Chapter 30.2, Problem 4MI

Summary Introduction

To state:

The definition of the given terms.

Introduction:

Mammals are the vertebrates whose body is covered with hair. They are found in a variety of habitats, mostly live on land and some of them are adapted to fly or live in water. The mammals are divided into different subclasses based on reproductive techniques. These are monotremes, marsupials and placentals.

Explanation of Solution

Monotreme: It is an egg-laying mammal. It has a single orifice for urination, defecation and reproduction called a cloaca. Like all other mammals, monotremes give milk but lack nipples.

Marsupial: It is a mammal that gives birth to underdeveloped embryos that innately climb into the mother’s pouch.

Placental mammal: Most diverse group of mammals whose females carry the fetus in their uterus where it is nourished through the placenta.

Therapsid: It is the extinct vertebrate which had both mammalian and reptilian features. The first mammals probably arose from the therapsid.