Question

Name any two animals showing external fertilization. Why are more gametes produced by such animals?

Answer 1

Hint:The word external means outside and hence external fertilization involves the fertilization of the male and female gametes outside the body of the female organism.

Complete answer:
Now, as the fertilization is external, there is a requirement of a medium for the fusion of both the gametes.
In the majority of the organisms, the female gamete is stationary and the male gamete is motile and therefore it has to reach the female gamete for the required fusion.
Now, this is to note that if the fusion is internal, the medium and path both are sorted into the female's body and therefore there is no requirement of so many male gametes. But, in external fertilization the case is different. So, for the motile male gametes to reach the stationary female gametes the medium here is generally water. But, the path inside the water is not sorted for the male gametes to swim to the female gametes. Hence, a large number of male gametes fail to reach the female gametes and in order to compensate this loss, male gametes are produced several thousand times to the number of female gametes produced.
Fertilization is external in organisms like fish and frog.

Note:Fertilization is the process of fusion of gametes to form a Zygote. Another name to the process of fertilization is Syngamy. Successful transfer and coming together of gametes is essential for fertilization to occur.