or abnormalities in the genome of an organism.

• A genetic disorder may be caused by a mutation in a single gene or multiple genes. It can also be due to changes in the
number or structure of chromosomes.

• Genes are the basic unit of heredity.

• They hold the genetic information in the form of DNA which can be translated into useful proteins to carry out life
processes.

• These genes undergo a mutation sometimes, which changes the instructions to formulate the protein, due to which the
protein does not work properly.

• Such disorders are known as genetic disorders.

 Genetic Disorders
• Some genetic disorders are innate, i.e., present by birth, while others are acquired due to mutations in a particular gene.

• The genetic disorders that are present by birth are inherited from parents, e.g. cystic fibrosis, haemophilia, sickle cell
anaemia, etc.

• The genetic disorders that are acquired during the lifetime are not inherited from parents, these occur due to mutations
that occur randomly or due to exposure to certain chemicals, environments or radiations such as cigarette smoke, UV
radiations, etc. Cancer is one such disease.

• The genetic disorders can be categorized into two types, namely Mendelian Disorders, i.e., a disorder in a single gene that
follows Mendelian inheritance pattern, and Chromosomal Disorders, i.e., damage or alteration in the chromosomes
structure or number, the chromosomes are either missing, duplicated or a part is translocated.
 Mendelian Disorders
The most common Mendelian disorders include:

I. Cystic fibrosis (autosomal recessive)

II. Haemophilia (sex-linked recessive)

III. Albinism (autosomal recessive)

IV. Sickle cell anaemia (autosomal recessive)

 Colour Blindness
• It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate
between red and green colour.

• This defect is due to mutation in certain genes present in the X chromosome. It occurs in about 8 per cent of males and
only about 0.4 per cent of females.

• This is because the genes that lead to red-green colour blindness are on the X chromosome. Males have only one X
chromosome and females have two. The son of a woman who carries the gene has a 50 per cent chance of being colour
blind.

• The mother is not herself colour blind because the gene is recessive. That means that its effect is suppressed by her
matching dominant normal gene. A daughter will not normally be colour blind, unless her mother is a carrier and her
father is colour blind.
 Haemophilia
• This is a type of sex-linked recessive disorders.

• According to the genetic inheritance pattern, the unaffected carrier

mother passes on the haemophilic genes to sons.

• This is a disorder in which blood doesn’t clot normally as the protein

which helps in clotting of blood is affected.

• Therefore, a person suffering from this disease usually has symptoms of

unexplained and excessive bleeding from cuts or injuries.

• This type of genetic disorder is caused when the affected gene is located
on the X chromosomes.

• Therefore, males are more frequently affected.

 Sickle-cell anaemia
• This is a type of autosomal recessive genetic disorder.

• According to Mendelian genetics, its inheritance pattern follows inheritance from two carrying parents.

• The mutant haemoglobin molecule undergoes a physical change which changes the biconcave shape into the sickle shape.

• This reduces the oxygen-binding capacity of the haemoglobin molecule.

 Phenylketonuria
• It is an inborn error caused due to the decreased metabolism level of
the amino acid phenylalanine.

• In this disorder, the affected person does not have the enzyme that
converts phenylalanine to tyrosine.

• As a result, phenylalanine accumulation takes place in the body and is

converted into many derivatives which result in mental retardation.
 Thalassemia
• This is also an autosome-linked recessive blood disease transmitted from parents to the offspring when both the partners
are unaffected carrier for the gene.

• This is a type of disorder in which the body makes an abnormal amount of haemoglobin.

• As a result, a large number of red blood cells are destroyed that leads to anaemia.

• Facial bone deformities, abdominal swelling, dark urine are some of the symptoms of thalassemia.
 Cystic Fibrosis
• This disease affects the lungs and the digestive system and the body produces thick and sticky mucus that blocks the lungs
and pancreas.

• People suffering from this disorder have a very short life-span.

 Chromosomal Disorders
• This type of disorder is usually fatal and affects many genes.

Some of the major chromosomal abnormalities are:

• Down’s syndrome - the addition of a chromosome 21 (trisomy)

• Turner’s syndrome - absence of an X chromosome (XO)

• Kleinfelter’s syndrome - addition of an X chromosome (XXY)

 Chromosomal Abnormalities
There are different types of chromosomal abnormalities that are as follows:

• Aneuploidy – It is a condition in which there is a loss or gain of chromosomes due to abnormal segregation of genes
during cell division.

• Polyploidy – It is a condition in which the count of the entire set of chromosomes increases due to the failure of
cytokinesis in cell division. It is mostly observed in plants.

• In humans, when there is an extra copy of a chromosome in one of the pairs, it is called trisomy and when one of the
chromosomes from the pair is lacking, it is called monosomy.
 Down syndrome
• This syndrome is a type of trisomy as there is an extra copy of chromosome 21. It is named after the person who
discovered this chromosomal disorder – Langdon Down.

• The symptoms in a person include the following:

I. The person is short and has a small and round head

II. Physical and mental development is retarded

III. Furrowed tongue and partially open mouth,

IV. Broad palm

 Klinefelter syndrome
• This genetic disorder arises due to the presence of an additional X
chromosome in males. Thus, resulting in a chromosome count of 47 (44 +
XXY) instead of 46.

• The symptoms include:

I. Such a person has a masculine physique but has feminine development like
the development of breasts

II. Such individuals are sterile, i.e.; they cannot reproduce.

 Turner syndrome
• Unlike Klinefelter syndrome, in this chromosomal disorder there is the absence
of one X chromosome in females. Hence, decreasing the chromosomes count to
45 (44 + X0).

• The symptoms include the following:

I. Such females are sterile

II. Have rudimentary ovaries and there is the absence of secondary sexual
characters.
 DNA
• “DNA is a group of molecules that is responsible for carrying and transmitting the
hereditary materials or the genetic instructions from parents to off springs.”

• Apart from being responsible for the inheritance of genetic information in all living
beings, DNA also plays a crucial role in the production of proteins.

• Nuclear DNA is the DNA contained within the nucleus of every cell in a eukaryotic
organism. It codes for the majority of the organism’s genomes while the
mitochondrial DNA (It is inherited from the mother to the child) and plastid DNA
play an essential role in photosynthesis.

• DNA is known as Deoxyribonucleic Acid. It is an organic compound that has a

unique molecular structure. It is found in all prokaryotic cells and eukaryotic cells.

• DNA was first recognized and identified by the Swiss biologist Johannes Friedrich
Miescher in 1869 during his research on white blood cells.
 RNA
• RNA is a ribonucleic acid that helps in the synthesis of proteins in our body.

• This nucleic acid is responsible for the production of new cells in the human body.

• It is usually obtained from the DNA molecule.

• RNA resembles the same as that of DNA, the only difference being that it has a single
strand unlike the DNA which has two strands and it consists of an only single ribose
sugar molecule in it.

• Hence is the name Ribonucleic acid. RNA is also referred to as an enzyme as it helps
in the process of chemical reactions in the body.
 Nutrition In Human Beings
• “Nutrients are the compounds in food that provide us with energy that facilitates
repair and growth and helps to carry out different life processes.” Not all
nutrients provide energy but are necessary for some form or the other.

• These nutrients are divided into two categories:

I. Macronutrients, which are required by the body in large amounts.

II. Micronutrients, which are required by the body in small amounts.

 Functions of Nutrients
The important functions of nutrients include:

1. They are the main source of energy for the body.

2. They help in building and repairing body tissues.

3. Increases the absorption of fat-soluble vitamins.

4. Helps in the synthesis of collagen.

5. Provides proper structure to the blood vessels, bones and ligaments.

6. They also help in maintaining the homeostasis of the body.

 Carbohydrates
• Carbohydrates are macronutrients and are one of the three main ways by which our body obtains its energy.

• They are called carbohydrates as they comprise carbon, hydrogen and oxygen at their chemical level.

• Carbohydrates are essential nutrients which include sugars, fibres and starches. They are found in grains, vegetables, fruits
and in milk and other dairy products.

• The food containing carbohydrates are converted into glucose or blood sugar during the process of digestion by the
digestive system. Our body utilizes this sugar as a source of energy for the cells, organs and tissues.

• The extra amount of energy or sugar is stored in our muscles and liver for further requirement.

• The general formula of this class of organic compounds is Cn(H2O)n.

• It is also involved in fat metabolism and prevents ketosis.

• Inhibits the breakdown of proteins for energy as they are the primary source of energy.

• An enzyme by name amylase assists in the breakdown of starch into glucose, finally to produce energy for metabolism.
 Classification of Carbohydrates
• The carbohydrates are further classified into simple and complex
which is mainly based on their chemical structure and degree of
polymerization.

• Simple Carbohydrates (Monosaccharides, Disaccharides and

Oligosaccharides).

• Simple carbohydrates have one or two sugar molecules.

• In simple carbohydrates, molecules are digested and converted

quickly resulting in a rise in the blood sugar levels.

• They are abundantly found in milk products, beer, fruits, refined

sugars, candies, etc.

• These carbohydrates are called empty calories, as they do not

possess fibres, vitamins and minerals.
 Sources of Carbohydrates
• Simple sugars are found in the form of fructose in many fruits.

• Galactose is present in all dairy products.

• Lactose is abundantly found in milk and other dairy products.

• Maltose is present in cereal, beer, potatoes, processed cheese, pasta, etc.

• Sucrose is naturally obtained from sugar and honey containing small amounts of vitamins and minerals.

