BIO120H1 Study Guide - Exponential Growth, River Ecosystem, Permafrost

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12 Apr 2012

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Chapter 3 Summary:
10. Although CO2 is scarce in the atmosphere, it is more
abundant in aquatic systems, where it dissolves to form
bicarbonate ions. The availability of carbon in aquatic
systems is limited, however, by the rate of diffusion of
CO2 gas and bicarbonate ions through water, especially
through the boundary layers of still water that form at the
surfaces of plants and algae.
11. Oxygen is abundant in the atmosphere, but is relatively
scarce in water, where its solubility and rate of diffusion
are low. Oxygen may be depleted by respiration
(producing anoxic conditions), especially in environments
where it cannot be replenished by photosynthesis.
12. The rates of most physiological processes increase by
a factor of 2 to 4 for each 10°C increase in temperature
within the physiological range. This factor is known as the
Q10 of a process. The generality of this temperature effect
has been captured in the metabolic theory of ecology.
13. Higher temperatures generally accelerate physiological
processes, but can also cause proteins and other biological
molecules to unfold and lose their structure and
function. Some extremophiles can tolerate very high temperatures
because their proteins are chemically designed
to generate strong forces of attraction to hold molecules
14. Organisms in cold environments withstand freezing
temperatures by lowering the freezing point of their body
fluids with glycerol or glycoproteins, or by supercooling
their body fluids.
15. Most organisms function best within a narrow range
of environmental conditions. This optimum is determined
by characteristics, such as the structure, function, and
quantity of its enzymes, that influence the organism’s ability
to function under various conditions.
16. The temperature of an organism is closely tied to its
thermal environment, which influences gains and losses
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of heat through radiation, conduction, convection, and
evaporation. Together with metabolically produced heat,
these factors make up the heat budget of the organism.
17. Maintenance of constant internal conditions, called
homeostasis, depends on negative feedback mechanisms.
Organisms sense changes in their internal environment
and respond in such a manner as to return those conditions
to a set point.
18. Homeostasis requires energy when a gradient between
internal and external conditions must be maintained. For
example, endotherms must generate heat metabolically to
balance loss of heat to their cooler surroundings.
Chapter 4 Summary:
11. Global climatic patterns result from differential input
of solar radiation at different latitudes and from the redistribution
of heat energy by winds and ocean currents.
12. Periodic climatic cycles follow astronomical cycles,
including the rotation of the earth on its axis (daily), revolution
of the moon around the earth (roughly monthly),
and revolution of the earth around the sun (annually).
Variations in atmospheric and ocean circulation occur at
longer periods of tens to many thousands of years.
13. Solar radiation and winds are responsible for the
evaporation and circulation of water vapor in the atmosphere
and thus for global and seasonal patterns of precipitation.
The equilibrium vapor pressure of water increases
with temperature.
14. Air is warmed and rises at the equator, where solar
radiation is most intense, then cools and sinks at about
30° north and south, forming Hadley cells over the tropics.
The sinking air of the Hadley cells drives secondary
cells, called Ferrel cells, over the temperate zones, which
in turn drive Polar cells at higher latitudes. This global pattern
is known as Hadley circulation.
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15. Variation in marine conditions is determined on a
global scale by wind-driven ocean currents. These currents
redistribute heat over the surface of the earth and
greatly affect climates on land. Upwelling currents, caused
by winds, ocean basin topography, and variations in water
density related to temperature and salinity, bring cold,
nutrient-rich water to the surface in some areas.
16. Thermohaline circulation, caused by differences in
the density of water masses, moves water masses at great
depth between ocean basins. This circulation pattern can
be interrupted by climate changes that melt glacial or sea
ice, changing the salinity of surface waters.
7. Seasonality in terrestrial environments is caused by
the tilt of the earth’s axis of rotation in relation to the sun.
In the tropics, the northward and southward movement
of the intertropical convergence, which follows the movement of the solar equator, results in
pronounced rainy and
dry seasons. At higher latitudes, the seasons are expressed
primarily as annual cycles of temperature.
8. Seasonal warming and cooling influence the characteristics
of lakes in the temperate zone that experience
surface freezing in winter. During summer, such lakes are
stratified, with a warm surface layer (epilimnion) separated
from a cold bottom layer (hypolimnion) by a sharp
thermocline. In spring and fall, the temperature profile
becomes more uniform, allowing vertical mixing.
9. Irregular and unpredictable variations in climate, such
as El NiñoSouthern Oscillation events, may cause major
changes in temperature and precipitation and disrupt biological
communities on a global scale.
10. Topography and geology superimpose local variation
in environmental conditions on more general climatic patterns.
Mountains intercept rainfall, creating arid rain shadows
on their leeward sides. At high latitudes, north- and
south-facing slopes receive differing amounts of sunlight.
Because temperature decreases about 6°C for every 1,000
m of elevation, conditions at higher elevations resemble
conditions at higher latitudes.
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