B(4-3) How do organisms interact?

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Vocabulary

competition

symbiosis

parasite

host

Limiting factors – competition for resources

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• Organism compete for space, light, food, water, and nutrients.

• Competition is the struggle among organisms for limited resources in an area.

• Every ecosystem has limited resources, so all species must compete to stay alive.

Limiting factors – competition for resources

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• There are several types of competition an ecosystem.

1. In one type one species might prevent another from using an important resource. ex. Some plants release certain chemicals that prevent other plants from growing.

2. When organisms use the same resources they usually have different niches. Ex. Warbler birds.

Limiting factors – competition for resources

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• The predator-prey relationship also affects competitions for resources in an ecosystem.

• A predator is an animal that feed on other living animals.

• Prey is an animal that predators eat.

Limiting factors – competition for resources

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Factors affect population:1. Plants supply affects the Hare population.2. The prey supply affect the predator population.

Organisms interact to meet their needs

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• Not all organisms in an ecosystem compete. Some organisms live together in a relationship called symbiosis.

• Symbiosis is a close relationship between organisms of different species in which one or both of the organisms benefit.

• There are three types of symbiosis.

Parasitism

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• In parasitism, one species benefits while the other is harmed.

• Parasite is an organism that lives in or on another organism.

• The organism that a parasite live in or on is called the host.

• Parasites are usually smaller than their hosts. Although they can weaken their hosts, parasites usually don’t kill them.

Parasitism

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• Some parasites live at the outside of their hosts. Ex. Ticks and flees.

• Other parasites such as the dog heartworm, live inside hosts.

• Plants can be hosts for parasites too. Ex. Red spider mites and tick like animals

Mutualism

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• In mutualism both organisms benefit.

Commensalism

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• In commensalism one organism benefits and the other is neither helped nor harmed.