The word science comes from a foreign word scientia which, literally, means knowledge.  But scientific knowledge is quite different from the knowledge contained in other areas. First and foremost, science believes in observation, experimentation and verification. If a particular scientist reports a new development, fellow scientists will not accept it u

nless his results are verified and found duplicable by them. Practical proof is the only parameter to test the validity of any scientific finding. Though science has greatly advanced from the days of the falling apple to the internet yet the basic guiding principles remain the same. Besides, science is self-correcting, i.e. it discards a finding which is not useful any longer and. It replaces it with a better, more plausible and acceptable scientific framework.

The last century has seen probably more dramatic scientific progress than any preceding century or even the last millennium. It may sound too fantastic to have a refrigerator telling you to order milk because it has been exhausted, or your going to a superstore to order the baby of your choice, but they seem to be possibilities quite visible in near future.

For convenience, we have divided our discussion into two, i.e. the physical world (dealing with non-living objects and the phenomena connected with them) and the living world, although a deeper study will reveal that such a division is purely artificial, i.e. biological and physical phenomena merge to produce the world as we see it.


A major part of the Earth comprises living beings, which make up the biological world. There are millions of unique varieties of plants and animals. All living beings are distinguished by their ability to move, respire, grow and reproduce, which are absent in non-living things.

Studying the millions of varieties is a Herculean task for any scientist. To achieve it, therefore, the scientists have grouped together similar types of plants / animals to simplify their study. By studying a representative of each group, we can know fairly well the unique features of the whole group. Such a system of grouping together living beings is known as classification.

Scientists in different parts of the world call the same animal / plant by different names. It may create a lot of problems in communication. To rid of this problem, a uniform system of naming has been proposed by Carl Von Linnaeus. According to this system, every organism has been assigned two names

  1. generic name known as genus and
  2. a special name known as species. For instance, both the common cat and the lion have a common genus Felis, but since there is considerable difference in their characters, each has a separate species name. Obviously, having a common genus name means great similarity in their basic biological features. The common names and the corresponding scientific names of some common living beings are elsewhere in this discussion.

ANIMAL GROUPS                                                                PLANT GROUPS

  1. Phylum Protozoa e.g. Amoeba, Plasmodium                   1. Algae e.g. Seaweeds, Spirogyra
  2. Fungi e.g. Penicillium
  3. Phylum Porifera e.g. sponges                                           3. Bryophytes e.g. Marchantia
  4. Phylum Coelentrata e.g. Corals, Jelly-fish, Star-fish         4. Pteridophytes e.g. Ferns
  5. Phylum Platyhelminthess e.g. Tapeworm                         5. Gymnosperms e.g. Pinus
  6. Phylum Nemahelminthes e.g. Ascaris                               6. Angiosperms e.g. Triticum
  7. Phylum Insecta e.g. Silver Fish, Cockroaches
  8. Phylum Echinodermata
  9. Phylum Mollusca
  10. Phylum Chordata e.g. Rat, Whale, Fishes

(Bacteria and viruses are excluded because they possess the features of both plants and animals. For instance, some bacteria can make their own food, which brings them closer to plants. Viruses, on the other hand are creatures which can multiply only on a living host, can survive extreme environmental conditions and possess features of both living and non-lining beings. Like living beings, they can multiply. And like non-living things, they can crystallize themselves under appropriate environmental conditions. Many bacteria and viruses are responsible for some major human diseases.)

Of these, the Chordates are the most advanced group in terms of biological organization. They are distinguished by the presence of a notochord or vertebral column. They are further divided into many types.

A. Pisces (Swimming Fishes)

  1. Amphibia
  2. Reptilia (Crawling Reptiles)
  3. Aves (Flying Birds)
  4. Mammalia (Child-Bearing Mammals)

Each animal group is marked by certain features unique to them e.g.

  1. Fish have gills for respiration in the adult stage, fins all over the body and internal fertilization. Therefore, swimming doesn’t define a fish nor does the name tag of fish attached to the name of an animal. For example, the commonly known animal Silver Fish is not fish at all (it is an insect), because it lacks gills, fins and other features exclusive to fishes.
  2. Amphibians are animals that can live on both land and in water.  A typical example is a frog which lives in ponds normally, but can come on earth.
  3. Reptiles have scales found all over the body. Since they live in dry places, it helps them in conserving body water to a large extent.
  4. From birds onwards, a true four-chambered heart is found in all animals, which means that pure and impure blood are actually separated in different chambers of the heart. Birds have wings (which are actually modified fore-limbs) and a constant body temperature, apart from a four-chambered heart. Of course, they can fly, but the ability to fly does not make an animal a bird.  For instance, many insects can fly with wings that are extensions of the skin. So technically speaking, they cannot be called birds.
  5. Mammals are the most advanced animal groups. Many features distinguish them other groups like
  6. The presence of hair all over the body.
  7. Internal fertilization (in groups, fertilization takes place outside the body, i.e. is external)
  8. Ability to give birth to young ones directly (birds and fishes lay eggs)
  9. A constant body temperature which does not change as per outside changes. Such constant-temperature animals are called warm-blooded while those whose body temperature changes with outside changes are called cold-blooded e.g. fish, reptiles.
  10. A constant internal temperature is a great advantage for an animal because it lets its body function without any hindrance (Most body processes need a suitable range of temperature). Its importance can be easily supported with frog, which is a cold-blooded animal. In winters when temperature dips very low, frogs bury themselves in the bed of the ponds (hibernation) to avoid the low temperature, which hinders their body functions. On the other hand, most mammals have internal biological mechanisms which adjust their temperature to avoid excessive heat or cold, thus creating a constant internal environment for the body reactions. (homeostasis)

