Ecological Succession Biology 1-2

Ecological Succession Ecological succession-process of biological community change. Ecological succession-process of biological community change. Usually the result of a disturbance. Usually the result of a disturbance. Also occurs when a new area opens up. Also occurs when a new area opens up. Succession is how an area recovers after the disturbance. Succession is how an area recovers after the disturbance.

Succession cont’d During succession... During succession... Species makeup changes quickly at first. Species makeup changes quickly at first. Size of the organisms increases. Size of the organisms increases. Diversity increases, then stabilizes. Diversity increases, then stabilizes. Switch from r-selected to K-selected species. Switch from r-selected to K-selected species. Each community changes the environment, allowing succeeding communities to replace them. Each community changes the environment, allowing succeeding communities to replace them.

Primary Succession Primary succession-area is initially barren and lifeless. Primary succession-area is initially barren and lifeless. No soil is present. No soil is present. Occurs following volcanic eruptions or glacier retreat. Occurs following volcanic eruptions or glacier retreat.

Primary Succession cont’d The first stage of succession is called the pioneer stage. The first stage of succession is called the pioneer stage. The first organisms are lichens and mosses. The first organisms are lichens and mosses. Wind carries spores to the new area. Wind carries spores to the new area. Can tolerate environments most organisms cannot. Can tolerate environments most organisms cannot. Reproduce rapidly to overcome losses. Reproduce rapidly to overcome losses. Prepare the area by breaking down rocks to create soil. Prepare the area by breaking down rocks to create soil. Make the environment suitable to others. Make the environment suitable to others.

Primary Succession cont’d After the pioneer stage are the intermediate stages. After the pioneer stage are the intermediate stages. Intermediate communities follow the pioneers. Intermediate communities follow the pioneers. Grasses and shrubs, followed by small trees and bushes. Grasses and shrubs, followed by small trees and bushes. Small mammals, birds, insects and reptiles move in. Small mammals, birds, insects and reptiles move in.

Primary Succession cont’d The intermediate stages lead to the climax stage. The intermediate stages lead to the climax stage. The climax community is the last community to appear. The climax community is the last community to appear. Will not change unless disturbed. Will not change unless disturbed. Characterized by tall trees and more complex interactions in the community. Characterized by tall trees and more complex interactions in the community.

Primary Succession cont’d The climax community forms and maintains equilibrium. The climax community forms and maintains equilibrium. K-selected species replace many r-selected species. K-selected species replace many r-selected species. Competition, predation and symbiosis become more extensive. Competition, predation and symbiosis become more extensive. All niches are filled. All niches are filled.

Secondary Succession Secondary succession The area is cleared out but the soil is left intact. Secondary succession The area is cleared out but the soil is left intact. Occurs following fires, floods, human activity, etc. Occurs following fires, floods, human activity, etc. Follows the same pattern as primary succession (pioneer to intermediate to climax). Follows the same pattern as primary succession (pioneer to intermediate to climax). The pioneer community is weeds and grasses. The pioneer community is weeds and grasses. Secondary succession is faster than primary succession. Secondary succession is faster than primary succession. Lichens and mosses are not needed to create soil. Lichens and mosses are not needed to create soil.

Disturbances and Recovery Some communities are adapted to periodic disturbances. Some communities are adapted to periodic disturbances. San Diego is a chaparral community. San Diego is a chaparral community. Fire climax community. Fire climax community. Fire clears out dead material and old growth, making way for new growth. Fire clears out dead material and old growth, making way for new growth. Many native plants have adaptations for surviving. Many native plants have adaptations for surviving. Community recovers and reaches the climax stage quickly. Community recovers and reaches the climax stage quickly.

Disturbances cont’d Fire prevents a more traditional climax community from forming. Fire prevents a more traditional climax community from forming. Fire kills saplings and the seeds of trees that would replace the local shrubs. Fire kills saplings and the seeds of trees that would replace the local shrubs. Trees lack adaptations to survive in the environment. Trees lack adaptations to survive in the environment. A traditional climax community is unstable and more open to change. A traditional climax community is unstable and more open to change.