• These simple sugars that consist of minerals and vitamins exist commonly in milk, fruits, and vegetables.

• Many refined and other processed foods like white flour, white rice, and sugar, lack important nutrients and hence, they
are labelled “enriched.”
 Vitamins
• Vitamins are organic compounds, found in natural foods which are required for normal growth and maintenance of the
body. Both humans and animals require vitamins for their growth.

• Vitamins act as a catalyst in the generation of energy by utilizing carbohydrates and fats properly. Humans cannot live
without vitamins and the human body cannot produce it on its own (except vitamin D and Vitamin B3).

• So it should be taken in required quantities through other sources such as the food we take, vitamin capsules etc. Vitamin
deficiency may cause some diseases and overdose also causes diseases.

Types of Vitamins

• Fat-soluble – which are dissolved in fat

• Water-soluble – which are dissolved in water

 Sources of Vitamins
The best sources of fat-soluble vitamins include:

• Vitamin A: Found in potato, carrots, pumpkins, spinach, beef and eggs.

• Vitamin D: Found in fortified milk and other dairy products.

• Vitamin E: Found in fortified cereals, leafy green vegetables, seeds, and nuts.

• Vitamin K: Found in dark green leafy vegetables and in turnip or beet green.

• Vitamin C are abundantly found in all citrus fruits.

 Sources of Vitamins
Other sources of Vitamin B and C include:

• Vitamin B1 or Thiamin: Found in pork chops, ham, enriched grains and seeds.

• Vitamin B2 or Riboflavin: Found in whole grains, enriched grains and dairy products.

• Vitamin B3 or Niacin: Found in mushrooms, fish, poultry, and whole grains.

• Vitamin B5 or Pantothenic Acid: Found in chicken, broccoli, legumes and whole grains.

• Vitamin B6 or Pyridoxine: Found in fortified cereals and soy products.

• Vitamin B7 or Biotin: Found in many fruits like fruits and meats.

• Vitamin B9 or Folic Acid: Found in leafy vegetables.

• Vitamin B12: Found in fish, poultry, meat and dairy products.

 Sources of Vitamins
Name Deficiency Diseases

Vitamin A Hyperkeratosis, night blindness, and keratomalacia

Vitamin B1 (Thiamine) Beriberi

Vitamin B2 (Riboflavin) Slow growth, sore eyes

Vitamin B3 (Niacin) Pellagra

Vitamin C Scurvy

Vitamin D Rickets and Osteomalacia

Vitamin E Heart problems, Haemolysis and sterility

Vitamin K Haemorrhage
 Minerals
• Minerals are also organic compounds found in nature, which helps in the growth of the human body. Minerals are
essential for the human body to work properly.

• Deficiency of minerals leads to several disorders.

• Minerals can be obtained from food such as cereals, bread, meat, fish, milk, nuts, etc. Not all minerals are required by the
body.
 Functions of Minerals in Food
Calcium

I. Helps blood clotting.

II. Helps muscle contraction and nerve function.

III. Essential for building strong and healthy bones.

Chloride

I. Maintains proper blood volume, blood pressure, and pH of our body fluids.

Copper

I. Formation of red blood cells.

II. Helps with the functioning of the nervous system.

 Functions of Minerals in Food
Iodine

I. Promotes the normal functioning of the thyroid gland.

II. Helps in the proper functioning of brain functions.

III. Promotes normal growth and development of cells.

Magnesium

I. Provides structure for healthy bones.

II. Produces energy from the food molecules.

III. Maintains proper functioning of muscle and nervous system.

 Functions of Minerals in Food
Iron

I. Helps in transporting oxygen to all parts of the body.

II. Produces and stores the energy for further metabolisms.

Manganese

I. Helps maintain water balance.

II. Controls nerve impulse transmissions.

Sodium

I. Maintains cellular osmotic pressure.

II. Helps in maintaining blood volume and blood pressure and fluid balance in the body.
 Functions of Minerals in Food
Sulfur

I. Involved in protein synthesis.

II. Protects your cells from damage.

III. Helps in promoting the loosening and shedding of Skin.

Potassium

I. Controls nerve impulses and muscle contractions.

II. Helps in maintaining fluid balance in the body.

III. Maintains proper functioning of muscle and nervous system.

 Functions of Minerals in Food
Zinc

I. Aids in wound healing.

II. Supports the immune system.

III. Helps in the formation of strong bones.

IV. Controls the functioning of the sense organs in the nervous system.

V. Important and essential process of cell division and reproduction.

Phosphorus

I. Helps the body store and use energy.

II. Works with calcium in the formation of strong, healthy bones and teeth.
 Vitamins & Minerals
Vitamins Minerals

Vitamins are organic compounds obtained from animals and

Minerals are inorganic compounds originated in the earth
plants

All the 13 vitamins are needed All the minerals are not needed by the body

Vitamins are easily broken down by heat and chemical Minerals are indestructible and are less vulnerable to heat
agents. It is difficult to shuttle vitamins to the body from the and chemical agents. Minerals in water and soil easily find
food. their way to the body through plants and animals.

Vitamins are classified as water soluble and fat soluble. Minerals are classified as macrominerals and microminerals.

Vitamins develop red blood cells and help in blood clotting.

Minerals help in blood coagulation and muscle contraction.
They also release energy from the food and help in
They also help in the bone and tooth formation.
maintaining healthy skin, eye, and hair.
 Fats
• In nutrition, biology, and chemistry, fat usually means any ester of fatty acids,
or a mixture of such compounds, most commonly those that occur in living
beings or in food

• Fat happens to be the most concentrated source of energy in the diet that
providing about 8 to 9 calories per gram, while on the other hand,
carbohydrates and proteins have only four calories per gram.

• Fat is known to have three elements which include carbon, hydrogen, and
oxygen. But, it has more carbon and hydrogen than oxygen, leading to nine
calories per gram.

• Fats are the source of energy in food, belong to a group of elements called
lipids, and they are all combinations of saturated and unsaturated fats.
 Type of Fats
Saturated Fat

• It is responsible for bad cholesterol.

• They are found in most animal products like cheese, milk, meat and so on and hence one must limit the quantity of intake.

• Unsaturated fat, on the other hand, is the substance that should be used in place of saturated fats to lower cholesterol
levels.

• Trans fatty acids that one gets from vegetable oils also play a role in increasing cholesterol levels. Consuming saturated fat
in large quantities is the most popular reason for heart disease as it causes cholesterol to block the arteries.
 Type of Fats
Monounsaturated fats

• Monounsaturated fats are healthy fats found in Avocados, Macadamia nuts, Peanuts, Olives and Olive oil.

• It plays a vital role in protecting the heart and is also involved in supporting insulin sensitivity, fat storage, weight loss, and
healthy energy levels.

Trans Fats

• Trans fats are also called unsaturated fatty acids or trans fatty acids. These fats are naturally obtained in several foods such
as beef, lamb, whole milk, cheese, cream, and butter from cattle.

• Trans fats are present in many processed foods such as baked food items, cookies, crackers, snack foods, deep-fried foods
and other food made or fried in partially hydrogenated oils.
 Type of Fats
Polyunsaturated Fats

• Polyunsaturated fats are healthy fats, which are abundantly found in both plant and animal foods, such as vegetable oils,
Walnuts, Flax seeds, salmon, etc. These fats include both Omega 3 and Omega 6 fats.

• Omega 3 helps reduce inflammation and supports healthy hormone levels and cell membranes. Omega 6 fatty acids play
an important role in supporting healthy brain and muscle functioning.

• We need a small amount of omega-6 fatty acids in our diet. Corn, soybean, safflower, cottonseed, grapeseed and
sunflower oils are all high in omega 6’s.

• Apart from these, omega-6 fatty acids are also found in most baked goods like bread and bakery snacks and packaged
foods like cookies, crackers, chips, and french fries, which are not stable.
 Proteins
• Proteins are polypeptides. They are linear chains of amino acids linked by peptide bonds arranged into different groups.
These fundamental amino acids sequences are specific and its arrangements are controlled by the DNA.

• They are large and complex macromolecules or bio-molecules which perform a major role in the functioning and
regulating of our body cells, tissues and other organs in the human body.

• They are also used in providing strength to our body in producing hormones, enzymes, and other metabolic chemicals.
They are also involved in functioning and regulating of our body cells, tissues and organs.

• Since our body cannot synthesize these essential amino acids by its own, we should have plenty of protein foods in our
everyday diet to keep our body metabolisms stable.

• The most common food which has a higher amount of protein are eggs, almond, chicken, oats, fish and seafood, soy,
beans and pulses, cottage cheese, Greek yogurt, milk, broccoli, and quinoa.
 Functions of Proteins
• Enzymes: Enzymes mostly carry out all numerous chemical reactions which take place
within a cell. They also help in regenerating and creating DNA molecules and carry out
complex processes.

• Hormones: Proteins are involved in the creation of various types of hormones which help
in balancing the components of the body. For example hormones like insulin, which helps
in regulating blood sugar and secretin. It is also involved in the digestion process and
formation of digestive juices.

• Antibody: Antibody also known as an immunoglobulin. It is a type of protein which is

majorly used by the immune system to repair and heal the body from foreign bacteria.
They often work together with other immune cells to identify and separate the antigens
from increasing until the white blood cells destroy them completely.

• Energy: Proteins are the major source of energy that helps in the movements of our
body. It is important to have the right amount of protein in order to convert it into
energy. Protein, when consumed in excess amounts, gets used to create fat and becomes
part of the fat cells.
 Functions of Proteins
Aspect Functions Examples

Storage Legume Storage, albumin, and proteins. Supplies food during the early stage of
the seedling or embryo.

