Question

What is the function of gill?

Answer 1

Hint: Gill is a respiratory organism, found in the aquatic animals, and their function extracts the dissolved oxygen from water, and release or excretes the carbon dioxide, and in some species, like Hermit crabs, gills are present in the land and they work by providing the moisture.

Complete answer:
Gills are tissues which are present as the short thread, and protein like structures called filaments.
And they have many functions, such as the transfer of ions, and water as well as, exchange of oxygen, carbon dioxide, and ammonia, etc.
In fish, gills have functions, which occur in many ways, which include, that fish intake the oxygen-rich water through mouth, and pass this water through gills, where the oxygen is extracted and the exchange of gases takes place. This is one mechanism.
While another mechanism includes gills that have capillaries, where the exchange of gases takes place in such a way when water moves in the opposite direction to the capillary flow, which is called a countercurrent exchange.
The gills push the oxygen-poor water to the outside, through the openings present at the sides of the pharynx.
In the case of sharks, multiple gill openings are present.
While, in the case of bony fish, a single gill opening is present.
Whereas the opening of the gill to the outside is usually covered by a bony covering called the Operculum.
In some aquatic life, gills are present externally, which derives the larval stage of amphibians.

Note:
Previously it was thought that species of some gills are derived from the endoderm, and some species are derived from ectoderm, but recent studies have proved that gills have arrived from the common ancestors.