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2.7 Changes in Ecosystems: Ecological Succession
Natural, gradual changes in the types of species that live in an area; can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time
Primary Succession
Begins in a place without any soil
Sides of volcanoes
Landslides
Flooding
Starts with the arrival of airborne pioneer species such as lichens that do not need soil
Soil starts to form as lichens, weather and erosion break down rock
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
Simple plants like mosses and ferns can grow in the new soil
The simple plants die, adding more organic material
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over
These plants die, and they add more nutrients to the soil
Shrubs and tress can survive now
Insects, small birds, and mammals have begun to move in
What was once bare rock now supports a variety of life
Secondary Succession
Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession
Example: after forest fires
Climax Community
A stable group of plants and animals that is the end result of the succession process
Indicator species: give early warning signs of damage or danger to a community
Common indicator species:
Birds
Butterflies
Amphibians
Why are amphibians declining?
Habitat loss and fragmentation: loss of wetlands, deforestation, development
Prolonged drought: dries up breeding pools, dehydration
Pollution: thin, permeable skins absorb pollutants from air, water, and soil
UV radiation: harms embryos
Parasitism: flatworms
Overhunting: where frogs are a delicacy
Nonnative species: competitors
Keystone species: have a larger impact on the community, if removed, than other species
Pollinators
Apex predators
Decomposers
specific ex: sea otter
feed on sea urchins, controlling their population
urchins would deplete the habitat's kelp
Kelp is the producer; the major source of food and shelter for the ecosystem.
What happens when you lose a keystone species?
Food webs and nutrient cycles disrupted
Population crashes
Extinctions
2.7 Changes in Ecosystems: Ecological Succession
Natural, gradual changes in the types of species that live in an area; can be primary or secondary
The gradual replacement of one plant community by another through natural processes over time
Primary Succession
Begins in a place without any soil
Sides of volcanoes
Landslides
Flooding
Starts with the arrival of airborne pioneer species such as lichens that do not need soil
Soil starts to form as lichens, weather and erosion break down rock
When lichens die, they decompose, adding small amounts of organic matter to the rock to make soil
Simple plants like mosses and ferns can grow in the new soil
The simple plants die, adding more organic material
The soil layer thickens, and grasses, wildflowers, and other plants begin to take over
These plants die, and they add more nutrients to the soil
Shrubs and tress can survive now
Insects, small birds, and mammals have begun to move in
What was once bare rock now supports a variety of life
Secondary Succession
Begins in a place that already has soil and was once the home of living organisms
Occurs faster and has different pioneer species than primary succession
Example: after forest fires
Climax Community
A stable group of plants and animals that is the end result of the succession process
Indicator species: give early warning signs of damage or danger to a community
Common indicator species:
Birds
Butterflies
Amphibians
Why are amphibians declining?
Habitat loss and fragmentation: loss of wetlands, deforestation, development
Prolonged drought: dries up breeding pools, dehydration
Pollution: thin, permeable skins absorb pollutants from air, water, and soil
UV radiation: harms embryos
Parasitism: flatworms
Overhunting: where frogs are a delicacy
Nonnative species: competitors
Keystone species: have a larger impact on the community, if removed, than other species
Pollinators
Apex predators
Decomposers
specific ex: sea otter
feed on sea urchins, controlling their population
urchins would deplete the habitat's kelp
Kelp is the producer; the major source of food and shelter for the ecosystem.
What happens when you lose a keystone species?
Food webs and nutrient cycles disrupted
Population crashes
Extinctions