Why do plants and animals living in the water have a simpler reproductive system than those living on land?

Answer 1

Because the ones in water developed it first, and then when evolution moved some of those plants and animals onto land, they had to overcome the less accessto water. And in order to reproduce they had to develop more complex systems to 'mimic' the water environment. That is why all land animals exchange body fluids in the process of reproduction.

Answer 2

simply put, all life came from the sea. reproductive systems of most species mimic the evolutiary ideal: a saline , oxygenated, temperature controlled hatchery. Water born organisms have many of these original conditions in their habitat. Terrestrial animals had to create an "on- board" version of these conditions. A nursery within themselves which mimics their aquatic heritage. I hope that is a good illustration. I recommend any of the writing of acclaimed late Natural Historian Stephen Jay Gould, or some of the work of Pulitzer Prize winning entymologist Edwin O. Wilson. Between the two, this is a commmon fulcrum of evolutionary change, and they express it beautifully.

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