Chapter 25.3, Problem 7MI

Summary Introduction

To compare:

The ways of mollusks reproduce in water and on land.

Introduction:

Mollusks are soft-bodied, triploblastic, coelomate and bilaterally symmetrical animals. Most of them are aquatic and few are terrestrial and found in moist soil. Mollusks reproduce sexually. sexes are separate or hermaphrodite.

Explanation of Solution

In water:

In aquatic mollusks sexes are separate. Male mollusk releases sperms and female releases egg in the water at the same time. Fertilization occurs in water. Thus fertilization is external.

On land:

Many land mollusks are hermaphrodites, i.e., both male and female sex organs are present in the same individual. Hermaphrodite mollusk produces both sperm and eggs in the mantle cavity and fertilization takes place within the animal. thus, fertilization is internal.

Conclusion

The mollusks which reproduce in water witness external fertilization and those who reproduce on land fertilization is internal.