Hormone Signalling Counterpart activities of different body Glucagon and Insulin.

parts.

Transport It transport substances throughout the Hemoglobin.

body through lump or blood cells.

Contraction To carry out muscle contraction. Myosin.

Digestive Enzyme Breaks down nutrients present in the Pepsin, Amyla

food into smaller portions so that it can
be easily absorbed
 Lipids
• “Lipids are organic compounds that contain hydrogen, carbon, and oxygen atoms, which form the framework for the
structure and function of living cells.”

• Many lipids have both glycerol and fatty acids. Here the fatty acids are found esterified with glycerol. They can be then
monoglycerides, diglycerides and triglycerides.

• These are also called fats and oils based on melting point. Oils have lower melting point (e.g., gingelly oil) and hence
remain as oil in winters.

• Some lipids have phosphorous and a phosphorylated organic compound in them. These are phospholipids. They are found
in cell membrane. Lecithin is one example. Some tissues especially the neural tissues have lipids with more complex
structures.

• In the human body, these molecules can be synthesized in the liver and are found in oil, butter, whole milk, cheese, fried
foods and also in some red meats.
 Properties of Lipids
• Lipids are oily or greasy nonpolar molecules, stored in the adipose tissue of the body.

• Lipids are a heterogeneous group of compounds, mainly composed of hydrocarbon chains.

• Lipids are energy-rich organic molecules, which provide energy for different life processes.

• Lipids are a class of compounds characterised by their solubility in nonpolar solvents and insolubility in water.

• Lipids are significant in biological systems as they form a mechanical barrier dividing a cell from the external environment
known as the cell membrane.
 Deficiency Diseases
Types of Vitamins Deficiency Diseases

A (Retinol) Night blindness

B1 (Thiamine) Beri-beri

B2 (Riboflavin) Retarded growth, bad skin

B12 (Cyanocobalamin) Anaemia

C (Ascorbic acid) Scurvy

D (Calciferol) Rickets

K (Phylloquinone) Excessive bleeding due to injury

 Deficiency Diseases
Types of Minerals Deficiency Diseases

Calcium Brittle bones, excessive bleeding

Phosphorus Bad teeth and bones

Iron Anaemia

Iodine Goitre, enlarged thyroid gland

Copper Low appetite, retarded growth

 Deficiency Diseases
Nutrients Deficiency Diseases

Carbohydrates Hypoglycaemia and Ketoacidosis.

Proteins Kwashiorkor and Marasmus.

Iodine Goitre, Anaemia, Hypothyroidism.

Calcium Muscle spasms, low bone density, and Hypocalcaemia.

Sodium Gastrointestinal Distress, the Improper functioning of nerves and muscles.

Phosphorous Weak bones and muscles, joint pains, nervous system disorders, obesity, etc.
 Deficiency Diseases
Nutrients Deficiency Diseases

Vitamin – A Night Blindness and other vision problems.

Vitamin -B Beriberi.

Vitamin -C Gum bleeding and Scurvy.

Vitamin -D Improper growth of bones and Rickets.

Vitamin -E Heart problems and Haemolysis.

Vitamin -K Haemorrhage.
 Diseases
• The disease can be simply defined as a disturbance in the normal functioning of the body, among which few affect only the
particular organ system and some affect the entire body of an organism.

• There are numerous diseases which vary in their signs, symptoms, and causes. Pathology is the branch of medicine which
mainly deals with the study of disease, the nature of diseases, its cure, diagnosis, etc.

• Based on duration, diseases can be of two types:

I. Acute disease

II. Chronic disease.

• An acute disease is such a type of disease which occurs for a short interval of time. An acute disease if not treated properly
can eventually become a chronic disease.e.g. common cold, burn, etc.

• Chronic disease is a disease which lasts for a long period of time e.g. Heart and kidney diseases.
 Diseases
• A disease, which spreads from one person to another person, is termed communicable disease. It is also referred to as
infectious diseases or transmissible diseases.

• Infectious diseases are the diseases caused by various pathogenic microorganisms such as virus, bacteria, protozoan, fungi,
and other parasites.

• These infectious diseases can be transmitted by animals, humans, insects or other agents.

• Infectious agents are present all around us, and they come in different shapes and sizes. They can be categorized based on
some common characteristics.

• Some are single-celled animals such as fungi, bacteria and viruses. Other multicellular organisms such as worms are known
to cause diseases too.
 Diseases
• These infections are caused, when an organism invades into the body cells, releases toxins and triggers various reactions in
the host tissues.

Infectious Diseases Pathogen

Common cold, influenza, AIDS, dengue fever Viruses

Typhoid, Cholera Bacteria

Kala-azar Leishmania (Protozoa)

Acne Staphylococci (Bacteria)

Sleeping sickness Trypanosoma (Protozoa)

Elephantiasis Worms
 Types of Infectious Diseases
Viral Infections

• There are millions of viruses existing in the world. They are the main cause of viral infections such as common cold,
influenza, etc.

• The virus invades the body of a host and attaches itself to the cell where it releases its genetic material.

• The cell replicates and the virus multiplies. The cell lysis and releases more viruses that infect new cells.

• Few viruses change the function of the cells instead of killing the cells. For eg., Human Papillomavirus, Epstein-Barr Virus
causes uncontrolled replication of cells that leads to cancer.
 Types of Infectious Diseases
• Viruses are small infectious agents which are present in food, air and in water. They are smaller than bacteria and can be
seen only under an electron microscope.

• They penetrate very easily into our body through the mouth, nose, cuts, injuries, scratches on the skin from the
environment (from the soil, water, and air) and causes severe infections which may also lead to the person’s death.

• Viral infections can be easily transmitted from person to person. Viruses are obligate intracellular parasites and are
considered non-living outside the cell.

• Some viruses are transmitted through an insect vector. E.g.: Dengue virus. Antibiotics are ineffective against viruses.

• AIDS, Polio, Measles, Influenza are a few examples of infections caused by a virus.
 Types of Infectious Diseases
Bacterial Infections

• Bacteria can survive in any environment from extreme heat to extreme cold and even radioactive waste. There are
numerous bacterial strains some of which cause diseases.

• The bad bacteria cause diseases while good bacteria destroy bad bacteria and prevent diseases. Cholera, tuberculosis,
diphtheria, typhoid are some of the infectious diseases caused by bacteria.

• They can be treated by antibiotics but some bacteria become antibiotic-resistant and cannot be treated.

• There are millions and billions of bacteria present all around us. Few among them are present both inside and outside our
body and protects our body from the disease-causing microbes.

• These bacteria are called beneficial bacteria. The other group of bacteria, cause harm by entering into our body. The
harmful bacteria cause diseases in the body. These bacteria generally, engulf, reproduce kill the protective bacteria and
cause harm to the host cells by releasing toxins. Tuberculosis, Whooping cough, Typhoid, Cholera, are a few examples of
infections caused by bacteria.
 Types of Infectious Diseases
Fungal Infections

• A fungus decomposes and absorbs organic material with the help of an enzyme. Many fungal infections appear in the
upper layers of the skin while some penetrate to the deeper layers. Fungal spores when inhaled can lead to fungal
infections that affect the whole body..

• Some fungi are infectious and cause diseases in human beings. The fungal body is thread-like, known as hyphae.
Ringworm, Athlete’s foot are a few examples of infections caused by fungi.

• There are other agents, which act as a carrier or vectors and they carry the disease-causing microorganisms and spread
from one person to another person. These vectors include mosquitoes, rats, house flies, etc.
 Types of Infectious Diseases
Protozoa

• They are single-celled, microscopic, eukaryotic organisms. Malaria and other immune system disorders are few examples
of infections caused by the protozoan.

Diseases Microorganisms

Cold Rhinovirus

German Measles Rubella

Chickenpox Varicella zoster

Whooping cough Bardotella pertussis

Bubonic plague Yersinia pestis

Ringworm Trichophyton rubrum

Tuberculosis Mycobacterium tuberculosis

Malaria Plasmodium falciparum

Athlete’s foot Trichophyton mentagrophytes

 Microbes
• Microbes are minute, unicellular organisms that are invisible to the naked eye. They are also known as microorganisms or
microscopic organisms as they could only be seen under a microscope. They make up almost 60% of the earth’s living
matter.

• The term “microbes” is used to describe several different life forms with different sizes and characteristics.

• Microbes can be useful as well as harmful. Certain microbes cause severe infections and diseases and can also spoil food
and other materials. While others play an important role in maintaining environmental balance.
 Microbes
Bacteria

• Bacteria are unicellular, microscopic, prokaryotic microorganisms that contain no true nucleus.

• Their cell wall is made up of peptidoglycan. They have a flagellum that facilitates locomotion.

• Bacteria are of different types depending on their shapes and sizes. E.g., spherical-shaped bacteria are known as cocci;
rod-shaped bacteria are known as bacilli; spiral-shaped, spirilla, etc.

• They reproduce through binary fission, transfer of genetic material occurs through transformation, transduction and
conjugation, and through sporulation.

• Bacteria play an important role in human survival. They break down nutrients in the digestive system into simpler forms.

• Few bacteria such as Rhizobium are involved in nitrogen fixation.

• They are also used for making antibiotics and can also be used in agriculture as biopesticides.
 Microbes
Fungi

• These can be unicellular or multicellular with the cell wall made of chitin.

