In nature, very often there are relationships in which one of the organisms benefits, the other is oppressed (+ -). There are two types of such relationships: predation and parasitism.
Predation (+ -) is a type of relationship between populations in which representatives of one species eat (destroy) representatives of another.
The predator usually catches and kills his prey himself, after which he eats it in whole or in part. Therefore, hunting behavior is characteristic of predators.
Example: wolves and moose. Cats and mice. Lions and zebras. Lynxes and hares.
There is a large group of predators that do not hunt, but get food by simply collecting it. This group can be called gatherer predators.
Example: Predatory gatherers include insectivorous birds that collect insects in the crown of trees and on the ground.
Parasitism (+ -) is a relationship between species in which the organism of one species (parasite) uses the organism of another species (host) as a habitat and a source of food.
The parasite not only feeds on the tissues of the living host, but also lives in it permanently or temporarily. Most often, animals are parasites, but parasitic species are also found among plants.
Unlike predation, when attacked by a parasite, the host does not die immediately, but is oppressed (often for a long time). In other words, the parasite weakens, but does not destroy the host, as this ensures its existence. This means that parasitism can be viewed as a weakened form of predation.
The relationship between some organisms is intermediate between predation and parasitism.
Example: a fish leech that feeds on fish blood.