The interactions in an ecosystem can be between two living organism, or a living organism and a non living organism.$^1$

Between Living Organism

Parasitism

• Parasitism is a non mutual relationship between two organisms in which one benefits at the expense of the other.

Parasitism is an example of a relation between two living organisms. Where one organism, usually the larger one, is negatively impacted and the other, usually the smaller one, gets positively affected. For example, ringworm and humans. Another example is the Cuscuta, which is a parasitic plant.$^1$

Commensalism

• One benefits, and one is unaffected (no benefit nor negative impact)

This is an interaction between two living organisms where one is benefited and one is unaffected. For example, orchid growing on the branches of a mango tree or barnacles on the body of a whale. In these examples, there is no effect to the mango tree or the whale, but the barnacles and the orchids get positively affected.$^1$

Mutualism

• Both organisms benefit

This interaction results in a positive impact for both animals. It is mutually beneficial for both organisms. For example, the sea anemone lives on the shell of a hermit crab. The sea anemone gets transported to new places for food, and in return protects the hermit crab using its cnidoblasts.$^1$

Predation

• One eats the other (predator eats prey)

it is a type of interaction between members of two different species in which one member is being killed by another. The organism that kills is the predator and the organism that dies is the prey. It is nature’s way of transferring energy to a higher tropic level. Overexploitation of prey species might lead to their extinction. Therefore, the prey species have evolved various defenses to lessen the impact of predators.$^1$