Category Archives: Biology

CHAPTER – 1 (Introduction to Biology)

Introduction to Biology





Our universe operates under certain principles. For understanding of these principles, the experiments are done and observations are made; on the basis of which logical conclusions are drawn. Such a study is called “Science”. In brief science is the knowledge based on experiments and observations.


The Scientific study of living organisms is called Biology. The word biology is derived from two Greek words “bios” meaning life and “logos” meaning thought, discourse, reasoning or study. It means that all aspects of life and every type of living organism are discussed in biology.

Branches of Biology

Biology is divided into following branches:


The study of form and structure of living organisms is called morphology. It can be further divided into following two parts:
1. The study of external parts of living organism is called external morphology.
2. The study of internal parts of living organism is called internal morphology or anatomy.


The study of cells and tissues with the aid of the microscope is called Histology.

Cell Biology

The study of structure and functions of cells and their organelles is called Cell Biology.


The study of different functions performed by different parts of living organism is called Physiology.


The study of organisms in relation to each other and their environment is called Ecology or Environmental Biology.


Living organisms are classified into groups and subgroups on the basis of similarities and differences. This is called classification Taxanomy is that branch of biology in which organisms are classified and given scientific names.


The study of development of an organism from fertilized egg (zygote) is called embryology. The stage between zygote and newly hatched or born baby is called embryo.


The study of methods and principles of biological inheritance of characters from parents to their offspring is called genetics.


The body parts of ancient organisms or their impressions preserved in rocks are called fossils. The study of fossils is called paleontology. It also includes the study of origin and evolution of organisms.
It can be divided into two parts:
1. The study of fossils of plants is called Palaeobotany.
2. The study of fossils of animals is called Palaeozoology.


The study of metabolic reactions taking place in living organisms is called biochemistry. These reactions may be constructive or destructive. The assimilation of food is a constructive process and respiration is a destructive process.


It is the branch of biology which deals with the practical application of organisms and their components for the welfare of human beings e.g. disinfections and preservations of food, preservations of insulin and biogas from bacteria etc.

Relationship of Biology with other Sciences

In ancient times, there was no distinction of biology and other sciences. Different fields of sciences like biology, chemistry, physics and mathematics are met together in the writings of ancient scientists. In ancient times, these subjects were studied under one head “science”, but with the passage of time, the science developed very much and the huge scientific knowledge was then divided into different branches.
However even today the interrelationship of these branches cannot be denied.


The study of various biological phenomena according to principles of physics is called biophysics. For example, movement of muscles and bones based on principles of physics.


The study of different biochemical like carbohydrates, proteins and nucleic acids etc found in cells of living organisms and hundreds of the underlying chemical reactions in cells of organisms is called biochemistry.


The data obtained from observations and experiments on living organism is analyzed by various statistical methods. This is called Biometry.


The study of plants and animals and the basis of geographical distribution is called Biogeography.


The study of living organisms from economic point of view is called Bio-Economics. It includes the study of cost effectiveness and viability of biological projects from commercial point of view.

Biological Method of Study or Method Used to Solve the Problem of Malaria


Most of the biological investigations start with an observation. After selecting, specific biological problem, observations are made to collect relevant information. For example; take the case of Malaria. Malaria is the greatest killer disease of man for centuries. Malaria was one among many other diseases for which a cure was needed.
In 1878, A French physician, Laveran, studied the blood sample of Malaria patient under microscope and observed tiny creatures in it. These creatures were later called Plasmodium.


To solve a scientific problem, one or more possible propositions are made on the basis of the observations. Such a proposition is called a Hypothesis. The hypothesis is tested by scientific method.


A good hypothesis has the following merits:
1. It is close to the observed fact.
2. One or more deductions can be made from this.
3. These deductions should be confirmed doing experiments.
4. Results whether positive or negative should be reproducible.
To know the cause of malaria, following hypothesis was made:
Plasmodium is the cause of Malaria.”
Note: One or more than one possible deductions can be made from the hypothesis.


The logical conclusion drawn from a hypothesis is called deduction. Testing one deduction and finding it correct does not necessarily mean the hypothesis is correct and scientific problem is solved. Actually, if more deductions are found to be correct; the hypothesis will be close to solution of the problem.


Following groups are designed to perform experiments:

Experimental Group
It is the group of those people who are affected in some way and we do not know the real cause e.g. a group of malarial patients.

Control Group
It is the group of unaffected people e.g. persons group of healthy persons.
By keeping both of these groups under similar conditions, the difference between them is determined. To know the real cause of malaria, the experts examined the blood of about 100 malarial patients (experimental group). On the other hand, the experts examined the blood of about 100 healthy persons (control group).


During the experiments mentioned above; the plasmodium was found in blood of most of malarial patients. The plasmodim was absent in the blood of healthy persons. These results verified the deductions and thus the hypothesis i.e. the plasmodium is the cause of Malaria, was proved to a considerable extent.


If hypothesis is proved to be correct from repeated experiments and uniform results, then this hypothesis becomes a theory.

Scientific Principle

When a theory is again and again proved to be correct, then it is called a scientific principle.

Contributions of Muslims Scientists in the Field of Biology

Many Muslim scientists contributed a lot in the field of biology but the following names are more respectable:


Period: 722-817 A.D
Books: Alnabatat and Alhaywan
Contribution: He studied the life of plants and animals and wrote many books about them.


Period:741 A.D
Books: Al-Kheil, Al-Ibil, As-Sha, Al-Wahoosh, Khalaqul Insan.
Contributions: He described the body structure and functions of horses, camels, sheep, wild animals and human beings in detail.

Abu-Usman-Umer Al-Jahiz

Books: Al-Haywan
Contribution: He explained the characteristics of about 350 species of animals. He wrote on the life of aunts especially.

Al-Farabi and Abu-ul-Qusim Al-Zahravi

Period: 870-950 A.D
Books: Al-Nabatat, Al-Haywanat
Contribution: The above mentioned books were written by Al-Farabi. On the other hand, Al-Zahravi was famous for removal of stone from urinary bladder.


Period: 965-1039 A.D
Books: Al-Manazir, Mizan-ul-Hikma
Contributions: Both of these books were famous and well known at that time. These books were translated into Latin, Hebrew, Greek and other western languages. He explained the structure and functions of eyes and suggested the cornea as a site of vision.

Bu-Ali Sina

Period: 980 A.D
Book: Al-Qanoon Fil Tib Al-Shifa
Contribution: He wrote about plants, animals and non-living things in one book. He was expert in mathematics, astronomy, physics and paleontology.


Contribution: he described the blood circulation in the human body.

Ali Ibne Isa

Contribution: He worked on structure, functions of eye and about 130 diseases of eyes and their treatment.

Non-Muslim Scientists

There is long list of non-Muslim scientists who contributed a lot in the field of biology. But, the following scientists are very well known.


Period: 382-322 A.D
Book: Historia Animalia
Contribution: He classified the animals and called as founder of biological classifications. He classified animals into two units, genus and species which was called Oedos.


Contribution: He accepted sex in plants and desired about 500 plants. He is known as father of botany.


Period: 1514-1564 A.D
Contribution: He wrote a book on human body structure in which he described bones, muscles and orans in detail.

William Harvey

Period: 1578-1657 A.D
Contribution: He described the blood circulation in human body.

Carolous Linnaeus

Period: 1507-1778 A.D
Contribution: He described the blood circulation in human body.

Carolous Linnaeus

Period: 1578-1657 A.D.
Contribution: He gave a system of binomial nomenclature. He is known as father of taxonomy.

Schlelden and Schwann

Contribution: Scheiden (1838) studied the cells of plants and Schwann (1839) studied the cells of animals. They proposed the cell theory.

Louis Pasteur

Period: 1822-1895 A.D
Contribution: He proved that microbes are found in the air which spoils the food items.

Edward Jennar

Period: 1796 A.D
Contribution: He invented method of vaccination against Small Pox.

Robert Koch

Period: 1845-1910 A.D.
Contribution: He discovered bacteria as causes of main diseases like Tuberculosis.

Joseph Lister

Period: 1860 A.D
Contribution: He made antiseptic medicines like Iodine and Carbolic acid.

Charles Darwin

Period: 1859 A.D
Book: Origin of Species by Natural Selection
Contribution: He explained concept of evolution in his book.

Gregor Mendel

Period: 1822-1884 A.D
Contribution: He conducted experiments on Pea plants. He formulated the laws of inheritance. He is known as father of modern genetics.

William Lawrence and William Henry

Period: 1882 A.D
Contribution: They discovered X-ray crystallography to understand the structure of deoxyribonucleic acid (DN). They were father and son.

Francis Crick and James Watson

Period: 1953 A.D
Contribution: He discovered the double helix model of DNA and proved that DNA is found in cells of all living organisms.

Significance of Biology or Impact of Biological Study on Human Life

The present high level achievements of man are largely due to the advanced biological research. The study of biology is very important in routine matters of our life as described below.

Food Production

Food has basic importance in our life. Due to researches in biology, there are great achievements in agriculture. For the production of cereal crops; the best varieties of seeds were selected. The yield of wheat corn, rice, sugarcane and cotton has been enormously increased bringing healthy effect and prosperity. Today, the man has overcome the problems of balanced diet, food storage and famine.

Control on Diseases

Health is basic necessity of life. Due to researches in biology, the discovery of new antibiotics for many infectious diseases like plague, cholera, pneumonia, tuberculosis and typhoid has made the life easy. The infant mortality has reduced due to discovery of vaccines for fatal diseases like small pox, polio, tetanus and diphtheria. Today AIDS is problem for world. The germs of this disease destroy the natural resistance and immunities against diseases.
A medicine called AZT has been found effective for AIDS. Similarly many drugs have been discovered for treatment of cancer. Many organisms are used to produce drugs e.g. bacteria and fungi. We have controlled many infectious diseases by using drugs like penicillin and streptomycin. We have eliminated many harmful pests like locusts, flour beetle, termites, fungi, shipworm etc by using pesticides.

Genetic Engineering

Genetic engineering is a technology in which useful genes are inserted into the bacteria etc, to get required beneficial results. Using this technique, manipulation of heredity material is done and new species are produced e.g. Doli sheep. Today human insulin gene is inserted into DNA of bacteria to synthesize insulin on commercial bases. This insulin is found to be very useful in treatment of diabetic patients.

Pollution Control

Due to increasing urbanization, industrialization and automobiles, the man and other organisms have to face a great danger, “the environmental pollution”. due to pollution of air, land and water there is danger to humans aid wild life. Many plants and animals have been maintaining the balance in our environment for millions of years and now at the verge of extinction due to pollution. By biological research, scientists are busy to find out causes and ways to control the pollution. The biology thus, has greatly improved the quality of our life.

