B contraction :) it's a basic function of all muscles.
But my guess its a oxygen? Or carbon dioxide?
Answer:
Marine ecosystems are characterized by factors such as availability of light, food and nutrients. Other factors that affect marine ecosystems include water temperature, depth and salinity, as well as local topography. Changes in these conditions can change the composition of species that make up the marine community.
I believe the answer is: <span>Variety
The smaller groups that exist in a </span><span>Variety usually happen because they possess a certain feature that distinguishes them from another group of the species.
This happen due to the adaptation process in response to things such as different climate or different geographical location.</span>
