Write a note on “Struggle for existence”.

Answer: Struggle for Existence. Intra-specific struggle: It is the competition among the individuals of the same species. This type of struggle is very severe, because the need and approach of all competing organisms is precisely same. e.g. struggle between cow and cow, […]

Describe Darwin’s theory of natural selection. State the objections raised against this theory.

Answer: Darwin’s theory of natural selection.  Charles R. Darwin was a British biologist. He postulated the “Theory of origin of species by natural selection”. Principles of Darwinism: Darwin’s theory of organic evolution by natural selection is based on the following principles: i. […]

Give an account of Urey and Miller’s experiment.

Answer : Urey & Miller’s experiment  i. Stanley Miller and Urey designed an apparatus and created conditions similar to primitive atmosphere. ii. The apparatus had a spark chamber with two tungsten electrodes, flask for boiling water, side tube connected to a […]

Describe Oparin — Haldane theory of chemical origin of life.

Answer:  Oparin — Haldane theory of chemical origin of life.  The Russian scientist Alexander Ivanovich Oparin (1924) and British scientist J.B.S. Haldane (1929) proposed the ‘Theory of chemical evolution of life’. According to this theory, life originated from non-living matter, some three billion […]

What are polygenes? Explain with suitable example.

Answer:  Polygenes: Characters are determined by two or more gene pairs, and they have additive or cumulative effect. Such genes are called cumulative genes or polygenes or multiple factors. Example Human skin colour: i. Population derived from marriage between negro and white […]

Distinguish between: Phenotype and Genotype.

Phenotype and Genotype Phenotype Genotype 1.  It is the physical appearance of an organism. It is the physical appearance of an organism. 2.  It can be directly seen. It is determined by inheritance pattern. 3. Phenotype can be determined from […]

Distinguish between: Dominant and Recessive character.

Dominant and Recessive character Dominant character Recessive character  1.  The characters that are expressed in F1 generation are dominant. The characters that are not expressed in F1 generation are recessive. 2.  It is expressed in presence of dominant as well […]