CHAPTER 5 :- ORIGIN AND EVOLUTION OF LIFE

Q. : What is saltation?

Ans. : Mutation is the cause of speciation. This is called as saltation.

Q. : Write a note on geological time scale.

Ans. : 1) The first geological time scale was developed by Giovanni Avduoina in 1760.

2) The total life span of the earth from the time of origin is called as geolgocial time.

3) The crust of the earth shows layers of rocks one above the other formed by sedimentation of deposition of materials.

4) Using radioactive techniques it is possible to calculate the age of rocks.

5) Geologists have divided the geological time into intervals which are characterized by significant events that occurred in the organization of organisms.

6) The major divisions of geological time scale are called as era which are further divided into epoch.

7)  The ears, periods and epochs are arranged on times scale in order of their age. This arrangement is called as geological time scale.

8) It helps to trace out different evolutionary changes in the organisms.

9) The various era are : Azoic, Archezoic, Proterozoic, Palaeozoic, Mesozoic, and Coneozoic.

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.