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An Introduction to Ecology and the
Biosphere
Ecology - the study of the
interactions between organisms
and their environment
Ecology - levels
1. Organismal ecology
2. Population ecology
3. Community ecology
4. Ecosystem ecology
5. Biosphere ecology
Biosphere
Ecosystem
Community
Population
Organism
The environment of any organism
includes the following components:
Abiotic factors: non-living factors
Ex: temperature, light, water
nutrients
Biotic Factors: effect of other
organisms (living
components)
Ex: competition, predation,
herbivores
Abiotic Factors
1. Temperature
6. Rocks and Soil
2. Water
7. Disturbance
3. Salinity
4. Sunlight
5. Wind
Temperature
• affects biological processes
Cold – cells will rupture if they
expand while freezing
Hot – many proteins denature
above 45oC
• life can only exist over a fairly
narrow temperature range
Water
• cells must maintain a correct water
potential (keep from exploding or
drying out)
Salinity
Salt concentration of water in the
environment affects the water
balance of organisms through
osmosis
• most aquatic organisms are
restricted to either freshwater or
saltwater habitats by their limited
ability to osmoregulate
• many terrestrial organisms can
excrete excess salts from
specialized glands or in feces
• Salt flats and other high-salinity
habitats typically have few
species of plants and animals
Sunlight
• provides energy for
photosynthesis, which drives most
food webs
• plants often compete for light
because of shading or absorption
of light by deep columns of water
• also important to the development
and behavior of organisms that are
sensitive to photoperiod
photoperiod – relative lengths of
daytime and nighttime
Wind
• affects temperature (wind-chill
factor)
• contributes to water loss by
increasing the rate of evaporation
for many organisms (both plant
and animal)
Rocks and Soil
• physical structure, pH, mineral
composition of rocks and soil limit
where plants can grow
• plants limit what animals can be
found in an area
Disturbance
• disturbance is often an important
part of an environment
• allows organisms to re-colonize an
area
Ex: fire
humans
wind
Climate
Four abiotic factors are the major
components of climate
temperature
precipitation
sunlight
wind
• climate shapes environments and
what organisms can live in a
particular area
• particularly temperature and
water availability
• climate patterns can be described
on two scales: macroclimate and
microclimate
Macroclimate – patterns on the
global, regional, and local level
Microclimate – very fine patterns,
such as those encountered by the
community of organisms that live
beneath a fallen log
Global Climatic Factors
• Solar Radiation and Latitude
• Axis Tilt/Seasons
• Air/Water Circulation Patterns
Solar Radiation and Latitude
• changes the amount of light and
energy delivered per surface area
Result
• poles: less light
• equator: more light
• the unequal heating causes air and
water to circulate
Seasonality
• caused by the Earth's tilt
• day length changes over time
• many organisms are restricted in
range by how well they adapt to
changing seasons
Global Air Patterns
• air rises when heated,
sinks when cools
• zones of rising/sinking are created
• Earth's rotation causes zones to
"twist”
Result
• air circulation patterns
• rainfall patterns
rising air: wet areas
descending air: dry areas
Mountains
Mountains affect the amount of
sunlight reaching an area and
consequently the local temperature
and rainfall
• south-facing slopes in the
Northern Hemisphere receive
more sunlight than nearby
north-facing slopes and are
therefore warmer and drier
• these abiotic differences
influence species distribution
Altitude and Latitude
• mirror each other
their biomes are similar because
the environments are similar
Ex: Alpine = Tundra
When warm, moist air approaches a
mountain, the air rises and cools,
releasing moisture on the windward
side of the peak
On the leeward side, cooler, dry air
descends, absorbing moisture and
producing a “rain shadow’ effect
• deserts commonly occur on the
leeward side of mountain
ranges
examples: Mojave Desert of
North America, Gobi Desert
of Asia