Extreme care of the young is a special feature of this group. Generally speaking, the more advanced the animal on the scale, the more the degree of parental care. A highly developed Central Nervous System, which allows them to think, plan and reason, is an essential aspect of their intelligence. Of course, no animal apart from humans can speak but some remarkable research shows that chimpanzees can definitely communicate with special sign languages.

Common Name                      Scientific Name

Wheat                                      Triticum
Rice                                         Oryza sativa
Onion                                       Allium cepa
Pea                                          Lathyrus odoratus
Cat                                           Felis domesticus
Man                                         Homo  sapiens
Frog                                         Rana tigrina



Robert Hook was the first to observe cells in a living being. All living beings are made of tiny chambers called cells. A cell is the smallest functional and structural unit of a living organism.  By functional unit, we mean that a cell works as a whole and no part of a cell can function independently of other parts. A group of cells that performs a special function for the body is known as a tissue. Many tissues make up an organ and many organs together make up an organ-system. For example, the human digestive system has many different organs, the tissues in which are highly specialized to perform digestive functions and not functions of any other type. Many systems together make constitute a living organism.

This organization of cell- tissue- system-body is not uniform throughout the living world. There are many animals which consist of just one cell (e.g. protozoa) and there are creatures that have many cells, but those cells are not organized into specialized tissues.  However, the typical cell- tissue- system-body outline above is true of all higher animals.

Many animals living together in a particular habitat make a population. All the different animals or plant species living together in mutual inter-link with one another in a habitat make a biological community. And a community of living organisms, living together with its physical environment, makes it an ecosystem. The study of the interactions between the living creatures themselves and their physical environment and vice-versa is known as ecology.

Mitochondria and centriole are some major parts of a cell. In fact, the animal and plant cells do not differ much in structure and function, except that all plant cells are additionally covered by a cell wall and that they lack centriole. The nucleus controls all the cell functions while the actual production of energy takes place on the mitochondria. This energy is released in the form of ATP molecules (Adenosine Triphosphate) and that’s why mitochondria are often known as the powerhouse of the cells. Inside the nucleus, a thread-like network of chromatin can be seen. During cell division, this network is clearly differentiated into chromosomes, bodies that contain genes responsible for transmission of traits from one generation to the next.


Every species has a fixed number of chromosomes in all body cells. For example, in case of humans, the number of chromosomes is 46, which is organized into 23 pairs. The chromosomes and the genes always occur in pairs.

A cell keeps on growing until a certain stage, beyond which it has to divide. The cell can divide in two ways: mitosis and meiosis.


This is an equational division in which a cell divides into two equal halves, each containing all the essential parts. In such a division, first the chromosome number gets doubled i.e. each chromosome gets divided into two, thereby doubling the total number of chromosomes in the cell. Later on, each half receives half the chromosomes. For example, each human cell has 46 chromosomes, which become 92 in number in mitosis. Each new mitotic cell gets half of it, i.e. 46. Thus the chromosome number remains constant in the species in each cell.

This type of division continues in the body cells (except sex cells) all the time and is the major source of repair, growth and development.


Meiosis is a special cell division found only in sex cells (sperms and eggs). In this, a reduction division takes place first i.e. after duplication of each chromosome, the 92 chromosomes thus produced get divided into four parts, each having 23 chromosomes. Thus each daughter cell gets 23 chromosomes. That is why this is called a reduction division. Each of the four sperms containing 23 chromosomes combines with an egg having 23 chromosomes, thus giving rise to a zygote having 46 chromosomes in all. Thus the number of chromosomes again remains the same in the species.2


When two offspring are born at the same time, they are referred to as twins. Depending upon the mode of formation, they are of two types.

Such twins develop from a single fertilized egg, which divides into exactly two halves some time after fertilization. The twins born from such a division are called identical twins and they share virtually identical physical and psychological features.


Fraternal twins are the result of fertilization of two eggs with two separate sperms. The twins produced as a result of such separate fertilization are just like ordinary siblings.


Heredity is the process of transmission of characters from one generation to the next. It studies how those characters are transmitted from parents to their offspring, what are the basic laws applicable to such processes etc. The field of genetics studies heredity in detail.

Gregor John Mendel, an Austrian monk, was responsible for formulating the basic laws of heredity on the basis of his studies on the Garden Pea. For this reason, he is remembered as the Father of Heredity.
In the present century, much more has been learnt about the mechanism of heredity. Much of the credit for this research goes to Morgan Hunt, an American biologist who has added to our genetic knowledge tremendously by way of his experiments on the butterfly Drosophila.


Each chromosome has many individual hereditary units called genes. A gene is a segment of Deoxyribonucleic Acid (DNA), which is the actual carrier of all genetic information. The DNA molecule looks like a twisted ladder or a double-stranded helix as shown alongside. The gene, a segment of the DNA molecule gives coded instruction to the cell, directing it to perform a particular function (usually to make a particular protein).

