Chapter 42, Problem 1SQ

The end product of cleavage is a __________.

1. a. gamete
2. b. blastula
3. c. gastrula
4. d. zygote

Summary Introduction

Concept Introduction: Cleavage is a process of repeated mitotic divisions where the enormous amount of cytoplasm is distributed to form several small cells. Cleavage is a part of development.

Answer to Problem 1SQ

Correct answer:  The end product of cleavage is a blastula. Therefore, option b. is correct.

Explanation of Solution

Reasons for the correct statement:

The sperm and egg unite to form the zygote. The zygote then undergoes several mitotic divisions repeatedly. These repeated mitotic divisions are collectively called as cleavage. At the end of cleavage the blastula is formed. The blastula has a covering called as blastoderm and the cavity inside called as blastocoel. The blastula is made of cells called as blastomeres. The size of the blastula varies from species to species.

Option b. is given as “blastula”

As blastula is formed at the end of all cleavage divisions, option b. is correct.

Reasons for the incorrect statements:

Option a. is given as “gamete”. The gamete is produced at the end of gametogenesis not cleavage. Therefore, option a. is incorrect.

Option c. is given as “gastrula”. At the end of cleavage, the blastula is formed first and then the gastrula is formed.

Therefore, option c. is incorrect.

Option d. is given as “zygote”. The zygote undergoes cleavage to form the blastula.

Therefore, option d. is incorrect.

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

Conclusion

The end product of cleavage is a blastula. The cleavage is of various patterns based on which the development of the animal is determined.