How does species diversity vary with (a) latitude in terrestrial communities, (b) ocean depth, and (c) pollution?

It varies greatly...

Explanation:

(a) Latitude is one of the main factors that pushes the evolution toward adaption to a environment. For example, at higher latitude, the diversity is a little low than on lower or average latitude due to the availability of resources that are easily available on ground level relatively.

(b) As we goo deep in ocean, the diversity of life increases as seen in graph but then after a peak point declines rapidly. This is because at normal depth life thrive in normal conditions of temperature and pressure but deep down low, the pressure of water is so intense that it can even crush lead. So, the little amount of organisms that are living in those depths are highly evolved to that intense environment...

(c) Pollution puts a opposite effect on diversity either it is air, water or ground type of pollution. Marine biodiversity take a great loss from chemicals waste as well as the ground animals in which the viable environment gets completely destroyed. This is the main cause of extinction of various animal and plants species.