Space Biology

On Mars, some evidence of life has been found which is still under further investigation. During exploration of space the scientists have been conducted experiments on different plants, animals, fungi and bacteria in space and they have obtained very useful information.

Islamic concepts About Origin of Life

We have got much information about origin of life by studying the Holy Quran.

Ultimate Creator

The first thing learnt from teachings of Quran is that Allah is the ultimate creator of everything whether plants, animals or non-living things.
“Allah is the creator of all things and He is Guardian of overall things.” – (Surah Zamar-Ayat 62)
Not only plants, animals and non-living things and human beings but also the heavens and whole universe have been created by Allah.

Origin of Life from Water

The second important fact we get from Quran is that Allah has created all living thins from water.
“We made every thing from water.” – (Sura Ambia – Ayat 30)
Viruses, bacteria, algae, fungi, different plants, all animals and humans are all living things. According to Quranic verses, all diverse living things were created from water.

Common Origin

From above mentioned sayings of God there is an indication for common origin of living things or we can at least say that all living things have come out from water.

Creation of Man

Allah also sys in Quran:
“He created man from clay like the potter’s.” – (Sura Rehman – Ayat 14)
It seems that there were following two sages for creation of man:
1. Creation from water.
2. The first created thing, on admixing with clay was transformed into more advanced beings.
The same can also be applied to other animals because there are certain similarities between structure of man and other animals. In vertebrate animals, the structures of digestive system, respiratory system, blood circulatory system, excretory system and reproductive system etc are similar to great extent, although differ in other details. Reproduction in living things.
Once the life had been created, Allah implemented the process of reproduction for the continuity of races of animals and other organisms. The various stages of reproduction have been described in sura in following way:
“Then fashioned we drop a clot, then fashioned we clot a little lump, then fashioned we the lump bones, then clothed the bones with flesh.” – (Sura Almominoon Ayat 14)

Classification and Evolution

“Allah has created every animal from water some of them creep up on their bellies, other walk on two legs, and others on four, Allah creates what the pleases. He has power overall thins.” – (Sura Nur Ayat 45)
“Hath there come upon man (every) any period of time in which he was a thing unrememberd?” – (Sura Dahar Ayat 1)
The close study of above sayings of God reveals that all animals had a common origin but they gradually underwent changes after words and became different from each other i.e. some animals became crawler, some bipedal and some other tetra pods. The present animals are advanced forms of the past animals who achieved this form after passing through many changes.

Concept of Abiogenesis and Biogenesis for Origin of Life on Planet Earth

Scientific Views About Origin of Life

How did life originate on this earth? This may never be know for certain to science because neither it is possible today to make observation of primitive events when the life actually originated nor there is any fossil record of first formed soft bodied organisms. However, in 1950 some scientists created the primitive earth condition (approximately 4 billion years ago) in the laboratory and performed experiments. On the basis of results obtained from these experiments, scientists formulated some ideas. These ideas seem to be close to reality.

Abiogenesis and Biogenesis

In ancient times, there were two views about the origin of life:
1. According to one view, offspring are produced from their parents by process of reproduction, this is called concept of Biogenesis.
2. According to other view, living things are produced spontaneously from non-living things. This is called concept of Abiogenesis.
Because at that time, there was neither so much advancement in science nor scientific tools like microscope and other instruments were invented, which could help in detailed observations about reality. According to some people, insects are produced from dewdrops, rats from debris, frogs from mud, and maggots from putrefied meat. Some scientists like Copernieus, Bacon, Galileo, Harvey, and Descartes also believed this concept.
From 16th to 18th century many scientists performed experiments to test this concept. They found some animals to be developed from non living matter. Therefore this concept seemed to be correct.
Later on, scientists performed experiments with more care. First of all an Italian scientists, Francesco Redi, (1668) proved that this concept was wrong.

Redi’s Experiment

Redi took four bottles. He put a dead snake in one bottle, a few dead fish in second bottle, dead eel in third bottle and a piece of meat in the fourth bottle. All these bottles were left open. The flies could enter these bottles. Then he took four more such bottles. He put some dead animals in all four bottles but covered the mouth of bottles.
(Figure from book)
After few days, maggots were produced in four open bottles. Maggots were not produced in closed bottles. Moreover, no flies were seen. Therefore, it was proved that maggots were not produced spontaneously by produced due to flied which were visiting the open bottles. The maggots were the larvae produced from the eggs of the visiting flies.

Needham’s Experiment

In 1948, an English scientist Needham boiled the meat in the water and prepared gravy. He poured this gravy into the bottles and closes their mouth with corks. After some days, many microscopic organisms were produced. In this way, the believers of abiogenesis were once again gain courage.
(Figure from book)

Experiment of Spallanzani

In 1767, an Italian scientists Spallanzani criticized the experiment of Needham. He said that air entered the bottles through the pores of cork and hence living organisms were produced.
(Figure from Book)
Spallanzani put the boiled meat and vegetables in clean bottles and then sealed the mouth of bottles by heat. He placed these sealed bottles in boiled water to kill the possible germs. After some days, he found no organisms. He left the same boiled meat and vegetables in open bottles at the same time. Some living organisms were produced in these bottles. This supportd the concept of Biogenesis. But the believers of Abiogenesis said that air removed by Spallanzani was necessary for living things so no organisms were produced in sealed bottles. When oxygen was discovered the supporters of Abiogenesis said that Spallanzani had removed oxygen where by no life could be produced in his experiment.

Experiment of Louis Pasteur

The argument on Biogenesis and Abiogenesis continued up to the middle of, 19th century. A well-known French scientist, Louis Pasteur proved, after simple but very careful experiments, that abiogenesis could not occur in present environment of earth. He proved that living organisms could only be produced from their parents.
In 1864, Pasteur performed his experiment in front of the commission formed to solve the issue. He took flasks, which had long curved S-shaped necks. He placed fermentable infusion (Yeast + sugar + water) in flasks and left their mouth open.
(Figure from Book)
He boiled the yeast infusion in the flasks. After this, he allowed to cool them and kept them as such. He observed that no life ws produced even after the lapse of several days, because microscopic organisms entering along with air got stuck up in on the curved walls of the glass necks. Then he broke up the curved necks, so that air containing microscopic organisms could reach the infusion. Now he noted that microscopic organisms were produced within 48 hours. This proved that if care was taken and no microscopic organisms and reproductive structures (eggs or spores) approach the infusion, no life could be produced because thee is no spontaneous generation of life from non life. After Pasteur, no further experiments were performed on origin of life for the next 60 years. In 1920, a Russian biochemist Alexander Oparin and a British biologist J.B.S 1-Ialdane suggested that life on earth was originated after a long and gradual molecular evolution and there was no spontaneous and miraculous origin of life on earth.

Chemical and Organic Evolution of Life on Earth

The modern view of the origin of life stresses on the idea of chemical evolution. According to Oparin and Haldane, the origin of first life had been initiated from the time of the existence of the solar system (the sun with its nine planets). The earth, like the sun was made up of light and heavy elements. Heavy elements like iron, nickel etc were present in the nucleus of the earth, while the light elements and compounds like hydrogen, methane, nitrogen, carbon, ammonia, nitrogen oxide, etc in the form of vapours existed on the surface of the earth. These light elements and compounds were responsible for the first life on earth.
The earth had high temperature and radiation and had frequent and abundant discharges. In these conditions, the first life originated. Oparin and Haldane suggested that simple inorganic molecules slowly and gradually combined to produce complex organic molecules from which the simplest form of life (bacteria) came into existence. This process took a long time.
Haldane proposed that primitive earth’s atmosphere had only carbon dioxide, ammonia and water vapours. If a mixture of these gases is exposed to ultraviolet radiation, it leads to the formation of organic compounds like sugar and amino acids. As free oxygen was not available to check the radiation from reaching the earth so substances like sugar and amino acids went on accumulating under such conditions.
About 15 billion years ago, there was a huge explosion (Big Bag). The universe started expanding and the temperature dropped drastically. In time, about 4.6 billion years ago our earth and other planets appeared as part of the solar system. The primitive atmosphere of the earth was rich in hydrogen.
With the passage of time, the atmospheric temperature gradually dropped. This allowed condensation and heavy rains, which caused formation of oceans. Thunder and lightning sparks together with ultraviolet radiation caused reactions of the atmospheric gases resulting in the formation of simple organic molecules. These molecules came down with the rains and accumulated in the seas, oceans, lakes, rivers and the soil over a very long period of time. These molecules interacted and produced amino acids and proteins which are the body building substances.
The fossil evidence indicates that the earliest forms of organisms lived about 3.8 billion years ago. From this it is speculated that the origin of life started about 4 billion years ago.
The earliest organisms were heterotrophs. The depletion of the pre-existed food from the environment led to the evolution of organisms capable of making their own food. They became autotrophs, and added free oxygen into the atmosphere.
For at least the first 2 billion years of life on earth, all organisms were bacteria. About 1.5 billions years ago, the first eukaryotes appeared.
The idea of organic evolution was supported by scientists like Lamarck and Charles Darwin.

Differentiate between Biogenesis and Abiogenesis


A theory which describes the origin of life on the earth from pre-existing living organisms is called Biogenesis.
It was based on practical experiments and material evidence.
It was supported by the experiments performed by Redi and Pasteur.
It was based on practical basis.
It describes the process of reproduction as an essential ability of living organisms.


A theory which describes the origin of life on the earth from non living things is called Abiogenesis.
It was based on observations and national thoughts.
It was supported by the fungus of bread: and production of frogs in the mud.
It was based on theoretical basis.
It gives no scientific reasoning about the production of life.

Differentiate between Hypothesis and Theory


The process of making some possible answers for the related biological problem is called Hypothesis.
It is the step of biological methods which gives the way to carry on the research.
Hypothesis is an uncertain intelligent statement.
Hypothesis is formed from observations and collected facts.


The final explanation which is given on the basis of hypothesis and deduction if they are found correct is called theory.
It is the step of biological method which gives actual reason to biological method.
Theory is certain intelligent statement.
Theory is formed by experimentation, physical evidence to explain the laws of nature.


CHAPTER – 3 (Classification of Living Organisms)

Classification of Living Organisms





The arrangement of organisms into groups and subgroups on the basis of similar characters is called classification.

Basis of Classification

The classification of organisms is based on such features or characters, which are similar in one kind of organisms and different in different kind of organisms. These characters may be about internal morphology, (anatomy), external morphology, physiology, cell structure, especially the number of chromosomes and chemical composition (especially of proteins) and embryology of the organisms. These characters help in study of intra specific (within the same species) and intra specific (between different) species differences.
The presence of similar characters in different organisms indicates their common ancestory. This similarity because of common ancestral origin is called Homology e.g. arm of a monkey, flipper of a whale and wing of a bat show homology. They are dissimilar apparently but their internal structure (arrangement of bones and muscles) is same. These organs are called homologous organs. Due to this homology, we can, say that monkey, whale and bad had common ancestors and are placed in same large group “vertebrate”. This homology is proved to be very helpful in classification.

