Predation
This is where one organism hunts and eats the other organism. The organism hunting is called predator, while the organism being hunted is called prey. Energy received from the sun is transferred from animals when the prey is eaten by the predator. The predator now has its prey’s energy.
A predator is usually a carnivore that hunts, kills and eats other animals. For example a snake eating a mouse, the snake is considered the predator because it is consuming the mouse. In another example, a striped marlin is a predator. It lives in the Pacific Ocean and preys on sardines, also a Pacific animal. Similarly, various birds eat earthworms.
However, a predator can become the prey of another larger predator. For instance, a snake may become a meal for a hawk.
"In ecology, predation is a mechanism of population control. Thus, when the number of predators is scarce, the number of preys should rise. When this happens, the predators would be able to reproduce more and possibly change their hunting habits. As the number of predators rise, the number of preys decline. This results in food scarcity for predators that can eventually lead to the death of many predators." (www.Biology-Online.org)
Because of this, predation is called a "positive-negative" relationship. (Campbell)
Read more about this topic: Ecological Relationship, Oppositional Relationships