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Biological Communities

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Biological Communities

How is a community of people like a community of organisms?

Different species have different jobs within their community. Some are the farmers, some are traders, some are the janitors, and others have different roles.

Biological Communities

A population consists of all individuals of a single species that exist together at a given place and time. A species is a single type of organism that can interbreed and produce fertile offspring. All of the populations living together in the same area make up a community .


An ecosystem is made up of the living organisms in a community and the nonliving things, the physical and chemical factors, that they interact with. The living organisms within an ecosystem are its biotic factors ( Figure below ). Living things include bacteria, algae, fungi, plants, and animals, including invertebrates, animals without backbones, and vertebrates, animals with backbones.

A plant, invertebrate, and vertebrates are all part of an ecosystem

(a) The horsetail Equisetum is a primitive plant. (b) Insects are among the many different types of invertebrates. (c) A giraffe is an example of a vertebrate.

Physical and chemical features are abiotic factors. Abiotic factors include resources living organisms need, such as light, oxygen, water, carbon dioxide, good soil, and nitrogen, phosphorous, and other nutrients. Nutrients cycle through different parts of the ecosystem and can enter or leave the ecosystem at many points. Abiotic factors also include environmental features that are not materials or living things, such as living space and the right temperature range. Energy moves through an ecosystem in one direction.


Organisms must make a living, just like a lawyer or a ballet dancer. This means that each individual organism must acquire enough food energy to live and reproduce. A species' way of making a living is called its niche . An example of a niche is making a living as a top carnivore, an animal that eats other animals, but is not eaten by any other animals ( Figure below ). Every species fills a niche, and niches are almost always filled in an ecosystem.

The top carnivore niche is filled by lions on the savanna, wolves in the tundra, and tuna in the oceans

The top carnivore niche is filled by lions on the savanna, wolves in the tundra, and tuna in the oceans.


An organism’s habitat is where it lives ( Figure below ). The important characteristics of a habitat include climate, the availability of food, water, and other resources, and other factors, such as weather.

Birds living in a saguaro cactus

Birds living in a saguaro cactus. A habitat may be a hole in a cactus or the underside of a fern in a rainforest. It may be rocks and the nearby sea.


  • All of the individuals of a species that exist together at a given place and time make up a population. A community is made up of all of the populations in an area.
  • The living and nonliving factors that living organisms need plus the communities of organisms themselves make up an ecosystem.
  • A habitat is where an organism lives and a niche is what it does to make a living.


Use this resource to answer the questions that follow.


1. What are the biotic components of an ecosystem?

2. What is a species?

3. What is a population?

4. List two examples of populations.

5. What is a community?

6. How can a natural community vary in size?

7. What does abiotic mean?

8. What effects do the abiotic tractors have on the populations that live there?

9. How does the Earth's tilt effect life?


1. Define species, population, community, niche, habitat, biotic factor, and abiotic factor.

2. Diagram how the words listed above relate to each other.

3. Choose a type of wild organism that you're familiar with and list the biotic and abiotic factors that it needs to live.

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