Population, Community, Habitat & Ecosystem (Edexcel IGCSE Biology: Double Science)

• There are several key terms that we use when referring to the various different components of an ecosystem and their levels of organisation:
  • A population is defined as a group of organisms of the same species living in the same place at the same time
  • A community includes all of the populations living in the same area at the same time
    • Within a community, each species depends on other species for food, shelter, pollination, seed dispersal etc
    • If one species is removed it can affect the whole community
    • This is called interdependence
  • A habitat is the place where an organism lives
    • E.g. badgers, deer, oak trees and ants are all species that would live in a woodland habitat
  • An ecosystem is defined as all the biotic factors and all the abiotic factors that interact within an area at one time
    • The term 'biotic factors' includes all the living components such as plants and animals
    • The term 'abiotic factors' includes all the non-living components such as light intensity, mineral ions, water availability
    • Ecosystems can vary greatly in size and scale
      • A small ecosystem might be a garden pond
      • A large ecosystem might be the whole of Antarctica

Levels of organisation in an ecosystem