• These are heterotrophic and cannot synthesise their own food.

• They comprise membrane-bound organelles.

• Yeasts, moulds, mushrooms are some of the important fungi.

• They decompose dead plants and animals, extracting nutrients from them.

• Few fungi are harmful and cause fungal infections like ringworm. The others are used in making antibiotics like penicillin.

• Fungi such as yeast are used in the baking industries and also in the beer and wine industries.
 Microbes
Viruses

• Viruses are a connecting link between living and non-living.

• They are non-cellular microorganisms, composed of protein, nucleic acids, and lipids.

• They are measured in nanometers with sizes ranging from 20 nanometers to 250 nanometers and could only be seen with
an electron microscope.

• They contain the core of nucleotides surrounded by a protein coat which could invade living cells.

• They are active inside host cells and reproduce inside them by infecting living cells.
 Microbes
Protists

• These are unicellular, microscopic organisms that are neither plants nor animals.

• They may be autotrophic or heterotrophic.

• They reproduce mainly through binary fission or budding.

• This group includes plant-like protists such as diatoms, dinoflagellates, animal-like protists such as amoeba, and fungus-like
such as slime moulds.

• Protists supply us with oxygen and recycle crucial nutrients to make it available to other life forms.
 Microbes
Archaea

• These are unicellular prokaryotic organisms and have a structure similar to bacteria.

• Their cell wall is different from bacteria and contains unique lipids that enable them to survive in extreme conditions.

• They are also found in human gut and skin.

Biology - Lecture 3
 Topics
1. Human Biology
 Human Brain
• The brain, along with the spinal cord, constitutes the central nervous system. It is responsible for thoughts, interpretation
and origin of control for body movements.

• On average, an adult brain weighs between 1.0 kg – 1.5 kg. It is mainly composed of neurons – the fundamental unit of
the brain and nervous system.

• The brain is enclosed within the skull, which provides frontal, lateral and dorsal protection. Anatomically, the brain is
contained within the cranium and is surrounded by the cerebrospinal fluid.
 Human Brain
• The human brain is well protected by the skull. Inside the skull, the brain
is covered by cranial meninges consisting of an outer layer called dura
mater, a very thin middle layer called arachnoid and an inner layer
(which is in contact with the brain tissue) called pia mater.

• The Cerebrospinal Fluid (CSF) is a fluid that circulates within the skull
and spinal cord, filling up hollow spaces on the surface of the brain.

• The primary function of the CSF is to act as a buffer for the brain,
cushioning mechanical shocks and dampening minor jolts.

• The brain can be divided into three major parts: (i) forebrain, (ii)
midbrain, and (iii) hindbrain.
 Forebrain – Largest part of the brain
• It is the anterior part of the brain. The forebrain parts include: Cerebrum, Hypothalamus and Thalamus

• Forebrain Function: Controls the reproductive functions, body temperature, emotions, hunger and sleep.
 Cerebrum
• The cerebrum is the largest part of the brain. It consists of the cerebral cortex and other subcortical structures. It is
composed of two cerebral hemispheres that are joined together by heavy, dense bands of fibre called the corpus
callosum.

• The layer of cells which covers the cerebral hemisphere is called cerebral cortex and is thrown into prominent folds.

• The exterior portion of the cerebrum is called the cortex or the cerebral mantle.
 Cerebrum
• The brain consists of two types of tissues: Grey matter and White matter. The neuron cell bodies are concentrated here
giving the colour.

• Fibres of the tracts are covered with the myelin sheath, which constitute the inner part of cerebral hemisphere. They give
an opaque white appearance to the layer and, hence, is called the white matter.
 Cerebrum
The cerebrum is further divided into four sections or lobes:

• Frontal lobe: It is associated with parts of speech, planning, reasoning, problem-solving and movements.

• Parietal lobe: Help in movements, the perception of stimuli and orientation.

• Occipital lobe: It is related to visual processing.

• Temporal lobe: This region is related to perception and recognition of memory, auditory stimuli and speech.
 Cerebrum
The cerebrum also includes:

• Sensory areas: To receive the messages.

• Association areas: These areas integrate the incoming sensory information. It also forms a connection between sensory
and motor areas.

• Motor areas: This area is responsible for the action of the voluntary muscles.

Cerebrum Function

• The cerebrum is responsible for thinking, intelligence, consciousness and memory.

• It is also responsible for interpreting touch, hearing and vision.

 Thalamus
• The thalamus is a small structure, located right above the brain stem responsible for relaying sensory information from the
sense organs.

• It is also responsible for transmitting motor information for movement and coordination.
 Hypothalamus
• The hypothalamus is a small and essential part of the brain, located
precisely below the thalamus.

It is considered the primary region of the brain, as it is involved in the

following functions:

• Receives impulses & Regulates body temperature.

• Controls the mood and emotions and sense of taste and smell.

• Synthesises the body’s essential hormones and is involved in the

regulation of sexual behaviour.

• Coordinates the messages from the autonomous nervous system.

• Controls appetite, peristalsis, the rate of heartbeat, and blood

pressure.

• Forms an axis with the pituitary gland which is the main link between
the nervous and the endocrine systems.
Midbrain: Smallest and central part of the brain
• The midbrain is located between the thalamus/hypothalamus of the
forebrain and pons of the hindbrain. A canal called the cerebral
aqueduct passess through the midbrain.

• The midbrain consists of: Tectum and Tegmentum

 Tectum
• The tectum is a small portion of the brain, specifically the dorsal part of the midbrain.

• It serves as a relay centre for the sensory information from the ears to the cerebrum.

• It also controls the reflex movements of the head, eye and neck muscles.

• It provides a passage for the different neurons moving in and out of the cerebrum.
 Tegmentum
• Tegmentum is a region within the brainstem. Three major regions make up the brain stem; mid brain, pons and medulla
oblongata. Brain stem forms the connections between the brain and spinal cord.

• It is a complex structure with various components, which is mainly involved in body movements, sleep, arousal, attention,
and different necessary reflexes.

• It forms the platform for the midbrain and connects with the thalamus, cerebral cortex and the spinal cord.
 Hindbrain: The lower part of the brain
• The hindbrain is composed of: Cerebellum, Medulla, Pons

• Hindbrain functions: The three regions of the hindbrain coordinates all

processes necessary for survival. These induce breathing, heartbeat,
sleep, wakefulness and motor learning.
 Cerebellum
• The cerebellum is the second largest part of the brain, located in the posterior portion of the medulla and pons.

• The cerebellum has the cerebellar peduncles, cerebellar nuclei, anterior and posterior lobes.

• The cerebellum consists of two hemispheres, the outer grey cortex and the inner white medulla.
 Cerebellum
The main functions of the cerebellum include:

• It is mainly responsible for coordinating and maintaining the body balance during walking, running, riding, swimming, and
precision control of the voluntary movements.

• It senses equilibrium, coordinates eye movement and Transfers information.

• It enables precision control of the voluntary body movements.

• Predicts the future position of the body during a particular movement.

• Both anterior and posterior lobes are concerned with the skeletal movements.

• The cerebellum is also essential for making fine adjustments to motor actions.

• Coordinates and maintains body balance and posture during walking, running, riding, swimming.
 Medulla Oblongata
• The medulla oblongata is a small structure present in the lowest
region of the brain.

• It mainly controls the body’s autonomic functions such as heartbeat,

breathing, and digestion.

• It plays a primary role in connecting the spinal cord, pons and the
cerebral cortex.

• Also, it helps us in maintaining our posture and controlling our

reflexes.
 Pons
• The pons is the primary structure of the brain stem present between the midbrain
and medulla oblongata.

• It serves as a relay signals between the lower cerebellum, spinal cord, the
midbrain, cerebrum and other higher parts of the brain.

The main functions of the pons include:

• Controlling sleep cycles and Regulating the magnitude and frequency of the
respiration.

• Transfers information between the cerebellum and motor cortex.

• Pons is also involved in sensations, such as the sense of taste, hearing and
balance.
 Human Anatomy – Skeletal System
• Skeletal system consists of a framework of bones and a few
cartilages.

• The framework that enables us to do all activities is the skeleton.

Humans have as much as 300 bones at birth. However, the bones
start to fuse with age.

• At adulthood, the total number of bones is reduced to 206.

• The skeleton also protects several vital organs such as the heart,
lungs and the liver.

• Bones are attached to other bones through ligaments, a fibrous

connective tissue.
 Human Anatomy – Skeletal System
• It is grouped into two principal divisions – the axial and the
appendicular skeleton.

• Axial skeleton comprises 80 bones distributed along the main axis

of the body. The skull, vertebral column, sternum and ribs
constitute axial skeleton.

• The skull is composed of two sets of bones – cranial and facial,

that totals to 22 bones.

• Cranial bones are 8 in number. They form the hard protective

outer covering, cranium for the brain. The facial region is made
up of 14 skeletal elements which form the front part of the skull.

• A single U-shaped bone called hyoid is present at the base of the

buccal cavity and it is also included in the skull.

• Each middle ear contains three tiny bones – Malleus, Incus and
Stapes, collectively called Ear Ossicles.
 Human Anatomy – Skeletal System
• Our vertebral column is formed by 26 serially arranged units
called vertebrae and is dorsally placed.

• It extends from the base of the skull and constitutes the main
framework of the trunk.

• Each vertebra has a central hollow portion (neural canal) through

which the spinal cord passes.

