Question

External fertilization occurs in
A. Starfish
B. Dog
C. Birds
D. Elephant

Answer 1

Hint: Fertilization is a result of sexual reproduction. It is a process of fusion of gametes from two different parents. It results in the formation of a zygote which develops to form an individual. Fertilization can occur inside as well outside of the female body. In mammals, it occurs inside the female body and in echinoderms, it occurs externally.

Complete answer: Fertilization is an important event that needs to occur for the reproduction in sexually reproducing organisms. It is an important process through which two gametes from different parents come close and fuse to form a diploid zygote. The gametes are haploid and thus, need to restore their chromosome numbers by forming a zygote. Fertilization can occur inside as well as outside of the female body. In mammals such as elephants and dogs, the young ones develop inside the mother. They are surrounded by amniotic fluid and sac. In birds, fertilization occurs inside the female body. Although the young ones develop outside in a shell called an egg, the fusion of gametes occurs inside the female. Starfish is an echinoderm and fertilization occurs externally. Most of the starfish species release their eggs directly into the water. The male starfish then releases sperms over the secreted eggs and fertilizes them to form zygotes. In this type of fertilization, the chances of fertilization are less. But It is compensated by a large number of eggs and sperms released.
Hence, the correct answer is option A.

Note: Internal fertilization is more safe and has more potential as compared to external fertilization. In the case of internal fertilization, the developing zygote stays protected inside the mother’s womb. The zygote derives its nutrition from the mother. Zygotes formed by external fertilization are exposed to their predators.