Transcript Biomes of the World - MDC Faculty Home Pages

Biomes
How can I make sense of all this
diversity?
• The world’s major ecosystems are called
biomes. Each of these may have a number of
different communities within it.
• Many aquatic biomes haven’t been as well
studied as the terrestrial biomes because of their
inaccessibility. It has been said that we know
more about the moon, than we do about the
depths of the oceans.
• On the following pages you will see some
examples of the major biomes of the planet
earth.
Oceans are the largest biome, covering more
than 70% of the Earth’s surface
• Marine (salt-water) communities are many and varied. They range
from the intertidal zone, which is covered and uncovered with each
cycle of the tides, to benthic communities more than 6 miles below
the surface.
Zones in the aquatic marine biome
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The intertidal zone is the area
between the high and low tide
marks. It can consist of rocky
shores or sandy beaches.
Seaward, the continental shelf
extends to about 100-200 meters
depth. This is a very productive
area due to the runoff of nutrients
from the lands. The world’s great
fisheries are located over the
continental shelf. It is also very
vulnerable to man’s impact.
The seafloor is the benthic zone
and is home to many attached and
burrowing organisms.
The open ocean is the pelagic
zone. It supports communities of
Zones in the aquatic marine biome (CONT.)
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The pelagic zone also contains populations of organisms that have weak
powers of locomotion and drift with the current. Phytoplankton are plantlike drifters (mostly algae and cyanobacteria), while the zooplankton are
small drifting animals such as copepods and krill that feed on the
phytoplankton.
Vertically, the open ocean is divided into the photic zone and the aphotic
zone. The photic zone is usually with in the upper 100 meters of the water
colun. Here, there is enough light for photosynthesis to occur. The aphotic
zone is dark with little or no light penetrating from the surface.
Estuaries are where freshwater merges with the sea. These are the bays
and the mouth of rivers that empty into the ocean. These can be areas of
very high productivity.
Mudflats and salt marshes are the coastal wetlands that border the coast.
Freshwater Biomes
• Freshwater biomes consist of
rivers, lakes, streams, ponds,
springs, and wetlands.
• The habitat to the right is the
Wakulla River which originates
at Wakulla Springs, a large
freshwater spring in North
Florida.
• Temperature, light, and
nutrients have profound
effects on fresh-water
habitats. Excess nutrient
runoff can lead to a rapid
aging to a lake, a process
known as eutrophication.
Lakes
Terrestrial Biomes
Tropical Forests
• Tropical forests occur in areas
near the equator where the
temperature and day length
are constant throughout the
year.
• Soils in tropical forest are
nutrient poor, and most of the
nutrients are contained in the
existing vegetation.
• Species diversity is very high.
• Tropical rain forest have
abundant rainfall (200-400
cm/yr)
Tropical Rain Forests
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A mature tropical forest will consist of several canopy layers, each with its
own plants and animal communities. Epiphytes, such as orchids and
bromeliads are common, and woody vines may reach several hundred feet
into the upper parts of the canopy. (think of Tarzan swinging on the vines)
Savannas
• Savannas are dominated by grasses and scattered trees. They
exist were temperature are warm all year. Fires and the grazing of
large herbivorous keep trees from invading these grassy areas.
The Serengeti plains of Africa are a good example of the Savanna
biome.
Deserts
• Dryness characterizes the
desert biome. Rainfall is less
than 30 cm./yr., and can be
very irregular. Some desert
have almost no rainfall for
years or decades at a time.
• Plant and animal life is
adapted to conserve water.
• The cacti seen in the figure at
the right have a thick outer
surface and no leaves. This
helps control water loss.
• Desert animals are often
burrowers and are active at
night when temperatures are
cooler.
Chaparrel
• This biome is found in
mid-latitude coastal
regions. The climate has
mild, wet winters and hot
dry summers. The
vegetation is adapted to
periodic fires, and some
plants have seed that
must be exposed to fire
before they germinate.
Temperate grasslands
• Grasslands such as these once covered much of the central U.S.
And provided food for millions of bison. This habitat provided
space for colonies of prairie dogs. Today little remains of our
temperate grasslands. Most are now wheat and corn fields,
however, Central Asia still has vast areas of grasslands.
Temperate Broadleaf Forest
Temperate Broadleaf Forest
• These forests contain a diverse assemblage of deciduous trees,
such as oak, maple and poplar.
• Most of the eastern U.S. was (is) covered by this type of forest.
• In the fall of the year these tree drop their leaves, and the color
changes that accompany this process is what many persons travel
to New England and North Carolina to see.
• The soils are rich in both organic and inorganic material. This has
made these soils prized farm landland.
• Although little virgin temperate forest remains, this type of forest
does regenerate over time and secondary growth forests can be
seen in much of the eastern U.S.
Coniferous Forests
Coniferous Forests
• These forests lie to the north of the deciduous broadleaf forests. In this hemisphere they can be seen in
Canada and the Pacific Northwest of the United States.
• This biome is dominated by evergreen conifers, such as
hemlock, Douglas fir, and hemlock.
• Coniferous forests are also called tiaga.
• Tiaga is characterized by long, cold winters, and short
wet summers.
• This is the land of moose, elk, bears, wolves, and
grouse.
Tundra
• The last of our terrestrial biomes is tundra. There are no trees.
Instead the vegetation is dominated by mosses, lichens, and
dwarfed shrubs. The subsoil remains frozen all year (permafrost).
Current studies indicate that global warming may be having an
effect on this biome and that permafrost in some areas is melting.
Exaples of tundra vegetation can also be seen at high elevations,
above the tree line.