Biotic Factors

Biotic factors are living elements that influence another organism or shape its environment. Some examples are:

  • Food availability
  • Predators
  • New pathogens
  • Competition

Effects of Biotic Factors

Food availability

A high abundance of food means that organisms will have less competition for resources and therefore an increased chance of survival. This means that they can reproduce successfully, which increases the population.


Predators have a large impact on an ecosystem. They keep the number of prey down to a reasonable size. In a balanced ecosystem, predators avoid catching too much prey to avoid wiping them out completely.

  • An increase in the number of predators increases the likelihood of organisms being preyed on. Therefore, the chance of survival is relatively lower.
  • A decrease in the number of predators decreases the likelihood of organisms being preyed on. Therefore, the chance of survival is relatively higher.

New pathogens

When organisms enter an ecosystem, they may introduce new pathogens. The existing population in the ecosystem is unlikely to have immunity or resistance to these new pathogens. So they are more vulnerable to getting completely wiped out before they can develop immunity.


In an environment with multiple species competing for the same resources, one species might be better adapted than others.

The better-adapted species will outcompete the less-adapted species. This will decrease the numbers of the less adapted species until they have too few members to breed successfully.


Consider two species of giraffes living in the same habitat: one with a shorter neck and another with a longer neck. The species with the longer neck can reach tall trees and access leaves more easily. Therefore they are better adapted to the environment.

On the other hand, the species with shorter necks will struggle to access food from tall trees. As a result, they may face starvation, which can reduce their ability to reproduce. Eventually, shorter-necked giraffes will get completely wiped out, whereas longer-necked giraffes will increase in number.

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