Chapter 28, Problem 6A

Summary Introduction

Introduction:

Fishes live in aquatic habitats like lakes, seas, rivers, ponds, etc. Some fishes live in complete darkness at the bottom of the deep ocean whereas others live in the freezing water of the Polar Regions and have special proteins in their blood to keep the blood from freezing. There are about 24,600 species of living fishes found.

Answer to Problem 6A

Correct answer:

The correct answer is option (B) swim bladder.

Explanation of Solution

Explanation/justification for the correct answer:

Option (B) swim bladder. The swim bladder is an internal organ. It is filled up with gas. The swim bladder regulates the buoyancy of many bony fishes. Swim bladder allows a fish to control its depth. So, the correct answer is option (B).

Explanation for incorrect answer:

Option (A) operculum. Operculum is a movable membrane that covers and protects the gills. It also helps to pump water into the mouth and gills. So, this is an incorrect option.

Option (C) lateral line. The lateral line system is receptors for the sense of smell in fishes. It enables fishes to detect movement in the water and also help to keep them upright and balanced. So, this is an incorrect answer.

Option (D) jaws. Most of the fishes have jaws. The fish catch the prey with their teeth and instantly kill them with strong jaw muscles. Jaws also provide a biting defense against predators. So, this is an incorrect answer.