Question

On the basis of four characteristic features, how can you differentiate the mammal from other vertebrates?
A. Presence of diaphragm
B. Four chambered heart
C. Rib cage
D. Homeothermy

Answer 1

Animals are divided into two groups: vertebrates and invertebrates. Vertebrates are creatures with a backbone that runs through their whole body. Fish, amphibians, reptiles, birds, and mammals are the primary categories. Backbones are absent in invertebrates. Worms and jellyfish have a soft body, while spiders and crabs have a hard outer case protecting their bodies.

Complete answer:
Option: A – Diaphragm is a muscular organ which separates the thoracic cavity from the abdominal cavity and is also a major organ involved in breathing. It is unique to mammals and is not found in other vertebrate classes.
Thus, option A is correct.
Option: B – Four chambered hearts are found in crocodiles, alligators, birds and mammals. This feature is found in reptiles and aves as well so is not unique to mammals.
Thus, option B is not correct.
Option: C – Rib cage is found in many vertebrate classes and hence this character cannot be used to differentiate mammals from other vertebrates.
Thus, option C is also not correct.
Option: D – Homeothermy is one of the mechanisms of thermoregulation. Homeothermy or stable internal body temperature is a characteristic feature of both birds and mammals and therefore homeothermy cannot be utilized in the differentiation of mammals from other vertebrate classes.
Thus, option D is also not correct.

Therefore, Option A. Presence of a diaphragm is the correct answer.

Note:
Mammals are endothermic (warm-blooded) vertebrate creatures with a variety of distinguishing traits. These are found in most mammals: Hair or fur can be found, presence of sweat glands, Mammary glands are specialised glands that make milk, three bones in the centre of the ear, the neocortex is a brain area that specialises in vision and hearing, teeth have a specific function. A heart with four chambers.