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Mount St. Helens. Erupted in 1980 All life destroyed What happens after that?. Ecological Succession. A series of predictable changes that occur in a community over time.

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Mount St. Helens

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mount st helens
Mount St. Helens
  • Erupted in 1980
  • All life destroyed
  • What happens after that?
ecological succession
Ecological Succession
  • A series of predictable changes that occur in a community over time

Slow changes occur after a sudden natural disaster. For example, fires or volcanoes. Can occur after human activity, like the clearing of a forest.

primary succession
Primary Succession
  • Occurs on surfaces where no soil exists (after a volcanic eruption or after a glacier retreats)
  • The first species to populate the area is the pioneer species.

Lichens are usually pioneer species. Why?

secondary succession
Secondary Succession
  • Occurs after a disturbance that destroys a community without destroying the soil (fire, disease, clearing of a forest)
marine succession stage 1
Marine Succession – Stage 1
  • Begins when a whale dies and sinks to the ocean floor
  • Attracts scavengers & decomposers, which eat the soft tissue of the whale
marine succession stage 2
Marine Succession – Stage 2
  • After 1 year, most of the soft tissue has been eaten
  • Decomposition of the body enriches the sediment with nutrients, which attracts more marine life
marine succession stage 3
Marine Succession – Stage 3
  • Begins when only the skeleton remains
  • Bacteria decompose the oils inside the bones
  • The bacteria can support a community of marine life
did you know
Did you know?
  • The water we have on Earth today is the same water that was on Earth 4.5 billion years ago!


biogeochemical cycles
Biogeochemical Cycles
  • Energy is transferred in one direction.
  • Matter is cycled through the ecosystem in the biogeochemical cycles!
the water cycle
The Water Cycle
  • How water moves through the air, land, and organisms
    • Evaporation: water  vapor from surface of bodies of water
    • Transpiration: water  vapor from plants
    • Condensation: vapor  water in clouds
the carbon cycle
The Carbon Cycle
  • Carbon Dioxide (CO2) cycles through the ecosystem through air, water, land, and organisms.

Carbon enters the atmosphere through fossil fuel emissions & animal respiration.

Photosynthesis takes up CO2 from the atmosphere.

the nitrogen cycle
The Nitrogen Cycle

Nitrogen (N) cycles through the atmosphere, organisms, and soil.

nitrogen fixation
Nitrogen Fixation
  • Nitrogen Fixation- bacteria take nitrogen (N2) from the atmosphere and change it into a form that plants can take up from the soil called ammonium (NH4).
  • Nitrification- ammonium not taken up by plants are converted to nitrates and nitrites by bacteria which other plants can take up.
  • Denitrification- bacteria can turn the ammonium back to atmospheric nitrogen
the nitrogen cycle1
The Nitrogen Cycle
  • Consumers eat and take in N in order to make proteins.
  • Dead organisms can return N to the soil or to the atmosphere with the help of bacteria
the phosphorous cycle
The Phosphorous Cycle

It does not enter the atmosphere, but rather is cycled through the soil, oceans, and organisms through consumption and decomposition

nutrient limitations
Nutrient Limitations
  • An ecosystem needs a particular amount of each nutrient to thrive. A single nutrient can limit its success.

An excess of a particular nutrient can cause over production of algae and plant growth.

(Red Tide!)

human effects on biogeochemical cycles
Human Effects on Biogeochemical Cycles
  • Carbon- burning fossil fuels releases previously isolated carbon back to the atmosphere
  • Nitrogen and Phosphorus- we add fertilizers to assist crop growth and much of it gets washed away into rivers, lakes and oceans