Ecosystems

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  • Created by: mbull
  • Created on: 01-04-18 15:11

What is an ecosystem?

Ecosystem - a unit that includes all the biotic and the abiotic parts in an area. 

  • There are often complex interrelationships (links) between the living and the non-living components of an ecosystem. 

Biotic components - the living features of an ecosystems such as plants and fish.

Abiotic components - the non-living features environmental factors such as climate (temperature and rainfall), soil, water temperature and light. 

Ecosystems can be identified at different scales:

  • A local small-scale ecosystem can be a pond, hedgerow or woodland. 
  • A global - scale ecosystem can be a tropical rainforest or deciduous woodland. 

Global ecosystems = biomes. 

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Biotic parts of an ecosystem

The organisms in ecosystems can be classed as:

  • Producers - organisms that uses sunlight energy to produce food, e.g, plants and bushes.
  • Consumers - organisms that gets its energy by eating other organisms, it eats other producers or other consumers.E.g, insects.
  • Decomposers - an organism that gets its energy by breaking down dead material, e.g, bacteria and fungi.
  • Food chain - shows what eats what.
  • Food web - shows lots of food chains and how they overlap.

Nutrient cycling - 

  • When dead material is decomposed, nutrients are released into the soil.
  • The nutrients are taken up from the soil by plants.
  • The plants may be eaten by consumers.
  • When the plants or consumers die, the nutrients are returned to the soil.
  • The transfer of nutrients = nutrient cycling. 
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Interdependence of species

Some parts of an ecosystem depend on the others. E.g, consumers depend on producers for a source of food adn some depend on them for a habitat. 

If one part changes, it affects all the other parts that depend on it. 

Example:

  • Hot, dry summer.
  • Reduced plant growth.
  • Fewer berries for birds in the winter.
  • Numbers of sparrows and thrushes fall.
  • Fewer birds for sparrowhawks to hunt, to number of sparrowhawks fall. 
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Impacts of change on an ecosystem

Ecosystems can take thousands of years to develop their sustainable balance, yet global-scale changes and local-scale changes can upset this balance.

1. Natural changes

  • Slow natural changes have few harmful effects but rapid changes have serious impacts.
  • E.g, extreme weather events like droughts can be devastating to freshwater ponds.
  • Natural factors: drought, fire, flood, disease.

2. Changes due to human activities

  • E.g, fertilisers, woods cut down, plants removed, ponds drained.
  • Changes to human management: fish stocking, altering drainage of land, changing pH of water, altering nutrient levels of water.

Any of these could result in the collapse of a food chain.

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Global ecosystems

Large-scale ecosystems are known as global ecosystems or biomes.

Global ecosystems form broad belts across the world from west to east, paralllel to the lines of latitude. This is because the climate and characteristics of ecosystems are determined by global atmospheric circulation. 

Variations in west-to-east belts of vegetation are due to factors such as:

  • Ocean currents.
  • Winds.
  • The distribution of land and sea.

These factors produce small variations in temperature and moisture which in turn affect the ecosystems.

E.g, the Mediterranean region -with its dry, hot summers and warm, wet winters - has its own global ecosystem.

The climate in an area determines what type of ecosystem forms. Different parts of the world have different ecosystems because they have different climates.

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The distribution of global ecosystems

Tropical rainforest

  • Close to the equator.
  • High temperatures and heavy rainfall associated with low pressure belts create ideal conditions for plants to grow.

Desert

  • Roughly 30 degrees north and south of the Equator.
  • Deserts have sub-tropical high pressure belts.
  • Sinking air stops clouds from forming, making it hot during the day and cold at night.

Polar

  • Arctic/Antarctic.
  • Cold air sinks at the north and south Poles, causing low temperatures and dry conditions.

Deciduous and coniferous forests

  • Roughly 50-60 degrees north and south of equator.
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More global ecosystems

Temperate grassland

  • Roughly 30-40 degrees north and south of the Equator.  Also isolated locations south of the Equator.
  • Pressure belts migrate slightly north and south during the year. 

Mediterranean

  • Roughly 40-45 degrees north and south of the Equator. Also isolated locations south of the Equator.
  • Hot, sunny and dry summers and mild winters.
  • Pressure belts migrating slightly north and south during the year.

Tropical grassland (savanna)

  • Between 15 to 30 degrees north and south of the Equator.
  • Tropical climate in low latitudes with wet and dry seasons. 

Tundra

  • From Arctic Circle to around 60-70 degrees north and very small areas in Southern hemisphere due to lack of land.
  • Winters are very cold, summers are brief and there is little rainfall.
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Map of global ecosystems

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