Aims/Objectives of Classification

These are given below:
1. To determine similarities and differences between different organisms.
2. To arrange organisms on the basis of similarities and differences.
3. To identify the organisms on the basis of their structure and other prominent characters and study them systematically and logically.
4. To find out inter-relationships of organisms.
First of all, Aristotle classified the organisms on the basis of their resemblances. After this, Theophrastus classified the plants. Then, after a long time, Carolous Linnaeus (1707-1778), suggested a new system of classification. In this way, he started modem taxonomy.

Units of Classification

The basic unit of classification is specie (Plural specie). A species is a group of organisms that can breed with one another in nature and produce fertile offspring. All members of a species have same number of chromosomes and also have many other features in common. All the mustard plants belong to one species. All the human beings belong to another species. The members of one species differ from members of other species and do not breed naturally with each other. Such different species, which are closely related, they are grouped in large group called genus (plural; genera) e.g. Brassica is a genus. It includes several species like mustard, cabbage and turnip. Similarly, Felis is a genus. It includes several species like lion, tiger and cat. Similarly, many closely related genera are placed in a bigger group called Family, families are grouped into an order, orders are grouped into a class and classes are grouped into a phylum (plural, phyla) or division (plural; division) in case of plants. The phyla or divisions are grouped into kingdom. All these units are divided into subunits e.g. sub genus, sub phylum and sub kingdom etc. The smallest the group or unit, the organisms found in this group, would be more similar, they have more number of of similar character.

Difference between Homologous and Analogous Organisms

The fruit of all plants, whether sweet, or sour, small and dry or large and fleshy, all are the homologous structures because they develop from ovary of flower. Their origin is common. On the other hand, wings of an insect, and a bird, despite having same function, are not homologous because their origin is different. Similarly green leaf of moss plant and that of any vascular plant are not homologous. These organs are similar in function but different in basic structure and origins are called analogous organs.

Biological Classification of Mustard Plant

Common Name —————– Mustard
Phylum or Division ———- Anthophyta
Class ———————– Dictyledonae
Order ———————– Capparales
Family ———————- Brassicaceae
Genus ———————– Brassica
Species ——————— Brassica Campestris

Classification of Human Beings

Common Name —————- Human
Kingdom ——————– Animalia
Phylum ——————— Chordata
Class ———————- Mammalia
Order ———————- Primates
Family ——————— Hominidae
Genus ———————- Homo
Species ——————– Homo sapiens
Scientific Name ———— Homo sapiens

Kingdoms of Organisms

The classification is not static, nor has only one system of classification been followed rather it is dynamic. Whenever any new knowledge is available about organisms, it is used in classification. Therefore, many systems of classification have been used. Living organisms are classified into two to five kingdoms.

Two Kingdom Systems

All organisms were classified into two kingdoms before present time.
1. Plant Kingdom (Plantae) – It includes all the small and large plants.
2. Animal Kingdom (Animals) – It includes all the animals.

Important Characters of Plants and Animals

Presence of cell wall and ability to prepare their own food were considered the most important characters of plants.
Lack of cell wall and inability to prepare food and characteristic mode of nutrition and especially the ability to locomote were considered the most important characters of animals.
Plant kingdom and animal kingdom were divided into large groups.

Binomial Nomenclature

The method of giving scientific names to organisms is called nomenclature. Same animal or same plants may be known by different names. It must have one scientific name so that there may be no confusion. To give such names to living organisms, the method was formulated by carolous Linnaeous (1753). This method is called Binomial Nomenclature. Because tis system is simple and comprehensive, so it is accepted and used in whole world.

Rules of Binomial Nomenclature

1. According to this method, every species of living organisms is given a Latinized scientific name consisting of two parts.
2. The first part is the name of genus and is called generic name. It starts with a capital letter.
3. The second part is the name of species and is called specific name. It starts with a small letter.
4. Both parts of scientific name of a species are either underlined separately or italicized.
The scientific name of mustard plant is Brassica campestris. The scientific name of rose plant is Rose indica. Similarly the scientific name of frog is Rana tigrina and that of human is Homo sapiens.

Significance of Binomial Nomenclature

Before establishment of binomial nomenclature, the names of organisms consisted of many words. These words were based on the characters of these plants or animals. In different countries, even in different parts of same country; local names were used for plants and animals. The same organism may be given different names e.g. turnip, shaljam, gongloo, thipar, and gogroon are all names of same plant. In England, there are at least fifty names for pansy. Similarly a single common name may be used for different kind of organisms e.g. the word “raspberry” is used for about 100 kinds of plants. This confusion can be avoided by giving each organism a scientific name according to binomial nomenclature proposed by Carolous Linnaeus in 1753. It is adopted by all taxonomists.

Biological Classification of Man

Common Name —————– Man
Kingdom ——————— Animalia
Phylum ———————- Chordata
Class ———————– Mammalia
Order ———————– Primates
Family ———————- Hominidae
Genus ———————– Homo
Species ——————— Homo sapiens

Biological Classification of Frog

Common Name —————– Frog
Kingdom ——————— Animalia
Phylum ———————- Chordata
Class ———————– Amphibia
Order ———————– Salientia (Anura)
Family ———————- Ranidae
Species ——————— Rana tigrina


CHAPTER – 4 (Virus, Bacteria and Cyano Bacteria)

Virus, Bacteria and Cyano Bacteria





A large number of living things are present in this world. Some of them are large and some are small. Majority of the organisms are so small that they re not seen with naked eyes. For their observation, we need a light microscope or even an electron microscope. These microscopic organisms are called micro-organisms.

Micro-organisms As a Heterogeneous Group

Micro-organisms are a heterogeneous group. It includes different kinds of organism viruses, bacteria, cyanobacteria, protozoa, certain algae and some fungi. On the basis of structure they range from sub-cellular to cellular for example, viruses are sub-cellular and all other micro-organisms are cellular. Bacteria, and cyanobacteria are prokaryotes (without nucleus) where as algae, fungi and protozoa are eukaryotes (with nucleus). On the basis of mode of nutrition algae are autotrophic while fungi and protozoa are heterotrohic. Therefore, micro-organisms differ in their structure and mode of characteristics of viruses, they are studied in a separate group where as bacteria and cyanobacteria, being prokaryotes, are included in kingdom Monera.


1. Virus is a Latin word which means “Poison”. Viruses are so small that they can only be seen with electron microscope.
2. Viruses have charcteristics of both living and non-living things.
3. Structurally they are not like, cell and are only made up of proteins and nucleic acids.
4. When they enter the body of any living organisms, they reproduce there like living organism.
5. They look like non-living crystals when they are out of the body of a living organism.
6. That is why they are placed between living and non-living things.
7. All viruses are parasites and cause different diseases in their hosts.
8. Viruses were discovered by Iwanowsky in 1892 from infected tobacco leaves. In 1935 W.M. Stanley isolated viruses in crystalline form from infected leaves of tobacco and observed them under electron microscope.

Size of Virus

Viruses are of different sizes. Their size varies from 0.01um to 0.03um(um is micrometer = 1/10,00,000 meter)

Shape of Virus

Viruses are of different shapes some are rounded, few are rod shaped, few polyhedral while some viruses look like tadpoles.

Structure of Virus

Viruses have same biochemical nature. In spite of their different shapes, they are made up of only two parts, an outer “coat”, and an inner “core”. The core is made up of DNA or RNA (never both) and the coat is made of protein. The outer protein coat determines the shape of viruses. e.g. in bacteriophage (virus that lives in bacteria) protein coat consists of two parts, head and tail. DNA is present in the head region but the tail has only protein. Most of the animal viruses contain DNA whereas plant viruses have RNA core bacteriophage is also called phage virus.

Viral Diseases in Plants

Ring spot in different plants, yellow in sugar beet and mosaic disease in tobacco, potato, tomato, bean and cabbage are the various diseases of plants, caused by viruses.

Viral Diseases in Animals

Mouth and foot disease in cattle and cowpox in horses, buffalo and cows are caused by viruses.

Viral Diseases in Humans

In human beings, viruses produce common cold, influenza, small pox, yellow fever, polio, infectious hepatitis, cancer and AIDS.

Ways of Viral Transmission

1. Through droplets produced during coughing and sneezing.
2. Through contact.
3. By air, contaminated water and food.
4. Through insects.
5. By reuse of already used syringes.
6. By un-sterilized surgery equipments.


Bacteria are found every where in air, water, living and dead bodies of organisms and even in glaciers and hot springs. These are unicellular micro-organisms.

Discovery of Bacteria

Leeuwenhoek discovered bacteria in 1697 for the first time. Later, Louis Pasteur and Robert Koch worked on them. They discovered that bacteria produce many diseases in men and animals.

Size of Bacteria

Bacteria (singular : bacterium) range from 1um to 10um in length and from 0.2um to 1um in width and can be observed under light microscope.

Types of Bacteria

On the basis of shape and form, bacteria are of four types. These are as follows:
1. Rounded – Cocci (singular; coccus)
2. Rod-like – Bacilli (singular; bacillus)
3. Spiral shaped – Spirilla (singular; spirillum)
4. Comma like – Vibrios (singular; vibrio)
Bacteria occur both singly and in colonies. Cocci bacteria are found in groups of two or four, or in irregular groups and even in the form of long beads. Baccilli are found singly or may join end to end to form long threads. But Spirilla and Vibrios occur singly.

Structure of Bacteria

1. Bacteria are single celled prokaryotic organisms.
2. Bacterial cell is surrounded by a cell wall which is made of carbohydrates and amino acids.
3. Some bacteria have an additional slime capsule around their cell wall, which protects them and prevents them from drying.
4. Ribosomes help in synthesis of proteins. Nucleus is absent in bacterium. However, only a single large circular molecule of DNA is present which is surrounded by a clear zone of cytoplasm. It is known as nucleoid. This is not bounded by a nuclear membrane.
5. In addition to main bacterial DNA small, circular molecules of DNA called plasmids are also found. Plasmids play an important role in transmission of some heredity characteristics. Plasmids are also used a vectors in genetic engineering.
6. Motile (which can move) bacteria like bacilli are spirilla have one or more thread like flagella (singular; flagellum) which help them in their locomotion. Non motile bacteria like cocci lack flagella.

Economic Importance of Bacteria

It is generally thought that bacteria are fatal and harmful organisms and there is no beneficial aspect. But this is wrong impression. There are number of bacteria which are not only beneficial for mankind but are also essential for living system. Bacteria play very important role in the life of living organisms.

