The amount of organisms in a given space is called the

Population, community, or environment

Explanation:

It depends on if you are asking the amount of the same species, the place they live in,  or if you are asking different organisms

If you are talking about the same species than the answer is population

If you are talking about different species interacting it would be community

If you are talking about the place in which they live, it would be environment :)

Hope this helps, I'm just a little confused on the question :)

parasites can detrimentally affect their host, but also must not allow their host to die before they can complete their life cycle. some parasites have complex life cycles with many different hosts, and have had to find ways of persisting in many different environments during the change from one host to another. ectoparasites live outside the body of the host, and can more easily  disperse, but are  more exposed to predators, parasites, parasitoids. endoparasites live inside the body of the host, and are therefore protected from the outside environment. but they can be  attacked by the host's immune system. they have therefore developed  mechanisms for dispersal such as  complex life cycles.

a scenario where a cell may be needed to perform a form of endocytosis is when transporting large molecules. a scenario where a cell may be needed to perform a form of exocytosis is when releasing the large molecule from the cell.