Lesson 07 – Species Interactions

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Read About Species Interactions


Read the vocabulary terms to understand the reading better.

Organisms are living things that can grow, use nutrients, and produce young.

A community is a group of plants and animals living in a specific area and their natural surroundings.

Resources are things that can be used to help an organism live, such as food, water, and shelter.

Symbiosis is a close relationship between two or more organisms, with at least one organism getting benefits from the relationship.

Mutualism is a relationship in which both organisms receive benefits from the relationship.

Commensalism is a relationship in which one organism benefits and the other organism is not affected in any way from it.

Parasitism is a relationship in which one organism benefits and the other is harmed in the process; over a long period of time, one organism could die.

Species Interactions

All organisms in a community have specific roles to play. Each species interacts with one or more other species. Most interactions involve competition for resources. Resources are things an organism needs to survive. These include food, water, air, sunlight, and shelter.

In a healthy community, there is a balance of organisms so each one gets what it needs. An example is the food pyramid. There are more species and individuals at the bottom of the pyramid. There are fewer and fewer as you move up the pyramid. When a community works the way it should, there is a balance in the number of species at all levels.


Some organisms have a special relationship with other organisms. Symbiosis is a close relationship between two or more organisms. At least one organism receives a benefit from this relationship. There are three categories of symbiosis.

To learn more about symbiosis, watch the video by Everything Science on Youtube.

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