Chapter 34, Problem 13STP

Summary Introduction

To classify:

Monotreme characteristics similar to reptiles or mammals.

Introduction:

Mammals are the vertebrate organisms that are classified by the presence of mammary glands that produce milk in females to feed their young ones. Reptiles form another class of vertebrates that are ectothermic and are capable of breathing in air. Reptiles lay eggs after fertilization.

Explanation of Solution

The characteristics features of mammals include giving birth to young one, producing milk to feed the young ones, maintaining internal body temperature (endothermic), presence of three bones in the middle ear, the neocortex, single lower jaw bone, and hair or fur on the body.

Reptiles are characterized by the characteristics of laying eggs, scaly and dry skin, inability to maintain internal body temperature (ectothermic), and a four-chambered heart.

Monotremes are the organisms that are basically classified under mammals but possess characteristics of both mammals and reptiles.

Characteristics of monotremes similar to mammals include the production of milk for feeding young ones, maintaining internal body temperature, three bones in the middle ear, hair on the body, and a single lower jaw bone.

Characteristics of monotremes similar to reptiles include egg-laying, absence of corpus callosum, and similar shoulder skeleton to reptiles.

The chromosomes in monotremes are a mix of those seen in mammals and reptiles.

Conclusion

Characteristics of monotremes similar to mammals include production of milk for feeding young ones, maintaining internal body temperature, three bones in the middle ear, hair on the body, and a single lower bone.

Characteristics of monotremes similar to reptiles include egg-laying, absence of corpus callosum, and similar shoulder skeleton to reptiles.

The chromosomes in monotremes are a mix of those seen in mammals and reptiles.