Bio B4

• recycling materials

  • the recycling of materials is essential as they provide the building blocks for future ogrnaisms
• carbon cycle

  • carbon is present in all living organisms
  • when organisms die, the carbon is recycled so that it can be used for future generations
• water cycle

  • the cycle describes how water moves on, above or just below the surface of our planet between different location such as rivers, oceans and the atmosphere
  • for the cycle to be completed, the water much change state
• nitrogen cycle

  • nitrogen is present in all living organisms
  • it moves through food chains and is recycled when organisms die
• the nitrogen cycle

  • Plants absorb nitrates (a form of nitrogen) from the soil through their roots to grow. They do this with the help of bacteria living in their roots (called root nodule bacteria)
  • Plants can also absorb nitrogen from the air
  • Farmers may add fertilisers (containing extra nitrates) to the soil, which plants can absorb
  • The nitrogen is passed-on to animals that eat the plants
  • When plants and animals die, bacteria recycle nitrogen back into the soil through decomposition
  • When lightning strikes soil, nitrogen is released back into the air
• ecosystem

  • made up of biotic and abiotic parts
  • there are different levels of organisation
• individuals

  • smallest part of an ecosystem
• populations

  • populations of individuals make up a single species
• communities

  • made up of populations of different species
• competition for resources

  • organisms need resources from both abiotic and biotic parts of an ecosystem to survive and reproduce
  • resources are not infinite
  • different species compete for resources
• competition between plants

  • plants often compete for water and minerals from the soil, as well as for light and space
• competition between animals

  • animals often compete for food, mates and territory
• species interdependence

  • one species may rely on another species for different things:
  • food
  • pollination
  • shelter
  • seed dispersal
• stable communities

  • when all species and environmental factors are balanced and population sizes stay more or less constant
• mutualism and parasitism

  • in addition to predator-prey or producer-herbivore relationships, there are other types of relationships between species in a community
• mutualism

  • both species benefit
• parasitism

  • one organism benefits, the other is harmed