The Living World

• What is an ecosystem

  A natural system made up of plants, animals and the environment.
• Components of an ecosystem

  • Abiotic (non-living environmental factors such as climate, soil, water temperature and light)
  • Biotic (the living features such as plants and animals)
• Nutrient recycling

  Nutrients are foods that are used by plants or animals to grow.

  There are 2 main sources:

  • Rainwater washes chemicals out of the atmosphere
  • Weathered rock releases nutrients into the soil.
  • When plants or animals die, the decomposers help to recycle the nutrients making them available once again for the growth of plants and animals.
• What is a producer, consumer and decomposer?

  • Producers - convert energy from the environment (mainly sunlight) into sugars
  • Consumers - get energy from producers
  • Decomposers - break down plant and animal material and return the nutrients to the soil
• Causes of change to ecosystems

  • Global scale changes, such as climate change
  • Local scale changes, such as changes to a habitat, e.g. when a hedge is removed
• Natural changes to ecosystems

  • Hot dry summer reduces plant growth, fewer berries for birds in winter, number of sparrows and thrushes fall, fewer birds for sparrowhawks to hunt, so number of sparrowhawks falls
  • Droughts can cause ponds and lakes to dry up, changing the edge-of-pond environment, plants will dry out and die, fish starved of oxygen might not survive
• Human changes to ecosystems

  • Hedgerow trimmed, fewer habitats for ladybirds, greenfly and spiders, so numbers fall, sparrows and thrushes have less to eat, so numbers fall, fewer birds for sparrowhawks to hunt, so number of sparrowhawks falls
  • Agricultural fertilisers can lead to eutrophication: nitrates increase growth of algae, depleting oxygen and causing fish to die
  • Ponds drained for farming, aquatic plants and animals will die
  • Woods cut down destroying habitats for birds and affecting the nutrient cycle
  • Hedgerows removed to increase field size, habitats destroyed altering the plant/animal balance
• Examples of large scale global ecosystems

  • Hot deserts found between 15 and 35 north and south of the equator where there is little rainfall
  • Tropical Rainforest (TRF) found at the equator between the tropics, an area of lush forest
  • Polar ecosystems found around the north and south poles, very cold, icy and dry
  • Temperate Deciduous Forest found mainly in the mid-latitudes with 4 distinct seasons
  • Grasslands including Savannah and Temperate grasslands
• What are the physical characteristics of a tropical rainforest (TRF)

  • Climate: Hot all year round with no definite seasons, rainfall high at around 2000mm per year
  • Plants: Evergreen with a continual growing season
  • Soils: Infertile due to leaching
  • Animals: TRFs contain more animal species than any other ecosystem
  • People: Home to indigenous tribes who have adapted to life over many generations.
• Interdependence in the tropical rainforest ecosystem

  • Warm and wet weather means dead plant material is decomposed quickly, making the surface soil high in nutrients for plants to grow.
  • Plants pass on their nutrients when eaten by animals.
  • Deforestation can affect the whole ecosystem, reducing CO2 absorption and adding to greenhouse effect, and reducing rainfall and moisture.
• Tropical rainforests have more than 2/3s of the world's plant species and over 1/2 of the known animal species. They have high biodiversity due to the ideal growing conditions of warm and wet weather.