Beneficial Bacteria

Ecological Importance
These, along with fungi, help to decompose dead organisms and their refuse into simpler substances replenishing the raw materials in the soil and atmosphere and can thus purify the environment.

Bacteria and Nitrogenous Compounds in Soil
These bacteria are called nitrogen fixing bacteria. Another kind of bacteria live in the soil, called nitrifying bacteria which convert ammonia into nitrite and then to nitrate, enhancing the amount of nitrogen in the soil. In this way fertility of soil is increased.

Industrial and Commercial Purposes
1. These are used in manufacturing butter, cheese and yogurt.
2. These are used in processing of commercial fibers, leather, coffee, tobacco and vinegar.

Bacteria Synthesize Enzymes
Bacteria synthesize cellulose enzyme in the stomach of herbivore animals which helps in the digestion of food. Some bacteria also synthesize vitamin “B” and “K” in the large intestine of man and other mammals.

Bacteria as Bio-Insecticides
Recently the use of bacteria in bio-insecticides has become popular.

Harmful Bacteria

1. Bacterial decomposition on one hand is beneficial but on other hand causes damage to food, wood, clothes and other things.
2. Denitrifying bacteria in soil decrease the amount of nitrogen in soil and reduce the soil fertility. These are called identifying bacteria.
3. Many bacteria are harmful and cause many diseases in plants, such as canker disease in citrus fruits, rot and fire blight in peach, pear and apple, and potato scab in potato.
4. In animal like cattle bacteria cause T.B and anthrax. Bacteria also cause many diseases in man like T.B, Whooping Cough, Diphtheria, Typhoid, Pneumonia, Tetanus, Plague, Bacterial Dysentery, Cholera, Leprosy etc.

Ways of Bacteria Transmission

1. Whooping cough, Diphtheria, T.B and Pneumonia causing bacteria are transmitted from one person to other person through sneezes and cough droplets released in air.
2. Bacteria causing Typhoid and Cholera, are transmitted from one organism to another through contaminated water and food.
3. Plague and bacterial dysentery read through vectors like flies and animals.


1. Cyanobacteria are also called blue green algae. They are simplest living organisms which have the ability to manufacture their own food by photosynthesis.
2. Structurally they resemble bacteria. Bacteria and Cyanobacteria are prokaryotes and they are placed in kingdom Monera.
3. Generally Cyanobacteria are found in moist places like of trees, rocks and soil, fresh water and oceans.
4. Some of them are symbionts and some are epiphytes.
5. Cyanobacteria are usually unicellular and solitary.


A common example of cyanobacteria which has filamentous structure which is found in the form a ball is called Nostoc.

Characteristics of Nostoc

The important characteristics of Nostoc are:
1. It has a filamentous structure which form a ball like structure of Nostoc.
2. It floats on water.
3. Each filament of Nostoc is unbranched and has a single row of rounded or oval cells.
4. Each cell of Nostoc has double layered wall.
5. The protoplasm is differentiated into two parts.
6. Endoplasmic reticulum, mitochondria, golgi bodies and vacuoles are not present in the structure of Nostoc.
7. Heterocyst are found which help in nitrogen fixation.
8. Nostoc is an autotroph like other Blue-green-Algae.

Taxonomic Position of Nostoc

According to new classification, Nostoc belongs to kingdom prokaryota or Monera.

Structure of Nostoc

The structure of Nostoc is filamentous. The filaments are interring mixed in agelatinuous mass forming a ball like structure. It floats on water. A single filament looks like a chain of beads. Each filament is unbranched and has a row of rounded or oval cells.


CHAPTER – 5 (Fungi and Algae)

Fungi and Algae





During rainy season, a large number of umbrella-shaped mushrooms emerge on dung-piles. Fluffy mass of tangled threads like structure with black-dots of molds is also often seen growing on orages and bread, these mushrooms and molds are fungi.

Characteristics of Fungi

1. Fungi are simple heterotrophic eukaryotes which cannot manufacture their food and have absorptive mode of nutrition (e.g. absorbed prepared food).
2. Cell wall is made up of Chitin instead of cellulose.
3. Some fungi are parasitic while others are saprotrophs.

4. Parasitic fungi obtain their food from other living organisms.
5. Saprotrophic fungi get their food from dead animals, plants, their wastes and decaying materials.

Economic Importance of Fungi

Fungi are useful as well as harmful to humans. e.g.

Useful Aspects of Fungi

Saprotrophic Fungi
Saprotrophic fungi chemically break down dead bodies of organisms and their wastes into simple components. They clean the environment and also cause the recycling of nutrients.

Mycorrhizal Fungi
Mycorrhizal fungi improve the growth production of crop plants.

Edible Fungi
Mushrooms and some other fungi are edible.

Some antibiotics are also obtained from some fungi. For example, Penicillin, the first antibiotic discovered in 1928 by Alexander Flemming. Penicillin is obtained from the fungus penicillium.

Yeasts are used in making bread and alcohol.


1. During rainy season, a large number of umbrella like mushrooms emerge on dung piles.
2. Mycelium of mushroom is saprotrophic, spreading under group in the soil that contains, decaying and organic matter.
3. When spores are to be formed, many hyphae of mycelium come out of the soil to form umbrella shaped fruit bod, the familiar mushroom. It can be 3,4 inches in height.
4. Fruid body consists of two main parts; a lower stalk or stripe, and an upper umbrella shaped cap or pilens which bears annulus around it just below the cap.
5. On maturation, many radial plates or gills are seen on the underside of the cap on which enormous numbers of spores are produced.
6. Some mushrooms, like Agaricus, can be used as food before their fruit bodies become overripe. Agaricus is rich in protein. Some mushrooms, like Amanita, are deadly poisonous.


Algae are a group of simple eukaryotes in which, like plants, chlorophyll is found. They are photosynthetic autotrophs and have cellulose in their cell wall. However unlike plants but ike fungi, their organs are unicellular and body is simple, thallus. Therefore they are placed in another kingdom, the Protista.
Algae, are mostly (found in water). A large number of algae are found in vast saltwater oceans. These are called marine algae, other are found in lakes, ponds, puddles, streams and rivers. These are called fresh water algae. Some marine algae, called the helps and grow as long as 60 meters or more in a season. Some of them are used as food.

Characteristics of Algae

1. All the algae have chlorophyll so they are autotrophic; they make their own food by photosynthesis.
2. Their cell walls are made up of cellulose.
3. Algae are mostly marine found in the sea. While others are found in fresh water lakes, ponds, puddles, streams and rivers and they are also found in damp soil.
4. Their plant body is called a thallus without a true root, stem or leaf.
5. Algae are sometimes classified on the basis of the pigments they contain. Their green colour can be masked by the presence of other pigments.
6. Their reserved food material is starch.
7. Algae have a wide variety from unicellular algae, e.g. chlamydomanas and spirogyra to multicellular large seaweeds like sargassum.
8. Previously algae were regarded as plants and were placed in thallophyta.


It is fresh water green alga, commonly found in fresh pond and drains. It is single celled green algae which are seen only under a microscope.


1. Chlamydomonas is spherical, oval or pear-shaped.
2. The cell is enclosed by a cell wall which maintains its shape.
3. In the anterior part, the cell wall forms an outgrowth called apical papilla.
4. Two flagella (singular flagellum) arise from the cytomplasm below the apical papilla and come out through the cell wall. These help in swimming.
5. A thin cell membrane lies beneath the cell wall, it represents the ourter surface of cytoplasm.
6. In cytoplasm, there is, a cup shaped chloroplast, which is involved in production of food by process of photosynthesis.
7. The chloroplast contains, a spherical structure called pyrenoid in its posterior part, and a single red orange light-sensitive eye-spot on one side in its anterior regions.
8. The pyrenoid is supposed to store carbohydrates in the form of starch grains.
9. The eye spot helps chlamydomonas to determine its position nd direction according to changes in the intensity of light.
10. There are two contractile vacuoles near the base of flagella ‘which periodically expel excess water and waste from the cell.
11. A nucleus is present in the middle of chloroplast in the cytoplasm.
12. Although body, of chlamydomonas consists of a single cell, yet it performs all the basic functions of life. It reproduces both sex and asexual.


1. Spirogyra is a multicultural filamentous green alga. It is found in great abundance in fresh water ponds, lakes and streams. Its filamentous thallus consists of cylindrical cells.
2. These cells are joined end to end, to form un-branched filaments. Usually the filaments are found occurring in a large number.
3. The filaments are surrounded by a layer of mucilage that makes them slippery.
4. During day time, the oxygen produced during photosynthesis stores in the mucilage and the filaments start floating on the surface of water.
5. Each cell of Spirogyra is usually twice as long as broad.
6. The cell is surrounded by cellulosic cell wall. A peripheral layer of cytoplsm is present just inside the cell wall and around a large, central vacuole.
7. The vacuole is filled with cell sap.
8. A single nucleus is suspended near the vacuole by cytoplasmic strand.
9. The most prominent part of cell is its chloroplast. There may be one ore more than one chlrorplasts in each cell. The chloroplasts run along the; length of the cell in the form of spiral ribbon in the peripheral cytoplasm.
10. Numerous pyrenoids are located in a row in the chloroplast and are meant for storing starch. Spirogyra continually grows in length by cell division.
11. Each cell can be divide into two, so filament increases in length. The Spirogyra reproduces both sexually and asexually


CHAPTER – 6 (Bryophytes and Tracheophytes)

Bryophytes and Tracheophytes





Bryophytes are on of the two main groups of kingdom ‘Plantae’ the second being the ‘tracheophytes’. Bryophytes is a group of plants which are multicellular, photosynthetic eukaryotes; and their reproductive organs are multicellular; their zygote develops into small, protected embryo that develops into a complete new hence bryophytes have also been called embryophytes. The cell of these plants is made up to cellulose.

Characteristics of Bryophytes

The important characteristics of Bryophytes are as follows:
1. Bryophytes are plants without vascular tissue (xylem a phloem), whereas tracheophytes have vascular tissue. Therefore tracheophytes are vascular plants, whereas bryophytes are non-vascular plants.
2. Bryophytes are the simplest land plants. Bryophytes divided into three groups. Liverworts, hornworts, and mosses.
3. Marchantia is an example of liverworts; its plant body is a thick branched green thallus.
4. Anthoceros is a horn wort, and Funaria is a moss.
5. All bryophytes and generally found growing in moist habitants such as damp soil and rocks, moist brick walls, and along the banks of streams.

Life Cycle of Funaria Moss

It is a common moss found grwoing t moist places. Green leafy, moss plant of Furania, as like all Bryophytes, Funaria is haploid gametophyte, its height is about 0.5 – 1 inch.