Although all cells in the body contain the same genes, the special nature of each cell reults from the fact that only 5 to 10 percent of the genes are active in any given cell.  While developing from a fertilized egg, each cell “switches on” some genes and “switches off” all others. When “nerve genes” are active, for example, a cell becomes a neuron because the genes direct the cell to make chemicals necessary to perform neural functions.

Genes, like chromosomes, occur in pairs. One gene of each pair comes from the sperm chromosome and the other from the egg chromosome. Thus, a child receives only half of his genes from each parent’s total genes. The total number of genes in each human chromosome is around 100- perhaps higher. Since the number of genes is so high, it is extremely unlikely that two human beings would have the same heredity, even if they were siblings. The only exception is the identical twins, who have exactly the same genes.

An important trait of many genes is dominance or recessiveness. When both members of a gene pair are dominant, the individual manifests the form of the trait specified by those genes. When one gene is dominant and the other recessive, the dominant gene again decides the form of the trait expressed. Only if the genes contributed by both parents are recessive is the trait specified by them expressed. The genes determining eye colour, for example, act in a pattern of dominance and recessiveness; blue is recessive and brown is dominant. Thus, a blue-eyed child may have two blue-eyed parents, or one blue-eyed parent and one brown-eyed parent (who carries a recessive gene for blue eyes) or two brown-eyed parents (each of whom carries a recessive gene for blue eyes). A brown-eyed child, in contrast, never has two blue-eyed parents.

Some characteristics carried by recessive genes are baldness, hemophilia, and a susceptibility to poison ivy. However, not all gene pairs follow the dominant-recessive pattern and most human traits are determined by many genes acting together.

Some human characteristics are determined by a single gene pair. For instance, Phenylketunoria (PKU) and Huntington ’s disease. In case of PKU, the person is not able to digest an essential amino acid which gets logged in the nervous system.



The X chromosome may carry either dominant or recessive genes, the Y chromosome carries a few genes dominant for some male sexual characteristics, but otherwise carries only recessive genes. Thus, most recessive characteristics carried  by a man’s X chromosome (received from his mother) are expressed since they are not blocked by dominant genes. For example, colour-blindness is a recessive sex-linked characteristic. A man will be colour-blind if he inherits a colour-blind gene on the X chromosome received from the mother. Females are less often colour-blind, because a colour-blind female has to have both a colour-blind father and a mother who is colour-blind or who carries a recessive gene for colour-blindness. A number of genetically determined disorders are linked to abnormalities of the 23rd pair of chromosomes, or by recessive genes carried by this pair. They are called sex-linked disorders.


On rare occasions, a female may be born with only one chromosome instead of the usual XX. Such a condition is referred to as Turner’s syndrome.

Sometimes, when the 23rd chromosome fails to divide properly, the developing organism get an extra X or Y chromosome. An individual with XXY condition is said to be suffering from the Klinefelter’s syndrome. Such a person is physically a male, but with marked feminine traits. A person born with XYY composition will be known as a super male, a person with exaggerated male features.


The living world has millions of species and how they came into being has been a great mystery. The Biblical theory of Special Creation which says that God created the whole world in seven days flat, particular type of living beings being created on a particular day. Science does not believe in such theories. Several attempts have been made to account for this vast variety of living beings prominent among which are:

Originally proposed by Charles Darwin in his book Origin of Species in 1859, this theory proposes that nature favours the continuation of those specie which have better chances of survival in future. Animals having features favourable to survival get preference over others who do not have such features. This theory has by far the maximum number of followers.

This theory proposes that those organs which have some use for a particular animal are retained, while those which do not have any use for it, fall into disuse and are consequently lost in the next generation, after a number of such generations. He supports his theory with several examples including the giraffe, snake and vermiform appendix in humans. The giraffe, this theory says, did not have such a long neck in ancient times. Since it used to eat tree leaves and they were found at a great height, it had to raise its neck upwards to catch them. In this way, the neck became longer and still longer with each generation, and after millions of years, we see the giraffe with such a long neck.



Mutations are sudden, dramatic and irreversible biological changes in an organism due to changes in genetic structure. This theory believes that evolution is a sudden process of change, not a slow and continuous process as proposed by Darwin and Lamarck. A well-known example quoted is that of the Anchon sheep, which suddenly developed very short legs. Most modern biologists combine this theory with Darwin’s to give a satisfactory explanation of biological evolution.

The Human Body



It is a red, viscous fluid which circulates in the human body. It is basically a connective tissue which is contained in the blood vessels. A healthy man possesses on an average, 5litres of blood in the body.

Composition: It is made up of two chief constituents:

(a) Plasma (fluid) constitutes the major part while

(b) Blood cells (solid), which constitutes the minor part.

The blood cell corpuscles are of two types: (1) RBC (2) WBC. The RBC is red blood corpuscles which contains a pigment called haemoglobin which is responsible for the red colour of the blood. Iron is the element which is present in the haemoglobin. The WBC are white blood corpuscles winch are primarily responsible for combating with the infection of the body or they fight with the foreign harmful organisms of the body.


