|Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; email@example.com; http://www.employees.csbsju.edu/ssaupe/|
Region of earth
where organisms live. The
biosphere essentially forms a thin coating on the surface of the earth.
If the earth were an apple, the biosphere would be the peel.
includes biotic components (life) and abiotic
(non-living) components (earth/rock/soil - lithosphere; air - atmosphere;
water - hydrosphere).
Environment - an
organisms surroundings. Habitat
- place where an organism lives. These
terms are sometimes used synonymously though refer to slightly different
Organisms interact with one another.
These interactions can be positive (i.e., plants and pollinators; ants and acacias) or negative (i.e., predation, competition, disease), We discussed this, among other places, in our Community lecture.
Organisms interact with their environment.
Organisms are affected by various abiotic factors such as: (a) water availability; (b) salinity; (c) nutrient availability; (d) light (quality and quantity); (e) oxygen (aerobic/anaerobic); (f) elevation; (g) soil type; (h) wastes; (i) temperature; and (j) countless others.
affect their environment. For
example, vegetation plays a role in water recycling and recall that plants
absorb carbon dioxide and release oxygen.
Consider the Gaia Hypothesis and the explanation for why the
temperature of the earth has remained relatively stable even though solar
output has increased. How can
this be? Plants and other
critters have essentially regulated the degree of insulation (carbon dioxide
Biosphere is comprised of diverse assemblages (biomes) of species.
Wallace divided the biosphere in to biogeographic realms (Nearctic � North America; Palearctic � Europe; N. Asia, Australia; Ethiopian � African, Oriental � SE Asia; Neotropical - Central and South America). Within these realms, major ecosystem types, or biomes, predominate.
The major terrestrial biomes include: (1) desert; (2) grassland (prairie, veldt, steppe, savanna); (3) tropical forests; (4) temperate deciduous forest; (5) evergreen coniferous forests (also called boreal forest or taiga); (6) tundra (arctic and alpine). Note that there are many subdivisions of these that we will not discuss.
For each terrestrial biome, know: (1) location; (2) general climate, (3) general appearance, and (4) characteristic species (plants and animals).
B. There is no sharp boundary between biomes, they grade into one another.
C. Biome type is ultimately determined by:
type and bed rock.
Note - soil is a mixture of organic materials such as partially decayed animals and plants, fecal matter (humus); inorganic materials such as minerals in various particle sizes; gases such as oxygen and carbon dioxide; and liquid (like water).
The prevailing weather conditions are determined by factors such as temperature, humidity, wind, precipitation, cloud cover.
(graph of mean annual temperature vs. precipitation).
Terrestrial biome distribution is largely influenced by temperature and precipitation. If we plot the distribution of biomes on a climograph (plot of mean annual temperature vs. mean annual precipitation) it is appararent that they sort out nicely.
There are several factors that influence climate:
Because the earth is a sphere and at an angle relative to the sun, there is unequal heating of the earth's surface. Hotter at equator than poles.
Rotation of the earth.
This is responsible for air currents (belts of easterlies and westerlies), rainfall patterns at different latitudes (i.e., dry at 30 degrees N and S; moist at 60 degrees), seasonal variations, and ocean currents.
Distribution of continental land masses and oceans
These are important in the rainshadow effect, ameliorate temperature
Presence of periodic disturbances (e.g., fire)
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Last updated: May 10, 2004 � Copyright by SG Saupe