Gamatophyte Generation

It consists of 3 parts:
1. A vertical stem like structure.
2. Leaf like photosynthetic structures arranged on the stem, which are composed of a single layer of cells, and without stalk.
3. Numerous multicellular rhizoids, arising from the lower side of the stem and which absorb water and salts, and anchor the plant to the soil.
Male sex organs, called antheridia (singular antheridium) are located at the tip of male branch, and the female sex organs, called archegonia (singular archegonium) are located at the tip of female branch.
Fertilization takes place in the presence of water within the archegonium located at the tip of female branch. The zygote develops into the embryo (2n). The embryo forms the sporophyte (2n). The sporophyte remains attached to the tip of female branch. The sporophyte gets water, slts and also part of its food, from the parent gametophyte plant.

Sporophyte Generation

The sporophyte consists of three parts:
1. A foot
2. A long stalk like seta
3. Capsule
The foot is anchored to the female branch and absorbs nutrients from the gametophyte. The seta elevates the capsule in the air. Within the capsule, haploid spores are produced by meiosis. The spores are dispersed by wind. Each spore develops eventually into new haploid gametophyte plant, and the life cycle continues.
Like other bryophytes, Funaria also has well defined alteration of generations; haploid gametophyte generation is dominant, whereas diploid sporophyte is attached to and more or less dependent on the gametophyte.


1. Unlike bryophytes the plant body in Pteridophytes is differentiated into root, stem and leaves.
2. In contrast to other vscular plants Pteridophytes do not bear flowers, fruits and seeds.
3. Due to presence of vascular tissues, they are similar to gymnosperms and angiosperms.
4. Although the dominant generation in Pteridophytes is also the sporophyte but unlike gymnosperms and angiosperms both sporophyte and gametophyte generations are independent and free living. However, the gametophyte in much reduced and smaller in size.


Seed plants or Spermatophytes are that group of vascular plants which produce seeds. Seed is a ripened ovule. It contains a young plant with embryonic root, stem and one or more leaves, which has stored food material and is protected by a resistant seed coat or testa.
Spermatophytes like pteridophytes possess vascular tissues. They also have life cycles with alternation of generations. Unlike bryophytes and pteridophytes, spermatophytes do not have free living gametophyte; instead the gametophyte is attached to and nutritionally dependend upon the sporophyte generation.

Main Groups of Spermatophytes

They produce seeds which are totally exposed or borne on the scales of cones.

They are flowering plants which produce their seeds within a fruit.

Pinus and Thuja – The Typical Gymnosperm

Pinus is normally grows at an altitude of 5000 ft to 8000 ft. It has many types e.g. chir, kail, chilghoza etc. However, some species are found in the plains. It is also grown as ornamental plants. Pinus tree is a sporophyte, which is evergreen and quite tall. It consists of an extensive root system and a strong, stout and woody stem and its branches. The upper branches progressively become shorter in length. In this way, the tree assumes a symmetrical conical shape.


Thuja (common known as Mor Pankh) is a short tree. It has profuse branches, which are covered with small, dark green scale leaves. It is conical in appearance. It is grown as ornamental plant in parks and homes.

Leaves of Thuja
Thuja has small scale like green leaves that cover the stem.

Female Cone of Thuja
In Thuja the female cones are spherical or oval in shape. These are about the size of a bair (berry). They consist of hard, brown colour scales with triangular apices.


Pinus has two types of shoots.

Shoots of Pinus
Long Shoots or Shoots of Unlimited Growth
They are formed on the main stem and continue growth indefinitely by buds borne at their apices. They are covered by scale leaves.
Dwarf Shoots or Shoots of Limited Growth
These shoots originate in the axils of the scale leaves on the long shoots. They are very short (only a few millimeters in length). Each dwarf shoot bears 1 t 5 foliage leaves in addition to scales leaves.

Leaves of Pinus

Scale Leaves
These are small, membranous and brown in colour. They cover the stem.

Foliage Leaves or Needles
These are commonly long and narrow, tough, and leathery. In contrast to scale leaves they are green and photosynthetic. Depending upon the type of species, a cluster of 2 to 5 needles is produced on each dwarf shoot. Each dwarf shoot with its cluster of needles is called a spur.

Reproduction in Pinus
Pinus tree produces reproductive structures known as cones every year. Cones are of two types, male and female c9ones. Both male and female cones are produced on the same tree but on different branches.

Male Cone of Pinus
Male cones, usually 1 cm or less in length, are much smaller than the female cones. They are produced in clusters. These are generally born on the lower branches of the tree. Each male cone is composed of spirally arranged leaf-like structures called scales or microsporophylls. Each microsporophyll has two long sacs called pollen sacs of microsporangia on it are under surface. Asexual reproductive cells, microspores or pollen grains are produced by meiosis in the microsporangia. Pollen grains are haploid. After being transferred to the ovule, the pollen grain forms pollen tube. It is the male gametophyte in which male gametes or sperms are produced.

Female Cone of Pinus
The female cones are much larger than the male cones. These are usually found on the upper branches. Each female cone is also made of spirally arranged scales which are called megasporophylls. These scales become woody on maturity. Two ovules are present side by side at the base of each scale. Haploid megaspores are formed in the ovule by meiosis. Measpores give rise to female gametophytes which produce female gametes. Fertilization results in the formation of embryo after which the ovule is ripened to form seed. Female cones normally remain attached for three years on the plant. On maturity the cones open up and the seeds are set free and dispersed.


Angiosperms are the flowering plants which are most successful plants. They are more important than the gymnosperms. They have adapted to almost every type of environment. There are about at least 235,000 species. They are dominant plants. Angiosperms are vascular plants which bear flowers. Their seeds are produced within fruits. The fruit protects the developing seeds and also helps in their dispersal. Seed and fruit producing habit have helped flowering plants in their evolutionary success.
Angiosperms are found in wide variety of sizes and forms. Ensize they range from over 300 ft in height (some species of Eucalyptus) to searcely 1mm in length (duckweed, Woiffia).
On the basis of size and woody texture, angiosperms are classified as herbs, shrubs (bushes) and trees. Herbs are the plants which are small in size. Their stems are Herbs which are then cut or pulled from the soil. In contrast shrubs and trees have hard woody stems, which retain their shape even after being cut. Shrubs are shorter than trees but have more branches. In addition to tracheids, angiosperms have efficient water conducting structures known as vessels in their xylem.

Classes of Angiosperms

On the basis of the number of cotyledons in the seed, angiosperms are divided, into two classes.
1. Monocotyledons or Monocots
2. Dicotyledons or Dicots


1. Monocot seeds have only one cotyledon or embryonic leaf.
2. A nutritive tissue called “endosperm” is usually present in the mature seed.
3. Monocots are mostly herbs with long narrow leaves.
4. Leaves have parallel veins i.e. in the lamina of the leaf veins run parallel to one another.
5. The floral parts of most flow3ers usually occur in threes or multiples of three (i.e. 3, 6, 9 …)
6. Monocots include different grasses, cereals (wheat rice, maize etc) ,palms, onions and lilies.


1. Dicot seeds have two cotyledons.
2. In mature seed, te endosperms is usually absent.
3. Their leaves vary in shape but usually are broader than monocot leaves.
4. Leaves have reticulate veins i.e. branched veins resembling a net. The flower parts are four or five in number or multiples of 4 or 5.
5. Dicots include rose, peas and pulses, sheesham, Kiikar (Acacia), sarsoon (mustard), cacti, mango, orange and sunflower etc.


CHAPTER – 7 (Invertebrata)






1. According to two-kingdom classification, protozoa are the first phylum of invertebrate animals but according to five kingdom classification it is placed in a separate kingdom, “protista” in which all other eukaryotic unicellular organisms are also placed.
2. Body of all protozoans consists of one cell and istherefore called unicellular.
3. They are so small in size that they cannot be seen with naked eye. They can be seen with the help of a microscope.
4. They are unicellular but they intake food, respire, reproduce.
5. Protozoans mostly live in damp, watery places. Their habitat is mostly moist soil, decaying matter of animals and plants. Most of them live singly but some form colonies. In a colony, unicellular organisms become partially interdependent and limit themselves to perform specific functions in a group. If separated from group they still can perform all life activities and can live independently.
6. Some protozoans are parasites and causes different diseases e.g. a type of Amoeba causes dysentery, plasmodium causes malaria.
7. Protozoans are also useful for man because they feed and destroy bacteria which are harmful for human health, for example Amoeba can feed on bacteria.


It is unicellular animal which is found in pools and ponds. It is slipper shaped its body is covered with cilia. Cilia are small hair like out structures arising from protoplasm. Their lashing movement in water acts as oars and help in swimming (locomotion) of the animal. Paramecium feed on algae. Bacteria and other small protozoans, through an oral groove provided with cilia. Cilia push food inside the protoplasm through a canal called gullet making a food vacuole in the protoplasm. There are two contractile vacuoles, one at each end of the body for discharging surplus water there are two nuclei one large, mega nucleus which controls almost all functions of cell other small, micro or reproductive nucleus which controls reproduction. Many protozoa like Amoeba and Paramecium are unicellular but they respond to the intensity of light like all other multicellular organisms. They can detect high intensity of light and move towards the area having low intensity of light.

Phylum Porifera

1. This phylum is called porifera because animals belonging to this phylum have numerous small pores on their bodies.
2. They are also called sponges.
3. They are multicellular but they have no organs or true tissues.
4. Every cell performs its all function.
5. Sponges are aquatic animals. Most of them are found in sea water but some live in fresh water.
6. Sponges have different colours.
7. Green colour of sponge is due to algae that live in their body. Algae produce oxygen during photosynthesis which is used by sponges and the sponges release carbondioxide, which is used by algae for photosynthesis. This association in which both the organisms benefit from each other is called mutualism.

Phylum Cnidaria

1. Animals belonging to this phylum have a special cavity in their body which is called coelenteron and due to this reason they are called coelenterates.
2. They are diploblastic animals as their bodies have two layers of cells. Outer layer is called ectoderm and inner layer is called endoderm. Between these layers a jelly like substance the mesoglea is present.
3. Coelentrates are aquatic animals. They are mostly marine but few live in fresh water.
4. Most of the animals of this phylum can move freely but a few remain attached to stones or rocks throughout their life.
5. Hydra, Jellyfish and Sea anemone are common examples of this phylum.

Phylum Platyhelminthes

They are triploblastic animals because their body is made of three layers, an outer ectoderm, a middle mesoderm and an inner endoderm layer. They are also called flat worms because their body is thin, flattened and tape like. Some animals are free living but most are parasite. Parasites live in liver, stomach and intestine of other animals. They attach themselves to the walls of intestine of their host by sucker and suck blood and food. Tape worm sucks food from intestine and sometimes grows up to 40 feet in length. Liver fluke, tape worm and planaria are common examples of this phylum.

