1. Fill in the blanks.
(a) The first systematic explanation of the concept of evolution was given
by Charles Darwin
(Charles Darwin, Willard Libby, Louis Leakey)
(b) Mammals are the most evolved animals among vertebrates.
(Aquatic animals, Amphibians, Mammals)
2. Answer each question in one sentence.
a) What do we call animals which live in water and also on land?
Ans. Mammals that live in water and also on land are called amphibians.
b) Where did the first humans appear?
Ans. The first humans appeared in the grasslands.
3. Give reasons for the following:
(a) The species of dinosaurs, which were enormous in size, suddenly became extinct.
Ans. The species of dinosaurs, which were enormous in size, suddenly became
extinct because of some natural disaster or environmental change.
b) In the course of time, a new species with characteristics different from the original species is created.
Ans. In the process of survival by adapting to environmental changes, certain internal physical changes occur in some animals of a species. Over a period of time, these internal changes become inherited characteristics of the all following generations. Thus, a new species with characteristics different from the original may be created.