12.2: Ecological Organization

How is your school organized?

Your school is organized at several levels. Individual students and teachers are divided into classes. These classes are organized into an entire middle school. Your middle school and other nearby schools are organized into a school district. Just like schools are organized, ecosystems are also organized into several different levels, and an ecosystem can be studied at any one of the various levels of organization.

Levels of Ecological Organization

Ecosystems can be studied at small levels or at large levels. The levels of organization are described below from the smallest to the largest:

• A species is a group of individuals that are genetically related and can breed to produce fertile young. Individuals are not members of the same species if their members cannot produce offspring that can also have children. The second word in the two word name given to every organism is the species name. For example, in Homo sapiens, sapiens is the species name.
• A population is a group of organisms belonging to the same species that live in the same area and interact with one another.
• A community is all of the populations of different species that live in the same area and interact with one another. A community is composed of all of the biotic factors of an area.
• An ecosystem includes the living organisms (all the populations) in an area and the non-living aspects of the environment (Figure below). An ecosystem is made of the biotic and abiotic factors in an area.

Figure \(\PageIndex{1}\): Satellite image of Australia’s Great Barrier Reef, an example of a marine ecosystem.

• The biosphere is the part of the planet with living organisms (Figure below). The biosphere includes most of Earth, including part of the oceans and the atmosphere.

Figure \(\PageIndex{2}\): The global biosphere, which includes all areas that contain life, from the sea to the atmosphere.

Ecologists study ecosystems at every level, from the individual organism to the whole ecosystem and biosphere. They can ask different types of questions at each level. Examples of these questions are given in Table below, using the zebra (Equus zebra) as an example.

Ecosystem Level	Question
Individual	How do zebras keep water in their bodies?
Population	What causes the growth of a zebra population?
Community	How does a disturbance, like a fire or predator, affect the number of mammal species in African grasslands?
Ecosystem	How does fire affect the amount of food available in grassland ecosystems?
Biosphere	How does carbon dioxide in the air affect global temperature?

Summary

• Levels of organization in ecology include the population, community, ecosystem, and biosphere.
• An ecosystem is all the living things in an area interacting with all of the abiotic parts of the environment.

Explore More

Use the resource below to answer the questions that follow.

• Ecology Levels and Populations at http://www.youtube.com/watch?v=1JSS8XIYcgU (5:31)

1. What is the relationship between an individual and a community?
2. What characteristics define a population?
3. Why is the distinction between a community and an ecosystem important to ecologists?

Review

1. Define species.
2. What is an ecosystem?
3. Define population. How is a population different from a community?