NCERT gives two reasons why the mammals did well when the reptiles declined, and one reason why…
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NCERT gives two reasons why the mammals did well when the reptiles declined, and one reason why South American mammals were lost.
- Name the two features of the first mammals that helped them.
- What happened to the mammals of South America when it joined North America?
- Why did the pouched mammals of Australia not meet the same fate?
Need a reminder? The key ideaShow
Order in time: first cells, invertebrates, plants on land, fish with strong fins, amphibians, reptiles, mammals. A strip of cm for million years has one centimetre for million years, so a distance from the left end is .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) The mammals were viviparous, so they protected their unborn young inside the mother's body. They were also better at sensing and avoiding danger.
Step 2. (b) The mammals of South America, which looked like horses, hippopotamuses, bears and rabbits, were overrun by the animals of North America.
Step 3. (c) Australia was cut off by continental drift, so no other mammals competed with its pouched mammals.
Answer: (a) viviparity and better sensing of danger; (b) they were overrun by the North American animals; (c) there was no competition in Australia.
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