Blood groups: They are of four types, viz.

(i) A-type       (ii) B-type          (iii) AB-type       (iv) O-type


AB – type is called universal recipient as it can receive all the four types (mentioned above) of blood and O-type is called universal donor as it can be given to any of the four types of blood groups.

Bones: (i) There are 206 bones in the skeletal system of an adult.

(ii)The largest bone is the femur present in the thigh.

(iii) The shortest bone is the stirrup which is present in the middle ear.


  • The largest organ of the human body is the
  • The heart is responsible for regulating the circulation of blood in the body. The heartbeat of an adult male is 72 beats per minute.
  • The liver is the largest gland in the human body. It is concerned with the digestion of food. Two kidneys are responsible for the filtration of nitrogenous wastes in the body and throw it all in the form of urine.
  • The pituitary gland is called the master gland as it influences the growth and metabolism by controlling the other ductless glands, viz: thymus, thyroid, adrenal, prostrate, pancreas and gonads.
Vitamins —   Sources and Deficiency Diseases


Vitamin                                     Sources                               Deficiency Disease/s


Vitamin A                               Milk, carrot, egg                    Night blindness


Vitamin B1(Thiamine)              Cereals, pulses                       Beriberi


Vitamin B2 (Riboflavin)           Liver, kidney, milk                               Dermatitis


Vitamin B6 (Pyridoxine)          Yeast, cereals, liver                 Anemia


Niacin (Nicotinic acid)             Peas, tomato, eggs                 Polyneuritis


Folic Acid                              Green leafy vegetables, egg     Anemia


Pantothenic Acid                     Kidney, meat, yeast                 Dermatitis


Vit. B12                                    Milk, liver, meat                    Pernicious anemia


Vitamin C                               Citrus fruit                                Scurvy, common cold
Vitamin D (Calciferol)              Sun rays, eggs, fish, milk         Rickets
Vitamin E                               Milk, Soyabean, egg yolk         Reproductive disorders


Vitamin K                               Fish, peas, green vegetables   Delayed clotting of blood


Human Diseases
Disease                Caused by                                                  Affected part
Anemia              Deficiency of haemoglobin                  Blood


AIDS                 HIV Virus                                              Weakness of immune system


Asthma              Allergens                                              Lungs


Diabetes           Insufficient insulin                                  Pancreas and blood


Diphtheria         Bacteria                                                 Throat


Glaucoma         High pressure in the eyes                      Eyes


Goitre              Iodine deficiency                                   Throat


Hepatitis           Virus (mainly)                                         Jaundice


Malaria               Plasmodium                                          Blood, Liver


Polio                 Virus                                                         Legs


Rheumatism      Streptococcus bacteria                       Joints


Tonsillitis          Bacterial and viral infection                   Throat glands


Tuberculosis     Bacteria                                                 Lungs


Major Digestive Enzymes


Body Part          Enzyme                                       Action


Mouth                Amylase (Ptyalin)                    Converts starch into disaccharides


Stomach           Pepsin and Renin                    Act on proteins


Intestine            Lipase                                        Trypsin converts proteins into amino acids and

carbohydrase converts monosaccharides into glucose.




Our diet contains substances known as proximal principles, essential for maintenance of life and health.

Fats and Energy Producers: Fats are in oils, ghee and butter. Carbohydrates are in sugars, starches, etc. Unsaturated fats are good from the health point of view, and are advised for heart-patients. Saturated fats create cholesterol in the arteries, which can block them, leading to heart problems.\

Carbohydrates, Proteins and Vitamins are body builders. Found in eggs, meat, pulses beans, milk and cheese. Water and Vitamins are necessary for health.

A balanced diet is one which contains all the necessary proximal principles in the right proportion required for the maintenance of health. We cannot get all these in a single article of food. To get these in right proportion, we have to mix certain articles in our diet and thus we require a `mixed diet’ or a balanced diet. Vitamins are found naturally in certain foods and the absence of any of these leads to one or the other of the ‘deficiency disease’ which may even cause death.  Vitamins are both water soluble and fat soluble.
Vitamin A:  It is a general health-giving vitamin and it increases resistance to infection and tones up the whole system. It ensures good appetite, promotes growth and makes for long life. Its deficiency causes night blindness, disorders of skin, stomach growth and respiratory diseases. Found in milk, butter, egg yolk, ghee, carrot, tomatoes, fresh leafy and yellow vegetables, fresh fruits and cod liver oil.

Vitamin B: Present in cereals, peas and beans. Protects the body from nerve diseases such as beriberi, pellagra, and it cures pernicious anemia, degeneration of sex glands and enlargement of liver and adrenals.
Vitamin C: Ensures healthy teeth, bones, and protects the body against scurvy. Present in fresh vegetables, orange, lemon, lettuce, tomato, cabbage, turnip.

Vitamin D: Present in milk, butter, ghee, cod liver oil, yolk of eggs, and it is also produced under the skin by rays of the sun. Promotes bone formation and prevents rickets.

Vitamins E: It has vital influence on organs of reproduction. Its absence causes sterility. It is present in germinating wheat.
Vitamin K: Found in fish, oats, and wheat. It helps in proper clotting of blood in case of injuries.


