Answer:
The species that develop in aquatic environments, need to be able to have an adequate locomotion and according to the hydrostatic pressure in the water, which this pressure has the opposite direction to gravity in terrestrial life.
Explanation:
Vertebrates that have a skeleton are accustomed to gravitational forces, and this bone structure is what allows adequate locomotion to perform movements as a function of the force of earth's gravity, in water the force of gravity has no effect, since that the hydrostatic force predominates, which the direction is opposite to the gravitational forces.
Amorphous bodies, with few solid structures, not bony, make them better adapt to movements in water masses that are promoted by hydrostatic forces.