Phylum Mollusca

1. This phylum is one of the largest phyla of animal kingdom. It has about fifty thousand species.
2. Mollusca are a latin word which means “soft”. Their body is soft so in most of the animals and external shell is present for support and protection.
3. Some animals have internal shell and some lack shell. They are also known as shell fish.
4. They are found in aquatic and moist habitat.
5. Most of Mollusca are used as human food.
6. Buttons are made from their shell.
7. The pearls are produced by these animals.
8. Their body is quite complicated.
9. They have a muscular foot for locomotion and gills for respiration.
10. Snails, Fresh water mussel, Cuttle fish, Octopus and Oyster are common examples of this phylum.

Phylum Arthropoda

1. The bodies of these animals are also segmented but these segments are external.
2. Their bodies are covered with the hard shell composed of chitin, forming an exoskeleton.
3. They have jointed legs on their body and therefore they are called arthropoda (arthro means jointed and poda means foot)
4. These animals are found in all habitats, in air, water and on land.
5. Common examples are Prawn, Crab, Spider, Scorpion, Centipede, Millipede and Insects.

Phylum Echinodermata

1. The animals of this phylum are exclusively marine.
2. They are called echinoderms because their bodies are covered with spines or spicules.
3. All animals have internal skeleton consisting of dermal caleareous ossicles.
4. They have a water vascular system and dermal gills.
5. These animals are considered to be closest to the chordates from evolutionary point of view, Sea star (known as star fish). Brittle star, Sea urchin and Sea cucumber are examples of this phylum.

Phylum Annelida

1. Animals in this group have elongated segmental body.
2. Annelids occur in water as well as on land.
3. They have well developed systems in their bodies.
4. They have close type circulatory system.

Phylum Nematode

1. Nematodes or round worms have long smooth cylindrical body which is pointed at both the ends.
2. The body is un-segmented.
3. Nematodes have a complete and one way digested tube.
4. They are free-living as well as parasites of animals, man and even plants.


CHAPTER – 8 (Chordata and Vertebrata)

Chordata and Vertebrata




Characters of Class Pisces (fishes)

1. The class of fishes is called Pisces. They are aquatic vertebrates.
2. According to their size and shape, the fishes are of many kinds.
3. They have a head, a trunk and a tail.
4. The head and trunk are directly jointed together and neck absent.
5. Body of fish is flexible tapering at both ends and streamlined. This type of body helps in swimming.
6. They can swim with fins, which are attached to the trunk.
7. They body is covered with scales which remain moist by special type of secretion of body.
8. Breathing organs are gills which are present in the hollow spaces found on both sides of the head for exchange of gases i.e. oxygen and carbon dioxide.
9. Mouth has teeth, which is used for grasping instead of grinding of food.
10. In some fishes air pouch is present, which is called air bladder. The air bladder is used for buoyancy.

Class Amphibia

1. This group of animals can live both in water and on land.
2. They need water for reproduction. Therefore they are called Amphibians.
3. The skin is thin, moist and slimy.
4. Small teeth are present in the upper jaw which is only used for grasping the prey.
5. Breathing organs are two lungs. Skin is also used for the exchange of gases.
6. Eggs are laid in water or moist places and their outer shells are not hard.
7. They are cold blooded animals e.g. they cannot maintain their body temperature constant.
8. They become very slow and bury themselves in the mud. This process is called hibernation.
9. During the process of reproduction fertilized egg is changed into adult passing through a number of physical changes. This process is called metamorphosis.
10. The fertilized egg develops into larva. The larva of frog is called Tadpole. It has tail and gills. This larva later changes into adult.

Class Reptilia

The animals of this class are called reptiles. They have following features.


1. Most of the reptiles are terrestrial and only a few five in water.
2. They are also called crawlers.
3. They have thick, dry and rough skin.
4. The skin is covered with scales which originate from the ectoderm.
5. There are present lungs for respiration.
6. Teeth are present in their buccal cavity, which are used for cutting and biting.
7. The locomotary organs are legs but snakes and a few types of lizards have no legs.
8. Most of the lizards are not poisonous except members of the genus Heloderma which are found in American desert.
9. All the reptiles lay their eggs on land. Water dwelling reptiles e.g. turtle also lay their eggs on land.
10. Their eggs have a tough outer shell of calcium carbonate.

Class Aves

The animals included in this class are called Birds. Their distinguishing characters are as follows.
1. Birds have a single unique feature, which makes them different from other animals which is the presence of feathers. Their forelimbs are modified to form wings while hind limbs help in walking, wading and sitting on the branches.
2. All the birds have horny beaks without teeth.
3. All the birds lay eggs.
4. All the birds must have two wings for support and propulsion, strong but light and hollow bones.
5. Their digestive system is able to digest high caloric food.
6. They have a higher blood pressure and higher metabolic rate.
7. Nervous system and especially eye sight is very well developed so that they can track their path even at a very high speed.
8. They migrate during winters towards warmer places covering thousands of miles.
9. It is the most studied and most observable class in the world.
10. The birds are very beautiful and have melodious voices.

Types or Groups of Birds

Running Birds (Ratitae)

They have following characters:
1. They have flattened sternum.
2. Their pectoral muscles are weak.
3. Their examples are Ostrich, Emu, Rhea and Casso wary.

Flying Birds (Carinatae)

They have following characters:
1. A keel is present on sternum in these birds.
2. Keel is vertical bony part that is present below the sternum in the centre from anterior to posterior end.
3. Pectoral muscles are very strong, powerful and are inserted on the keel. These muscles help them to fly.
4. Their common examples are pigeon, hen, crow, kite etc.

Class Mammalia

All the animals included in this class are called “mammals”. These animals are highly advanced vertebrates. There are almost four thousand species of mammals including man.

Characteristics of Mammals

Their distinguishing characters are given below:

The body of mammals is covered with hair. In most of the mammals hair may cover the whole body but in a few may be restricted to some areas. The hair conserves heat of the body.

Their skin is provided with sweet glands, scent glands, sebaccous glands and mammary glands.

Two occipital condyles, secondary bony palate, three bones in middle ear and fused pelvic bones and seven cervical vertebrae are present in their skeleton.

External Ear
Fleshy external ears are present in mammals.

Moveable eyelids are present in mammals.

Two sets of teeth are present. Milk teeth are replaced by permanent set of teeth.

Brain is higly developed. It perform more functions than that of other vertebrates.

Cranial Nerves
Twelve pairs of cranial nerves are present.

Circulatory System
Circulatory system has four chambered heart, persistent left aorta and non-nucleated biconcave red blood corpuscles are present in female.

Sexes are separate i.e. there are two individuals, male and female.

Most of them have internal fertilization and fetus developed inside the uterus of female giving birth to their children.

Breast Feeding
They feed the children by milk from mammary glands.

They are endothermic i.e. they can maintain their body temperature according to the environment. It means that they are warm-blooded animals.

Egg Laying Mammals

These mammals lay eggs. Mostly two eggs are laid in one year. Fertilization of egg is internal i.e. inside the body of mother. Eggs are laid in burrows of animals. Young ones are hatched from the eggs. Mother feed their children with milk. Their egg laying character shows their relationship with reptiles. Duck bill platypus and Spiny ant eater are the examples of egg laying mammals.

Pouched Mammals or Marsupial Mammals

These mammals have a pouch outside the belly called marsupium, this is the reason that they are also known as Marsupial mammals.
1. Fertilization of eggs and development of embryo is internal.
2. The embryo is at first encapsulated by shell membrane and floats free for several days in the uterine fluid.
3. There is no placenta.
4. After hatching from the shell membranes, the embryo does not implant or “take root” in the uterus and absorb nutrient secretions from the vascularized yolk sac.
5. The gestation period is brief and the marsupials give birth to tiny young that is effectively still an embryo.
6. These young creeps into the marsupium where it gets milk from mother through nipple.
7. It lives in marsupium until it can take care of itself.
8. Examples are Kangaroo, Koala, Tasmanian wolf and Wombat etc. These are found in Australia and Tasmania, Opossum is found in America. It lives on trees.

Placental Mammals

This is common group of mammals in which embryo completes its development inside the mother’s uterus. After gestation period young ones are born. Embryo remains in the uterus and gets its nourishment from mother through umbilical cord and placenta. Gestation period of these mammals is longer than those of other mammals. Pregnancy is called Gestation Period. In man it is of 9th months.
In mice it is 21 days, in rabbit 30 to 36 days, in cats and dogs 60 days, in cattle 250 days and in elephants 22 months. It is lengthier in large mammals.
The conditions of young ones at time of birth are different in different mammals. For example in antelope, at the time of birth, the body of young is covered over, with heavy fur, eyes are open and it can walk about. In case of rat, young is very weak, eyes are closed and has no hair on the body.

Flora and Fauna of Pakistan


“Different types of plans present in a particular region constitute its flora.”

1. Hilly regions of Pakistan have snow fall and low temperature. These regions have thick forests where trees of Juniper (Sanober), Cedar, Chir, Chalghoza, Olive Apple, Plum Peach and Loqaut are very common.
2. Plain areas of Pakistan have fertile and less fertile soils. In areas where rainfall is low, desert environment is present in which Aeacia (Babool), Kikar, Ber, Pilas etc grow.
3. Fertile plains have trees of Sheesham, Bakain, Cane, Bamboo and Eucalyptus. These are source of timber whereas; fruit trees include mango, banana, Kino, Orange, Grapes, Jamman etc.
4. Plain and hilly areas have natural pasture lands that provide fodder for cattle.
5. In sea, rivers, ponds, canals and streams, algae are abundant, which on one hand are the source of food for aquatic animals and on the other hand they provide oxygen to atmosphere.
6. A large number of plants are used as ornamental plants. These include flowering plants like rose, motia, jasmine, lady of night, chrysanthemum etc.
7. Besides this wheat, maize, rice, oats, burley, grams garlic, onion, potatoes, carrots, cabbage and turnips etc are cultivated in plains and hilly areas to meet our food requirements.



“Different kinds of animals present in a particular region are known as its Fauna.”

