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Ecosystem Ecology

Ecosystem Ecology. Chapter 55. Succession. Populations ebb & flow over time, but sometimes there is a dramatic disturbance that destroys an ecosystem Called a blowout Such as forest fires, volcanic eruptions, flooding Human activity: clear cutting of a forest or strip mining

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Ecosystem Ecology

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  1. Ecosystem Ecology Chapter 55

  2. Succession • Populations ebb & flow over time, but sometimes there is a dramatic disturbance that destroys an ecosystem • Called a blowout • Such as forest fires, volcanic eruptions, flooding • Human activity: clear cutting of a forest or strip mining • Ecological Succession – the process of sequential rebuilding of an ecosystem following a dramatic destruction • 2 Types of succession: • Primary Succession • Secondary Succession

  3. Primary Succession • When ecosystem is rebuilt from a lifeless area • Characterized by lack of soil • The essential operation is soil replenishment 1. Lichens & mosses occupy the land • called Pioneer organisms 2. Weathering and decay begins to build soil 3. Pioneer organisms are overrun by other organisms, such as grasses & brushes • Finally, there is a climax community • Final stable community

  4. Secondary Succession • Blowout event that does NOT destroy the soil • Technically, this disaster does not “denude” the soil • Since soil is intact, the regeneration process occurs relatively quickly • In 1988, Yellowstone forest fire occurred, the ecosystem began to recover in less than a year • By contrast, primary succession takes about 10,000 years to fully recover

  5. Keystone Species • Occupy an important ecological niche in an ecosystem • Dramatically affect the diversity of an ecosystem • Dominant species • Highest dry biomass in the community

  6. Primary Production • Def. – Amount of light energy converted to chemical energy by autotrophs in an ecosystem • Sets the limit on available energy in an ecosystem • Less primary production = less energy for the higher trophic levels • Gross Primary Productivity • Total photosynthesis or primary production • Net Primary Productivity • Photosynthesis – Respiration • Energy available to consumers

  7. Nitrogen Cycle • Nitrogen-fixing bacteria • Nodules in roots of legumes which convert free nitrogen into the ammonium ion • N2 + 4H2  2NH4 • Nitrifying bacteria • Convert NH4 to nitrites then to nitrates • Denitrifying bacteria • Convert nitrates  free atmospheric nitrogen

  8. Biological Magnification • DDT – popular pesticide in 1950’s • Responsible for malaria control • Rachel Carson wrote Silent Spring about DDT proliferation • Eventually led to a ban on DDT usage in the US • ONLY in the US, many other countries still use DDT • DDT is on every square kilometer on Earth • DDT enters the food chain at a low level but then bioaccumulates in the tissues of organisms consuming the organisms that ingested DDT • Most severe effects in tertiary consumers or organisms at the top of a food chain

  9. Biological Magnification (Page 2) • Bald Eagle • Symbol of America almost became extinct because of biological maginification of DDT • DDT entered the food chain with the bald eagle at the top • DDT interferes with the deposition of calcium in eggshells • Thin-shelled eggs were easily broken, which led to a substantial decrease in the number of eagle hatchlings • Hence the bald eagle (symbol of America) was saved from extinction by human intervention (stopping DDT spraying) What is the definition of irony!?!

  10. Separated at birth?

  11. Acid Precipitation • Humans are altering the Biosphere, is it a bad thing? • Threat of inhabitability due to population explosion • Natural resources are being exploited at an astronomical rate • Air & water are being rapidly polluted • Acid rain • Caused by airborne pollutants • These pollutants emanate from combustion of fossil fuels • Nitrogen & sulfur pollutants become nitric, nitrious, sulfurous, and sulfuric acid • Precipitates kills organisms & damages stonework

  12. Toxins • Cattle & chickens contain antibiotics & hormones which accelerate animal growth, but may have serious ill affects on humans who consume the meat • Carcinogens or teratogens accumulate in human fatty tissue due to biological magnification

  13. CFCs (Chlorofluorocarbons) released into the air caused the formation of a hole in the ozone layer • Ozone layer protects the Earth’s surface from ultraviolet (UV) light • It is thought that increased UV exposure is associated with increased incidence of skin cancer (melanomas)

  14. Global Warming • Excessive burning of fossil fuels has increased concentrations of atmospheric CO2 • Causes greenhouse effect • CO2 and water vapor trap infrared radiation reflected off the Earth’s surface in the atmosphere • Leads to increase in temperature (global warming) • An increase in 1.0°C could cause polar ice caps to melt, raising the sea level • Which may lead to major coastal cities being flooded away

  15. Exotic Species • Introduction of exotic species can have dramatic consequences for the ecosystem • The zebra mussel (Balkan native) that found its way to the Great Lakes, USA • Clogged intake pipes for local water supply • Caused millions of dollars in damage & brought native species to extinction

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