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Ecosystems are the result of interactions between abiotic
and biotic
components. Ecosystems vary in size-from as small as a puddle
or as large as the Earth itself. Within each ecosystem there are
habitats, which also vary in size.
Scientists have mapped 867 land-based distinct ecoregions around
the planet, which can be seen by visiting the National Geographic
Terrestrial
Ecoregions Map.
Ecological communities are grouped into biomes.
Biomes can be terrestrial or aquatic, and are classified as follows:
Terrestrial Biomes
- Forest
- Tropical Forests occur within 23.5 degrees north
or south of the equator. Ranging from the hot, moist jungles
of the rain forests to the dry forests and savannas, they
provide habitat for millions of species of plants and animals.
One of the major characteristics of tropical forests is their
distinct seasonality: winter is absent, and only two seasons
are present (rainy and dry). The length of daylight is 12
hours and varies little.
Berkeley
- The World's Biomes:Forests
USDA
Forest Service
- Temperate deciduous forests are located in the mid-latitudes
(between the polar regions and the tropics.) These regions
are exposed to all the world's air masses, and have four distinct
seasons, with cold winters and hot, reasonably wet summers.
The average annual temperature is about 10°C.
During the autumn, trees change colour and then lose their
leaves, in preparation for their dormant period through
the winter. They flower, grow and produce fruit during the
spring and summer growing season.
NASA
Earth Observatory
Radford
University:Biomes
-
Taiga. Between the tundra to the north and the deciduous
forest to the south lies the large area of coniferous  forest
(taiga.) The northern boreal forest is found in 50°
to 60°N latitudes. The temperate coniferous forest grows
in lower latitudes of North America, Europe, and Asia, in
the high elevations of mountains.
Coniferous forests consist mostly of conifers, trees that
grow needles instead of leaves, and cones instead of flowers.
Conifers tend to be evergreen, that is, they bear needles
all year long. These adaptations help conifers survive in
areas that are very cold or dry.
NASA
Earth Observatory
Radford:Biomes
Bishop's
College: Biomes
- Deserts. Deserts are characterised by extrmely
low rainfall (less than 300 mm per year) Daytime temperature averages
38°C while in some deserts
 it
can get down to -4°C at night. The temperature also varies
greatly depending on the location of the desert.
Since desert conditions are so severe, the plants that live
there need to have adaptations to compensate for the lack of
water (cacti store water in their stems, for example. Others
store water in large root systems.) Some desert plant species
have a short life cycle of a few weeks that lasts only during
periods of rain.
Berkeley:Biomes
- Grasslands are generally open and continuous,
fairly flat areas of grass. They are often located between temperate
forests at high latitudes and deserts at subtropical latitudes.
In the tropics, grasslands are called savannas.
NASA
Earth Observatory
Berkeley:Biomes
- Shrublands include regions such as chaparral,
woodland and savanna. Shrublands are the areas that are located
in west coastal regions between 30° and 40° North and
South latitude. Some of the places would include southern California,
Chile, Mexico, areas surrounding the Mediterranean Sea, and southwest
parts of Africa and Australia. These regions are usually found
surrounding deserts and grasslands.
Shrublands usually get more rain than deserts and grasslands
but less than forested areas.
NASA
Earth Observatory
- Tundra is the coldest of the biomes. It also receives
low amounts of precipitation, making the
tundra similar to a desert. Tundra is found in the regions just
below the ice caps of the Arctic, extending across North America,
to Europe, and Siberia in Asia. Much of Alaska and about half
of Canada are in the tundra biome. Tundra is also found at the
tops of very high mountains elsewhere in the world. Temperatures
are frequently extremely cold, but can get warm in the summers.
Tundra is defined as an area that contains permafrost - permanently
frozen ground. Winter mean temperatures can be well below freezing,
since very little to no sunshine is received in this area during
the winter months.
NASA
Earth Observatory
Berkeley:Biomes
NASA
Classroom of the Future
Aquatic Biomes
The aquatic biomes can be broken down into two basic regions,
freshwater (i.e, ponds and rivers) and marine (i.e, oceans and
estuaries).
In a very real sense, the marine biome is integral to all of
the five major biome divisions (Forest, Desert, Grassland, Tundra,
Aquatic) in that it  covers
three quarters of the earth, and wetlands are included in all
other biomes except extreme desert. Aquatic regions house numerous
species of plants and animals, both large and small. In fact,
this is where life began billions of years ago when amino acids
first started to come together.
Without water, most life forms would be unable to sustain themselves
and the Earth would be a barren, desert-like place. Although water
temperatures can vary widely, aquatic areas tend to be more humid
and the air temperature on the cooler side.
Berkeley
Biomes
Napier
University:Life on Earth - Biomes
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