Ecology and the Distribution of Life
: What is Ecology?
• Ecology: scientific study of the rich and varied interactions between
organisms and their environment.
• Communities: embracing all the organisms living together in the same area
• Ecosystems: embracing all organisms in an area plus their physical
• Biosphere: system that embraces all regions of the planet where organisms
• Environment: encompasses both abiotic and biotic factors
: How are Climates Distributed on Earth?
• Climate of a region is the average of the atmospheric conditions found over a
• Weather is the short-term state of those conditions.
• Climates vary greatly because different places receive different amounts of
Solar energy drives global climates
• Every place on Earth receives the same total number of hours of sunlight but
not the same amount of solar energy; this depends primarily on the angle of
• Higher latitudes experience greater variation in both day length and the
angle or arriving solar energy over the course of a year = greater seasonal
variation in temperature.
• Air temperature decreases with elevation: when air rises, it expands, its
pressure and temperature drop, and it releases moisture; when a parcel of air
descends, it is compressed, its pressure rises, its temperature increases, and
it takes up moisture.
• Global air circulation patterns result from the global variation in solar energy
input and from the spinning of Earth on its axis.
• Air rises when it is heated by the sun and is replaced by air that flows in
toward the equator from the north and south produces the intertropical
• Cool air cannot hold as much moisture as warm air, so heavy rains fall in the
intertropical convergence zone.
• Air that moves into the intertropical convergence zone to replace the rising
air is replaced by air from aloft that descends at roughly 30N̊ and 30S ̊. It now
descends, warms, and takes up moisture. (Earth’s deserts such as the Sahara
and Australian deserts are located here).
• At about 60N̊ and 60S ̊, air rises again and moves either toward or away from
the equator. •