The Life Science of Biology

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The Life Science of Biology

The Life Science of Biology

The aim of biology is to explain the living world in terms of scientific principles. Aristotle, the great Greek philosopher and teacher, is known as the father of biology and the French naturalist, Jean Baptiste de Lamarck, was the first to used the word ‘biology’ in 1800. Biology today is subdivided into numerous branches based on the molecule, the cell, the organism and the population.

Living and Non Living Biology

There are seven characteristics that can be observed, more or less, in all living organisms. In order to maintain themselves and prevent disintegration, organisms have an inbuilt self regulating system to ensure that there is no net energy loss. This control is referred to as homeostasis and operates at all levels of biological organisation, from the molecular level to the community level.

The Heart

Heart average weight is about 340 grams in men and 255 grams in women. The left half and the right half of the heart is divided by a wall called septum. Each half, in turn, is divided into an upper chamber called the auricle and a lower chamber called the ventricle. The auricle receives blood from the veins and the ventricle pumps blood into the arteries.

Heartbeats :  In a normal, healthy adult, the contraction and relaxation mechanism of the ventricles results in a heartbeat of about 70 – 72 / minutes in males and 78 – 82 / minutes in females.

Functions : The functions of the heart are :General Studies Question Bank CD

  1.  to supply pure blood to all parts of the body ; ( through arteries )
  2.  to collect impure blood from organs / tissues ; ( through veins )
  3.  to pump impure blood into the lungs for purification ; and
  4.  to collect pure blood from the lungs.

Biology The Cell Theory

The Cell : Foundation of All Living Things

Cells are the basic units of life. They are the smallest parts of a living organism that can lead an independent existence. Singly, or in association with other cells, they make up the bodies of all living things.

Structure of Cell

Every cell is surrounded by a membrane or a living covering. Within the membrane is the protoplasm.

Parts of the Protoplasm :

The nucleus controls and directs the activities of all the other parts of the cell. The remainder is known as cytoplasm, where any vital activities of the cell take place. Following are the parts of a Cell –

  1. Cell Wall Found only in plant cells, it consists of non-living substances, eg, linguin, pectin, cellulose etc.,
  2. Cell membrane ( Plasmalemma ) This is the outer membrane of the cytoplasm, found both in animals and plants. It consists of living substances such as proteins,
  3. Endoplasmic reticulum ( ER ) It is a network of tubes or channels of membrane in the cytoplasm, which helps in protein synthesis and conduction of material,
  4. Ribosomes They are extremely small, dense, granular, spherical bodies found in free state in the cytoplasm, composed of RNA and proteins. They help in the synthesis of protein from amino acids,
  5. Golgi apparatus ( Golgi bodies ) They are bag-like structures formed of stacks of membrane. Their functions include secretion of various substances, secretion of pectic material of cells wall in plants, and helping in the formation of cell during cell division,
  6. Vacuoles Are fluidfilled sacs within a cell. In animals they are tiny. Their functions include osmo – regulation and maintenance of cell turgidity,
  7. Mitochondria Rod – like or spherical semi-solid structures containing DNA in its matrix along with some enzymes, which are found in all cells. They synthesise ATP ( energy storing molecules ),
  8. Plastids Small bodies found in the cells of higher plants. They are of two types, viz, Leucoplasts, which are colourless and store starch, protein or lipids; and Chromoplasts, which are coloured and are of two varieties :
    •  Non – photosynthetic chromoplasts, which provide colour to flowers, fruits and leaves,
    •  Photosynthetic chromoplasts, which manufacture food from carbon dioxide and water in the presence of sunlight, in green plants,
  9. Nucleus Each nucleus is bound by the nuclear membrane, which contains nucleoplasm. Nucleoplasm consists of chromatin and nucleoli. Chromatin consists of DNA, RNA and proteins. The nucleus controls all cell activities and is responsible for the transfer of heredity characters and also assists in cell division,
  10. Centrosome A rather dense area of protoplasm, it lies close to nucleus. It is usually found in animal cells. In the middle of the centrosome are two small dot – like bodies called centroils. They form a spindle during cell division and lower plants,
  11. Cilia and flagella These are fine extensions of the cell surface and are similar in structure. Their functions are to help in locomotion or movement, and in some animals they also help in feeding,

Animal Cell
An animal cell typically contains several types of membrane- bound organs, or organelles. The nucleus directs activities of the cell and carries genetic information from generation to generation. The mitochondria generate energy for the cell. Proteins are manufactured

Biology Food Groups

The essentials of good diet are :

  1. Vitamins : These are a group of substances that are essential in small quantities for normal functions of the body. Their deficiency causes sickness and improper development of body. At present six of these are recognised as essential to human nutrition. These are A, B, C, D, E and K. The richest sources of vitamins are green vegetables, milk, butter, fruits, eggs, etc.
  2. Proteins : These are complex compounds of carbon, hydrogen, oxygen, nitrogen and sulphur. These are found in eggs, meat, pulses, etc. These build tissues of the body and repair them when torn out.

