Learn Biology: Keystone Species vs Indicator Species





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Published on Dec 30, 2010

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Mahalo biology expert Mary Poffenroth discusses 
Keystone Species vs Indicator Species.

While all life has the right to exist, there are two groups of animals that are more important to an ecosystem than other animals. These are known as keystone species and the indicator species. These are not interchangable terms, and each species within these groups have a very specific role to play.

The loss of either the keystone species in
ecosystem or the indicator species can have very serious consequences for the ecosystem. It is up to humans to help ensure that our actions do not interfere with the health of the ecosystem by watching both the keystone species and the indicator species for their health and numbers.

Keystone Species

Keystone species have large influences on the environment relative to the species' population. Like a "keystone" in an arch helps support the entire arch, a keystone species supports an ecosystem; without that species, the ecosystem will collapse. 
California sea
otters were almost hunted to extinction, for example, which started to cause a collapse in the ocean ecosystem. Otters eat sea urchins, sea urchins eat kelp; without the otters, the sea urchin population exploded and started to eat all the kelp. Kelp provides protection and spawning for fish - so a lack of otters, meant a lack of fish. Once the otters were not hunted any longer, the ecosystem began to regain its equilibrium.c 

Indicator Species

Indicator species are those plants and animals that are highly sensitive to the changes within the environment. These changes can involve the populations of other animal species to the pollution levels in the air, soil or water. The increase or decrease of the species indicates a bettering or failing of the ecosystem respectively.
Lichens, for example, are very sensitive to sulfur dioxide and ozone. If these elements are in the air, the lichens will get sick or die off. Thus, their health is an indicator for the pollution in their environment.

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