Understanding Populations

1. Understanding Populations How Species Interact with Each Other

2. An organism’s niche • Is a unique role of a species within an ecosystem • Can include the species’ physical home, environmental factors necessary for survival and all of the species’ interactions with other species • An organism’s habitat is a location • A niche is NOT the same as a habitat

3. Ways in Which Species Interact • There are 5 major types of interactions: competition, predation, parasitism, mutualism and commensalism. • These categories are based on whether each species causes benefit or harm to the other species in a given relationship.

4. Competition • A relationship in which different individuals or populations attempt to use the same limited resource. • Can occur both within and between species • Species can compete even if they never come into direct contact with each other, this is indirect competition.

5. Competition Continued… • One way to reduce competition between species is by dividing up the niche in time or space. • Niche restriction occurs when each species uses less of the niche than it is capable of using. • In the presence of competition, the actual niche used by a species may be smaller than the potential niche.

6. Predation • An interaction where one organism feeds on another. • An organism that feeds on another organism is called the predator. • The organism that is fed upon is the prey. • Most organisms have evolved some mechanisms to avoid or defend against predators.

7. Parasitism • An organism that lives in or on another organism and feeds on it is a parasite. • The organism the parasite takes its nourishment from is known as the host. • Unlike predators, parasites usually do not kill their hosts. • However, the host is often weakened or exposed to disease by the parasite.

8. Mutualism and Commensalism • A close relationship between two species in which each species provides a benefit to the other. • Most organisms in a mutualistic relationship could not survive alone. • A relationship in which one species benefits and the other species is neither harmed nor helped.

9. Symbiosis and Coevolution • A relationship in which two species live in close association is symbiosis. • Symbiosis is most often used to describe a relationship in which at least one species benefits. • Over time, species in close relationships may coevolve. They may evolve adaptations that reduce the harm or improve the benefit of the relationship.