1. In the seas adjoining our coastal areas numerous types of animals are found starting from protozoa to mammals. The most noticeable are octopus, mussels, star fish, sea urchins, crabs, prawns, fishes, amphibians, whale, dolphin etc.
2. Many animals are used as food e.g. prawns, crabs and fish etc. Our rivers are rich in fish life particularly Rohu, Khagga, Malhi, Trout, and carps are abundant and used as human food, as well as a source of earning lively hood.
3. Frogs and toads are abundant.
4. The tortoises, turtles, snakes, crocodiles are also common.
5. On the plains of Pakistan we have very rich wild life. There is a great diversity of land fauna starting from earthworms, almost all kinds of insects, spiders, myriapods, snails, slugs to toads, lizards, snakes and enormous variety of birds and mammals.
6. Some of the birds peculiar to Pakistan are Houbara bustard, partridge, pheasant, falcons etc.
7. The mammals peculiar to Pakistan include Black buck, Blue ball, Brown bear, Musk deer, Urial, Ibex, Asiatic ass.etc.
8. Most of the animals provide milk, meat, hide and wool. Some are used for transportation. Some of the animals are now endemgered species because of their excessive hunting and pollution.


The animals which do not change their body temperature with the change of temperature in environment are called as Warm Blooded Animals. Their body temperature remains constant.

Common examples of warm blooded animals are following.
(i) Parrot
(ii) Sparrow
(iii) Pigeon
(iv) Ostrich
(v) Kiwi
(vi) Duck billed platypus
(vii) Kangaro
(viii) Oppossum
(ix) Elephant
(x) Whale
(xi) Monkey
(xii) Man


The animals in which the body temperature is changed with the changes of temperature in the environment are called Cold Blooded Animals.

Common example of cold blooded animals are following.
(i) Shark
(ii) Labeo (Rohu)
(iii) Trout
(iv) Hilsa (Pullah Fish)
(v) Cat Fish (Khagga)
(vi) Frog
(vii) Toad
(viii) Snake
(ix) Wall-Lizard
(x) Crocodile


CHAPTER – 10 (Respiration)






The oxidation of the absorbed food material in order to obtain energy is called respiration.

There are two types of Respiration in the organisms:
1. Aerobic Respiration
2. Anaerobic Respiration

1. Aerobic Respiration

In most of the higher and larger organism, the glucose etc is oxidized by using molecular oxygen. This type of respiration is known as Aerobic Respiration. In aerobic respiration a mole of glucose is oxidized completely into carbon dioxide and water releasing enormous amount of energy. One glucose molecule in this resnpiration produces 686,000 calories of energy. Aerobic respiration thus produces 20 times more energy than the anaerobic respiration.
In aerobic respiration food is oxidized in presence of molecular oxygen.
Stages of Aerobic Respiration

There are two stages of Aerobic Respiration:

(a) External Respiration
In this stage, the organisms take the air (containing oxygen) into their bodies. This is called external respiration. this stage includes the transport of oxygen obtained from the inhaled oxygen to each cell of the body.

(b) Internal Respiration
The second stage is called internal respiration. It consists of the oxidation of glucose, amino acid and fatty acids etc, with molecular oxygen. In this stage all these reactions are included which extract the chemical energy of glucose and other compounds and store it in the form of ATP molecule, this respiration is also called cellular respiration as it occurs within cells.
In the internal or cellular respiration glucose and other compounds are passed through such enzymatic reactions which release the chemical energy gradually in small amounts with the help of which ATP molecules are synthesized.

2. Anaerobic Respiration

Some organisms oxidize their food without using any molecular oxygen. This is known as Anaerobic Respiration. In this type of respiration considerably less amount of energy is released as compared with the other type of respiration.
In anaerobic respiration a glucose molecule is broken down into two molecules of lactic acid with a release of only 47,000 calories of energy.
Glucose ——–> 2 Lactic Acid + Energy (47,000 calories)

Importance of Anaerobic Respiration

1. When earth came into being its environment was totally devoid of oxygen. The aerobic organisms cannot lie in anaerobic environment. The early organisms started respiration in the absence of oxygen to produce energy for survival of organisms.
2. Some existing organisms like bacteria and parasites which live in oxygen environment have anaerobic respiration.
3. Many useful bacteria and yeasts are anaerobic.
4. Even in the aerobic respiration of the first phase is anaerobic. The glycolysis which is the first phase of carbohydrate metabolism involves reaction which does not require the expenditure of molecular oxygen. This proves the idea that aerobic organisms have evolved from anaerobic organisms.
5. In our skeletal muscles, although aerobic metabolism takes place but in sustained activity when the oxygen supply cannot keep pace with energy demand, anaerobic respiration supplies the energy continuously by the breakdown of glucose to lactic acid.

ATP (Adenosine Triphosphate)

It is a chemical compound. ATP is an abbreviation of adenosine triphosphate. Its name indicates that it contains adenosine and three phosphate groups. Adenosine is formed of a nitrogenous base called adenine and a sugar called ribose. In ATP three phosphate groups are attached to the adenosine in a series one after the other.

Significance of ATP

ATP is a big source of energy. The two terminal bonds between the phosphate groups contain large amount of the chemical energy. When these bonds are broken in enzymatic reaction, large amount of energy is released by which energy requiring activities are accomplished, like synthesis of various compounds of carbohydrates, fats, proteins and hormones etc or for carrying out any physical work like muscle contraction, heat production or transport of substances etc.
When the terminal bond is broken the ATP is changed into ADP and phosphate 7300 calories of energy are released.

Gaseous Exchange in Plants

Plants get their energy from respiration. Plants have no special organ or system fro exchange of gases. The gaseous exchange in plants occurs in cells, of every part of the plant i.e. roots, stems and leaves etc according to their energy demand. The conducting system (xylem and phloem) of plants transports water and nutrients but plays no role in the transport of gases. The air spaces present between the cells of parenchyma of leaves, stem and roots are involved in the gaseous exchange.

Gaseous Exchange in Leaves and Young Stems

In the leaves and young stems, gaseous exchange occurs through stomata. Some gaseous exchange also occurs through cuticle.

Gaseous Exchange in Woody Stems and Roots

In woody stem and roots, there are present dead cells beneath the epidermis which form cork tissue. Later on, this tissue becomes porous. The pores are called lenticels. These are involved in gaseous exchange.

Gaseous Exchange in Leaves

The aquatic parts obtain oxygen for their respiration by diffusion from the dissolved oxygen in water. Whereas the land plants get their oxygen from air directly through their stomata which are more abundant on the lower surface than the upper surface of leaves.

Gaseous Exchange in Roots

The roots get their oxygen for gaseous exchange through diffusion from the air existing in the space between soil particles.

Process of Respiration in Plants

The respiration in plants continues day and night. In this process, the oxygen from the airspaces in the leaves and stems is diffused into tissues and cells after getting dissolved in the film of water which is present over the cells. In the cells this oxygen oxidizes the carbohydrates and other organic compounds into carbon dioxide and water to produce energy. Some of the water (vapours) comes in the airspaces from where they diffuse out to the atmosphere through lenticels and stomata. The elimination of carbon dioxide is more evident from the parts without chlorophyll like growing seeds and buds. The water produced in this process becomes a part of the already present water in the body of plants. The various chemical reactions of respiration are controlled by the specific enzymes. This process occurs at a faster rate in the parts of the plant having rapid growth like growing seeds, buds, apical meristem of roots and shoots, because these parts require more energy to accomplish the growth process.

Relationship between Respiration and Photosynthesis

The gaseous exchange in plant is not very evident during the day time as the products of respiration i.e. carbon dioxide and water are used in the process of photosynthesis. In the bright sunshine, because of high rate of photosynthesis the carbon dioxide produced in respiration falls short and therefore, some carbon dioxide has to be taken into the plant from outside for photosynthesis.
In the day time the plants therefore, take in carbon dioxide and expel out oxygen. The process of photosynthesis occurs in chloroplasts whereas the process of respiration takes place in cytoplasm and mitochondria.

Gaseous Exchange in Animals

The gaseous exchange in different animals takes place by different methods and organs. In unicellular aquatic animals like amoeba, the dissolved oxygen in water diffuses directly through their cell surface into the interior of the animal and the carbon dioxide similarly diffuses out from their bodies into the external water. This is the simplest way of gaseous exchange and it can occur only in small animals with a diameter of less than one millimeter. These animals have greater surface area of volume ratio and have low rate of metabolism.
During evolution, as the animals became complex and complex and grew in their size, their skin or external body surface become impervious to water. Thus the gaseous exchange became impossible through diffusion. In large animals certain organs were developed for exchange of gases w.g. the moist vascular skin, gills, lungs and tracheoles. These large animals have developed blood vascular system which transports oxygen from the respiratory surface to the deep cells and tissues in all parts of the body. The blood in all animals has some respiratory pigments like haemoglobin which carry large amount of oxygen efficiently from respiratory surface to the interior cells.
Properties of a Respiratory Surface

1. Respiratory surface should have large surface area.
2. Respiratory surface should be moist.
3. Respiratory surface should be thin walled.
4. Respiratory surface should have blood supply.

Gaseous Exchange Through Skin

For the exchange of gases through the skin the skin must be moist and richly supplied with blood. The oxygen is diffused from the external water to the blood and the carbon dioxide is diffused from the blood to exterior water. In amphibia and fishes the gaseous exchange occurs through the skin besides through the gills or lungs. The frogs and tortoises breath through the skin during their hibernation period.

Gaseous Exchange by Gills

The gills are very effective for gaseous exchange in aquatic animals. Gills are of two types:
(a) External Gills
(b) Internal Gills

(a) External Gills
Some animals have external gills which project out of body of animals. These gills have very thin and highly vascularized surfaces e.g. the dermal papillae of star fish and arthropods.

(b) Internal Gills
These are present inside the body inner to skin e.g. in fishes and arthropods. Have you ever examined a fish closely? How ill you know that the fish is fresh or not? If the colour of gills is red then it is fresh but if the colour of gills is changed, it is definitely not fresh. The red colour of the fish gills shows the presence of oxygenated blood.

Gills of Fish

In fishes the gills are present in the branchial cavity present on lateral sides of the body behind the head. This branchial cavity is covered over by an operculum. There is a counter current flow of water and blood in gills which ensures maximum exchange of oxygen and carbon dioxide between the blood and the bathing water. Water enters through the mouth, flows over the gills and goes out of the body from the opercular aperture.

Human Respiratory System

In humans, there is very efficient respiratory system. It consists of certain organs which are called respiratory organs these include nose, pharynx, larynx, trachea, bronchi and bronchioles.


The air enters through the external nostrils into the nasal cavity. This is lined with mucous secreting epithelium and ciliated epithelium. The nostrils are lined with hairs. The nasal cavities, located above the oral cavity and behind the nose are covered with epithelial tissue.
The beating of cilia creates a current in the mucus that carries the trapped particles towards the back of the nasal cavity. From here the mucus drips into the throat and is swallowed. Mucus keeps the nasal cavities moist. Bones of the nose warm up the air. Mucus moistens the air. Hair filter the air and stop the dust particles bacteria and any other foreign substance from going to next part of respiratory system. In this way air is purified and is then pushed into the pharynx.
A number of cavities called sinuses open into the nasal cavity. The sinuses are lined with mucus secreting epithelium. The opening of sinuses into the nasal cavity is very narrow. If these openings are closed due to cold or inflammation, the sinuses get filled up with mucus this results in headache and changed voice.


