The number of organisms that the environment in an ecosystem can handle is called its
growth rate
carrying capacity
population density

The answer to this question is "carrying capacity." The term "growth rate," refers to how fast a population grows, and the term "population density," refers to the number of organisms located within a specific area. Carrying capacity is correct because is directly addresses the maximum number of organisms that an ecosystem can handle, as opposed to how fast they are growing or how many there currently are.

Covalent bonds share electrons while ionic bonds transfer their electrons.