Chapter 31, Problem 6STP

Summary Introduction

Introduction:

The structure and sizes of fishes vary a lot but they all have several common characteristics. Most fishes have a vertebral column, gills, jaws, paired fins, single-loop circulation, and also they are unable to synthesize amino acid.

Answer to Problem 6STP

Correct answer:

The correct answer is Option (a) gills and a closed circulatory system.

Explanation of Solution

Explanation/justification for the correct answer:

Option (a) is gills and a closed circulatory system. Gills in aquatic animals give the ability to get oxygen from water and transport it to the body cells.

The closed circulatory system allows animals to transfer blood to various areas of the body, moving blood faster and further. This is why larger animals also have closed structures common to birds, mammals, fish, reptiles, amphibians, and some invertebrates. Thus, this answer is correct.

Explanation for incorrect answer:

Option (b) is gills and an open circulatory system. Fishes do not have an open circulatory system, they work on a closed circulatory system. Thus, this answer is incorrect.

Option (c) is lungs and closed circulatory system. Fishes do not have lungs but they work on a closed circulatory system. Thus, this answer is incorrect.

Option (d) is lungs and open circulatory system. Fishes do not have lungs and open circulatory systems but they work on a closed circulatory system. Thus, this answer is incorrect.

Conclusion

Gills and a closed circulatory system are the structures that are used by fishes to take in oxygen and transport it to body cells.