The nasal cavity opens into the pharynx (throat) through two small apertures which are called internal nares or internal nostrils. The pharynx is muscular passage which extend from behind the nasal cavities to the opening of oesophagus and larynx. The air goes from the pharynx into the larynx.


The upper most part of the wind pipe (trachea) is called the larynx. The larynx is a cartilaginous box. Two fibrous bands called vocal cords are located in this box. These vibrate to produce sound. Larynx is, also called sound box or voice box. The air enters the larynx through a small aperture called glottis which is guarded by a muscular flap called epiglotis which fits into this opening while the food is being swallowed into the oesophagus. It prevents the food from entering into the trachea and choking it. During breathing epiglottis keeps the glottis open so that air goes to trachea.


The air tube (wind pipe) is known as trachea. It is about 12 cm long and lies in front of the oesophagus. It has incomplete C shaped cartilagenous rings which are regularly placed in its wall and all along its length. These rings prevent the collapsing of the tube nd thus keep the air passage wide open all the time. Trachea is also lined with ciliated mucous epithelium. Any foreign particles present in the inhaling air get trapped in the mucous that is moved out of the trachea by breathing of the cilia in the upward direction. In trachea air is further cleansed and filtered and then moved towards the lungs.


The trachea while passing the chest cavity divides into two smaller tubes which are called bronchi (single bronchus). Bronchi are similar in structure to the trachea but are smaller in diameter and they have in their walls small irregular catilageuous plates. Each bronchus enters into the lungs of its own side. The right bronchus divides into three secondary bronchi and the left bronchus divides into two secondary bronchi which serve the 3 right and 2 left lobes of the lungs respectively.


the secondary bronchi further divide into very fine branches until they end in thousands of passage ways called respiratory bronchioles. The bronchioles have not cartilaginous plates in their walls. They have smooth muscle and elastic fibers.


The walls of the respiratory bronchioles have clusters of tiny branches(like bunches of grapes) that along with the respiratory bronchioles re the sites of gaseous exchange, these pouches or air sacs are called alveoli (singular: alveolus). The alveoli are enormous in number. Each lung has about three hundred million alveoli.
Pulmonary artery brings deoxygenated blood from the heart into the lung. Here, it divides and re-divides until it forms a network of fine capillaries over the wall of each alveolus. The walls of alveoli are very thin (1/1000 mm thick) and moist. Thus, alveoli are efficient site for gaseous exchange.

The Lungs

There is a pair of lungs present in the chest in man. Actually, the masses of alveoli constitute lungs and their lobes. The lungs re protected by the chest box from sides and by a doem shaped muscular diaphragm from below. Chest box or ribcage is made up of ribs. Between the ribs, there are present inter-costal muscles. The diaphragm is a muscular sheet which partitions the chest and abdomen.
The two lungs re covered by a double layered membrane called pleural membrane. There is a thin film of fluid in between the two layers. This watery fluid makes the movements of the lungs (expansion and contraction) easy. It also protects the lungs from external injuries.

Mechanism of Breathing

Breathing occurs in two phases:
1. Inspiration
2. Expiration

1. Inspiration

1. During inspiration, the dome-shaped diaphragm contracts and becomes flat some what and thereby lowering the floor of the thoracic cavity.
2. The external inter-costal muscles contract raising the ribcage. A combined action of these two events expands the thoracic cavity, which in turn expands the lungs.
3. The air pressure within the lungs decreases.
4. Thus air from the environment outside the body is pulled into the lungs to equalize the pressure of both sides.

2. Expiration

1. The diaphragm relaxes and assumes dome like shape. During expiration, the external inter-costal muscles relax and the internal inter-costal muscles contract as a result of which ribcage drops.
2. The combined action of these two event decreases the volume of the thoracic cavity which in turn decreases volume of lungs.
3. The air pressure with in the lungs increases.
4. The air is thus forced out of the lungs.

Bad Effects of Smoking on Heath

Smoking is injurious to human health. The smoke contains many chemical and gases. Dried tobacco leaves are used in cigarettes. The tobacco on burning produces a number of dangerous and toxic compounds.

Chemicals Present in Cigarette Smoke and Their Harmful Effects

(a) Nicotine
1. Man is addicted to cigarette damages brain tissues.
2. Causes blood to clot more easily.
3. Harden walls of arteries.

(b) Tar
1. Kills cells in air passages and in lungs.
2. Increases production of mucous and phlegm in lungs.
3. Causes lung cancer.

(c) Carbon Monoxide
Prevents red blood cells from combining with and transporting oxygen around the body.

(d) Carcinogens
promote the growth of cancerous cells in the body.

(e) Irritants
1. Irritate air passages and air sacs in the lungs.
2. Kill cells at the surface of air passages.
3. Causes smoker’s cough and lung cancer.


A chemical reaction in which a substance combines with oxygen and produce heat, light and flame is called Combustion.


A process that liberates chemical energy from organic molecules when oxidized is called Respiration. It occurs in all living cells. In fact respiration is a series of complex oxidation and reduction reactions in which energy is released bit by bit.


The process in green plants by which green plants manufacture their own food by using carbon dioxide and water with the help of energy absorbed by chlorophyll from sunlight is called photosynthesis.

Relation of Combustion, Respiration and Photosynthesis

Combustion is the process of burning in which wood, coal, methane, gas etc are burnt in the presence of oxygen, producing carbon dioxide and water accompanied with the release of energy. It is an exothermic chemical reaction.
Cellular respiration can be compared to burning of fuel in which organic food (carbohydrates, fats and proteins) rich in carbon burn in the presence of oxygen producing carbon dioxide, water and energy.
Respiration like combustion is a catabolic exothermic chemical process. However, the difference between the combustion and respiration is that the combustion takes place in one go, releasing the entire energy as the heat, which may be utilized or is lost into the environment. the respiration completes in several small steps. Each step is under the control of a specific enzyme, releasing energy in small amounts which can be stored in the form of ATPs. Photosynthesis, another metabolic process, is just opposite to combustion. Combustion is a catabolic process; the photosynthesis is an anabolic process. In photosynthesis organic substance is synthesized from carbon dioxide and water in the presence of sunlight energy and chlorophyll. The molecular oxygen is evolved as the by-product combustion is exothermic and releases energy, photosynthesis is endothermic and absorbed energy.
Photosynthesis and respiration are the two metabolic reactions opposite to each other. Photosynthesis takes place only in the gree parts of the plant body having chlorophyll, whereas respiration takes place in all the living cells of plants and animals. Mitochondria are the cellular organelles where respiration takes place while the organelles for photosynthesis re chloroplasts. Photosynthesis takes place during the day time only, whereas respiration takes place day and night. In photosynthesis body weight is increased but in respiration weight is decreased. Respiration is an oxidation reaction whereas photosynthesis is a reduction reaction and can be well understood by comparing their chemical reactions.

Chemical Equation in Respiration

Glucose + Oxygen ——-> Carbon dioxide + Water + Energy (In presence of mitochondria and enzymes)
Chemical Equation In Photosynthesis

Carbon dioxide + Water ——–> Glucose + Oxygen (In presence of chloroplast and solar energy)

Respiratory Organs of Insects

The respiratory system of insects is called the Tracheal system. It is a network of interconnecting air filled tubes called trachea delivering air directly to the body tissue cells. Trachea open outside through pores called spiracles.
Each trachea has chitinous cuticle lining which prevents it from collapsing.
A pair of spiracles is usually located on the sides of each segment of the thorax and abdomen. Spiracles have valves to open or close them regulated by special muscles. This controls water loss from internal body tissue.

Trachea break up into numerous smaller tubes called tracheoles which ramify among the body tissues ending blindly. Tracheoles lack a chitinous lining. At rest the tracheoles are filled with watery fluid through which gaseous exchange tkes place in dissolved state.
Ventilation is brought about by contraction and relaxation of abdominal muscles which result in a rhythmic pumping of air into and out of the trachea.
Gas exchange takes place in tracheoles which are permeable to gases and are filled with a fluid in contact with the body tissue. Since oxygen diffuses directly into the tissue cells, blood of insects does not have hemoglobin so it is white. However, removal of carbon dioxide is dependent on blood plasma which takes it up for removal via spiracles.







Vitamins are very complicated compounds. When vitamins were discovered, their chemical nature was not well known. Therefore, they were denoted with English letters as A, B, C, D, E and K. Now it is known that vitamin B is not a single vitamin but a group of vitamins call ed as vitamin B complex. It has eight different compounds as B1, B2 etc although they have no energy value but they are essential in small quantities for the normal activities of life. It has been observed that when animals were given a diet rich in carbohydrates, fats and proteins but lacking vitamins, the growth and development of the organisms were affected and the animal suffered from various diseases. Vitamins are needed for healthy growth and development of the body. They also serve as enzyme.
Plants can prepare their vitamins from simple substances but animals obtain it directly or indirectly from plants. Fifteen or more vitamins have been isolated and most of them seem to act as essential part of coenzyme involved in chemical changes taking place in the body.
If our diet has variety and consists of fresh fruit and vegetables, our body will receive all those vitamins which are necessary for us.

Fat Soluble Vitamins

Some vitamins are fat-soluble and can be stored along with fat.

Water Soluble Vitamins

Some vitamins are water soluble and hence cannot be stored in the body, thus their in take is required continuously


Unicellular Organism (Amoeba)

Unicellular Organism (Amoeba)



The organisms consisting of only one cell are called unicellular organisms e.g. Amoeba, Paramecium etc.

1. It is mostly found in fresh water pond or pool.
2. In the ponds, it is found moving about around the weeds and stones. Some species are found in the moist soil.
3. Amoeba is a large protist.
4. It does not have the permanent shape.
5. Its size is about the end of pin or it measures about 0.25mm. Therefore it is observed under the microscope.
6. Its structure is very simple.
7. It consists of nucleus and cytoplasm, which are surrounded by a cell membrane.
8. Cell membrane protects it.
9. Cytoplasm is divided into two parts. Outer clear and transparent part is called ectoplasm while the inner, viscous, translucent and granular part is called endplasm.
10. Endoplasm contains food vacuoles of different sizes. These food vacuoles help in the digestion of food.
11. The food of Amoeba consists of microbes present in the water of pond.
12. Contractile vacuole maintains the concentration of water in the body. It removes surplus water out of the cell.
13. In Amoeba, the exchange of gases and removal of waste.
14. In Amoeba, there are also present mitochondria, golgi bodies and ribosomes.
15. Nucleus changes its place with the movement of the organism.