Ecology is the study of the distribution and abundance
of organisms.
Biosphere: Portion of the earth inhabited by life:
sum of all ecosystems.
This area is a relatively thin layer of seas, lakes, streams,
land to soil depth of a few meters, and atmosphere to an altitude of a
few kilometers.
Organisms in the biosphere are acted upon by abiotic factors
(non-living).
1. Temperature: affects metabolism, range is between
0 degrees and 50 degrees centigrade.
2. Water: adaptations for water balance and conservation
help determine a species' habitat range.
3. Light: Solar energy drives nearly all ecosystems.
Availability of light can determine habitat. Aquatic environments, water
selectively reflects and absorbs certain wavelengths; therefore, most photosynthesis
occurs near the surface of the water. Animal and plant behavior is often
sensitive to photoperiods.
4. Soil: Physical structure, pH, and mineral composition
of soil limit distribution of plants and hence animals that feed on them.
5. Wind: amplifies the effects on temperature by increasing
heat loss by evaporation and convection.
Principle of Allocation: Each organism has a limited,
finite amount of total energy that can be allocated for growth, reproducing,
obtaining nutrients, escaping predators and coping with environmental changes.
Species living in stable environments: Lead a good life in
a small area.
Species living in unstable environments: Lead a rough life
over a wider range.
Terrestrial Biomes: Most often named for the predominant
vegetation but each is also characterized by animals adapted to that particular
environment
a). biomes grade into each other without sharp boundaries.
b). May be patchy, with several communities represented in
one biome.
c). Prevailing climate, particular temperature and rainfall,
is most important factor in determining what kind of biome develops.
A climatograph plots temperature and rainfall and
shows the impact of climate on the distribution of biomes.
A. Tropical Forest (rain forest): found near the equator,
temp varies little from 25 degrees C. and day light varies from 12 hours
by less than one hour. Lowlands receive very little rain fall, and develop
thorn forests. Nearer the equator regions have distinct wet and dry seasons
and tropical deciduous forests occur. Trees releaf following heavy rains.
Near the equator, where rainfall is abundant ,and the dry
season lasts less than a few months is tropical rain forest. Contain more
plant and animal species than any other community. Competition is strong
for light, soil is poor due to the rapid recycling of nutrients. Animals
are mostly tree dwellers.
B. Savanna: is a grassland with scattered individual
trees. Found covering: Central South America, central and South Africa,
and parts of Australia. Soil is generally porous with a thin humus layer.
3 distinct seasons: cool and dry; hot and dry, and warm and wet in that
order. Frequent fires inhibit invasion of trees. Large herbivores ( giraffes,
zebras) are commonly most active.
C. Desert: is characterized by low precipitation less
than 30 cm / year, not by temperature: both cold and hot deserts exist.
Hot deserts occur in S.W. USA, W. South America, North Africa, Middle East,
Central Australia. Cold deserts occur: E. Argentina, central Asia, and
west of the Rocky Mountains. Reptiles and seed eaters are common. Cacti
and succulents are also common.
D. Chaparral: scrub land are
regions of dense, spiny shrubs, with tough evergreen leaves found along
coasts where cool ocean currents circulate offshore making mild rainy winters
and long hot dry summers. Mediterranean , California coastline, Chile,
S.W. Africa, and S.W. Australia. Deer, snakes, fruit eating birds are common.
E. Temperate Grasslands: similar
to savanna but occur in cold regions. Veldts of S. Africa, the pusta of
Hungary, pampas of Uruguay and Argentina, steppes of Russia, and the plains
of the USA, are examples.
F. Temperate Forests: grow throughout
the mid latitude regions that contain enough moisture to support large
broad-leaved, deciduous trees. Occur in Eastern US, Middle Europe, and
E. Asia. There is a 5-6 month growing season, very cold winters, and very
hot summers. High precipitation and evenly distributed through out the
year. Soil rich in nutrients.
G. Taiga: ( coniferous or boreal
forest) is characterized by harsh winters and occasionally warm summers.
N.America, Europe, Asia, and at high elevations in more temperate latitudes.
Soil thin and acidic. It forms slowly.
H. Tundra: is the northern most
limits of plant growth and at high altitudes plant forms are limits to
shrubs and mat-like vegetation. Arctic Tundra: encircles the North Pole.
Brief warm summers are marked with nearly 24 hours of sunlight. Permafrost,
saturated soil prevent large plants from growing. Alpine Tundra: occurs
at high elevations at all latitudes.
Water
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