 |
Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe/ |
|
Concepts of Biology (BIOL116) - Dr. S.G. Saupe; Biology Department, College of St. Benedict/St. John's University, Collegeville, MN 56321; ssaupe@csbsju.edu; http://www.employees.csbsju.edu/ssaupe/ |
I. Definitions/Introduction.
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.
The biosphere
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
ideas.
II.
Interactions.
A.
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.
B.
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.
Organisms
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
surrounding earth).
III.
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.
A.
General.
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:
Soil
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).
Climate.
The prevailing weather conditions are determined by
factors such as temperature, humidity, wind, precipitation, cloud
cover.
Climograph
(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: