What is one biotic factor that affects the size of a population in an ecosystem?

Question:- What is one biotic factor that affects the size of a population in an ecosystem?

Answer: A major example of biotic factors that directly impact on the population size of an ecosystem is predation. As it is with any given ecosystem, the predators capture and feed on other organisms, which affects the population of such organisms negatively. For instance, in a forest; the amount of deer (food) is partly determined by wolves (killers). When there are many wolves, they kill more deer leading to a decrease in the number of deer. On the other hand, should the number of wolves reduce, then those of the deer may increase. It acts as an exchange that maintains the equilibrium since deer cannot overpopulate an area when the latter is scarce, as are wolves. Such interactions are important for the conservation of the species and ecosystem balance.