1) Communities

•  An ecosystem is all the organisms living in a habitat and the non-living parts of the habitat.
• There are different levels of organisation in an ecosystem:

  individual organisms

  populations - groups of individuals of the same species

  • communities - made up of many populations living together
• To survive and reproduce, organisms require certain resources from their habitat and the other living organisms there.
• Trying to get enough of these resources results in competition.
•  Plants in a community or habitat often compete with each other for light, water, space and mineral ions from the soil.
• Animals often compete with each other for food, mates and territory.
• As well as competing with each other, species also rely on each other for food, shelter, pollination, seed dispersal, etc. This is called interdependence.
• Because of interdependence, removing one species from a habitat can affect the whole community.
• In a stable community, all the species and environmental factors are in balance so that population sizes stay fairly constant.
• Tropical rainforests and ancient oak woodlands are examples of stable communities.