Succession

Science 1206

Ecological succession refers to the series of ecological changes that every community undergoes over long periods of time.

The process of succession begins with relatively few pioneering plants and the animals that are associated with these plants.

Each successive community develops through increasing complexity until it becomes a final, sustainable, stable, or self-perpetuating community, of dominant organisms, known as a climax community.

The climax community is the final stage of ecological succession.

Pioneer plant

Climax Community

Primary Succession Secondary Succession Contributing Factors

Primary succession:

primary succession which refers to a sequence beginning in an area where there is no soil or previous forms of life.

Primary succession occurs in an area such as a freshly cooled lava field, or a newly formed sand dune.

In terrestrial habitats, primary succession is a very slow process because it begins with the formation of soil. (how is soil formed? Weathering)

Large rocks are broken down into smaller pieces and eventually bacteria, fungi, and lichens inhabit the area.

These organisms are known as pioneer organisms because they are the first type of life to inhabit the region.

The pioneer organisms add organic matter to the primitive soil, changing the conditions of the microenvironment so that mosses, ferns, and other primitive plants begin to take over.

Grasses may eventually replace the more primitive plants and when they die, they make the soil even richer.

Shrubs grow and shade the grass causing it to die. Then trees may grow and shade out the shrubs.

Seedlings of other trees may grow well in the shade.

In this way, one community of trees will be succeeded by another community with different trees.

Secondary succession

Secondary succession occurs in an area in which an existing community has been partially destroyed and its balance upset, either by natural causes, such as fire, or as a result of human activity, such as the cutting of a forest, or abandoning a farm.

major difference between primary and secondary succession in a terrestrial environment is that in secondary succession, soil already exists.

Seeds of plants will begin to grow. The seeds will come from dormant seed already in the soil, or from plants in communities nearby.

secondary succession will eventually result in a climax community that is often the same as would normally be found in the typical climax community in the region.

An abandoned farm may become a forest given enoughtime.

Factors that contribute to ecological succession:

climate (temperature, precipitation, and availability of sunlight),

soil (salinity, fertility, moisture, texture, etc.),

geographical features (latitude, altitude, and proximity to mountain ranges or large bodies of water).

Some biologists say there is no such thing as a climax community because the entire earth is in constant change or upset, due to:

Natural change: flood, fire, volcanic activity, climate change, species extinction, etc.

Human influenced: acid rain, ozone depletion, enhanced global warming, pollution, habitat destruction, monoculture farming, clear-cut logging, over-fishing

Read page 48-49Activity:1. What does equilibrium mean in terms of a forest

ecosystem? 2. Identify at least four conditions which help maintain

equilibrium in a forest ecosystem. 3. In what ways have humans affected natural

ecosystems such as a forest or large lake? 4. What are some of the human activities in your area

that are having a negative impact on an ecosystem near you?

5. What can be done to help your local ecosystem recover?

1. What is succession? a. one community type replaces another over time

b. a forest is destroyed and replaced by a pondc. a climax community is destroyed foreverd. a series of natural changes leading from climax to pioneering community

2. Which is a major difference between primary and secondary succession? a. The types of climax community are different.

b. Soil with seeds is characteristic of secondary succession.c. Soil with seeds is characteristic of primary succession.d. The steps leading to the climax community are identical in both.

3. What factors might result in a primary succession? a. A forest is destroyed by fire.

b. A farmer abandons his fields.c. Pollution causes rapid plant growth in ponds. d. An island is formed by volcanic activity.

4. What is a climax community? a. The final stable community in a succession.

b. Bare rock represents the climax community. c. The first types of plants and animals to be established.d. The point when all life forms become extinct.

5. Which statement is true of succession? a. Pioneer organisms represent the dominant forms of plant life.

b. Grasses and shrubs are often replaced by mosses and lichens.c. Primary succession generally occurs more slowly than secondary succession.d. Pioneer organisms are often the same as the climax organisms.

1. What is succession? a. one community type replaces another over time

b. a forest is destroyed and replaced by a pondc. a climax community is destroyed foreverd. a series of natural changes leading from climax to pioneering community

2. Which is a major difference between primary and secondary succession? a. The types of climax community are different.

b. Soil with seeds is characteristic of secondary succession.c. Soil with seeds is characteristic of primary succession.d. The steps leading to the climax community are identical in both.

3. What factors might result in a primary succession? a. A forest is destroyed by fire.

b. A farmer abandons his fields.c. Pollution causes rapid plant growth in ponds. d. An island is formed by volcanic activity.

4. What is a climax community? a. The final stable community in a succession.

b. Bare rock represents the climax community. c. The first types of plants and animals to be established.d. The point when all life forms become extinct.

5. Which statement is true of succession? a. Pioneer organisms represent the dominant forms of plant life.

b. Grasses and shrubs are often replaced by mosses and lichens.c. Primary succession generally occurs more slowly than secondary succession.d. Pioneer organisms are often the same as the climax organisms.