Presentations
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Primary succession starts with rock and ends with a stable ecosystem (shown below). The first organisms to grow on bare rock are lichens, likely carried there by wind or visiting birds. Organisms that live in inhospitable places, without soil or shelter, are called pioneer species. They slowly create conditions suitable for other organisms.
Secondary succession occurs in developed communities that have been disturbed and is usually faster than primary succession. This is because a disturbance such as a forest fire does not remove the soil or completely destroy all of the organic matter in the area, and conditions are suitable for grasses and shrubs to become established quickly.
A Lichens produce acidic compounds that break down the rock and release nutrients from the rock. The nutrients are then absorbed by the lichens. Decaying matter from dead lichens begins the process of soil formation.
B The lichens are joined by tiny plants, such as mosses that can grow in very thin soil. Insects and other small animals visit or settle around the vegetation to find shelter and food, forming the first ecological communities.
C The organisms help to break down the rock substrate. Soil begins to form in cracks in the rock where moisture collects. Eroded particles of rock are mixed with decomposing plant and animal materials. Larger plants, such as ferns, begin to take root in these cracks and accelerate the changes.
D As the decomposing materials build up, the soil is able to hold more water. The environment is now suitable for grasses, wildflowers, and other plants. These plants attract bees, butterflies, and other insects.
E One species gradually replaces another as the new plants and animals crowd out the pioneer species, which cannot survive in shadier, wetter conditions. As the new organisms continue building the soil, they alter their environment and, in turn, are replaced by taller shrubs and trees.
B The lichens are joined by tiny plants, such as mosses that can grow in very thin soil. Insects and other small animals visit or settle around the vegetation to find shelter and food, forming the first ecological communities.
C The organisms help to break down the rock substrate. Soil begins to form in cracks in the rock where moisture collects. Eroded particles of rock are mixed with decomposing plant and animal materials. Larger plants, such as ferns, begin to take root in these cracks and accelerate the changes.
D As the decomposing materials build up, the soil is able to hold more water. The environment is now suitable for grasses, wildflowers, and other plants. These plants attract bees, butterflies, and other insects.
E One species gradually replaces another as the new plants and animals crowd out the pioneer species, which cannot survive in shadier, wetter conditions. As the new organisms continue building the soil, they alter their environment and, in turn, are replaced by taller shrubs and trees.
Projects, Labs & Assignments
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Ecological succession assignment:
Make a 3-D model, accurate in scale, accompanied by labels and brief descriptions for each stage of primary and secondary ecological succession.
Make a 3-D model, accurate in scale, accompanied by labels and brief descriptions for each stage of primary and secondary ecological succession.