Succession and Change in Ecosystems Topic 6 Science 7

Succession The gradual process by which some species replace other species in an ecosystem

Primary Succession The gradual growth of organisms in an area that was previously bare, such as rock.

Secondary Succession The gradual growth of organisms in an area that previously had a number of organisms. (ex. Burned forest)

Changes are caused by human activity Some species adapt better than others

Pest Control Sometimes when a pesticide like DDT is used to kill one species it ends up killing beneficial organisms living in the same environment.

Biological Control Using a pest’s natural enemy to control pests But BEWARE when introducing new species

Introduced Species Species brought to an environment where they are not naturally found. Zebra mussels were introduced by accident to the Great Lakes from ships. With no natural predators their population exploded and they took over the niche of naturally occurring species (plus they clog pipes!)

Species in Danger Extinct: organisms that no longer exist anywhere in the world Some causes: Habitat loss Introduced species Pollution Changes in climate

Extirpated When a species no longer exists in a habitat it used to exist in. caribou

Endangered When a species is threatened with extinction