Question

In some of the organisms like birds female heterogamety is present.if so, which gamete is motile-male or female,and in the body of which organism does the fusion takes place-how?

Answer 1

Reproduction in Birds
How do birds reproduce? We know that chickens lay eggs. But how do they do that?
It all starts with behavior aimed at attracting a mate. In birds, this will involve a type of display, usually performed by the male. Some displays are very elaborate and may include dancing, aerial flights, or wing or tail drumming. Most male birds also sing a type of song to attract females. If they are successful at attracting a female, it will lead to breeding.
Birds reproduce by internal fertilization, during which the egg is fertilized inside the female. Like reptiles, birds have cloaca, or a single exit and entrance for sperm, eggs, and waste. The male brings his sperm to the female cloaca. The sperm fertilizes the egg. Then the hard-shelled egg develops within the female. The hard-shelled eggs have a fluid-filled amnion, a thin membrane forming a closed sac around the embryo. Eggs are usually laid in a nest.