Ecosystems: Change & Challenge

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AQA A2 Geography

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Alex Buckingham 1
Ecosystems: Change and Challenge
Ecosystems: Change and Challenge
The Nature of Ecosystems
An Ecosystem is defined as `a living system of plants and animals which interacts with its environment. They can be looked at
on any scale and a biome is an example of an ecosystem on a global scale. These run in strips across continents very much
dependent on the climate of the area.
Ecosystems are made up of both biotic (living) and abiotic (dead) organisms which include:
o Trees
o Animals
o Micro organisms
o Decomposers
o Soil
o Climate
o Relief
o Rocks
Energy Flows, Trophic Levels, Food Chains and Webs
Energy flows flow through an ecosystem from one stage to another. Trophic levels are different stages in the hierarchy of an
ecosystem and show the feeding levels. Initially, photosynthesis takes place which allows the plants to produce glucose
thereby making their own food. The next trophic level feeds on the producers which gives them the name herbivores.
However they do not get all of the energy that is available but only 10% of it, 90% is used. Therefore there is a smaller number
of species as the trophic level gets higher.
The movement of energy up the trophic levels shows the food chain as each trophic level occupies a different position.
However food chains, in reality, are often more complicated than this. Some species can occupy more than one position in every
food web ­ may be prey to more than one animal etc.
Nutrient cycles in an ecosystem take place between the biotic and abiotic components of the ecosystem. This can be shown
through the Gersmehl diagram.
Nutrients have three stores ­ the soil, litter and biomass.
Nutrients are transferred through the three stores through fall of dead tissue, absorption through plant roots and
decomposition etc.
Inputs of nutrients include precipitation and the weathering of parent rock
Outputs include loss from runoff and leaching
Ecosystems in the British Isles Over Time
Succession and Climax
Time is an important factor in the development of ecosystems as there are certain number of seres that appear and grow over
time. The complete sequence of seres is known as a primary plant succession ­ or a prisere. The pioneer plants are the first
stage in succession, hardy plants including mosses and lichens. They are able to adapt to survive in tough conditions and then
create a `better' surface allowing the next sere to develop. The pioneer species is succeeded by a more complex range of
species as it develops, this is because conditions improve, a more humus and nutrient rich base develops. Eventually (although
often prevented) the climatic climax species develops. At this point the plants and animals within the ecosystem become a
stable community in balance with their environment.
Temperate Deciduous Woodland
Temperate deciduous woodland is a high energy biome which has a relatively high productivity. It is found in mid latitudes on
the borders of continents where there is adequate moisture.

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Ecosystems: Change and Challenge
Temperature ranges from 5 ­ 17 in Winter and Summer
500-2,000mm of rain per year, varies seasonally
Low pressure systems
Westerly winds
Broadleaved deciduous trees are the dominant species ­ shed their leaves
There is a series of seres evident with grass, herbs, shrubs trees etc.
Growth varies seasonally
Brown Earth soil 1.…read more

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Ecosystems: Change and Challenge
Great animal migrations occur meaning that biodiversity drops at certain times
40% of the land in Tanzania has been designated as a National Park to help conserve biodiversity
African Elephant, Black Rhino, Zebra and Cheetah are endangered
Ecosystems on a Local Scale
This process has meant that ecosystems in urban areas are much more important that they used to be. Over the last 200 years
urbanisation has built up urban areas.…read more

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Ecosystems: Change and Challenge
Ecosystems Issues on a Global Scale
Human activity can have good and bad impacts
Biodiversity is the number of different species within an ecosystem. the more the better as a general rule. as a whole the
planet has huge biodiversity which has decreased dramatically over the last 200 years. Sustainability means that the future
generations can enjoy the resources of today as much as we do.…read more

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Ecosystems: Change and Challenge
Variety of different species would please bird watchers etc.
Some parts are managed and some are left to nature meaning that there is a range of different habitats
Educational values with nature trails.
Central Amazon Conservation Complex
The destruction of the Amazon rainforest has been particularly harmful to the biodiversity there. To prevent this some places
have been protected by law meaning that they are undisturbed.…read more

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Ecosystems: Change and Challenge
Community Wildlife Management Areas have been put in place around the Serengeti to encourage the locals to make
decisions about the wildlife. This is hoped to reduce poaching. The nomads way of life is being threatened as the population
grows rapidly there is increasing pressure for resources including land.…read more


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