• The vertebral column protects the spinal cord, supports the head
and serves as the point of attachment for the ribs and
musculature of the back.
 Human Anatomy – Skeletal System
• There are 12 pairs of ribs. Each rib is a thin flat bone connected
dorsally to the vertebral column and ventrally to the sternum.
 Human Anatomy – Skeletal System
• The bones of the limbs alongwith their girdles constitute
the appendicular skeleton.

• Each limb is made of 30 bones. The bones of the hand

(fore limb) are humerus, radius and ulna, carpals (wrist
bones – 8 in number), metacarpals (palm bones – 5 in
number) and phalanges (digits – 14 in number).

• Femur (thigh bone – the longest bone), tibia and fibula,

tarsals (ankle bones – 7 in number), metatarsals (5 in
number) and phalanges (digits – 14 in number) are the
bones of the legs (hind limb).

• A cup shaped bone called patella cover the knee ventrally

(knee cap).
 Joints
• Joints are the points at which two or more bones meet. They enable a range of movements like rotation, abduction,
adduction, protraction, retraction and more.

• Based on flexibility and mobility, joints can be further classified into movable joints and immovable joints.

• Movable joints are flexible while immovable joints (also called fixed joints) are non-flexible since the bones are fused.
 Joints
• Fibrous joints do not allow any movement. This type of joint is shown by the flat skull bones which fuse end-to-end with
the help of dense fibrous connective tissues in the form of sutures, to form the cranium.
 Joints
• In cartilaginous joints, the bones involved are joined together with the help of cartilages. The joint between the adjacent
vertebrae in the vertebral column is of this pattern and it permits limited movements.
 Joints
• Synovial joints are characterised by the presence of a fluid filled synovial cavity between the articulating surfaces of the
two bones. Such an arrangement allows considerable movement. These joints help in locomotion and many other
movements.

• Ball and socket joint (between humerus and pectoral girdle), hinge joint (knee joint), pivot joint (between atlas and axis),
gliding joint (between the carpals) and saddle joint (between carpal and metacarpal of thumb) are some examples.
 Muscles
• Muscles are specialised tissues which assist the bones in locomotion. Muscles are attached to the bones through tendons.

• Movement of limbs happens due to the contraction and relaxation of the corresponding muscles present in that region.

• Based on their location, three types of muscles are identified : (i) Skeletal (ii) Visceral and (iii) Cardiac.
 Muscles
• Skeletal muscles are closely associated with the skeletal components of the body.

• They have a striped appearance under the microscope and hence are called striated muscles.

• As their activities are under the voluntary control of the nervous system, they are known as voluntary muscles too.

• They are primarily involved in locomotory actions and changes of body postures.
 Muscles
• Visceral muscles are located in the inner walls of hollow visceral organs of the
body like the alimentary canal, reproductive tract, etc.

• They do not exhibit any striation and are smooth in appearance. Hence, they are
called smooth muscles (nonstriated muscle).

• Their activities are not under the voluntary control of the nervous system and
are therefore known as involuntary muscles. They assist, for example, in the
transportation of food through the digestive tract and gametes through the
genital tract.
 Muscles
• Cardiac muscles are the muscles of heart.

• Many cardiac muscle cells assemble in a branching pattern to form a cardiac muscle. Based on appearance, cardiac
muscles are striated.

• They are involuntary in nature as the nervous system does not control their activities directly.
 Muscles
• Joints help in the flexibility of bones, but a bone cannot be bent or stretched until a muscle acts on it.

• In other words, the muscles attached to that bone pulls it to the direction of movement.

• Furthermore, most movement involves muscles that work as a pair.

• For example, when we bend our arm, muscles in that region contract, become shorter and stiffer and pull the bones to the
direction of movement.

• For relaxation (stretching), muscles in the opposite direction have to pull the bones towards it.
 Disorders Of Muscular And Skeletal System
• Myasthenia gravis: Auto immune disorder affecting neuromuscular junction leading to fatigue, weakening and paralysis of
skeletal muscle.

• Muscular dystrophy: Progressive degeneration of skeletal muscle mostly due to genetic disorder.

• Tetany: Rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.

• Arthritis: Inflammation of joints.

• Osteoporosis: Age-related disorder characterised by decreased bone mass and increased chances of fractures. Decreased
levels of estrogen is a common cause.

• Gout: Inflammation of joints due to accumulation of uric acid crystals.

 Human Body Structure
• There are different cavities in the human body that house various organ systems.

• The cranial cavity is the space within the skull.

• The lungs are protected in the pleural cavity.

• The abdominal cavity houses the intestines, liver and spleen.

 Circulatory System
• A network of organs that allow the circulation of blood throughout the body is also known as the
cardiovascular system or vascular system. The vital function of the circulatory system is to transport
blood to all parts of the body, which is extremely important because it carries nutrients, oxygen,
carbon dioxide, hormones and blood cells which are required for the nourishment and growth the
cells of every organ.

It is a closed network consisting of :

• The heart

• Blood

• Blood vessels

• These with the help of certain other organs such as the lungs, are responsible for the circulation of
blood in the human body
 Blood
• Blood is a fluid connective tissue which plays an essential role in the circulatory
system.

• It also regulates the temperature and acidic balance of the body.

• Blood flows through a specified set of pathways called blood vessels.

• Blood cells, blood plasma, proteins, and other mineral components (such as
sodium, potassium and calcium) constitute human blood.
 Plasma
• The liquid state of blood can be contributed to plasma as it makes up
~55% of blood. It is pale yellow in colour and when separated, it consists of
salts, nutrients, water and enzymes.

• Fibrinogen, globulins and albumins are the major proteins. Fibrinogens are
needed for clotting or coagulation of blood. Globulins primarily are
involved in defense mechanisms of the body and the albumins help in
osmotic balance.

• Plasma also contains small amounts of minerals like Na+, Ca++, Mg++,
HCO3 –, Cl–, etc. Glucose, amino acids, lipids, etc., are also present in the
plasma as they are always in transit in the body.

• Factors for coagulation or clotting of blood are also present in the plasma
in an inactive form. Plasma without the clotting factors is called serum.

• Hence, blood plasma transfusions are given to patients with liver failure
and life-threatening injuries.
 Formed Elements
• Erythrocytes, leucocytes and platelets are collectively called formed elements and they constitute nearly 45 per cent of
the blood.
 Red Blood Cells (RBC) (Erythrocytes)
• Red blood cells consist of Haemoglobin, a protein, give blood its red colour. They are produced by the bone marrow to
primarily carry oxygen to the body and carbon dioxide away from it.

• RBCs are biconcave cells without nucleus in humans. Their main function is to transport oxygen from and to various tissues
and organs.

• A healthy individual has 12-16 gms of haemoglobin in every 100 ml of blood. RBCs have an average life span of 120 days
after which they are destroyed in the spleen (graveyard of RBCs).
 White Blood Cells (WBC) (Leucocytes)
• Leucocytes are colourless blood cells. They are colourless because it is devoid of haemoglobin.

• They are further classified as granulocytes and agranulocytes. WBCs mainly contribute to immunity and defence
mechanism.

• White blood cells are responsible for fighting foreign pathogens (such as bacteria, viruses, and fungi) that enter our body.

• They circulate throughout our body and originate from the bone marrow.
 Platelets (Thrombocytes)
• Tiny disc-shaped cells that help regulate blood flow when any part of the body is damaged, thereby aiding in fast recovery
through clotting of blood
 Blood Vessels
There are three types of blood vessels in the human body:

• Artilleries – They carry blood away from the heart. The arteries in the systemic loop carry oxygenated blood to different
parts of the body while the ones in the pulmonary loop carry deoxygenated blood to the lungs.

• Veins – They carry deoxygenated blood from the body and oxygenated blood from the lungs into the heart.

• Capillaries – Arteries break down into a minuscule network of capillaries, which are the smallest blood vessels and present
in the lungs and muscles.
 Functions of Blood
Fluid Connective Tissue

• Blood is a fluid connective tissue composed of 55% plasma and 45% formed elements including WBCs, RBCs, and platelets.
Since these living cells are suspended in plasma, blood is known as a fluid connective tissue and not just fluid.

Provides oxygen to the cells

• Blood absorbs oxygen from the lungs and transports it to different cells of the body. The waste carbon dioxide moves from
the blood to the lungs and is exhaled.

Transports Hormones and Nutrients

• The digested nutrients such as glucose, vitamins, minerals, and proteins are absorbed into the blood through the
capillaries in the villi lining the small intestine. The hormones secreted by the endocrine glands are also transported by the
blood to different organs and tissues.
 Functions of Blood
Homeostasis

• Blood helps to maintain the internal body temperature by absorbing or releasing heat.

Blood Clotting at Site of Injury

• The platelets help in the clotting of blood at the site of injury. Platelets along with the fibrin form clot at the wound site.

Transport of waste to the Kidney and Liver

• Blood enters the kidney where it is filtered to remove nitrogenous waste out of the blood plasma. The toxins from the
blood are also removed by the liver.

Protection of the body against pathogens

• The White Blood Cells fight against infections. They multiply rapidly during infections.
 Lymph (Tissue Fluid)
Lymphatic Ducts or Vessels

• It is also known as tissue fluid. It is produced by the lymphatic system

which comprises a network of interconnected organs, nodes and ducts.
These vessels are like veins.

Lymph

• All vertebrate possess a lymphatic system. It can be defined as blood

minus RBC’s. It is a yellowish fluid present in the lymph vessels. Lymph
consists of salts, proteins, water, which transport and circulates digested
food and absorbed fat to intercellular spaces in the tissues. Unlike the
circulatory system, lymph is not pumped; instead, it passively flows
through a network of vessels.

