Given below are two statements:
Statement I: In South America, there were mammals resembling horse, hippopotamus, bear and rabbit, which were overridden by North American fauna when South America joined North America due to continental drift.
Statement II: Due to continental drift, the placental mammals of Australia survived because of lack of competition from any other mammal.
In the light of the above statements, choose the most appropriate answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Statement I is correct but Statement II is incorrect.
When the reptiles declined, mammals took over the earth. Continental drift then changed their fate in two places in opposite ways: in South America the local mammals lost out, while in isolated Australia the pouched mammals (marsupials) survived.
Statement I: In South America, there were mammals resembling horse, hippopotamus, bear and rabbit, which were overridden by North American fauna when South America joined North America due to continental drift. — True. Once the two continents joined, the North American animals moved in and the South American mammals could not hold their place.
Statement II: Due to continental drift, the placental mammals of Australia survived because of lack of competition from any other mammal. — False. It was the pouched mammals (marsupials) of Australia that survived. Continental drift kept Australia cut off, so they faced no competition from any other mammal.
NCERT Extract:
A Brief Account of Evolution – “… When reptiles came down mammals took over this earth. There were in South America mammals resembling horse, hippopotamus, bear, rabbit, etc. Due to continental drift, when South America joined North America, these animals were overridden by North American fauna. Due to the same continental drift pouched mammals of Australia survived because of lack of competition from any other mammal.”