Chapter 17, Problem 1SQ

Bilateral symmetry in the animal kingdom is best correlated with

1. a. an ability to sense equally in all directions.
2. b. the presence of a skeleton.
3. c. motility and active predation and escape.
4. d. development of a body cavity.

Summary Introduction

Introduction:

The animals divided the sagittal plane into two equal parts called bilateral symmetrical animals. The plane divides the body into two equal halves, but the inner organs need not be symmetric in the bilaterally symmetrical animals.

Answer to Problem 1SQ

Correct answer:

Bilateral symmetry in the animal kingdom is best correlated with motility and active predation and escape. Therefore, option c. is correct.

Explanation of Solution

Reason for the correct statement:

The bilateral symmetrical animals do have a distinct head end, which is the association of nerve ganglia, mouth, and the sensory organs. The head end helps in the development of the organ called the brain.

The collective working of the head end and the brain lead to the quick responses to the external stimuli, such as threat, food, and others. This benefits the bilateral animals in locomotion, including swimming, walking, crawling, and jumping. The bilateral animals learn to predate other animals using these movements.

Option c. is given as “motility and active predation and escape”.

 “The bilateral symmetry helps the animals in locomotion. The animals can easily predate others by locomotion activities, and can also escape when they are in danger” is the right answer.

Hence, option c. is correct.

Reasons for the incorrect statements:

Option a. is given as “ability to sense equally in all directions”.

The bilateral symmetrical animals can sense more efficiently in the moving direction as compared to other directions. Hence, it is a wrong answer.

Option b. is given as “the presence of a skeleton”.

The flatworms and annelids are included in the bilaterally symmetrical animals, but they lack true skeleton. Hence, it is a wrong answer.

Option d. is given as “development of a body cavity”.

The body cavity is the space that divides the body wall from the digestive tract of an animal. The body cavity does not relate to the bilateral symmetry because the bilateral symmetry defines the two equal halves of the outer body.

Hence, options a., b., and d. are incorrect.

Conclusion

The bilateral symmetrical animals are motile, active predators, and can easily escape from the danger.