Lymph capillaries

• Small, thin, lined by endothelium resting on a basement membrane.

One end unites to form lymphatic ducts and one end is blind.
 Types Of Blood Circulation
The systemic circulation

• It carries oxygenated blood from the heart to all parts of the body
through a complex system of arteries and capillaries. It also carries
deoxygenated blood from these organs back to the heart through
veins.

The pulmonary circulation

• After the heart receives the deoxygenated blood from different parts
of the body, it pumps those to the lungs for expelling the carbon
dioxide and other impurities and collect oxygen, after which the
oxygenated blood is sent back to the heart for systemic circulation.
 Types of Circulatory System
Open Circulatory System

• In the open circulatory system, blood flows from lacunae, large open
spaces and through sinuses among the tissues.

• Blood comprises very low pressure in this system. They are usually found
in higher invertebrates namely insects, prawns, etc. Tissues are in direct
contact with the blood.

• Exchange of nutrients and gasses takes place between the tissue and the
blood directly.

• The flow of blood cannot be stopped as it flows in open space. The

respiratory pigment is present in the blood flowing through this system is
dissolved in plasma. Red Blood Cells are not present.
 Types of Circulatory System
Closed Circulatory System

• The blood does not come in direct contact with tissue. Blood comprises
very high pressure in this system. This circulatory system is found in
molluscs, echinoderms and in all vertebrates.

• The respiratory pigment is present in the blood flowing through this

system is found in Red Blood Cells. Closed Circulatory System is more
efficient as the volume of blood can be regulated by the contraction and
relaxation of the smooth muscles of the blood vessels.

• The flow of blood is quite rapid in this system. In the closed circulatory
system, blood flows through a closed system of chambers the heart and
blood vessels. Nutrients and gasses pass through the capillary wall to the
tissue fluid.
 Features of Circulatory System
The human circulatory system consists of blood, heart,
blood vessels, and lymph:

• The human circulatory system circulates blood through

two loops (double circulation) – One for oxygenated
blood, another for deoxygenated blood.

• The human heart consists of four chambers – two

ventricles and two auricles.

• The primary function of blood vessels is to transport

oxygenated blood and nutrients to all parts of the body.

• It is also tasked with collecting metabolic wastes to be

expelled from the body.
 The Heart
• The heart is a muscular organ, located roughly at the body’s midline in the thoracic region, and responsible for the
pumping of blood in the body.

• The heart is divided into four chambers: Right atrium, right ventricle, left atrium and left ventricles.

• The atriums collect the blood in the heart and the ventricles pump it to different organs.
 Structure of the Human Heart
• The human heart is about the size of a human fist and is divided into
four chambers, namely two ventricles and two atria.

• The ventricles are the chambers that pump blood and the atrium are
the chambers that receive blood.

• Among these both the right atrium and ventricle make up the “right
heart,” and the left atrium and ventricle make up the “left heart.”

• The structure of the heart also houses the biggest artery in the body
– the aorta.
 Structure of the Human Heart
• The right and the left region of the heart are separated by a wall of
muscle called the septum.

• The right ventricle pumps the blood to the lungs for re-oxygenation
through the pulmonary arteries.

• The right semilunar valves close and prevent the blood from flowing
back into the heart.

• Then, the oxygenated blood is received by the left atrium from the
lungs via the pulmonary veins.
 Internal Structure of Heart
Chambers of the Heart

• Vertebrate hearts can be classified based on the number of chambers

present.

• For instance, most fish have two chambers, and reptiles and
amphibians have three chambers.

• Avian and mammalian hearts consists of four chambers. Humans are

mammals; hence, we have four chambers, namely:

• Left atrium and Right atrium

• Left ventricle and Right ventricle

 Internal Structure of Heart
• Atria are thin and have less muscular walls and are smaller than
ventricles. These are the blood-receiving chambers that are fed by
the large veins.

• Ventricles are larger and more muscular chambers responsible for

pumping and pushing blood out into circulation.

• These are connected to larger arteries that deliver blood for

circulation. The right ventricle and right atrium are comparatively
smaller than the left chambers.

• The blood originating from the right side flows through the
pulmonary circulation, while blood arising from the left chambers is
pumped throughout the body.
 Internal Structure of Heart
Blood Vessels

• Veins supply deoxygenated blood to the heart via inferior and superior vena cava, and it eventually drains into the right
atrium.

• Capillaries are tiny, tube-like vessels which form a network between the arteries to veins.

• Arteries are muscular-walled tubes mainly involved in supplying oxygenated blood away from the heart to all other parts
of the body.

• Aorta is the largest of the arteries and it branches off into various smaller arteries throughout the body.
 Arteries and Veins
ARTERIES VEINS

Functions

Involved in carrying oxygenated blood except for pulmonary arteries Involved in carrying deoxygenated blood except for pulmonary veins

Walls

Consists of three distinct layers, which are rigid, thicker and highly
Consists of three distinct layers, which are thinner and less muscular.
muscular.

Position

Located deep within the body. Peripherally located closer to the skin.

Appearance

Red in colour. Blue in colour.

Transports

Carry blood away from the heart to various parts of the body. Carry blood towards the heart from the various parts of the body.

Rate of pressure

High pressure, as the blood flows by the pumping pressure of the

Low pressure, as the blood flows by the capillary action of the veins.
heart.
 Double Circulation
• The way blood flows in the human body is unique, and it is quite
efficient too. The blood circulates through the heart twice, hence, it
is called double circulation.

• Other animals like fish have single circulation, where blood

completes a circuit through the entire animal only once.

• The main advantage of double circulation is that every tissue in the

body has a steady supply of oxygenated blood, and it does not get
mixed with the deoxygenated blood.
 Digestive System
• The digestive system of the human body comprises a group of organs
that work together in converting food into energy and other basic
nutrients to power the body. The food we take in is digested and utilized
by our body, and the unused parts of the food are defecated.

• The digestive system of the human body is the sum of the

gastrointestinal tract (GIT; also called alimentary canal) and accessory
organs (tongue, liver, pancreas, etc.). These two parts together help in
the digestion process.
 Parts of the Human Digestive System
• The alimentary canal is the long tube through which the food that we
eat is passed.

• It begins at the mouth (buccal or oral cavity), passes through the

pharynx, oesophagus or food pipe, stomach, small intestines, large
intestines, rectum and finally ends at the anus.

• The food particles gradually get digested as they travel through various
compartments of the alimentary canal.

• Accessory organs are organs which participate in the digestion process

but are not actually a part of GIT. They stimulate the digestion by
releasing certain enzymes that help in breaking down the food.
 Digestive System
Mouth

• Food starts its journey from the mouth or the oral cavity. There are
many other organs that contribute to the digestion process, including
teeth, salivary glands, and tongue. Teeth are designed for grinding food
particles into small pieces and are moistened with saliva before the
tongue pushes the food into the pharynx.

Pharynx

• A fibromuscular y-shaped tube attached to the terminal end of the

mouth. It is mainly involved in the passage of chewed/crushed food
from the mouth through the oesophagus. It also has a major part in the
respiratory system, as air travels through the pharynx from the nasal
cavity on its way to the lungs.
 Digestive System
Oesophagus

• This is a muscular tube that connects the pharynx, which is a part of an

upper section of the gastrointestinal tract. It supplies swallowed food
along with its length.

Stomach

• It serves as a muscular bag which is situated towards the left side of the
abdominal cavity, beneath the diaphragm. This vital organ acts as a
storage for the food and provides enough time to digest meals. The
stomach also produces digestive enzymes and hydrochloric acid that
maintains the process of digestion. The exit of food from the stomach is
regulated by a sphincter muscle which releases it in small amounts into
the small intestine.
 Digestive System
Mucous

• It is an aqueous secretion produced by the mucous membranes. It

functions by protecting the stomach lining and gastric pits from the acid,
which is produced by the glands to destroy the bacteria that entered
along with the food particles.

Digestive enzymes

• They are the group of enzymes which functions by breaking down

polymeric macromolecules like biopolymers into their smaller and
simpler substances.

Hydrochloric acid

• It is the digestive fluid formed by the stomach during the process of

digestion. It functions by destroying harmful microorganisms present in
the food particles.
 Small Intestine
• Ironically, the longest part of the alimentary canal is the small intestine.
It is a highly coiled structure of about 7.5 meters in length.

• It is a very narrow tube with a large internal surface area. It is the site of
complete digestion in humans. It absorbs digested food completely. It
secretes intestinal juice. It receives bile juice from the liver and
pancreatic juice from the pancreas.

The small intestine is divided into three parts:

I. Duodenum

II. Jejunum

III. Ileum
 Functions of Small Intestine
Complete Digestion of Food

• The partially digested food is absorbed by the duodenum of the small intestine along with the digestive juices from the
liver, pancreas and its own walls.

• The liver secretes the bile juice, which converts fat into tiny droplets so that their digestion becomes easy.

• The pancreas produces pancreatic juice that breaks down fats into fatty acids and glycerol.

• The intestinal juice secreted by the walls of the small intestine breaks down starch and carbohydrates into simple sugars.

• These sugars are known as glucose. It also converts the proteins into amino acids.

• All these simple, broken down forms are called the digested food.
 Functions of Small Intestine
Absorption of Digested Food

• The food that is digested is absorbed into the blood vessels in the walls of the intestine.

