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BIOL 103 (103)


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BIOL 103
Peter T Boag

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Mar 22/11 52.2 The environment’s Impact on the Distribution of Organisms Each species usually functions best over a limited part of the range of environmental conditions known as their fundamental niche. Temperature has an Important Effect on the distribution of Plants & Animals - Temperature is most important factor in distribution of organisms because of its effect on biological processes and because of the inability of most organisms to regulate their body temperature precisely. o Ex. Coral reefs secrete calcium carbonate shell that is accelerated at high temperature (i.e. warm water about o 20 C) - Isotherms: a line on a map connecting points of equal temperature. - Cold temperature (i.e. frost) can rupture cells if the water they contain freezes o Ex. In the Sonoran desert, saguaro cacti can withstand frost for one night as long as temperatures rise above freezing the following day. - High temperatures also limiting because few species can survive internal temperatures above metabolic optimum. o When temperatures are too high, the symbiotic algae living in coral die and are expelled  coral bleaching. - However, some species depend on frequent, low-intensity fires for reproductive success. o Ex. Jack pine cones remain closed by resin until melted by fire. - The temperatures measured for constructing isotherm maps aren’t always the temperatures organisms’ experience, local variations of the climate (i.e. if it’s a shady area) within a given area – microclimate – are important. - Greenhouse effect warms the earth: solar radiation heat surface of Earth  atmospheric gases absorb this infrared energy and reradiate it to Earth’s surface  temperature rise. - Caused by small group of gases making up less than 1% of total volume: CO . CO2 NO, CFCs Global Warming - A gradual elevation of Earth’s surface temperature. - Global warming may occur too rapidly to be compensated for by normal evolutionary processes, like Natural selection. Wind can Amplify Effects of Temperature - Wind is created by temperature gradients: air heats up  less dense and rises  cooler air rushes in to take its place. - Increases heat loss by evaporation (also water loss) and convection (wind chill factor) - Winds also intensify oceanic wave action – seaweeds survive heavy surf with holdfasts and flexible structures. Availability of Water has important Effects on the Abundance of Organisms - Water acts as a solvent for chemical reactions, takes part in hydrolysis, waste elimination, plant support, hydrostatic skeleton. o Alpine trees can be affected by frost drought  stop growing at the point where they can’t take up enough moisture to offset transpiration losses ‘timberline’. - Animals face problems of water balance too since plants are their food supply. o Buffalo in Serengeti area of Africa: correlation between buffalo density and rainfall. Light can be a limiting Resource for Plants and Algae - Light  photosynthesis : it’s a limiting resource for plants. o Ex. Eastern hemlock grow lest in shady conditions  ¼ full sunlight = best photosynthesis. o Sugarcane, or desert shrub Larrea continue to increase photosynthetic rate as light intensity increases. - C 3 C 4 CAM affect photosynthetic rate. - For aquatic environments, most aquatic plants and
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