- EVOLUTIONARY ECOLOGY
SMOUSE - SPRING 2011
Organisms live in an environment, and that environment determines
which individuals are best adapted (= most fit). It is easy to say it, but not always easy to convey
the flavor of it. The study of the environment, as experienced by organisms, is
. We don’t
have time to do that subject justice here, but we ought to flag some useful points in passing.
is the study of how the environment impacts the organism; the
idea is that organisms receive input from the physical environment, but not the reverse.
is the study of how organisms impact each other; the idea is that organisms
influence each other in both directions. This dichotomy is inexact, but more important, it
ignores the fact that organisms impact the physical environment itself.
Global Climate Patterns
– But let’s start with autecology. The planet contributes the largest
environmental effects, through its own dynamics, relative to the sun and moon. The factors that
seem to be the most important are energy and water, without which there is no life. We get our
energy mostly from the sun, and most of that hits the earth in tropical latitudes.
Elevated temperatures in tropical latitudes evaporate water from the surface. Hot air rises. As
it cools, the water vapor condenses, and precipitates as rain. The air moves at high elevation
toward both poles. By the time it has reached about 30
latitude, it has little moisture left, has
cooled, and descends. Most of the hot deserts occur in subtropical latitudes.
From the surface, air moves both pole-ward and toward the equator. By about latitude 60
meets air coming from polar regions, heats, rises, again picking up moisture. Once it reaches
high elevation, it moves back toward tropical latitudes or toward the pole. The pattern is the
same, going both north and south. Because the planet rotates, there is angular momentum,
and that translates into prevailing winds and oceanic circulation currents.
Figure 4.1 (Page 60) Futuyma, 3
The largest environmental effects influencing the biota come from climate, basically from
energy inputs and water availability.