• The finger-like projections known as villi, drastically increase the surface area of the small intestine for greater absorption
of the digested food.

• The blood carries the absorbed food material to different parts of the body.

• Glucose breaks down to form oxygen and carbon dioxide and releases the energy required for various life processes.

• The undigested and unabsorbed food passes from the small intestine to the large intestine.
 Large Intestine
• The large intestine is wider and shorter than the small intestine. It is about 1.5 meters in length. It is a combination of the
cecum, colon, rectum, and anal canal.

• The colon is the largest portion of the large intestine. It has three parts- Caecum, Colon, and Rectum.
 Large Intestine
Caecum

• It is a small sac-like structure containing symbiotic microorganisms.

The vermiform appendix (vestigial organ) is attached to it.

Colon

• It is divided into four regions- ascending, transverse, sigmoid and

descending.

Rectum

• Waste products are passed into the end of the large intestine called
the rectum and eliminated out of the body as a solid matter called
stool. It is stored in the rectum as semi-solid faeces which later exits
from the body through the anal canal through the process of
defecation.
 Accessory Organs
Pancreas

• It is a large gland present just behind the stomach. The

pancreas releases digestive enzymes to complete the process
of chemical digestion.

Liver

• The liver is a roughly triangular, reddish-brown accessory

organ of the digestive system located to the right of the
stomach. It produces bile, which helps in the digestion of fat
in the small intestine. The bile is stored and recycled in the
gallbladder. It is a small, pear-shaped organ which is located
just next to the liver.
 Human Teeth
• Humans have different types of teeth that perform various functions such as cutting, tearing, shearing, grinding and
crushing.

• The teeth are powered by the jaw muscles and lubrication is done with the help of saliva, which is produced in the salivary
glands.

• Teeth are one of the strongest parts of the human body. It is mainly composed of proteins (collagen) and minerals
(calcium).

• Apart from the digestion, teeth also play an important role in our speech.

• An adult will have 32 teeth, including the Wisdom teeth.

• Molars are the first permanent teeth to develop in, and most of the adults will have their complete set of permanent teeth
in place by the age of 21.
 Human Teeth
• Overall adults have 32 teeth in total, called permanent or secondary
teeth, and it includes:

• Eight incisors – Four incisors in the upper jaw and four incisors in the
lower jaw.

• Four canines – Two canines in the upper jaw and two canines in the
lower jaw.

• Eight premolars – Four premolars in the upper jaw and four premolars in
the lower jaw.

• Twelve molars - Six molars in the upper jaw and six in the lower jaw. It
also includes four wisdom teeth.
 Human Teeth
Incisors

• Incisors are present at the front of the mouth. These teeth have sharp edges and are adapted for cutting food into small,
chewable pieces. Humans have eight incisors, four incisors in the upper jaw and four in the lower jaw.

Canines

• Canines are also called cuspids. They are situated at the ‘corners’ of the dental arches. They are characteristically sharp,
elongated and pointy surface. Their primary function is to grip and tear food (tough food such as meat). Humans have four
canines, two in the upper jaw and two in the lower jaw.
 Human Teeth
Premolars

• Premolars are also called bicuspids and are located behind the canines. These teeth have a flat surface with ridges, which
is adapted for crushing and grinding food into smaller portions. Humans have eight premolars, two on each side of the
jaws.

Molars

• Molars are the largest and strongest teeth. It has a large and flat biting surface, which is well-adapted for grinding food.
Humans have 12 molars, six in each jaw. Four of those are wisdom teeth, which is also called the third molar, which come
in between the ages of 17 to 25.
 Human Respiratory System
• Human Respiratory System is a network of organs and tissues that helps us breathe. The primary function of this system is
to introduce oxygen into the body and expel carbon dioxide from the body.

Features of the Human Respiratory System

• The energy is generated by the breakdown of glucose molecules in all living cells of the human body.

• Oxygen is inhaled and is transported to various parts and are used in the process of burning food particles (breaking down
glucose molecules) at the cellular level in a series of chemical reactions.

• The obtained glucose molecules are used for discharging energy in the form of ATP- (adenosine triphosphate)
 Nose
• Humans have exterior nostrils, which are divided by a framework of
cartilaginous structure called the septum. This is the structure that
separates the right nostril from the left nostril.

• Tiny hair follicles that cover the interior lining of nostrils act as the body’s
first line of defence against foreign pathogens. Furthermore, they provide
additional humidity for inhaled air.
 Pharynx
• The nasal chambers open up into a wide hollow space called the pharynx. It
is a common passage for air as well as food. It functions by preventing the
entry of food particles into the windpipe.

• The epiglottis is an elastic cartilage, which serves as a switch between the

larynx and the oesophagus by allowing the passage of air into the lungs, and
food in the gastrointestinal tract.

• Talking while we eat or swallow may sometimes result in incessant

coughing. The reason behind this reaction is the epiglottis.

• It is forced to open for the air to exit outwards and the food to enter into
the windpipe, triggering a cough.
 Larynx
• Two cartilaginous chords lay the framework for the larynx. It is found in
front of the neck and is responsible for vocals as well as aiding respiration.

• Hence, it is also informally called the voice box. When food is swallowed, a
flap called the epiglottis folds over the top of the windpipe and prevents
food from entering into the larynx.
 Trachea
• The trachea or the windpipe rises below the larynx and moves down to the
neck.

• The walls of the trachea comprise C-shaped cartilaginous rings which give
hardness to the trachea and maintain it by completely expanding.

• The trachea extends further down into the breastbone and splits into two
bronchi, one for each lung.
 Bronchi
• The trachea splits into two tubes called the bronchi, which enter each lung
individually.

• The bronchi divide into secondary and tertiary bronchioles, and it further
branches out into small air-sacs called the alveoli.

• The alveoli are single-celled sacs of air with thin walls. It facilitates the
exchange of oxygen and carbon dioxide molecules into or away from the
bloodstream.
 Lungs
• Lungs are the primary organs of respiration in humans and other
vertebrates. They are located on either side of the heart, in the thoracic
cavity of the chest.

• Anatomically, the lungs are spongy organs with an estimates total surface
area between 50 to 75 sq meters.

• The primary function of the lungs is to facilitate the exchange of gases

between the blood and the air. Interestingly, the right lung is quite bigger
and heavier than the left lung.
 Types of Respiration
Aerobic respiration

• It is a type of cellular respiration that takes place in the presence of oxygen to produce energy. It is a continuous process
that takes place within the cells of animals and plants. This process can be explained with the help of the chemical
equation:

• Glucose(C6H12O6) + Oxygen(6O2) → Carbon dioxide(6CO2) + Water(6H2O)+ Energy (ATP)

Anaerobic respiration

• It is a type of cellular respiration that takes place in the absence of oxygen to produce energy. The chemical equation for
anaerobic respiration is

• Glucose(C6H12O6) → Alcohol 2(C2H5OH) + Carbon dioxide 2(CO2) + Energy (ATP )

 Disorders Of Respiratory System
• Asthma is a difficulty in breathing causing wheezing due to inflammation of bronchi and bronchioles.

• Emphysema is a chronic disorder in which alveolar walls are damaged due to which respiratory surface is decreased. One
of the major causes of this is cigarette smoking.

• Occupational Respiratory Disorders: In certain industries, especially those involving grinding or stone-breaking, so much
dust is produced that the defense mechanism of the body cannot fully cope with the situation. Long exposure can give rise
to inflammation leading to fibrosis (proliferation of fibrous tissues) and thus causing serious lung damage. Workers in such
industries should wear protective masks.
 Human Reproductive System
There are two types of reproduction – asexual and sexual.

• Sexual Reproduction –This process of reproduction is very complex that involves the formation and transfer of gametes,
followed by fertilization, the formation of the zygote, and embryogenesis.

• Asexual Reproduction — This process of reproduction involves only one parent and the new offspring produced is
genetically similar to the parent.
 Reproduction in Human Beings
• All human beings undergo a sexual mode of reproduction. In this process, two parents are involved in producing a new
individual.

• Offspring are produced by the fusion of gametes (sex cells) from each parent. Hence, the newly formed individual will be
different from parents, both genetically and physically. Human reproduction is an example of sexual reproduction.

• In human beings, both males and females have different reproductive systems; hence, they are known to exhibit sexual
dimorphism. Males have testes- also called testicles, while the females have a pair of ovaries.

• The reproduction in human beings involves the fusion of male and female gametes produced in their reproductive system.
The male reproductive system is different from the female reproductive system, both in structure and in function.
 Male Reproductive System
• The male reproductive system is located in the pelvis region.

• The male gametes, i.e., sperms are produced within the male reproductive system.

• Sperms are small unicellular structures with a head, middle piece, and a tail.
 Male Reproductive System
• Testicles (testes): A pair of oval-shaped organs masked in a pouch called the scrotum. They are responsible for the
production of sperms and the male hormone testosterone.

• Scrotum: It is a sac-like organ that hangs below the penis and behind it. It is the houses of the testicles, or testes, and
maintains a temperature (2–2.5oC lower than the normal internal body temperature) that is required for the production of
sperm by it.

• Vas deferens: The sperms produced in testes are stored in a tube called the epididymis. Here the sperms get matured and
pass to urethra through the muscular tube called vas deferens.
 Male Reproductive System
• Accessory glands: This includes three glands, namely seminal vesicles, prostate gland, and Cowper’s gland. The secretions
from the three glands mix to form a fluid called semen. Semen nourishes the sperm, increases the volume and helps in
lubrication.