The diseases caused by the lack of essential ingredients or vitamins in food such as scurvy, rickets, anemia.

Scurvy: It is due to the deficiency of vitamin C. Vitamin C is found in fruits and vegetables like lemons, oranges, tomatoes, etc. The gums swell and bleed, and there are bruises underneath the skin.

Rickets: A disease of bones caused by the deficiency of Vitamin D. A disease (caused by the deficiency of vitamin B) characterized by gastric disturbance, skin eruption and nervous derangement.

Beriberi: It is caused by the lack of vitamin B1 which is mostly found in the outer covering of grains. People eating polished rice polished rice suffer from it. The symptoms are neuritis (degeneration of the nerves) which leads to the weakness of muscles, swelling of the limbs, etc. Its cause was discovered by Eijkman.

Maras us and Kwashiorkor: Both are caused due to Protein Energy Malnutrition.


DISEASE                  ORGAN                                           DISEASE                 ORGAN 
Arthritis                   Joints                                         Asthma                  Bronchial Muscles
Cataract                  Eyes                                          Diabetes                Pancreas
Diphtheria               Throat                                        Eczema                  Skin
Goitre                     Thyroid gland                             Jaundice                Liver
Malaria                   Spleen                                       Ottis                       Ears
Paralysis                Nerves                                       Polio                      Legs
Pyorrhea                 Teeth                                          Bronchitis               Respiratory path
Rheumatism            Joints                                         Pneumonia             Lungs
Glaucoma                Eyes                                            Trachoma              Eyes
Elephantiasis           Lymph vessels                            Alzheimer’s            Nervous system
Sinusitis                 Bones                                        Typhoid                  Intestines
Tonsillitis                Glands                                       Meningitis               Brain
Tuberculosis           Lungs                                            Diabetes                Pancreas
AIDS                        Immune system                            Syphilis                    Sexual organs
Osteoporosis          Bones                                         Leukemia              Blood
Malaria                    Liver, Spleen                             Scurvy                    Gums
Atrophy                    Death of tissues in a body part


Those transmitted from one person to another by means of air, nonliving objects, water, wounds and direct physical contact with the affected person e.g. cholera, dengue, plague, H1N1 (Swine Flu), SARS (Severe Acute Respiratory Syndrome), dysentery, tetanus, cholera, malaria, typhus, AIDS, syphilis, herpes and common cold etc.


A vaccine is a biological preparation which gives the vaccinated person immunity from a specified illness for a considerable time. In most vaccines, either dead or weakened germs of a particular diseases (the germs are always of the same diseases against which the person is to be secured) are injected (or given orally in certain cases) into the body.

The germs, upon entering the body, prompt it to create its internal defence against the germs, in the form of antibodies (antibodies are chemicals released by the body to fight any external disease). Since the germs injected are too weak to cause any disease but the body is ready with its own defence to fight it,

a vaccine provides protection against a disease for a considerable period. In future, if an actual attack of a disease takes place, the body is always ready to fight it. It can be likened to a defence force put on constant alert which can repel the enemy attack any time. In theory, a vaccine can be developed only for a disease caused by a microbe because their entry in the body triggers anti-bodies.


The tuberculosis of lungs is known as Consumption. It is caused by tubercle bacillus and the major risk factors are – dusty occupation, over-work, chronic worry, starvation, intemperance, malaria and influenza. All these variables make the person more susceptible to TB by way of lowering general vitality and disease resistance.


Caused by a virus. The onset of the disease is sudden, with headache and backache followed by vomiting, fever and a running nose. Eruption on the skin marks the onset of the disease and small red pimples turn into pocks on the third day. The scabs fall off after two weeks, leaving behind scars on the skin.


Caused by Cholera vibrio and marked by copious, colourless stools and vomiting, back pain, cramps and suppression of urine.


Spread by a toxin secreted by Bacillus tetanus, which lives on soil and dust.


Spread by the bite of female Anopheles mosquito. The malarial parasites (Plasmodium vivax) enter the red-blood corpuscles in the blood where they multiply till the RBCs burst. Repeated, high fever with shivering and a feeling of cold, which goes away with sweating. Quinine obtained from the bark of Cinchona is widely used as a preventive medicine in cases of malaria.

However, a fatal type of malaria i.e. dengue fever is caused by Plasmodium falciparum (which is carried by Aedis egypti, a mosquito which is active at daytime). 

Caused by the bite of a male mosquito – it generally occurs in Bengal, Bihar and Orissa and practically all those places with poor drainage.


Spread by the bite of bed bug. Common in Bihar, Odisha.


The causal organism is a protozoan Trypansoma gambiense, carried by the Tsetse fly. Quite common in Africa. Sleepiness coupled with high fever is its major symptom.


The causal organism is Typhoid bacillus. The infection is conveyed mostly through water or milk.


Technically speaking, inflammation of the upper respiratory path.


An infection of the gums which causes edges of the tooth sockets to bleed easily. In the later stages, pus discharges constantly from the affected gums.


Spread by breath and secretions of the nose, mouth and throat. Sudden onset with high fever, shivering, vomiting and a sore throat, flushed cheeks, and marked pale circle round the mouth.


Also called ‘jail fever’. Overcrowding and bad hygiene are major causal factors. It is caused by a virus carried by lice.


