BIO326 : Individual : Environmental Variation : Lesson

The red line gives the best post-1992 Solar spectum estimate, and the yellow line shows the spectrum of a blackbody having temperature 5780 degrees Kelvin, which is the temperature needed to give the same total power, given by the integral over the spectrum, also known as the solar constant, which here is about 1370 W/m2. [Various measurements of the solar constant give values between 1365 and 1372. It is also not constant in time, but varies over the ~30-day solar rotation period, with an amplitude of about 4 W/m2, or about 0.3 percent, during the maxima of the 11-year solar sunspot cycle, and much less during sunspot minima.]

Original URL of this figure is http://climate.gsfc.nasa.gov/~cahalan/Radiation/SolarIrrVblackbody.html

Temperature, moisture, and light are seldom constant for long. Variations in these and other factors change the conditions under which organisms have to live. In this section, we will see the range of conditions in which organisms live.

I. Environmental Patterns: Global, regional, local

1. Global climate
   • Poles: cold and dry
   • Equator: hot and wet
   • Hadley cells contribute to the world's major deserts
   • Mountains produce rain shadows
   • Upwelling: areas of extreme productivity
   • Mediterranean climate occurs in the USA

2. Seasonal climate
   • Earth's tilt leads to summer and winter

Lake cycles Differences in temperature result in differences in water density Local seasonal "oscillations" Major oscillation: El Niño Topography and geology Gradients in elevation Gradients in moisture Gradients in substrate Landscape ecology Soils: chemically and biologically altered material Soil profile: horizons Weathering: physical and chemical alteration of rock

II. Biomes

1. Large scale distributions of species
   • Species distributions associated with physical conditions of the environment, e.g., climate
   • Local variations related to topography, soil, elevation
   • Specializations to moisture, temperature, and soil
   • Terrestrial examples: deciduous forest, temperate grassland, boreal forest, tundra, tropical rain forest

Aquatic systems Streams and rivers Pools and riffles Downstream drift Lakes Littoral Limnetic Benthic Estuaries Oceans: photic, neritic, oceanic

When you have completed this lesson, go on to Review Questions