Concept explainers
Introduction: The most advanced placental mammals are the primates. Primates are mammals that lead an arboreal mode of life, except humans who lead terrestrial mode of life. They evolved during the Cenozoic era. The primate evolution began from Africa and there are several excavated evidences to support this theory.
Answer to Problem 1TYU
Correct answer: The first primates evolved from shrew-like placental mammals. Hence, the correct answer is option (c).
Explanation of Solution
Reasons for the correct answer:
Evolution of animals is often explained with the help of fossil evidences, body structure, and DNA analysis of fossils. Based on the available evidences, paleontologists hypothesize that shrew-like placental mammals are the immediate ancestors of the first primates that evolved. The earliest known primate is Plesiadapis, which shares several features with shrews.
Option (c) is given as “shrewlike placental mammals”.
The first primates shared several features with the shrews; hence, they are said to have evolved from shrew-like placental mammals. Thus, the correct answer is option (c).
Reasons for incorrect answers:
Option (a) is given as “shrewlike monotremes”.
Shrewlike monotremes are not the ancestors of the first primates. Montremes are not placental mammals. Primates are placental mammals. Hence, option (a) is incorrect.
Option (b) is given as “therapsids”.
Therapsids gave rise to the first mammals. They are not the direct ancestors of primates. Shrew-like placental mammals are the direct ancestors of the primates. Hence, option (b) is incorrect.
Option (d) is given as “tarsiers”.
Tarsiers are not the first primates. They are the second level of primates to have evolved. Tarsiers evolved from Simians. Hence, option (d) is incorrect.
Option (e) is given as “shrewlike marsupials”.
Shrewlike marsupials are not the ancestors of the first primates. Marsupials are not placental mammals. Primates are placental mammals. Hence, option (e) is incorrect.
Hence, options (a), (b), (d), and (e) are incorrect.
The first primates shared several features with the shrews; hence, they are said to have evolved from shrew-like placental mammals.
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Chapter 22 Solutions
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