Page 5 - The World About Us

Bluebells
1.1.1
1.1.1

What and where are the global biomes?

A biome is a very large scale
ecosystem. There are eight major
terrestrial (land) biomes. The loca on
of these biomes is determined by the
climate of the region. This in turn is
determined by la tude, atmospheric
circula on, distance from the sea and
al tude.
The distribu on of terrestrial The Equator MAP
biomes is dependent on the availabil-
ity of water and the availability of
sunlight for photosynthesis. This last
factor is determined by la tude: the
biome’s distance from the Equator.
Areas closer to the Equator receive Hot deserts Grasslands Tundra
more solar radia on than those nearer Tropical rainforest Temperate woodlands Alpine and high mountains
the Poles. Land at the Equator
Mediterranean Temperate rainforest Boreal coniferous forest
receives three mes more solar
insola on than land at la tudes of fig.3 Simplified location map of terrestrial biomes.
60 . It is this solar insola on which
provides the energy for nearly every without which plants may wilt and die. descending air (high pressure).
ecosystem on the planet. The availability of water is deter- Low pressure zones are associated
The greater the availability of solar mined by atmospheric circula on and with rainfall, while high pressure is
energy the greater the poten al for the distance from the sea. The general associated with clear skies. It is this
photosynthesis by plants. However, for circula on pa erns of the atmosphere factor which is crucial in determining
photosynthesis to take place there have helped create dis nct clima c whether a biome has the available
also must be sufficient water present, zones of rising air (low pressure) and water for high rates of photosynthesis.

KEY TERMS

Ecosystem: the living and non-
living elements of an
environment linked together
fig.4 Hoh Forest, Washington, USA. through flows of energy and
nutrients.
The produc vity of ecosystems Food chain: the links in a food
web from the primary
The produc vity of any ecosystem is a trees is then passed up through the producers, through various
measure of how efficient that system is in trophic pyramid to other members of the consumers, to the apex
conver ng solar energy, water and other ecosystem as food. predators.
nutrients into living ma er. This is referred
to as the Net Primary Produc vity (NPP) of fig.5 NET PRIMARY PRODUCTIVITY. Food web: a system of
an ecosystem. NPP is measured by the Tropical rainforest 2,200 (g/m²/yr) interlocking and interdependent
average grammes of biomass produced Temperate forest 1,200 (g/m²/yr) food chains in an ecosystem.
each year in every square metre of the Tropical grasslands 900 (g/m²/yr) Trophic pyramid: the transfer of
ecosystem (g/m²/yr). It can also be Temperate grasslands 600 (g/m²/yr) energy and nutrients up through
measured in grammes of carbon con- Tundra 120 (g/m²/yr) a food web from producers to
verted into biomass each year (gC/m²/yr). Hot deserts 90 (g/m²/yr) apex predators and down
Under the right condi ons trees are Extreme ice desert 3 (g/m²/yr) through detrivores and
the most effec ve group of plants at (figures are an es mated mean) decomposers.
producing biomass. The biomass of the

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Ecosystems consist of interdependent components.