Question

Given below are a few statements related to external fertilization. Choose the correct statements.
(i) The male and female gametes are formed and released simultaneously
(ii) Only a few gametes are released into the medium
(iii) Water is the medium in a majority of organisms exhibiting external fertilization
(iv) Offspring formed as a result of external fertilization have better chance of survival than those formed inside an organism
A)(iii) and (iv)
B)(i) and (iii)
C)(ii) and (iv)
D)(i) and (iv)

Answer 1

External fertilization is used by many fish, amphibians, and other sexual marine species. External fertilization is useful because the forming offspring doesn't have to be externally borne by the mother.

Complete answer:
To ensure fertilization, it is important to release all of the gametes simultaneously. The male gametes require a means by which they can move to the female gamete. For most species, water is a source.

For example, in a frog.

A significant number of gametes in the surrounding medium are released during external fertilization. Since the eggs are laid in water or other medium after fertilization, the odds of the eggs being predated or washed away or swept away are higher, which may contribute to their demise and death and thus have a comparatively lower probability of survival than that of internal development.

As it avoids the desiccation or drying up of the gametes when released, water is used as a medium.
As they have to be shielded from their predators during their developmental stages, offspring produced as a result of external fertilization have less chance of survival.

Hence, the correct answer is option (B)

Note: Some unique migration forms are anadromous, where adult fish live in the sea and migrate to breed in freshwater, and catadromous, where adult fish live in freshwater and spawn in salt water.