Chapter 33, Problem 5STP

Summary Introduction

Introduction:

Placental mammals bear live young, the young get nourishment inside the mother uterus or womb. It is the specialized embryonic organs that attached to the uterus wall covering with the same membrane of the uterus inside the amniotic fluid. There is a total of 4000 discovered species of placental mammals. They are different from other mammals in that the female species carry the fetus inside themselves in the uterus and provide nourishment through placenta while in other mammals they do not have placenta.

Answer to Problem 5STP

Correct answer:

The correct answer is option (D) whales.

Explanation of Solution

Explanation/justification for the correct answer:

Option (D) whale. Whales are placental mammals they bear their young one inside the uterus to nourishment of the fetus from placenta. So, the correct answer is option (D).

Explanation for incorrect answer:

Option (A) hummingbird. Hummingbirds are not mammals they are aves, and aves do not give birth to young one directly else they lay eggs. So, this is an incorrect option.

Option (B) kangaroo. Kangaroo is not a placental mammal. It does not have the placenta for the nourishment of the fetus so the young one born in a few days after the fetus development. So, this is an incorrect answer.

Option (C) duck-billed platypus. Duck-billed platypuses are mammals but they lay eggs, therefore they are called egg-laying mammals. So, this is an incorrect answer.