Introduction to Biology, Notes & Key Points

The elements which occur in a particular organism are called bioelements.

There are 92 natural elements. 16 elements and a few others in an organism are the bioelements.

Bioelements are of two types: (i) MAJOR BIOELEMENTS: These are required in higher amounts. Examples are oxygen, carbon, hydrogen, nitrogen, calcium and phosphorus. (ii)MINOR BIOELEMENTS:These are required in smaller amounts. Examples are potassium, sulphur, iron and iodine etc.


  1. OXYGEN 65%
  2. CARBON 18%
  3. HYDROGEN 10%
  4. NITROGEN 3%
  5. CALCIUM 2%


These are Potassium (0.35%), Sulphur (0.25%), Chlorine (0.15%), Sodium (0.15%), Magnesium (0.05%), Iron (0.004%), Copper (trace), Manganese (trace), Zinc (trace), Iodine (trace).

In the human body only six bio-elements accounts for 99% of the total mass.

In the organisms, elements usually do not present in isolated forms.


Some important and abundant organic molecules in organisms are glucose, amino acids, fatty acids, glycerol and nucleotides (like ATP, ADP, AMP) etc.

A sub-cellular structure within a cell that performs a specific function is called an organelle. OR Organelle is a structure within a cell that performs a specific function.

Many different micromolecules and macromolecules are arranged in a specific way to form cells and their organelles.

PROKARYOTES have a limited number and kind of organelles.

EUKARYOTES have a large number and kinds of organelles including membranous organelles.

A cell membrane is present in both prokaryotic and eukaryotic cells.

Prokaryotes are Bacteria and Cyanobacteria (one kingdom).

Eukaryotes are Protists, Fungi, Plants and Animals (four kingdoms).

In multicellular animals and plants, groups of similar cells which form loose sheets or bundles and perform similar functions are called tissues.

Each tissue has a specific function. Muscle tissue is for contraction/movement. Glandular tissue for secretion. Xylem tissue for conduction of water and minerals. Phloem tissue for translocation of sugar and proteins etc.

Different tissues having related functions, assemble to perform efficient function is called an organ. Stomach is an organ.

The organs work in efficient way both qualitatively and quantitatively.

Two or more organs working together to carry out a specific body function is called as organ system.

In animals organ level is more complex as compared to plants because these organs form a system.

In a system many functions are involved in one process.

Different organs in plants and different organ systems in animals are assembled to form an organism.

Organ         SystemOrganism

FunctionProcess Activity

In animals the coordination occurs by nervous system and endocrine system.

In plants the long-term activities are coordinated and regulated by hormones.

A population is a group of living organisms of the same species located in the same place at the same time.

At population level we study gene frequency, gene flow, age distribution, population density and population pressure etc.

Populations of different species living in the same habitat form a community.

In a simple community little change can brought severe and long lasting effects.

In a complex community big change can brought slow, gradual and short-term effects.

At community level the organism interactions are of many types: These may be predation, parasitism, commensalism, mutualism and competition etc.

A biome is a large regional community primarily determined by climate.

In Genetic engineering, the genes of disease resistance and other desirable characters are introduced into animals and plants.

The organisms produced by genetic engineering are called as transgenic organisms.

The transgenic organisms can be propagated by cloning using special techniques such as tissue culture techniques etc.

Cloning is the production of genetically identical copies of organisms/cells by sexual reproduction.

Pests are controlled by using fungicides, herbicides and insecticides (pesticides).

Control by some living organisms is called biological control. OR Control of pests by disrupting their ecological status, as through the use of organisms that are naturalpredators, parasites, or pathogens. Examples of biocontrol include the use of ladybugs to prey on aphids and scale insects. “An aphid that attacks walnut tree is controlled biologically by a wasp that parasitizes this aphid”

Biopesticides are naturally occurring substances (biochemical pesticides) that control pests, microorganisms that control pests (microbial pesticides), and pesticidal substancesproduced by plants that control pests by nontoxic mechanisms. Some bacteria are used as bio-pesticides. Conventional pesticides are generally synthetic materials that directly kill or inactivate the pests.

In HYDROPONICCULTURETECHNIQUES the plants are grown in aerated water to which nutrient mineral salts are added.

The Hydroponic culture technique is used to test whether certain nutrient is essential for the plant or not.

Soil is complex medium and we cannot conduct experiments on nutrient requirements of plants by growing them in the soil. Astronauts may use HCT for growing vegetables.

One method of food preservation is pasteurization. It was developed by Louis Pasture and is used for preservation of milk and milk products. To kill non-spore bacteria at low heat (62-710C) is Pasteurization. The process of heating a beverage or other food, such as milk or beer, to a specific temperature for a specific period of time in order to kill microorganisms that could cause disease, spoilage, or undesired fermentation OR The process of pasteurization was named after Louis Pasteur who discovered that spoilage organisms could be inactivated in wine by applying heat at temperatures below its boiling point. The process was later applied to milk.

