Class 12th Biology 2017 Set2 Delhi Board Paper Solution

Question 10

Mention the evolutionary significance of the following organisms:

(a) Shrews

(b) Lobefins

(c) Homo habilis

(d) Homo erectus

Answer

The evolutionary significance of given organisms are as follows:

(a) Shrews

The first mammals were like shrews. These were long tailed, insectivorous, squirrel-like organisms. They gave rise to primitive primates. For example, leones, tarsiers at the beginning of the Palaeocene era.

 

(b) Lobefins

In 1938 a fish caught in South Africa happened to be a coelacanth which was thought to be extinct.These animals called lobefins evolved into the first amphibians that lived on both land and water. Modern day frogs and salamanders have evolved from them.



 

(c) Homo habilis

The first human-like primates, lived in Africa about 2 million years ago.Evidence shows that they haunted with stones weapons but especially ate fruits. They had brain capacity of 700 cc. Also called handy man as they were first and most skillful tool makers.

 

(d) Homo erectus

They appeared after Homo habilis , 1.7 million years ago. They had large brain capacities, i.e. 800-1100 cc and were omnivores. They used to hides to protect their body and buried their dead.