Succession & Biogeography

The study of where organisms live and how they got there is called biogeography.

1 2 3 4 5 6 7 8 9 10 11 12 Succession Notes (p. 616-618) Page 10-5 date Succession — the natural process by which one community of organisms slowly replaces another in an area. Occurs differently in different places Primary Succession Begins in a place without any soil. Pioneer species arrive. examples: Mosses and lichens (they do not need soil) They release acid, and with decay… examples add weathering and erosion; soil begins to form, organisms move in by dispersal. examples

After a disturbance destroys an ecosystem… 13 14 15 16 17 18 19 20 21 22 23 24 25 In time, the numbers and types of organisms no longer change rapidly, they come in balance with the resources. This is called Equilibrium. example A community which has reached this stable stage is called a Climax Community. example After a disturbance destroys an ecosystem… natural: wildfires, tornadoes, hurricanes, erosion caused by man: commercial development. …then you will get… Secondary Succession — soil is already there, dispersal also occurs; it is much faster. example Write key words in the column on the left page. Write a summary at the bottom of the left page. (thank you to M. Ward, College Station ISD, and others for example slides)

Primary Succession The processes involved in changing an area from one lacking any community (no plants, no animals, no insects, no seeds, AND NO SOIL) to one consisting of individuals, populations, communities, and ecosystems. Starts WITHOUT SOIL. This is the confusing part - there may have been a previous community, but if a disturbance removes or in some way covers the soil we would classify it as Primary succession. PIONEER Species of primary succession (e.g. lichens and mosses). Examples: Bare rock Volcanic eruption, and, pioneer species Glacier and Glacial retreat Man-made structures

Lichens

Primary Succession

Organisms move to a new place through dispersal. This can happen by wind, water, & living things. Wind Examples: seeds that blow in the wind (Dandelion), pollen, mold spores, viruses Water Examples: seeds floating, currents moving plants, tides moving mollusks Living Thing Examples: Sticker burrs on socks, parasites, bacteria, migration, digestion (mesquite trees)

Dispersal is limited by three things: physical barriers, competition & climate.

Recall that a community is all the different organisms that live together in an area.

When the numbers & species (in a community) do not change rapidly it is said to be in equilibrium.

CLIMAX COMMUNITIES (100 years or more to establish) Is where further changes take place very slowly, and the site is dominated by long-lived, highly competitive species. Example: when the populations of the large trees neither decrease nor increase in size.

Redwood National Park, which covers 455 sq km (176 sq mi) along California’s northwestern coast, represents one of the last remaining ancient redwood forests in the world. Here, heavy coastal rainfall and lack of exploitation by humans has encouraged the dramatic growth of some of the largest trees on earth. Some of these redwoods are believed to be more than 2,300 years old CLIMAX COMMUNITY

Secondary Succession Follows disturbance of an existing community that removes or damages the vegetation, but does not remove, destroy, or cover the soil. Starts WITH SOIL. PIONEER PLANTS of secondary succession (the first plants to become established after the disturbance) start from roots or seeds remaining in the soil or from seeds carried in by wind or animals from surrounding communities. Faster than primary succession.

Secondary Succession

Summary: Pioneer species colonize first. Pioneer species alter the environmental conditions remaining after the disturbance. Eventually new species of plants become established in the conditions altered by the pioneer species and displace the pioneer plants. Animals come in with or after the plants they need to survive. Further environmental change by the new plants and animals result in the establishment of different species.

Primary Succession Secondary Succession