Class 12 · Evolution

Mammalian Evolution & Continental Drift — NEET Biology

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📖 NCERT Source

The first mammals were like shrews. Their fossils are small sized. Mammals were viviparous and protected their unborn young inside the mother's body. Mammals were more intelligent in sensing and avoiding danger at least. 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.

NCERT Biology · Class 12 · Chapter 6 · Paragraph 42
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QuestionPractice Question

Assertion (A): Australian marsupials survived better than marsupials on other continents. Reason (R): Continental drift isolated Australia, and pouched mammals survived due to lack of competition from other mammals.

📖 Solution & NCERT Explanation
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Correct answer: A If both assertion and reason are true and the reason is the correct explanation of the assertion.

Both statements are true from NCERT. NCERT states “Due to the same continental drift pouched mammals of Australia survived because of lack of competition from any other mammal.” The Reason explains WHY Australian marsupials survived better - isolation prevented competition from placental mammals that displaced marsupials elsewhere.

❓ Frequently Asked Questions
What does NCERT say about first mammals were like?
The first mammals were like shrews. Their fossils are small sized.
Has this concept appeared in NEET?
Practice this NCERT concept with questions on MedicNEET.
Which chapter is this from?
Evolution, Class 12 NCERT Biology.

Through deep analysis of NEET and NTA, 176 of the 180 ReNEET 2026 (June 21) questions were already in the MedicNEET question bank before the exam.

176/180
of the ReNEET 2026 paper (all subjects) was already in the MedicNEET question bank

MedicNEET's Biology question bank is built from the same NCERT lines NTA picks repeatedly. Not random MCQs — questions crafted exactly like NTA crafts them.

176 of 180 ReNEET 2026 questions traced to MedicNEET17,000+ Biology questionsHindi + English
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