What could account for an organism which needs to spend part of its lifecycle dependant upon living in water?

Question

For example, a frog.

Answer 1

The most logical answer would involve the evolutionary history of the organism. Life evolved from water and many organisms still spend a part of their development in water.. even human still live inside the amnionic fluid until birth... water is essential to life especially during the early stages of a critters lifecycle. Water or a fluid like water (amnionic fluid which is similar to the primal oceans) provide the essential environment to allow all multicellular organism to develop. The water provides them with oxygen, nutrients and gets rid of the waste material. I hope this answers your question.

Answer 2

Mosquitoes, dragonflies and frogs all have an aquatic larval stage. Tadpoles are vegetarians, but frogs eat meat. Mosquito larvae eat smaller organisms, and the adults suck blood or plant juice.

I guess that is their way of life. Each organism is different.

Come to think about it. Life began at the ocean. It seems we have never left the ocean. Inside our body, every cell is still bathing in sea water (sodium chloride).

I hope this can help you.

Answer 3

That's true. Also some organisms (plants AND animals) need water for reproduction, as a means of spreading their sex cells to form a fertilized zygote. In this case, its reproductive phases would be spent in or around water.