A disease caused by the bite of a mad dog, cat or jackal. The best treatment available is the vaccine invented by Louis Pasteur.


Common among children. Diphtheria causes throat inflammation. It is highly infectious, and the best way to fight it is giving the diphtheria vaccine to prevent its onset.


Also called infantile paralysis. It is a viral infection which affects the nerves controlling limb movement. Usually the muscles affected are those of legs or arms, but if the lungs are affected, the consequences can be fatal. The onset is marked by a sore throat, fever and sometimes vomiting. The Salk vaccine can prevent polio infection.


Inflammation of the meningitis. It usually affects children and is marked by headache, high fever, back pain and stiff neck.


Encephalitis is a viral infection affecting the brain. Headache, sore throat and shivering are its major symptoms. The patient often turns delinquent and exhibits violent behaviour.


Acquired Human Immuno-Deficiency Syndrome is caused by the infection of HIV-3 virus. It leads to a progressive breakdown of natural immunity and its major visible symptoms are unexplained weight loss, opportunistic infections like pneumonia, TB etc.


So far, there is no known cure for this disease but the lifespan of the patient can be lengthened and the quality of life can be improved with anti-retroviral therapy.







Human blood consists of

(i) Red Blood Corpuscles (R.B.C.) or Erythrocytes

(ii) White Blood Corpuscles (Leukocytes, W.B.C.)

(!!!) Thrombocytes and

(vii)  Plasma


They are circular, bi-convex disc-like in shape and can be seen under a microscope. Pale yellow in colour, they contain haemoglobin, a compound of iron. They give the blood its typical colour due to their preponderance, their ratio being 500:1 for (RBC: W.B.C.) respectively. The haemoglobin present in RBCs reacts with pure oxygen to form oxy-haemoglobin, which is carried to different body parts for oxygen supply


White Blood Corpuscles are very few and have no definite shape. Their movements are like those of an Amoeba. Also called leucocytes, they act like soldiers of the body and protect it from microbial attacks. Plasma is a pale yellow liquid and contains 90% water. The corpuscles float in this medium.


Plasma consists of fibrinogen and serum. In the event of an external cut or injury on the body, fibrinogen is converted into fibrin which, being insoluble in serum, forms a network, in the meshes of which, blood corpuscles get trapped. It leads to the formation of a blood clot, which stops further bleeding, thereby helping the body conserve this crucial resource. Some people, due to a hereditary defect, do not experience the clotting of blood in case of injury. This medical condition is known as haemophilia.


(a) It supplies oxygen to various organs of the body.

(b) It removes nitrogenous waste products of the body.

(c) It supplies digested food to various organs of the body.

(d) It defends the body against the attack of germs.

(e) It carries the secretions of ductless glands (hormones) to different organs.

(f) It helps maintains a constant internal temperature inside the body, which is crucial to normal physiological working of the body.


It refers to the introduction of the blood with a similar composition and nature into a person suffering from a deficit of blood. It is absolutely safe to donate 250 c.c. or 8% of blood volume at a time if the blood groups have been properly matched.  Blood Banks are there in all big cities where people can donate blood, which is stored at low temperatures and used later. These days, it is possible to segregate different components of blood and use them separately for different patients as per their specific needs. This process avoids any kind of wastage of blood components.


Karl Landsteiner (1901) is credited with the idea of classification of blood. This idea is based on the concept of antigen-antibody reactions. His classification of blood groups is : AB, A, B, and O. Patients must be given a blood transfusion of their own group with the exception of Group O, which is a universal blood group (Can donate blood to any other blood group). A person with blood group AB, as per this system, is the universal recipient i.e. can receive blood of any other blood group.


Another popular classification of blood groups is based on the presence or absence of a chemical factor known as Rh factor (derived from Rhesus monkey). If a person has the Rh factor in his blood, he is referred to as Rh+ while an Rh – person does not have such a factor in his blood. This is an aspect to be considered while transfusing blood because mixing Rh+ with Rh – blood leads to agglutination (clumping together) and immediate death.




A gland is a collection of cells which creates a useful chemical for the body in its various reactions. Two kinds of glands are seen in the human body:

  1.  Exocrine glands – e.g. Liver, Spleen, Pancreas. Their secretions are taken to the desired part by a special channel called duct.
  2.  Endocrine or Ductless glands – e.g. Pituitary (The Master Gland), Suprarenal, Thyroid. Their secretions are transported by blood to the desired body part.


The largest gland in the body, the liver is a reddish-brown organ about 85 gm. The liver performs the following functions:

  1. Storage of excess sugar as glycogen (insoluble carbohydrate), which helps fat digestion.
  2. Manufacture of urine which is filtered from blood by kidneys.
  3. Manufacture of Vitamin A from Pro-carotene.
  4. Destruction of poisonous substances in the body.


The pancreas secretes a clear, colourless juice with important digestive properties. It is the only gland in the body to have an exocrine and an endocrine character. As an exocrine gland, it secretes pancreatic juice which, through the pancreatic duct, goes to the duodenum to help digestion there. As an endocrine gland, it secretes insulin which helps utilize sugar in the body. Insulin is secreted by special pancreatic cells called Islets of Langerhans. The deficiency of insulin causes diabetes, a disease in which the patient passes sugar in urine. The disease is cured by insulin injections invented by F. Banting.

