Biology Terms and Definitions

Terms of Biology

Ecology: Study of organisms in relation to environment is called ecology.

Physiology: Study of functions of different parts of body is called physiology.

Histology: Study of tissues with the help of microscope is called histology.

Genetics: Study of hereditary characters and their inheritance is called genetics.

Zoogeography: Study of geographical distribution of animals on earth is called zoogeography.

Molecular Biology: Study of structures of organisms, the cells and organelles at molecular level is called molecular biology.

Microbiology: Study of microorganisms (bacteria, viruses, protozoa etc.) is called microbiology.

Fresh Water Biology (Limnology): Study of life in fresh water bodies such as ponds, ditches, lakes is called as fresh water biology or limnology.

Marine Biology: Study of life in seas and oceans is called marine biology.

Biotechnology: It deals with the use of microorganisms in commercial processes is called biotechnology.

Parasitology: Study of parasites i.e., structure, mode of transmission; life histories, host parasite relationship is called parasitology.

Morphology: Study of form and structure of living organisms is called morphology.

Cytology: Study of cells is called cytology.

Paleontology: Study of fossils is called paleontology.

Embryology: Study of formation and development of embryos is called embryology.

Evolution: Study of origin of new species by diversification of older ones is called evolution.

Taxonomy: It deals with the naming and classification of organisms is called taxonomy.

Enzymology: Study of enzymes is called enzymology.

Ethology: Study of animal habits and behavior is called ethology.

Gerontology: Study of aging is called gerontology.

Teratology: Study of abnormal development and their causes is called teratology.

Levels of Biological Organization
Biosphere Part of earth inhabited by living organisms; includes both the living & nonliving components. Micromolecules have low molecular weight (CO2, H2O).
Ecosystem A community together with its non-living surroundings. Macromolecules have high molecular weight (starch, proteins).
Community Two or more populations of different species, living and interacting in the same area. Biological world has two types of molecules organic and inorganic.

Inorganic molecules include CO2, H2O etc.

Population Members of one species inhabiting the same area. Organic molecules are glucose, amino acids, fatty acids, glycerol, nucleotides like ATP ADP, AMP.
Species Very similar, potentially interbreeding organisms. Different and enormous number of micro-molecules and macromolecules arrange to form cells and their organelles.
Multicellular Organism An individual living thing composed of many cells. In bacteria and most of the protists entire body is made up of a single cell.
Organ System Two of more organs working together in the execution of a specific body function. In most fungi, plant and animals, the organisms may consists of up to trillions of cells.
Organ A structure normally composed of several tissue types that form a functional unit. Prokaryotes have only a limited number and type of organelles.
Tissue A group of similar cells that perform a specific function. Eukaryotes are rich in number and kinds of membranous organelles.
Cell The unit of life. Stomach is an organ. It has secretory epithelium which secretes gastric juice and a muscular tissue (smooth) for contracting the walls of stomach and mixing of food with enzyme.
Organelle A structure within a cell that performs a specific function. The organ level of organization is much less definite in plants than animals.
Micro-molecules and Macro molecules A combination of atoms. In animals the coordination is achieved by means of nervous system and endocrine system whereas in plants long term regulation of activities is brought about by hormones.
Atom The smallest particle of an element that retains the properties of that element. Communities are dynamic collections of organisms, in which – one – population may increase and other may decrease.
Subatomic Particle Particles that make up an atom. At population level we study gene frequency, gene flow, age distribution, population density, population pressure.


Major Bioelements
O 65%
C 18%
H 10%
N 3%
Ca 2%
P 1%
Total : 99%


Minor Bioelements
K 0.35%
S 0.25%
Cl 0.15%
Na 0.15%
MG 0.05%
Fe 0.004%
Total : 01%


Elements in Traces



In human body six bioelements account for 99% of the total mass.

A living thing is composed of highly structured living substance or protoplasm.

Genetic Engineering: The manipulation of genes is called genetic engineering.

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 transgenic organisms.

Transgenic Plants: The plants having foreign DNA inserted in their cells are called transgenic plant. Transgenic plants can be propagated by cloning and tissue culture.

