1. Organism: single living thing, such as a plant, animal, or microorganism.​

2. Population: group of the same type of organisms living in a specific area at the same time.​

3. Community: all the different populations of organisms that live and interact in a particular area.​

4. Ecosystem: all the living (biotic) and non-living (abiotic) components in a specific environment, interacting as a system.​

5. Biome: large geographic area defined by its climate, plants, and animals, such as deserts or forests.

6. Biosphere: global sum of all ecosystems, where life exists on Earth, including land, water, and the atmosphere.

Levels of Ecological Organization​

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Generalist, Specialist, Keystone, and Indicator Species

• A generalist species is a species adapted to thrive in a variety of habitats.

• A specialist species is a species adapted to thrive in a specific habitat.

• Keystone species are organisms that have a disproportionately large impact on their environment relative to their abundance.

• An indicator species is a species monitored for early warnings that a community or ecosystem is being damaged.

Extinction Rates

The background extinction rate is the rate at which organisms would naturally be expected to go extinct.
The background extinction rate is 50 to 100 times greater than what is expected by scientists.

The current extinction rate, or number of species that go extinct over a given period of time, is estimated to be 40,000 species per year.

Human Impacts on Biodiversity

The major causes of extinction today are:

• habitat destruction

• invasive species

• climate change

• overharvesting

• pollution

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