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10 0 10 20 30
0
Annual precipitation (cm)
0
100
200
300
400
Average temperature (°C)
Tropical
rain
forest
Temperate
rain forest
Temperate
forest
Tropical
seasonal
forest
Tropical
savanna
Desert
Tundra
Boreal
forest
Woodland
Grassland
Shrubland
Annual Precipitation v.
Temperature for Various Biomes
Latitude
Connection
EARTH SCIENCE
The distance
of any point on the surface of Earth north or
south from the equator is
latitude.
Latitudes
range from 0° at the equator to 90° at the poles.
Light from the Sun strikes Earth more directly
at the equator than at the poles, as illustrated in
Figure 4
on the previous page. As a result,
Earth’s surface is heated differently in different
areas. Ecologists refer to these areas as “zones.”
Polar zones extend to about 66° from each pole,
while tropical zones extend about 23° north and
south of the equator. Temperate zones are
found between the polar and tropical zones.
Climate
The average weather conditions in an area,
including temperature and precipitation,
describe the area’s
climate.
An area’s latitude
has a large effect on its climate. If latitude were
the only abiotic factor involved in climate,
biomes would be spread in equal bands encir-
cling Earth. However, other factors such as
elevation, continental landmasses, proximity to
mountains, and ocean currents also affect
climate.
Recall that a biome is a large group of ecosys-
tems that share the same climate and have
similar types of communities. It is a group of
plant and animal communities that have
adapted to a region’s climate and other abiotic
factors.
The graph in
Figure 5
shows how temperature
and precipitation influence the communities
that develop in an area, and help to define the
various biomes. Note that there is considerable
variation in temperature and precipitation in
most of the biomes.
There can be more than one ecosystem in a
biome. A biome’s ecosystems occur over a large
area and have similar plant communities. Even
a small difference in temperature or precipita-
tion can affect the composition of a biome.
Refer to
Figure 6
on the next page to learn how
Earth’s ocean currents and prevailing winds
affect climate. Also illustrated in
Figure 6
are
two ways humans might be affecting climate—
through the hole in the ozone layer and
through global warming. Global warming is in
part a result of the greenhouse effect.
Major Land Biomes
Biomes are classified primarily according to the
characteristics of their plants. Biomes also are
characterized by abiotic climate characteristics
such as temperature, precipitation, the amount
of sunlight, and the amount and type of wind.
The plants and abiotic characteristics in a
biome influence the types of animals that live
there. This section describes each of the major
land biomes.
Get It?
Explain
the difference between weather
and climate.
Figure 5
Temperature and precipitation are two major
factors that influence the kind of vegetation that can exist
in an area.
Analyze
Which biome would you expect in an area that
receives 200 cm of precipitation annually if the average
annual temperature is 10°C?
Lesson 2 • Terrestrial Biomes
55