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  1. Carbohydrates : These are the organic compounds of carbon, hydrogen and oxygen. These are found in rice, wheat, sugarcane, potatoes, starch in maize, etc. These produce heat and energy in the body. Their deficiency causes loss of weight and weakness.
  2. Fats : These have carbon, hydrogen and oxygen. They are obtained from animal and vegetable kingdoms. Butter, ghee and various vegetable oils are examples of fats. They also produce heat and energy in the body and build fatty tissues.
  3. Mineral Salts : These make food tasty and are useful for health. They are the sources of hydrochloric acid found in the digestive system. These are found in green vegetables.
  4. Water : It serves to dissolve food when digested and aids absorption. It helps in removing waste matters from the body. It also helps in circulation of blood.

Balanced Diet

A balanced diet is one which contains all principal food factors, i.e., vitamins, carbohydrates, mineral salts, fats, water, etc., in correct proportion. This should be able to give about 3,000 calories of energy per day.

Types of Vitamins

  1. Vitamin A : It increases resistance to infection and tones up the whole system. Its deficiency causes nightblindness, disorders of skin, stomach growth and respiratory diseases. It is found in milk, butter, egg – yolk, ghee, carrot, cod – liver oil, etc.
  2. Vitamin B : It is present in cereals, peas and beans. It protects the body from nerve diseases such as beri – beri, pellagra,etc., and it cures pernicious anaemia, degeneration of sex glands and enlargement of liver and adrenals. It is also called thiamine. It is considered to be a hormone.
  3. Vitamin C : It ensures healthy teeth, bones and protects the body against scurvy. It is present in fresh vegetables, orange, lemon, lettuce, tomato, cabbage, turnip, potato and mango.It is also called Ascorbic Acid.
  4. Vitamin D : It is present in milk, butter, ghee, codliver oil, yolk of eggs and it is also produced under the skin by the rays of the sun. It promotes bone promotion and prevents rickets.
  5. Vitamin E : It has vital influence on organs to reproduction. Its absence causes sterility. It is present in the germinating wheat. It is also called Alpha – tecopherol.
  6. Vitamin K : It is found in fish, oats and wheat. It help in the clotting of blood. Its absence cause haemorrhage.

The Theory of Evaluation

The French biologist Lamarck proposed, in 1809, a hypothesis to account for the mechanism of evolution, based on two conditions : the use and disuse of parts, and the inheritance of acquired characteristics. So, according to Lamarckism, as the theory came to be known, the long neck and legs of the modern giraffe were the result of generations of short-necked and short – legged ancestors feeding on leaves at progressively higher levels of trees.

Darwin’s Theory of Evolution

In November 1859, Darwin published the Origin of Species by Means of Natural Selection, proposing that natural selection is the mechanism by which new species arise from pre – existing species. The ‘struggle for existence’ described by Darwin was popularised by the coining of the terms such as ‘survival of the fittest’.

Modern Views of Evolution

The theory of evolution, as proposed by Darwin and Wallace, has been modified in the light of modern evidence from genetics, molecular biology, palaeontology, ecology, and ethology ( the study of behaviour ) and is known as neo- Darwinism ( neo or new ). This may be defined as the theory of organic evolution by the natural selection of inherited characteristics.

Human Evolution

Prehistoric People : Evidence of prehistoric people, such as fossils, tools, and other remains, is rare and often fragmented.

Pre Human Ancestors

Most scientists believe that human beings and apes, such as chimpanzees and gorillas, share a common ancestor. The ancestors of human beings probably began evolving separately from the ancestors of apes, between about 10 million and 5 million years ago. This evolutionary split marks the beginning of the development of hominids. Hominids are members of the scientific family made up of human beings and early humanlike ancestors. Most anthropologists believe the first hominids were humanlike creatures called australopithecines. The australopithecines first appeared more than 4 million years ago in Africa.

Types of Australopithecines

The australopithecines were members of the genus Australopithecus ( southern ape ). According to differences in the shape of the creatures’ jaws and teeth and the size of their brains, scientists have divided the genus Australopithecus into five species :General Studies Question Bank CD

  1. A. ramidus,
  2. A. afarensis,
  3. A. africanus,
  4. A. robusius, and
  5. A. boisei.

The most complete australopithecine fossil scientists have found is a partial skeleton of a female A. afarensis. It was found in Ethiopia. This creature, nicknamed “Lucy”, was probably more than 110 centimetres tall and weighed about 30 kilograms. By about 2.5 million years ago, A. africanus replaced A. afarensis. Many scientists believe that an evolutionary split occurred among the australopithecines during the time of A. africanus. This split resulted in the appearance of an additional evolutionary line, separate from A. africanus, that led to A. robustus and A. boisei. Scientists refer to these two species as the robust australopithecines.

