Question #baf47

1 Answer
Oct 10, 2015

Hydraulic pressure


The pressure from the dense molecules of water are able to support aquatic animals more. If you look at the evolution of vertebrates, once the fish started moving out of water and developed lungs, movement required more ossification to support their bodies, because gravity has a greater affect in air than in water. Many aquatic animals also have water-filled internal structures that they use for movement by this pressure, which they generate internally -even some terrestrial organisms have it, like the annelids.