Tissue Culture: Reproduction by growing tissues of plants is called tissue culture.

Plant pathogens are fungi, insects, bacteria and pests. These pests are controlled by fungicides, insecticides and pesticides.

Biological Control: Control of pests by some living organisms is called biological control. e.g., an aphid attacks walnut tree is controlled biologically by a wasp that parasitizes this aphid.

Biopesticides are naturally occurring substances produced by plants and microorganisms that control pests. e.g., some bacteria are used as biopesticides.

Hydroponic Culture Technique: The technique in which plants are grown in aerated water to which nutrient minerals are added. It is used to determine the mineral requirements of plants.

Astronauts used this technique to grow vegetables in space.

Pasteurization: This technique is used for preservation of milk and milk products.

Pasteurization kill non-spore forming bacteria.

Milk is heated at 62oC for 30 min. or 71oC for 15 second.

Vaccine: Dead or weakened bacteria or viruses or modified toxins that produce an active immunity.

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

Edward Jenner first developed the technique of vaccination in 1796 from cowpox pus.

Radiotherapy and chemotherapy is being used for treatment of cancer.

IDM: Combating diseases by using all methods and involvement of community is called IDM.

Cloning: The production of genetically identical copies of the organisms or cells by asexual reproduction is called cloning.

A clone is defined as a cell or individual and all its asexually produced offspring. All members of a clone are genetically identical except when mutation occur.

In 1997 scientists in Scotland succeeded in cloning a sheep (Dolly). Other mammalian species (mice and cows) have since been cloned

The fossils can be dated by sedimentary method or by radioactive method. The older sediment layers have less radioactive isotopes than the Younger layers.

Procedure: The nucleus from a fertilized egg is removed and a nucleus from a cell of fully developed individual is inserted in its place. The altered zygote is implanted in a suitable womb. The new individual method formed in this way is genetically identical clone of the individual whose nucleus was used.

Development of identical twins is also by cloning. Several insects and many plants reproduce by cloning.

53.1% Insects
17.6% Vascular plants
19.9% Animals other than insects
9.4% Algae, protozoa and prokaryotes


2,500,000 total known specie
Estimated total no. of species are 5 to 30 million.
Lead is being released by automobiles and chromium by tanneries.

Bioremediation: The removal or degradation of environmental pollutants or toxic materials by living organisms. e.g., algae reduce pollution of heavy metals by bioabsorption.

Biological Method

  1. Observations
  • Qualitative
  • Quantitative
  1. Hypothesis
  • Tentative explanation of observation
  • Deductive reasoning (from general to specific). It involves drawing specific conclusion from general principle.
  • Inductive reasoning (from specific to general). It begins with specific observations and leads to formulation of general principle.
  1. Deduction
  • Logical statement derived from hypothesis
  1. Experiment
  2. Theory
  • A series of hypotheses supported by the results of many tests
  • Predictive theory has — explanatory power
  • Productive theory — can suggest new hypothesis
  1. Law
  • An irrefutable theory which remains uniform and constant in science.

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

Geological Time Scale

Era Period Years Age Some Distinctive Features
Cenozoic Quaternary


70 M Modern man.

Large carnivores. First abundant mammal.

First placental mammal.

135 M
180 M
225 M
First flowering plant; climax of dinosaurs.
First bird, first mammal dinosaurs abundant.
First dinosaur. Abundant cycads and conifers.













270 M

350 M


400 M
440 M
500 M
600 M


Extinction of most kinds of marine animals, including trilobites. Southern glaciations.
Great coal forests, conifers. First reptile.

Sharks and amphibians abundant, numerous seed ferns.

First amphibian; fishes abundant.
First terrestrial plant.
First fish: Invertebrates dominant.
First abundant record of marine life; trilobites’ dominant.

Proterozoic Era




2000 M

Fossils extremely rare, consisting of oldest dated algae: oldest dated meteorites (4,500 million years).

First living organism appeared about 3000 M years ago.

Leave a Reply

Your email address will not be published. Required fields are marked *


Distributed by