ecosystems

• Ecosystem


  A community of plants and animals that interact with each other and their physical environment
• Components of an ecosystem

  • Abiotic (non-living) - sun, minerals, rain, temperature
  • Biotic (living) - animals, plants, bacteria
• Ecosystem


  • Interrelationships and balance
  • Very sensitive to change
  • Living and non-living components can be altered by natural factors or human management
  • Impacts on one species can have a knock-on effect on the entire ecosystem
• Trophic cascade


  An ecological process which starts at the top of the food chain (apex predators) having a knock on effect on the whole ecosystem
• Changes when wolves were reintroduced into Yellowstone National Park

  • Changed behaviour of deer, increased birds and beavers, more vegetation, stabilized rivers and reduced soil erosion
• Factors that can cause change in an ecosystem

  • Natural factors - disease, wildfires, flooding, droughts
  • Human factors - introducing new species, deforestation, hunting, overfishing, fertilizers, pollution
• Biodiversity


  The variety of life in an ecosystem
• Nutrient cycling


  1. Organisms extract minerals from soil/water

  2. Nutrients transferred up food web

  3. Decomposers break down nutrients and return to soil
• Nutrients such as carbon, sulphur, potassium, nitrogen and oxygen are used by plants to grow
• Rainwater and weathered rock deliver nutrients to the soil where they can be taken up by plants
• When plants or animals die, they become litter and decomposers break down the nutrients and return them to the soil
• The energy from the sun and the nutrients found in air and soil are taken in by the algae and fish in a pond ecosystem
• When biomass like the fish die, they turn into litter and decomposers turn them into the soil and water of the pond
• Producers


  Organisms that produce food and minerals for consumers
• Energy loss at each level in the food chain

  Energy is lost due to respiration
• Reduced primary consumers


  Secondary consumers will decline, producers will increase
• Decomposers


  Help return nutrients to the soil by breaking down organic matter and releasing the nutrients
• Major global biomes


  • Tropical rainforest
  • Temperate deciduous
  • Desert
  • Tropical grassland
  • Coniferous forest
  • Mediterranean
• The pattern of global biomes in Africa includes coniferous, tropical grassland, tropical rainforest, Mediterranean and desert biomes
• Global atmospheric circulation


  Most important factor determining the formation of latitudinal biome belts around the world
• Temperature changes according to latitude due to the concentration of the sun's energy, which determines the type of vegetation and biome
• Minor changes to these broad biome belts occur due to factors like wind moving warm air from land to sea, and ocean currents