CHAPTER 5:- ORIGIN AND EVOLUTION OF LIFE

Q. Explain Hardy – Weinberg’s principle as binomial expansion.

Ans.: 1) Hard Weinberg’s principle explains theoretical situation in which a population is not undergoing any evolutionary change.

2) It defines the genetic structure of non-evolving population.

3) Mutations introduce new genes into a species resulting a change in gene frequency.

4) If certain conditions existed, gene frequencies are supposed to remain fixed or even remain the same through generations.

5) The principle is also called as genetic equilibrium.

6) The essential conditions are

A) No mutation

B) No gene migration / gene flow

C) No genetic drift.

D) No   genetic recombination

E) No Natural selection pressure.

If all the five conditions are met gene frequencies will remain constant.

7) It can be explained by the following example.

Q.: Write a note on adaptive radiation.

Ans.: 1) Adaptive radiation is also called as divergent evolution.

2) The concept of adaptive radiation in evolution was developed by H.F. Oshorn in 1902.

3) Development of different structures from a common ancestral form is called as adaptive radiation.

4) Homologous organs show adaptive radiation.

5) The examples of adaptive radiation are as follows:

a) Darwin’s finches of Galapagos Island:

They had common ancestor but now have different types of modified beaks according to food habits. Darwin differentiated 13 species of finches and grouped them into 6 categories.

He concluded that all these insectivores’ varieties have evolved from common vegetarian ancestors.

b)  Australian Marsupials:

Darwin stated that adaptive radiation gave rise to a variety of marsupials (pouched animals) in Australia in the same process of adaptive radiation as found in the finches of Galapagos Islands.