Bluish-red organ to the left of the stomach. The white blood corpuscles are formed here, and the worn out red blood corpuscles are disposed of in the spleen pulp.


It is a reddish-grey gland hanging from the lower surface of the brain. Its secretion regulates growth and height, milk secretion in mammals, and influences sex organs. The pituitary gland secretes hormones which maintain homeostasis (stable internal environment) including trophic hormones that stimulate other endocrine glands. The Pituitary is also called the Master Gland because of its homeostatic role and its ability to influence other glands.




They are small, yellowish glands just above the kidneys, one on each side. Their secretion is known as adrenaline and noradrenalin. This secretion is released in emergencies i.e. Fight or Flight Response and prepares the body for such situations by releasing excess energy.

A brownish-red body located in front of the neck. An abnormal increase in its size is called goitre. Its secretion, known as thyroxin, is rich in iodine


DOWNS’ SYNDROME ( a k a Mongoloid Idiocy Or Mongoloid Syndrome)
Caused by the trisomy (three chromosomes) of the 21st chromosome, creating a total of 47 chromosomes instead of 46. It is characterized by a round face, broad forehead, projecting lower lip, short neck, stubby fingers, etc.


Causes a deficiency of an enzyme called phenylalanine in the liver. The body cannot digest certain essential proteins due to this deficiency and they keep on getting deposited in the body. Marked by mental retardation, hypo pigmentation of skin and hair, eczema.


A recessive gene trait which occurs due to the absence of thromboplastin or anti-haemophilia globulin. The blood cannot clot in case of even a minor injury.


The mothers with blood group O possess neither antigen A nor B but rather have anti-A and anti-B antibodies. The A or B group antibodies of the mother cause partial destruction of RBCs and the production of billirubin (causing mild anemia and jaundice in the baby’s body). Similarly, the A-group foetus in a B-group mother is attacked by the mother’s antibodies. The ABO hemolytic (RBC-destroying) disease of the newborn is quite common but less severe as compared to Rh-incompatibility.


Caused by a pair of recessive genes, results from a defective synthesis of haemoglobin. Causes excess of iron in the body, which deposits in the liver.


Caused by a recessive gene that causes abnormalities in haemoglobin resulting in sickle cell RBCs (rigid sickle cells obstructing the capillary blood flow).


Renders one unable to distinguish between two colours, mostly red and green. Though carried by females, it is mostly exhibited by males only. Similar to baldness in terms of genetic expression.



  1. Sense of Touch, Temperature, Pressure and Pain

Is due to the touch corpuscles present in the epidermis of the human skin.

  1. Sense of Taste

Is due to the taste buds in the papillae of the tongue. The tip of the tongue is the most sensitive to sweet taste, and the rear is sensitive to bitter taste. The middle part of the tongue is not sensitive at all i.e. can be used to place a bitter pill while ingesting it.

  1. Sense of Sight

To see an object, its image must be formed on the retina. The convexity of the lens of the eye increases when the object is nearer and decreases when the object is far away to get the image on the retina in each case. The property of the lens by which it can adjust its convexity to form distinct image of the object at various distances is called accommodation. When the ciliary muscles do no work properly to bring about accommodation of the lens, the eye becomes defective.

The human retina contains two types of cells

  1. Cone Cells – Meant for daylight vision, also responsible for colour vision
  2. Rod Cells: Meant for nighttime or low intensity vision.

Since humans have many more cone cells as compared to rod cells, they are much better at seeing the objects in bright intensity as compared to others. Humans see with both the eyes together and both the eyes form separate images of an object. These two separate images are then fused in the brain to create an impression of depth. (Otherwise, the human retina is a 2-D structure and cannot give a perception of depth). This difference in images in the two eyes is referred to as binocular disparity.


  1. Myopia (Short-sightedness)

When a person can see nearer objects distinctly but not the  ones lying far away, he is said to be suffering from myopia. In this case, the convexity of the lens of his eye cannot be sufficiently decreased to form the image of the distant object on the retina. It is remedied by the use of concave glasses.

  1. Hypermetropia (Long-sightedness)

Refers to a person’s ability to see the distant objects clearly but not the near ones. It is remedied by the use of convex glasses.

  1. Astigmatism

A person suffering from it can see the vertical lines clearly but not the horizontal ones, or vice versa.  It is remedied by the use of cylindrical glasses.

  1. Colour Blindness

If a person cannot distinguish between different colours (especially between red and green), he is said to be suffering from this defect. It is a sex-linked disorder i.e. occurs due to recessive genes on the 23rd pair of chromosomes.

  1. Sense of Smell

Owes to the presence of smell-perceiving cells present in the lining of nasal chambers.


  1. Sense of Hearing

Is due to the vibration of the ear membrane in the inner ear. Made possible by the incidence of sound waves on it.


  1. Sense of Hearing

Is due to the vibration of the ear membrane in the inner ear. Made possible by the incidence of sound waves on it.



