BIOMES OF THE WORLD
The Earth is divided into distinct climate zones that are created by global circulation patterns of wind and the oceans. The tropics are the warmest,
wettest regions of the globe, while high-pressure weather zones create dry biomes at about 30° latitude north and south. Temperatures and
precipitation are lowest at the poles. These conditions create biomes—broad geographic zones whose plants and animals are adapted to different
climate patterns. Since temperature and precipitation vary by latitude, Earth's major terrestrial biomes are broad zones that stretch around the globe
(Fig. 2). Each biome contains many ecosystems (smaller communities) made up of organisms adapted for life in their specific settings.
Another way to visualize major land biomes is to compare them based on their average temperature ranges and rainfall levels, which shows how
these variables combine to create a range of climates (Fig. 3).
Terrestrial Biomes
Terrestrial biomes are biomes found “on land” . Different sources will have slightly different names for biomes. Your book lists eight terrestrial biomes. It DOES NOT talk about
Antarctica or the North Pole. Additionally, it divides the
grasslands into 3 distinct biomes (not all sources make this
distinction).
Biomes are differentiated from each other based on
THREE criteria
1,Temperature range (with this, you need to consider the
amount of direct sun, and for how many months this
occurs)
2.Average precipitation (and in some cases, the seasons in
which the precipitation falls)
3.Vegetation (basically the major type or types of plants
that grow in this area)
The geography of the area (mountains, canyons craters,
hills or flat ground) can also make a difference
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Land biomes are typically named for their characteristic types of vegetation, which in turn influence what kinds of animals will live there.
Soil characteristics also vary from one biome to another, depending on local climate and geology. Table 1
compares some key characteristics of three of the forest biomes.
Table 1. Forest biomes. Source: UC-Berkeley Museum of Paleontology, "The World's Biomes,"
http://www.ucmp.berkeley.edu/glossary/gloss5/biome/.
Forest type
Temperature
Precipitation
Soil
Flora
Tropical
20-25°C
>200 cm/yr
Diverse (up to 100
Acidic, low in nutrients
species/km2)
Temperate
-30 to 30°C
75-150 cm/yr
Fertile, high in nutrients 3-4 tree species/km2
40-100 cm/year, mostly
snow
Thin, low in nutrients,
acidic
Boreal (taiga) Very low
Evergreens
Since biomes represent consistent sets of conditions for life, each biome will support similar kinds of organisms
wherever they exist, although the species in the communities in different places may have evolved independently.
For example, large areas of Africa, Australia, South America, and India are covered by savannas (grasslands with
scattered trees). The various grasses, shrubs, and trees that grow on savannas all are generally adapted to hot
climates with distinct rainy and dry seasons and periodic fires, although they may also have characteristics that
make them well-suited to specific conditions in the areas where they appear.
Species are not uniformly spread among Earth's biomes. Tropical areas generally have more plant and animal biodiversity than high latitudes, measured in species
richness (the total number of species present).This pattern, known as the latitudinal biodiversity gradient, exists in marine, freshwater, and terrestrial ecosystems in both
hemispheres.
Why is biodiversity distributed in this way? Ecologists have proposed a number of explanations:
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Higher productivity in the tropics allows for more species;
The tropics were not severely affected by glaciation and thus have had more time for species to develop and adapt;
Environments are more stable and predictable in the tropics, with fairly constant temperatures and rainfall levels year-round;
More predators and pathogens limit competition in the tropics, which allows more species to coexist; and
Disturbances occur in the tropics at frequencies that promote high successional diversity.
Of these hypotheses, evidence is strongest for the proposition that a stable, predictable environment over time tends to produce larger numbers of species. For example, both
tropical ecosystems on land and deep sea marine ecosystems—which are subject to much less physical fluctuation than other marine ecosystems, such as estuaries—have high
species diversity. Predators that seek out specific target species may also play a role in maintaining species richness in the tropics
YOUR TASK: Look at the Biome Table (it takes up two pages). Color in the biomes map, using a key. Use the diagrams at the beginning of the Biomes Questions handout to help you to
determine “where” to color, as well as the descriptions of the locations. Answer all questions on the question sheet
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Biome
Temperature Range
Tundra
-35 Winter to
50 F in summer
Average
YEARLY
preciptation
6-10 inches
Soil
Permafrost
Soil is only a few
inches deep.
