Question

In sea-walnuts and comb-jellies the fertilization is
A. External
B. Internal
C. Both
D. None

Answer 1

Hint:The sea-walnuts and comb jellies belong to the phylum ctenophora. Ctenophores are the marine animals that are free-swimming creators.

Complete answer:
In sea-walnuts and comb jellies, the fertilization is external. The fusion of male and female gametes is referred to as fertilization. Fertilization can also be defined as the fusion of sperm (male gamete) and ovum (female gamete). Which results in the formation of zygote.
There are two basic types of fertilization namely:
(a) Internal fertilization: When the fusion of male and female gametes take place in the maternal body it is called internal fertilization. Internal fertilization the sperms travels to reach the female gamete i.e. ovum. Where zygote formation takes place. The further development of zygote takes place inside the body of the female parent. Example: Human.
(b) External fertilization: In external fertilization the fusion of gametes takes place outside the maternal body in the environment. The gametes i.e. sperm and ovum are released in the environment. Where they fuse and form zygote. Example: Marine animals, salmon, cod etc.
Sea-walnuts and comb jellies belongs to class pentaculata and they are bisexual or hermaphrodite. In hermaphrodite organisms, both male and female sex is present in the same body. They are tree-spawning organisms. Since, both male and female sex organs are present they show the characters of both genders partially. In sea-walnuts and comb jellies, both the gametes are released into the water column. When fertilization and development of zygote takes place.

Therefore, the correct answer is option (A) External.

Note:External fertilization has many side effects as sometimes. The fusion of gametes does not take place and so, these gametes are wasted. Sometimes, the eggs are eaten up by other animals.