Question

In animals, which condition is necessary for external fertilization? 

A) the presence of carbon dioxide 

B) a motile egg cell 

C) the moist environment 

D) the absence of light

Answer 1

ANS. (C) The moist enviroment

• External fertilization is a male organism's sperm fertilizing a female organism's egg outside of the female's body.
• External fertilization occurs in water or a moist area because it gives the sperm external mobility to get to the egg.
• While in the water, the sperm and ova can shed simultaneously to fertilize the egg.The release of eggs and sperm into the water is known as spawning.
• When females spawn, they release a batch of eggs into a spot of their choice or just into the water, as in bottom dwelling or sessile species and all of the males start to release sperm that are in close proximity.
• Within vertebrates, it is the amphibians and fish that use external fertilization.
• When it comes to invertebrates, most are benthic, sessile, or benthic sessile combined animals such as coral, sea anemones, and tube dwelling polychaetes.
• The benthic zone is the lowest level of the ocean where organisms called benthos reside.
• An organism that is sessile does not have the ability to move or be mobile.
• Benthic marine plants such as algae also go through external fertilization to reproduce.
• Overall, environmental factors and the timing have a heavy influence over the success of external fertilization.In external fertilization some of the eggs laid by the animals gets wasted due to huge rainfall, floods etc.

        Internal fertilization, on the other hand, is the occurrence of internal insemination as the mode of combining sperm and egg.