Low in nutrients
and minerals (no
decomposition
Major plant
types that grow
in this area
Virtually no
trees, small
plants only
Unique characteristics
Biodiversity
Permafrost
Very strong winds
LOW
Few plant species (Very
few species (< 2000)
Low evaporation
Carbon sink (dead plants and animals don’t
decompose
Located only in Northern Hemisphere (southern is
too cold)
Taiga
Temperate
(deciduous)
forest
Rainforest
(Tropical
Forests)
Average
-30 F Winter to
55 (summer)
Hot and humid
(summer)
Cold (winter)
Average
40F – 77F
68 F – 93 F
12-33 inches
Low in nutrients,
high acidity due
to acidity in pine
needles
Mostly conifers,
some lichens and
mosses (due to
cold winters)
Animals are mainly predators (not much vegetation
to eat)
Birds come seasonally (for the insects and to
breed)
Only 48 land species
Diversity is difficult to
“renew” if damaged due
to slow growth
Fairly low. Most species
hibernate or migrate in
the winter
Only in the northern hemisphere (not enough
landmass in the southern hemisphere to create a
“taiga climate”.
30-60 inches
(75-150 cm)
50 -260 inches
(generally >
100 inches.
Constant high
humidity
Very fertile,
enriched with
decaying litter
(detritus)
Nutrient poor
soil due to a
short nutrient
cycle
(decomposition
is very rapid and
nutrients are
taken up
immediately.
3-4 tree species
per kilometer
Largest terrestrial biome
Four seasons, trees lose leaves in winter.
Almost all of these forests are located beside the
ocean (the ocean the wind play a large role in
climate change in this biome.
Trees greater
than 100 ft with
only a top
canopy, smooth
thin bark
Some animals hibernate in winter, others are
active or migrate
Less than 6% of earth’s surface but contain 50% of
ALL species Produce 40% of all oxygen
Three plant layers, canopy, understory (bottom)
lower canopy (smaller trees)
Understory plants have HUGE leaves to make up
for lack of light
Fairly diverse, some
areas are more
biodiverse than
others.(microbiomes)
High diversity of plants,
No dominant plant
(although canopy trees
in general are very
prevalent.
Many tree dwellers
predominant animal life
is insects
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Biome
Temperature Range
Temperate
grassland
average
20 F winter and
70 F Summer)
Savanna
AKA Tropical
grassland
Chapparal
(Grassland)
68 – 86 F
Basically warm all
year round, but
several degrees
cooler in the winter
30 – 100 F
Very hot and dry in
summer
Mild and “moist”
(not really rainy) in
the winter)
Desert
8 F – 119 F
Average
YEARLY
precipitation
10-30 inches
15-25 inches
Long dry
season
(winter)
Soil
Major plant
types that grow
in this area
Upper layers of
soil moist, and
rich while lower
layers dry  lack
of trees
Well drained
with only a thin
layer of humus
(organic
material)
Grasses, few
trees
1-10 inches
(depends on
the desert
Rocky and thin,
low in nutrients
(organic
material)
Sandy, almost no
nutrients
Biodiversity
The upper layer of soil is moist, but the lower layers
are dry making it difficult for trees to grow here.
A few large species (mostly herbivores)
Many have been turned into farmland
Low in diversity as
compared to Pampas
grasslands (fauna)
Carnivores (lions, leopards, cheetah ,jackals)
specialize in prey to decrease competition.
Plants have adaptations such as tap roots, thick
bark, leaves that drop or the ability to store water
due to long periods of “no water”
A wet
summer
season
(monsoon)
10-17 inches
almost all in
the winter
Unique characteristics
Fairly small
plants with hard
leaves (waxy
coating) or hairy
leaves (collect
moisture)
Blue oak (30 ft
tree)
And olive trees
are the largest
Small shrubs,
widely spaced
Herbivores can be grazers or leaf eaters. Highly
specialized so that competition is lowered. Wander
with the food supply
Plants must have waxy coat or hairy leaves to
survive the hot summers
Wide variety of flowers
and grasses
Some Savanna areas are
diverse, others are not.
Depends on the amount
of rain, the surrounding
biomes.
Overgrazing by
domesticated flocks is
causing deserts to
form.
Low compared to
forests,
Animals are highly territorial.
Hot and Dry deserts have only nocturnal animals
Cold and dry deserts will have antelope, jack rabbits
etc (has more rain and more plant life.
Low, due to lack of
nutrients.
Many plant adaptations for water storage including
Roots and leaves.
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