Important Branches of Science


Branch              Related To                                            Branch            Related To


Acoustics         Sound and sound waves                  Anthropology Origin and development of man


Aeronautics       Activities of flying                              Agronomy                Crops and soil management


Anatomy           Dissectional learning of animal and human body


Archaeology     Study of past remains                        Astronautics    Space travel


Astronomy        Planets and stars                              Biology                    Science of living organisms


Botany              Plants                                                Cardiology              Heart and related diseases


Ceramics          Manufacture of clay objects              Cosmology      Universe


Cytology           Structure and function of cells          Cryogenics                 Study of low temperature


Dactylography    Study of fingerprints                          Dermatology    Skin


Dietetics           Diet and nutrition                                Ecology      Organism- environment relationship


Entomology      Insects                                                Endocrinoloqy Endocrine glands


Etymology        Origin and history of words                Genetics        Heredity and its laws


Geology           Earth’s structure                                  Gynecology    Female reproductive system


Gerontology      Ageing process, problems and diseases


Hematology      Blood and related disorders                Histology                   Tissues


Immunology      Immune system                                  Mycology                   Fungi, fungal diseases


Morphology      External structure of living organisms Nephrology     Kidney


Ornithology       Birds                                                    Obstetrics       Pregnancy, child birth


Orthopedics      Human skeletal system                        Osteology       Study of bones


Paediatrics        Child diseases                                      Palaeontoloqy Fossils


Pathology         Mechanisms of diseases                      Psychiatry       Mental disorders


Pharmacology   Drugs, their effects on the body          Physiology       Life processes of living beings


Seismology      Earthquakes                                        Semiology        Sign language and signs


Theology          Religions                                             Toxicology          Toxic substances


Zoology            Animal life                                            Zymology                   Fermentation process


Important Units of Measurement


Unit                      Used to measure                     Unit                          Used to measure


Ampere              Electric current                          Angstrom        Wavelength of Light


Bar                   Atmospheric pressure              Calorie                           Quantity of heat


Candela            Luminous intensity                    Celsius                Temperature


Decibel              Sound level                              Coulomb        Electric charge


Dyne                 Force                                        Erg                  Work


Fathom              Depth of water                          Fahrenheit      Body temperature


Faraday            Electric charge                          Gauss                 Magnetic flux density


Hertz                  Frequency                                Henry                  Inductance


Horsepower      Power                                        Joule                 Work or Energy


Kelvin                Temperature                              Light Year         Distance (=2,97,600 km)


Newton            Force                                        Ohm                 Electrical resistance


Pascal               Pressure                                    Poise                  Viscosity


Volt                   Electrical potential                    Watt                  Power


Medical Discoveries


Discovery          Scientist                       Discovery                    Scientist


Penicillin           Alexander Fleming     Aspirin                      Felix Hoffmann


Blood Circulation Harvey                       Blood group            K. Landsteiner


Cholera             Robert Koch                 ECG                       William Einthoven


Heart transplant Christian Bernard       Malaria germs        A. Laveran







Important Scientific Inventions


Invention          Inventor                                  Invention    Inventor


Aeroplane         Wright Brothers                      Bicycle                 K. Macmillan


Celsius scale    A. Celsius                               Computer                        Charles Babbage


Diesel engine    Rudolf Diesel                          Dynamite                         Alfred Nobel


Dynamo            Michael Faraday                    Electric Lamp       Thomas Alva Edison


Fountain Pen     L.E. Waterman                      Gramophone        Thomas Alva Edison


Jet engine         Sir Frank Whittle                    Microphone         David Hughes


Microscope       Z. Jansen                              Radium              Marie and Pierre Curie


Safety Pin         William Hurst                         Safety Lamp        Sir Humphrey Davy


Sewing Machine Thimmonnier                        Shorthand            Sir Isaac Pitman


Television         John Logie Baird                     Telescope            Hans Lippershey


Thermometer     Galileo Galilei                         X-ray                   Wilhelm Roentgen




Scientific Instruments


Instrument      Function


Ammeter           Measures electric current


Barometer         Measures atmospheric pressure


Calorimeter       Measuring quantity of heat


ECG                  Measures heart movements graphically


Dynamo            Converts mechanical energy into electricity


EEG                  Records electrical waves of the brain


Electrometer     Measures small potential differences


Endoscope       Examines internal body organs, used in minor surgeries


Fathometer       Measures ocean depth


Galvanometer    Measures electric current


Hydrometer       Measures relative density of liquids


Hygrometer       Measures atmospheric humidity


Lactometer        Measures purity of milk


Manometer        Measures gas pressure


Micrometer        Measures distances/angles


Microscope       Magnifies small objects


Pyrometer         Measures very high temperature


Salinometer       Determines salinity of solutions


Sextant              Finds latitude of a place


Sphygmo             Measures blood pressure



Stethoscope     Analyzes heart and lung sounds


Tachometer       Measures distances and elevations


Telescope         Helps see distant objects


Transponder      Receives and transmits signals


Viscometer       Measures the viscosity of liquid


Voltmeter          Measures potential difference


Wattmeter         Measures power of an electric circuit






Important Vaccines


Vaccine               Discoverer                     Vaccine                 Discoverer


Smallpox          Edward Jenner             TB vaccine        Leon Calmette, Camille Guerin


Cholera, Rabies Louis Pasteur               Polio vaccine    Jonas E. Salk