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
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
- 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
- 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
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