BIL 160 Lecture Notes - Lecture 22: Irradiance, Subtropics, Natural Selection
BIL 160 Lecture 22
Ecology
• the study of interactions of organisms with each other and with their environment.
• Consists of biotic components (the living organisms) and abiotic components (nonliving like
light)
• Natural selection is driven by ecological interactions
species - similar organisms able to interbreed under natural conditions to produce fertile, viable
offspring
population - all members of a single species living in a defined location
community - all populations living in a defined location
ecosystem - the community and the abiotic components of its world
landscape - interactions between adjacent ecosystems
biosphere - all the earth's ecosystems, considered collectively
Solar Energy
Solar Irradiance
• Terrestrial irradiance is the solar radiation striking earth's surface
• Shorter and longer wavelengths are absorbed or reflected by atmospheric molecules such as
ozone and water vapor.
• Less than half of the solar radiation striking the earth's atmosphere successfully penetrates the
atmosphere to reach earth.
Sunlight Quality and Quantity
• Irradiance intensity and spectral distribution depend on
o environmental conditions
o sunlight angle of incidence
• The tropics lie between the
o Tropic of Cancer and the Tropic of Capicorn
o receive the highest annual input of solar energy
o are the only place on earth where the sun ever shines directly overhead
o This occurs on the equinoxes, March 21 and September 21.
• Subtropic lie
o Tropic of Cancer and 30oN in the northern hemisphere
o Tropic of Capricorn and 30oS in the southern hemisphere
Seasonal Changes in Sunlight
• The tilt of earth axis results in seasons
Global Air Temperature
• Solar warming creates movement of air and water vapor in the oceans and atmosphere.
• This generates characteristic climate patterns across the globe.
o Tropics: warm, high levels of precipitation
o Subtropics: relatively warm, arid
o Temperate: relatively warm, arid
o High Latitude Temperate: cool, high levels of precipitation
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