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BIOA02- Chapter_52.docx

Biological Sciences
Course Code
Mary Olaveson

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Biology: Chapter 52 Notes
Ecology: the scientific study of the rich and various interactions between organisms and
their environment
Communities: Systems embracing all organisms living in a certain area
Ecosphere: System embracing all organisms living in a certain area plus their physical
Biosphere: System embracing all regions of the planet where organisms live
Abiotic (physical/chemical factors)
Environment: Biotic (living organisms)
Climate: The average atmospheric condition (wind, temperature, precipitation) found in
all regions over a period of time
‘Weather’ is the short term conditions; climate is what you expect whereas weather is what you get
The temperature of a region depends on the amount of solar energy it receives based on the angle of
On average, temperature decreases 0.4® for every degree of latitude (1®=110km)
Also, temperature decreases with elevation. When air parcels rise, it expands, loses pressure and
temperature, and releases moisture. When it descends, it compresses, gains pressure and temperature,
and takes up moisture
This produces inter-tropical convergence zones: air parcels rise in tropical areas (due to more
concentrated solar energy) which causes expansion and the inability to hold moisture (therefore a lot of
rain). This air that rises is replaced by air that flows to the equator from the north and south (i.e.
convection cells)
The inter-tropical convergence zone shifts lattitdinally with seasons (based on earth’s rotation around
the sun) which causes rainy and dry seasons to be predicted
Many deserts are located where the air that once rose from the equator, and lost its moisture descends
to replace the new air that rises at the equator
At about 60® north and south of the equator, air rises again and either moves towards or away from the
Because the Earth’s rotation is faster at the equator than at the poles, the winds that go towards the
equator end up being slower than the earth beneath it and turn into the northeast/southeast trade
winds (jet stream). Air masses moving towards the poles become westerly winds.

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When these winds hit mountains, they produce rain shadows. The side of the mountain facing the winds
forms clouds and release moisture because as the winds climb the mountain, it cools, expands, and
releases moisture in form of rain and snow. Then the air descends, warms, and picks up moisture and
produces a dry side.
These movements are what drive currents, oceanic water patterns.
Dispersal: the movement of organisms from their birth place to somewhere else
Migration: A change in environments of an organism due to the repeated seasonal changes
Some environments are affected by the organisms which they affect (i.e. Earth’s soil, oxygen
atmosphere etc). Others are uninfluenced by the organisms which they affect (i.e. storms, heat waves,
cold fronts etc.)
Ecosystems can be classified as Biomes or Biogeography regions depending on what parts of the system
they intend to study.
Biome: A terrestrial environment defined by the growth form of its plants (i.e. forests,
grasslands, desserts, tundra etc.)
Largely influenced by annual patterns of temperature and rainfall
Species richness: Number of species in a biome.
Where one biome starts and another ends is very arbitrary; usually one slowly shifts into another rather
than a very sharp, distinctive change
Very few animal/plant species (more in tropical tundra than arctic tundra)
Found in arctic and high levels of elevation of mountain at all latitudes
The vegetation in arctic tundra is underlain by permafrost (soil whose water is permanently
Also, arctic tundra is very wet because the water cannot drain down through the permafrost.
Animals in tundra arctic usually only migrate there during the summer or are dormant for all
other periods
Tropical tundra is not underlain by permafrost therefore photosynthesis can occur (although
Boreal and Temperate Evergreen Forests
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