Summary
Chapter 2-5 ecology: economy of nature summary
Summary of chapter 2-5 Ecology: economy of nature
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The greenhouse effectSolar radiation provides the vast majority of the energy that warms Earth and that
organisms use. However, solar radiation alone is not sufficient to warm the planet; gases in
the atmosphere also play a critical role.
Greenhouse gases
Greenhouse gases, which play such a major role in keeping our planet warm, compose only
a small fraction of our atmosphere. This also means that even small changes in the
concentrations of greenhouse gases can have large impacts of Earth’s temperature. The two
most prevalent greenhouse gases are water vapour and carbon dioxide. These gases have a
variety of natural sources: H2O comes from large bodies of water and the transpiration of
plants; CO2 comes from decomposition, respiration of organisms, and volcanic eruptions;
CH4 comes from anaerobic decomposition; N2O comes from wet soils and low-oxygen
regions of water bodies; and O3 comes from UV radiation breaking apart O2 molecules in
the atmosphere and causing each molecule to combine with another O2 molecule.
There is unequal heating of Earth by the sun
Differences in solar radiation are determines by the angle of the sun striking different
regions of the globe, the depth of the atmosphere that this energy passes through, and
seasonal changes in the position of Earth relative to the sun. Three factors dictate this
pattern: the distance that sunlight must pass through earth’s atmosphere, the angle at
which the suns rays and the reflectivity of Earth’s surface. When they pass through the
atmosphere, gases absorb some of the solar energy. Following the path of the rays, you can
see that the distance travelled through the atmosphere is short at the equator than at the
polls. This means that less solar energy is removed by the atmosphere before it strikes at
the Equator. The unequal heating of Earth explains the general pattern of declining
, temperatures as we move from the Equator to the poles. At the equator, the sun’s rays lose
energy to the atmosphere, solar energy is spread over a smaller area, and the low albedo of
dark-coloured forest causes much of this energy to be absorbed. near the poles, however,
the sun’s rays lose much more of their energy to the atmosphere, solar energy is spread
over a larger area, and the high albedo of the snow-covered land causes much of the solar
energy to be reflected. This helps explain why the plant hardiness zone numbers we
discussed at the beginning of this chapter generally decrease as you move to higher
latitudes.
air currents
Earth’ uneven heating helps determine atmospheric convection currents. The patterns of
circulation play a major role in the location of tropical rainforest, deserts and grasslands
throughout the world.
Properties of air
Four properties of air influence atmospheric convection currents: density, water vapour
saturation point, latent heat release, and adiabatic heating or cooling
Air density
In regard to density, when air warms, it expands and becomes less dense. As a result, when
a becomes warmer next to the surface of earth, it becomes less dense and the air above it.
This causes the warm air to rise. This is the initial step in creating conviction currents.
Water vapour saturation point
As our temperature increases, its capacity to contain water vapour– The gases form of
water– increases. Although the capacity to contain water increases at higher temperatures,
there is always a limit, known as the saturation point. The relationship between
temperature and water vapour saturation affects patterns of evaporation and precipitation
around the world. This, in combination with air currents, determines the distribution of wet
and dry environment around the world.
Latent heat release
Latent heat release is significant because whenever water vapour exceeds its saturation
point, condensation will cause a release of heat that warms the surrounding air.
Adiabatic heating and cooling
The final factor to consider in regard to convection currents is the movement of air in
response to changes in pressure. Near the surface of earth, the gravitational pull on all
molecules in the atmosphere brings many of the molecules close to Earth’s surface. An
increase in the number of molecules causes an increase in air pressure near earth surface.
As one moves higher into the atmosphere, the air contains fewer total molecules, which
lowers the air pressure. As a result, when air between the surface of Earth and the
atmosphere, it experiences changes in pressure. air pressure is related to the frequency of
collisions among air molecules, which also influences temperature. Lower rate of collision
causes lower temperatures.
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