Chapter 31, Problem 4STP

Summary Introduction

Introduction:

The tube feet allow these animals to attach to the ocean floor and keep moving slowly. The starfish, with its muscles and hydraulic system, can drag much longer than any bivalve muscle can withstand.

Answer to Problem 4STP

Correct answer:

The correct answer is Option (c) by sucking up organic matter off the ocean floor.

Explanation of Solution

Explanation/justification for the correct answer:

Option (c) is Ancient fishes most likely filter feeders and suck up the organic debris from the ocean floor. Jaws offer an important ecological benefit to vertebrates as they significantly extend the variety of available food sources. They also improve the defensive abilities of vertebrates, such as sharks, which are part of this early, jawed class. After the evolution of the jaws, fishes became more efficient predators and the diets for the fishes changed dramatically. Thus, this option is correct.

Explanation for incorrect answer:

Option (a) is by grazing on phytoplankton at the water surface. Fishes feed from the organic matter from the ocean floor. Hence, this is an incorrect answer.

Option (b) is by living as parasites inside larger marine animals. Fishes feed from the organic matter from the ocean floor. Hence, this is an incorrect answer.

Option (d) is by using sharp teeth to break apart mollusks. Fishes feed from the organic matter from the ocean floor. Hence, this is the incorrect answer.

Conclusion

Hence, the correct answer is Option (c) by sucking up organic matter off the ocean floor.