The First Human Beings on Earth

Most anthropologists believe that the first human beings evolved from a gracile australopithecine about 2 million years ago. Homo habilis is considered by anthropologists to be the oldest human species. These prehistoric people lived in Africa about 2 million years ago. Homo erectus : Fossil evidenceindicates that about 1.5 million years ago Homo habilis had evolved into a more advanced human species. Scientists call this species Homo erectus.

Early Homo Sapiens Between 400,000 and 300,000 years ago, Homo erectus evolved into a new human species called Homo sapiens. The term Homo sapiens means ‘wise human being’. All people living today belong to this species. But early Homo sapiens differed greatly from modern people. Early Homo sapiens were about as tall as modern human beings. Neanderthals were a type of early Homo sapiens who lived in parts of Europe and the Middle East about 130,000 – 35,000 years ago. Neanderthals have become the most widely known of the early Homo sapiens mainly because they were the first prehistoric people to be discovered.

Rise of Modern Human Beings

The first prehistoric people with modern human features appeared about 100,000 years ago in either the Middle East or Africa. These people had a chin, a high forehead, and a smaller, less-protruding face than the earlier Homo sapiens had.


Composition of the Blood

Blood consists of a faintly yellow fluid, the plasma or liquor sanguinis, in which are suspended numerous minute particles, the blood corpuscles, the majority of which are coloured and give the blood its red tint.

Functions of Blood :

  1. Carries oxygen and essential nourishment through arteries to every living tissue in the body.
  2. Carbon dioxide and waste products generated in the body by metabolism ( Metabolism are all chemical processes which govern living organisms ), such as urea, are removed by the blood through veins.
  3. Controls body temperature.
  4. Defends against infections.

Constituents of Blood : There are two main constituents of blood, viz., the solid or cellular part called blood cells ( 35 per cent ) and fluid or humoral part called plasma ( 65 per cent ). Blood cells, called corpuscles, are of three types.

  1. Red Blood Corpuscles ( RBC ) RBCs, which are called erythrocytes, are disc-shaped cells. They have no nucleus and contain a pigment called haemoglobin which gives blood its red colour. RBCs are produced in the spleen. The life of an RBC is about 100 – 120 days.

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  1. White Blood Corpuscles ( WBC ) WBCs are the ‘soldiers’ of the body’s defence system. They are a little larger than RBCs.

Blood grouping :  K. Landsteiner, in 1900 – 02, classified human blood into four groups, A, B, AB, and O. The cells of these groups contain the corresponding antigens — A, B, AB, except O cells which contain neither antigen A nor B.
Blood Pressure :  It is the force exerted by the blood beating against artery walls. The highest point in the pressure range is called systolic pressure ( upper reading ) and lowest point in the pressure is called diastolic pressure ( lower reading ). 120 / 80 is the normal blood pressure.

Common Diseases in Humans

1. Malaria An insect – borne tropical disease.

  • Cause Malaria parasite ( Plasmodium ) which enters the blood through a mosquito bite ( female anopheles ).
  • Symptoms Shivering, fever, repeated attacks lead to enlargement of spleen. Also leads to anaemia, pigmentation of the face, and general weakness.
  • Cure / Prevention Administration of quinine or plaudrine. Prevented by keeping the surroundings free of mosquitoes.

2. Tuberculosis An infectious and endemic disease, both air-borne and caused by food, unhealthy living and working conditions.

  • Cause Mycobacterium tuberculosis ( detected by Robert Koch in the mid 19th century ), a type of bacteria. It attacks a person suffering from malnutrition, weak chest, unhealthy living and working conditions.
  • Symptoms General weakness, regular fever ( generally in the evening and not very high ), coughing, bloodstained sputum.
  • Cure / Prevention Streptomycin and surgery.

Prevented by BCG inoculation and healthy living and working atmosphere. BCG The vaccine was developed in 1922 by Leon Calmette and Camille Guerrin in Paris and called BCG after them. ( Bacillus Calmette – Guerin ).

3. Cholera An acute epidemic, water and food-borne disease.

  • Cause Cholera vibrio or Vibriocholerae which attacks during exposure to chill, when stomach is empty for a long duration, eating of unripe or overripe fruits, and stale food.
  • Symptoms Vomiting, stomach ache, frequent loose stools followed by fever and unconsciousness.
  • Cure / Prevention Avoiding consumption of cut fruits exposed to flies, and contaminated water. Anticholera drugs are administered.

