Habitats and Niches`

Habitats Organisms require certain things in order to survive such as food, light, shelter, and water. An organism’s habitat is the area where it can survive because it has these requirements in large enough amounts to support populations of the organism. A habitat is the environment where an organism lives.

Niche Pronounced “N-itch” A niche is an organism’s way of life. In includes the habitat, the food it eats, and all other organisms it interacts with. Another way to think about it is the organism’s job. Often a specific niche leads to evolution of similar traits.

Niche Fundamental niche All resources that could be used in absence of competition.

Realized Niche Realized niche Resources actually used in the presence of competitors.

Niche Overlap When the niche of two species overlaps and competition is apparent.

Competition is Expensive! Organisms try to avoid it by getting M.A.D., they would prefer to: Move Adapt Die

Resource partitioning It helps competing species share a resource. Occurs when species require different parts of the same resource.

Competition and niches Competitive exclusion If two species, with the same niche, coexist in the same ecosystem, then one will be excluded from the community due to intense competition. The Red Squirrel is native to Britain, but its population has declined due to competitive exclusion, disease and the disappearance of hazel coppices and mature conifer forests in lowland Britain. The Grey Squirrel - was introduced to Britain in about 30 sites between 1876 and 1929. It has easily adapted to parks and gardens replacing the red squirrel. The Grey Squirrel The Red Squirrel

Niches and resources Resource partitioning avoids competition; Realized niches divide resources (insects) among several species woodpeckers, nuthatches, & creepers. Each species evolved & adapted to specialized diet.

Galapagos Finches -from Grant 1986

But… While there are many habitats on the Earth, not all organisms can live in one habitat. Each habitat has a limiting factor. The limiting factor is one or more resources that controls the amount of organisms in the habitat.

Carrying capacity Since every habitat has a limited number of resources, scientists are able to establish a carrying capacity for each area. The carrying capacity is the maximum number of organisms that can survive over a long period of time in one area. Because there are limits like this to any habitat, organisms begin to compete for resources.

The End!