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Physical Environment

Physical Environment

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Physical Environment

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  1. Physical Environment Chapter 7 Abiotic Factors

  2. Physical Variables and Species Abundance • Liebig’s Law of the Minimum (1840) • The distribution of a species will be controlled by that environmental factor for which the organism has the narrowest range of tolerance

  3. Highest limit of tolerance Lowest limit of tolerance Physiological optimum Low tolerance Inability to survive Low tolerance Inability to survive Low population Species absent Species absent Low population Population density Physical gradient (e.g., pH)

  4. Temperature • Affects biological processes • Correlations between temperature and species distribution • Temperature at the local scale, is much more variable

  5. Fire • North America before the arrival of Europeans • Fires started by lightening • Frequent and regular

  6. Fire (cont.) • Consumed leaf litter, branches and undergrowth before great quantities accumulated • Large trees usually not damaged • Some species evolved to require fire • Serotinous cones

  7. Global warming • Two issues • Rate of global warming • Contribution by humans • Increased global warming = greenhouse effect • Atmosphere transmits short-wave solar radiation

  8. Greenhouse Effect Greenhouse effect

  9. 1800 360 Carbon dioxide Methane 340 1400 320 CO concentration (ppmv) CH concentration (ppmv) 300 1000 280 2 4 260 600 1750 1800 1850 1900 1950 2000 1750 1800 1850 1900 1950 2000 Year Year 0.3 310 Chlorofluorocarbon-11 Nitrous oxide 0.2 300 N O concentration (ppbv) CFC concentration (ppbv) 0.1 290 2 280 0.0 1750 1800 1850 1900 1950 2000 1750 1800 1850 1900 1950 2000 Year Year

  10. Greenhouse Gases Greenhouse gases

  11. 0.4 0.2 0.0 Change from 1940 temperature (°C) -0.2 -0.4 -0.6 1870 1890 1910 1930 1950 1970 1990 Year

  12. Greenhouse Gases Carbon dioxide and temperature

  13. Natural ecosystems & Global Warming • Profound changes in natural ecosystems • Most species cannot evolve significantly or rapidly enough to counter climate changes • Most species will not be able to disperse or migrate fast enough to keep up with climate change

  14. Wind • Can be caused by temperature gradients • Amplifies temperature effects on organisms • Increase heat loss through evaporation and convection • Increases animal evaporation and plant transpiration • Wind aids pollination • Wind disperses plant seeds • Affects mortality

  15. Salt • Increases osmotic resistance to water uptake • Occurs in arid regions • Important to agriculture in arid regions • Increases salt concentration • Decreases crop yield • Salt marshes • Halophytes

  16. pH • Few organisms can exist below pH 4.5 • Lake trout in Eastern US disappear when pH drops below 5.2 • Roots are damaged below pH 3 and above 9

  17. Acid Deposition Acid deposition

  18. Acid Rain Effect of air pollution in forests

  19. Water • Protoplasm is 85-90% water • Distribution of many plants limited by water availability • Animal distribution affected by desiccation • Tolerance and avoidance

  20. Applied Ecology • Diseases and Global Climate change • Spread of tropical diseases pole ward • Controlled by the range of their vectors • Ex. Mosquitoes and other insects • Insects are ectotherms • Increase in temperature = increase in range and activity of vectors

  21. Summary • Local distribution patterns are limited by certain physical or abiotic factors, such as temperature, moisture, light, pH, soil, salinity. • Temperature is one of the most important physical variable affecting plant and animal distribution • Resistance to high temperature and fire • Implication of climate change

  22. Summary (cont) • Wind can amplify the effects of temperature, and can affect species distribution directly. • Soil salt concentration and pH can affect water uptake in plants • Physical factors strongly influence population densities. • The physical environment can profoundly influence species richness