Communities

CommunitiesUnderstanding how populations of organisms interact in communities.

Mr. RoesLiving Environment

Community Interactions

One of the foundational understandings of ecology as a whole is that organisms in a community are all interacting with each other constantly in one way or another.

Community interactions such as competition, predation, and various forms of symbiosis, can powerfully affect an ecosystem.

Community interactions Every organism has a role that it fulfills—

each organism has a way in which they get the resources that they need in order to survive. This is the idea of a niche.

The niche of an organism involves all of the physical and biological conditions that the organism lives in, and the way in which it uses those conditions.

CompetitionIn nature, ecosystems often can be

limited in the amount of a resource that is available.

If two organism in the same community attempt to use the same resource, competition occurs.

Competition:

In nature, there is often a clear winner and loser in cases of direct competition.

The loser will fail to survive if it remains in the same niche.

In ecology, we have a basic knowledge which states that no two organism can occupy the same niche in the same habitat at the same time. This is called competitive exclusion.

Predation

Predator

Prey

An entire food web is filled with many examples of predator-prey relationships. In an ecosystem, an organism could be a predator on an organism in a lower trophic level, while being the prey of an organism in the next highest food level.

Symbiosis Sometimes in a community, there are

examples of organisms of two different species living in an intentional relationship with each other. We call this a symbiotic relationship.

Symbiotic relationships can be categorized into three different groups;

oMutualismoCommensalismoParasitism

Mutualism:A relationship in which both

organisms are benefitted.

Insects move from flower to flower, gathering their nectar, which the use as an energy source. The flowers benefit from the insects by being pollinated.

Nitrogen-fixing bacteria and leguminous plants.

Commensalism:A relationship in which one

organism is benefitted, and the second organism isn’t affected.

Parasitism:A relationship in which one

organism is benefitted, and the second organism is harmed

Draw this chart:

Organism 1

Organism 2

Mutualism + +Commensalism

+ 0Parasitism + -

What form of symbiosis?

What form of symbiosis?

What form of symbiosis?

What form of symbiosis?