• Penis: Penis is a cylindrical tube which serves as both reproductive organ and an excretory organ. It delivers sperms into
the vagina during sexual intercourse.
 Female Reproductive System
The female reproductive system is active before, during and after fertilization as well. It consists of the following parts:

• A pair of ovaries: Ovaries produce and store ovum in them. They also produce a female hormone called estrogen.

• Fallopian tubes (Oviducts): They are the site of fertilization. They connect ovaries with the uterus.

• Uterus: Uterus is the site of development for the embryo.

• Vagina: It is the part which connects the cervix to the external female body parts. It is the route for the penis during coitus
as well as a fetus during delivery.
 Female Reproductive System
Female reproductive system has two functions –

I. Production of female gamete called ovum/egg.

II. Providing nutrition and protecting the developing embryo.

• During puberty, eggs in the ovaries start to mature. One of the ovaries releases the matured ovum in every 28 to 30 days
and is called ovulation.
 Reproduction Process in Human Beings
• The process of fusion of sperm with egg (ovum) to produce zygote is called
fertilization. Fertilization is a crucial stage of reproduction in human beings.

• The fertilized egg is called the zygote. Zygote starts to divide into many cells and
develops into an embryo.

• Embryo moves into the uterus and gets attached to its walls.

• This process is referred to as implantation, and the implanted embryo eventually

develops into a foetus.
 Human Nervous System
• The characteristic behaviour of living entities is to respond to stimuli with the intervention of the nervous system.

• It is an organ system ascribed to send signals from the spinal cord and the brain throughout the body and then back from
all the body parts to the brain.

• The neuron acts as the mediator and is the basic signalling unit of the nervous system.

• Control and Coordination in simple multicellular organisms take place through only the Nervous system which coordinates
activities of our body.

• The nervous system or the neural system is a complex network of neurons specialized to carry messages.

• The complexity of the nervous system increases as we move towards higher animals.

• As we move further up the ladder, higher organisms such as vertebrates have a developed brain.

• In the human body, the neural system integrates the activities of organs based on the stimuli, which the neurons detect
and transmit.
 Human Nervous System
One of the most complex organ system to ever evolve, the human nervous system consists of two parts, namely:

• Central Nervous System (consists of the brain and spinal cord)

• Peripheral Nervous System (includes all the nerves of the body)

 Human Nervous System
Central Nervous System

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

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.
 Human Nervous System
Peripheral Nervous System

• Peripheral Nervous System (PNS) is the lateral part of the nervous system that
develops from the central nervous system which connects different parts of the
body with the CNS. We carry out both voluntary and involuntary actions with the
help of peripheral nerves.
 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.

• Dendrite stretches out from the cell body of a neuron, and it is the shortest fibre 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.

• 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
• A nerve is a cable-like structure within the body designed to conduct nerve impulses that relay information from one part
of the body to another.

• A typical nerve is made up of a bundle of fibres which are wrapped around layers of tissue and fat, and they stretch
throughout the body.

• These nerves transmit information along the axons to the respective organs. These are the basic elements that constitute
a nerve.

• Nerves are a part of the nervous system. They are primarily involved in control and the coordination of all the parts of the
body.

• The nervous system not only sends and receives messages but also processes them into chemical signals called impulses in
the human body.

• A wide network of nerves is spread throughout our body, which also runs through the brain, the spinal cord and many
organs.
 Types of Nerves
• There are three types of nerves in the human body which are classified based on
their functions. These are the sensory nerves, motor nerves and mixed nerves.

Sensory Nerves

• These are the nerves that send messages to the brain or the spinal cord from the
sense organs. These are enclosed in the form of a bundle like structures or nerve
fibres in the peripheral nervous system. They carry information from the PNS to the
CNS( Central Nervous System).
 Types of Nerves
Motor Nerves

• Motor nerves are those nerves those that carry the messages in the form of a response from the brain or the spinal cord
to other parts of the body such as the muscles and glnds. They are responsible for carrying the information from the CNS
to the PNS.
 Functions of Nerves
• The primary function of nerves to conduct an electrochemical impulse and convey information. These impulses are carried
by the individual neurons that make up the nerve.

• These impulses travel from one neuron to another by crossing a synapse. The messages are converted from electrical to
chemical and then back to electrical.

• The sensory nerves carry information from the receptor to the central nervous system where the information gets
processed.

• The motor nerves, on the other hand, carry information from the central nervous system to the muscles.
 Human Excretory System
The human excretory system organs include:

I. A pair of kidneys

II. A pair of ureters

III. A urinary bladder

IV. A urethra
 Human Excretory System
Kidneys

• Kidneys are bean-shaped structures located on either side of the

backbone and are protected by the ribs and muscles of the back.

• Each human adult kidney has a length of 10-12 cm, a width of 5-7
cm and weighs around 120-170g.

• The kidneys have an inner concave structure. The blood vessels,

ureter and nerves enter the kidneys through the hilum, which is a
notch at the inner concave surface of the kidney.

• The renal pelvis, a large funnel-shaped space is present inner to the

hilum, is has many projections known as calyces.
 Human Excretory System
Ureter

• A pair of thin muscular tubes called the ureter comes out of each
kidney extending from the renal pelvis. It carries urine from the
kidney to the urinary bladder.

Urinary Bladder

• It is a muscular sac-like structure, which stores urine. The urinary

bladder is emptied by the process of micturition, i.e. the act of
urination.

Urethra

• This tube arises from the urinary bladder and helps to expel urine
out of the body. In males, it acts as the common route for sperms
and urine. Its opening is guarded by sphincter muscles.
 Endocrine Glands And Hormones
• Endocrine glands lack ducts and are hence, called ductless glands. Their
secretions are called hormones.

• The classical definition of hormone as a chemical produced by endocrine

glands and released into the blood and transported to a distantly located
target organ has current scientific definition as follows: Hormones are non-
nutrient chemicals which act as intercellular messengers and are produced in
trace amounts.

• The Endocrine System is responsible for chemical coordination. Numerous

involuntary physiological activities are under the control of the endocrine
system. It consists of glands which release hormones. Endocrine glands are
also called ductless glands.

• Endocrine glands in animals are the hypothalamus, the pituitary gland, the
pineal gland, the thyroid, the parathyroid, the thymus, the pancreas, the
adrenal gland and the gonads.
 Hypothalamus
• This gland is a part of the brain that consists of neurosecretory cells. They
connect both the nervous and the endocrine system.

• The hypothalamus secretes various releasing hormones like gonadotropin-

releasing hormones and growth hormone-releasing hormones.

• These hormones act on the pituitary gland to stimulate other glands.

• The hormones produced by hypothalamus are of two types, the releasing

hormones (which stimulate secretion of pituitary hormones) and the
inhibiting hormones (which inhibit secretions of pituitary hormones).

• For example a hypothalamic hormone called Gonadotrophin releasing

hormone (GnRH) stimulates the pituitary synthesis and release of
gonadotrophins. On the other hand, somatostatin from the hypothalamus
inhibits the release of growth hormone from the pituitary.
 Pituitary Gland
• The pituitary gland is the master gland. It is a pea-sized gland that is
located at the bottom of the brain. It controls and regulates other glands
in the body.

• It produces growth hormone (GH), prolactin (PRL), thyroid stimulating

hormone (TSH), adrenocorticotrophic hormone (ACTH), luteinizing
hormone (LH) and follicle stimulating hormone (FSH).

• It also stores and releases two hormones called oxytocin and vasopressin,
which are actually synthesised by the hypothalamus.
 Pineal Gland
• This gland is also located in the brain. It releases the hormone called
melatonin which regulates the wake-up and sleep clock and helps in
immunity etc.

• In addition, melatonin also influences metabolism, pigmentation, the

menstrual cycle as well as our defense capability.
 Thyroid gland
• This is a butterfly-shaped paired gland located in the neck region. It
releases the hormones triiodothyronine (T3) and thyroxine (T4).

• These hormones regulate body metabolism. Iodine is vital for thyroxine

synthesis.

• Deficiency of iodine in our diet results in hypothyroidism and enlargement

of the thyroid gland, commonly called goitre.
 Parathyroid Gland
• This gland is located near the Thyroid gland in the neck region. The
hormone released by this gland is called Parathyroid hormone, which
regulates calcium and phosphorus level in bones.
 Pancreas
• The pancreas is an endocrine as well as an exocrine gland. That is why the
Pancreas is also known as a mixed gland.

• The pancreas secretes hormones like glucagon and insulin; these two
hormones balance the blood sugar level in the body.

• Other hormones secreted are somatostatin and pancreatic polypeptide.

 Adrenal Glands
• Adrenal glands have two regions known as the adrenal cortex and adrenal
medulla.

• The cortex region of the adrenal gland secretes the hormones cortisol,
aldosterone, and androgens while the medulla region secretes the
hormones adrenaline and noradrenaline.

• Adrenaline is the hormone responsible for the fight or flight response of

the body in times of emergency.

• These hormones increase alertness, pupilary dilation, piloerection (raising

of hairs), sweating etc.

• Both the hormones increase the heart beat, the strength of heart
contraction and the rate of respiration.
 Gonads
• Gonads are reproductive glands present in males and females. The male gonad is the pair of testes which secretes the
hormone testosterone. This is responsible for the secondary sexual characteristics in males.

• The female gonad consists of a pair of ovaries. They secrete two hormones estrogen and progesterone. Both of these
regulate secondary sexual characteristics in females.