Chapter 33, Problem 1SA

All vertebrates have _______ .

a. a closed circulatory system b. a two-chambered heart c. lungs d. hemolymph

Summary Introduction

Introduction:

The vertebrates are the organisms that are characterized by the presence of the solid backbone which is a bony structure that extends from the neck to the abdomen. It is absent in the invertebrates which makes them easily distinguishable from the vertebrates.

Answer to Problem 1SA

Correct answer:

All vertebrates have closed circulatory system. Hence, the correct answer is option a.

Explanation of Solution

Reason for correct answer:

Option a. is given as, “closed circulatory system.”

The invertebrates have an open circulatory system in which the blood is present freely in the body cavity while in the vertebrates, it is confined to the blood vessels.

Reason for incorrect answer:

Option b. is given as, “two-chambered heart.”

The vertebrates can have two, three or four-chambered heart. The number of chambers in the heart is not the defining feature of vertebrates. Hence, option b. is incorrect.

Option c. is given as, “lungs.”

Not all vertebrates have lungs. The fishes respire through gills, and they are members of vertebrates. So, the presence of the lungs does not define the vertebrates. Hence, option c. is incorrect.

Option d. is given as, “hemolymph.”

Hemolymph is the mixed fluid present in animals like Arthropods and Molluscs. It is an important constituent of their unique open circulatory system. The hemolymph helps to exchange the nutrients and the waste products from the body. It is not present in vertebrates. Hence, option d. is incorrect.

Hence, the options b., c., and d. are incorrect.

Conclusion

The presence of a closed circulatory system is a unique character of vertebrates. The vertebrates contain blood vessels, capillaries and a pumping organ known as the heart in their circulatory system. Thus, the correct option is a.