4. Tetanus

  • Cause Bacillus tetanus and Clostridium tetani which live in soil, dust, cow and horse dung. It attacks an open wound exposed to dust and soil.
  • Symptoms Painful contraction of muscles, usually of neck and jaws, followed by paralysis of thoracic muscles.
  • Cure / Prevention Preventing exposure of wounds to dust and administering of Anti – Tetanus ( ATS ) injection.

5. Diphtheria An acute infectious disease of the throat.

  • Cause Acute infection by diphtheria bacillus / corynebacterium diphtheria causing infection of throat.
  • Symptoms Inflammation of throat where a grey membrane ( a false membrane on mucous surface ) is formed. Pain and swelling of throat, with fever.
  • Cure / Prevention Immunisation vaccine of diphtheria antitoxin within 12 – 24 hours of appearance of symptoms.

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6. Typhoid A food – and water-borne infectious disease.

  • Cause Salmonella typhi bacillus transmitted through contaminated food and water, either directly by sewage or indirectly by hands and faulty hygiene.
  • Symptoms Temperature, slow pulse, abdominal tenderness, rosecoloured rash.
  • Cure / Prevention Rest and administration of chloromycetin, proper sanitation, protection of eatables.

7. Plague A contagious disease which takes the form of an epidemic.

  • Cause Pasteurella pestis, spread by infected rats. Transfer of infection from rat to man through flea bite or accidental contact with infected rats.
  • Symptoms Acute body ache, reddish eyes, sudden rise in temperatue, inflammation of neck glands and glands in armpits, and
  • Cure / Prevention Antiplague inoculation, isolation of patient, disinfection of patient’s clothes and utensils, burning of killed rats. Sulpha drugs and streptomycin administration.

8. Typhus A viral infection Cause Rickettsia prowazekii, usually caused by poor hygiene and malnutrition.

  • Symptoms High fever, skin eruptions, and severe headache.
  • Cure / prevention Sulphonamides and antibiotics.

9. Pneumonia

  • Cause Diplococus pneumonia
  • Symptoms Chills, pain in chest, rusty sputum, rapid breathing, abdominal pain.
  • Cure / Prevention Antibiotics

10. Gonorrhoea A venereal disease Cause Neisseria gonorrhea, through sexual intercourse with infected person.

  • Symptoms Redness, swelling, pus discharge through urethra, painful urination.
  • Cure Penicillin G, tetracycline.

11. Syphilis

  • Cause Treponema pallidum transmitted through sexual contact.
  • Symptoms A hard painless sore on the genitalia, skin eruption.
  • Cure / Prevention Penicillin, protected sexual intercourse.

12. Whooping Chiefly occurs among infants Cough and children.

  • Cause Nemophilus pertusis transmitted through air.
  • Symptoms Severe cough, usually at night.
  • Cure / Prevention Immunisation of infants with immunity serum

Classification of Humans

Linnaeus classified humans as animals. He recognised that people belonged with monkeys and apes in the taxonomic order Anthropomorpha, which he later renamed Primates. Linnaeus also recognised all humans as belonging to a common genus, Homo, and species, sapiens.

The Five Kingdoms

In 1969 R H Whittakar classified all living organisms into five main kingdoms. According to the system the five kingdoms are:

  1. Monera ( true – bacteria, bluegreen algae )
  2. Protista ( golden algae, yellow –  green algae )
  3. Fungi ( slime molds, bread molds, sac fungi )
  4. Plantae ( plants )
  5. Animalae ( animals )


Bacteria are the most ancient group of organisms, having appeared about 3500 million years ago, and are the smallest organisms with a cellular structure. Bacteria range between the lengths of 0.1 to 10 micro metre. They occupy many environments such as soil, dust, water, air, in and on plants and animals. On the basis of their importance bacteria can be divided into two parts:

  1. Helpful Bacteria : Certain types of bacteria live in the intestines of human beings and other animals. These bacteria help in digestion and also produce vitamins for the body. Bacteria that live in soil and water play a vital role in recycling carbon, nitrogen, sulphur and other chemical elements used by living beings.
  2. Harmful Bacteria : Some bacteria cause diseases in humans preventing the body from functioning properly by destroying healthy cells.

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Viruses are the smallest living organisms, ranging from sizes of 20 – 300 m m; on an average they are about 50 times smaller than bacteria.

Characteristics of Virus :

  •  They are the smallest living organisms.
  •   They do not have a cellular structure.
  •   They can only reproduce by invading living cells, therefore, they are all parasitic.
  •   Most viruses cause disease.

Bones of the Human Body


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