There are two primary methods of pasteurization: the liquid can be heated to 143 degrees Fahrenheit (62 degrees Celsius) and held there for at least thirty minutes, or the liquid can be pasteurized at 158 degrees Fahrenheit (71 degrees Celsius) for a minimum of 15 seconds. Pasteurization can be done using a continuous method, where the liquid flows through a pasteurization system, or by using a batch method, where one batch of the liquid is pasteurized at a time. Pasteurization must be performed on clean equipment. If bacteria are introduced after the liquid has been pasteurized, it can colonize it and potentially cause an outbreak of food borne illness.

Diseases can be controlled by preventive measures, vaccination / immunization and drugs treatment / gene therapy.

AIDS (Acquired Immune Deficiency Syndrome) is caused by HIV (human immunodeficiency virus). AIDS spreads by free sexual contract, through blood transfusion and by using contaminated syringes or surgical instruments etc.

Hepatitis is caused by H. virus which is spreaded through blood transfusion, by using contaminated syringes and surgical instruments etc.

VACCINE: Dead or weakened viruses or bacteria or modified toxins that produce an

VACCINATION: The administration of vaccine for the purpose of inducing active

Many diseases such as polio, whooping cough, mumps etc., are controlled by vaccination or “shots”.

IMMUNIZATION: The process of rendering an animal resistant to infection is called immunization.

DISCOVERY OF VACCINE: Edward Jenner first developed the technique of vaccination in 1796 from cowpox pus.

Cowpox pus is known as vacca (vacca is a Latin word meaning cow). From this word evolved the present term vaccination and vaccine.

Antibiotics are organic compounds that are synthesized and excreted by certain microorganisms (especially Bacteria but a few fungi) and kill or inhibit the growth of other microorganisms. Also chemicals which are active against microorganism have been isolated from a variety of organisms such as plants, insects and amphibians. The treatment of disease with chemicals is called chemotherapy. Sir Alexander Fleming isolated Penicillin.

Antibiotic may be biostatic (if they inhibit the growth and multiplication of microorganisms e.g. chloramphenicol, erythromycin, sulphonamide and tetracycline) or biocidal (if they kill microorganisms, e.g., streptomycin and penicillin etc.)

Antibiotics are useful only when the bacteria have not developed resistance against them.

In radiotherapy, the cancerous part is exposed to short wave radiations from the radioactive material.

Some drugs work better together than alone, often two or more drugs are given at the same time. This iscalled Combination chemotherapy.

In chemotherapy certain anticancer chemicals are given to the patients at regular intervals. These chemicals may kill both cancerous as well as normal cells.

In Gene therapy the defective gene is repaired. In this case the normal gene is isolated and is inserted into host through bone marrow cells.

DRUG THERAPY / PHARMACOTHERAPY: The use of a drug in the treatment of a patient with a specific disease or illness.

Fighting of disease by methods required and involvement of community in this program is known as IDM.

Effective control of a disease, or all the common diseases of a plant by using, suitable methods of disease control is called integrated disease management.

IDM is a very effective program for elimination and control of the dangerous diseases from the human society.

The direct or indirect alteration of the physical, chemical, thermal or biological properties of any part of the environment in such a way as to create a problem to health, safety or welfare of any living species is called pollution.

Heavy metals like Lead (Pb) from automobiles and Chromium from tanneries are very dangerous to human health.

Bioremediation is defined as removal or degradation of environmental pollutants or toxic materials by living organisms.

Algae reduce pollution of heavy metals by bioabsorption.

Many species of plants and animals have been disappeared from the earth due to our activities. These are extinct species.

The species which are about to extinct are endangered species.

CARCINOGEN: An agent that has been shown to cause cancer in a laboratory animal or person.

However there is controversy on the issue of human cloning.

Fossils are the pre-historic remains of organisms preserved in the rocks.

Study of fossils to find the evolutionary history of a group is called phylogeny.

The fossils can be dated by SEDIMENTARYMETHOD and by RADIOACTIVEMETHOD.

The older sediment layers have less radioactive isotopes than the younger layers.

Phyletic lineage is an unbroken series of species arranged in ancestor to descendant sequence with each later species evolved from former one.

Biodiversity is the number and variety of species in a place.

There are nearly 2,500,000 species of organisms. About 53.1% are insects. Animals other than insects are 19.9% (species). 17.6% are vascular plants and 9.4% are fungi, protozoa, and various prokaryotes.

Any problem associated with a living organism is called a biological problem.

The method used to study a biological problem scientifically is called as biological method.

Biological science has set methods which are studied through experimental inquiry.

Experimental inquiry always begins with chance observations.

Observations are made with five senses i.e. sense of vision, hearing, smell, taste and touch:

Observations can be qualitative and quantitative.

Quantitative observations are more accurate, measurable and can be recorded in the form of numbers.

A statement made on the basis of observations, data, experience and background knowledge of the event is the hypothesis. Ora statement which is to be tested is called hypothesis.

DEDUCTIVEREASONING involves drawing specific conclusion from some general principle/assumptions (general to the specific).

INDUCTIVEREASONING involves drawing general conclusion from some specific observation (specific to the general).

A series of hypotheses supported by the results of many tests is called a theory.

A theory may be predictive or productive.

A good theory is predictive and has explanatory power.

In the case of productive theory the testing goes on.

A scientific law is a uniform or constant fact of nature.

Biology is short in laws due to strange nature of life.

Examples of biological laws are: (i) Hardy-Weinberg law and (ii) Mendel’s laws of inheritance.