Ecosystems

• Producers


  Convert energy from the environment (mainly sunlight) into sugars (glucose). The most obvious producers are plants that convert energy from the Sun by photosynthesis.
• Consumers


  Get energy from the sugars produced by the producers. A pond snail is a good example of a consumer because it eats plants.
• Decomposers


  Break down plant and animal material and return the nutrients to the soil. Bacteria and fungi are good examples of decomposers.
• Food chain


  Shows the direct links between producers and consumers in the form of a simple line.
• Food web


  Shows all the connections between producers and consumers in a rather more complex way.
• Nutrients


  Foods that are used by plants or animals to grow. There are two main sources: rainwater washes chemicals out of the atmosphere, and weathered rock releases nutrients into the soil.
• Nutrient cycling


  When plants or animals die, the decomposers help to recycle the nutrients making them available once again for the growth of plants or animals.
• Ecosystems


  • Can adapt to slow natural changes with few harmful effects, but rapid changes can have serious impacts.
  • Extreme weather events like droughts can be devastating to ponds and lakes, causing them to dry up and changing the edge-of-pond environment.
• Agricultural fertilisers


  Can lead to eutrophication: nitrates increase growth of algae, which will deplete oxygen and cause fish to die.
• Ponds drained for farming

  Aquatic plants will die, as will fish and other pond life.
• Woods cut down


  Habitats for birds are destroyed, and the nutrient cycle is affected.
• Hedgerows removed


  Habitats will be destroyed, altering the plant/animal balance.
• Many farmers are trying to keep ecosystems in balance by using less fertiliser and planting hedgerows and grass margins to protect wildlife such as bees, insects and wildflowers.
• Characteristics of global ecosystems

  • Tropical rainforest
  • Desert
  • Polar
  • Deciduous and coniferous forests
  • Temperate grassland
  • Mediterranean
  • Tropical grassland (savanna)
  • Tundra
• Tropical rainforest


  • Located close to the Equator
  • High temperatures and heavy rainfall associated with equatorial low pressure belt creates ideal conditions for plants to grow
  • Rainforests cover 6 per cent of the Earth's land surface
  • More than half the world's species of plants and animals live in this global ecosystem
  • A quarter of all medicines come from rainforest plants
• Desert


  • Located roughly 30° north and south of the Equator
  • Deserts cover one fifth of the world's land surface
  • Hot deserts are associated with the sub-tropical high pressure belts
  • Sinking air stops clouds from forming, resulting in high daytime temperatures, low night-time temperatures and low rainfall
  • Plants and animals have to be well adapted to survive in these conditions
• Polar (Arctic/Antarctic)


  • Cold air sinks at the north and south Poles, resulting in very low temperatures and dry conditions
  • The main polar regions are Antarctica and Greenland where temperatures can fall below -50°C
• Deciduous and coniferous forests

  • Located roughly 50-60° north of the Equator
  • Deciduous trees shed their leaves in winter to retain moisture
  • Coniferous trees are cone-bearing evergreens, retaining their leaves to maximise photosynthesis during the brief summer months
  • The UK's natural vegetation is deciduous forest
  • Further north, for example in Canada and Scandinavia, coniferous forests dominate as they are better suited to colder climates
• Temperate grassland


  • Located roughly 30-40 north and south of the Equator, inland away from coasts, with hot summers and cold winters
  • Includes the vast areas of grassland in North America (prairies) and Eastern Europe (steppes)
  • Grasses can tolerate these conditions and this land is mainly used for grazing animals
• Mediterranean


  • Located roughly 40-45 north of the Equator, also isolated locations south of the Equator (South Africa, Western Australia)
  • Countries around the Mediterranean enjoy hot, sunny and dry summers, with mild winters
  • Mediterranean vegetation includes olive trees and fruit trees, such as lemons and oranges
  • Other parts of the world have a similar climate, for example California (USA) South Africa and parts of Australia
• Tropical grassland (savanna)


  • Located between 15-30 north and south of the Equator
  • Characterised by distinct wet and dry seasons
  • The dry season can be very hot and wild fires can break out
  • Violent thunderstorms can occur during the wet season
  • Large herds of animals graze on these grasslands, along with predators such as lions and leopards
• Tundra


  • Located from the Arctic Circle to about 60-70 north (eg Canada, Northern Europe)
  • Only very small areas of tundra in the southern hemisphere due to the lack of land at these latitudes
  • Characterised by low-growing plants adapted to retain heat and moisture in the cold, windy and dry conditions
  • A fragile ecosystem, easily damaged by humans and threatened by developments such as of exploitation and tourism
  • Animals such as reindeer are adapted to survive the cold