An ecosystem diagram. Image credit

An ecosystem diagram. Image credit

ZIMSEC O Level Combined Science Notes: Ecosystems


  • Is a self-contained system of interdependent organisms and their physical environment
  • An ecosystem can also be defined as a biological community of interacting organisms and their physical environment.
  • In an ecosystem a community of living organisms lives in conjunction with the nonliving components of their environment (things like air, water and mineral soil), interacting as a system.
  • For example in a typical grassland ecosystem the grasses/plants and animals depend on each other
  • They also depend on the soil, air and water in that area
  • The plants and animals live under certain conditions
  • The plants grow because they have the right amount of rainfall, light, air and soil conditions that suit them
  • The animals live there because they have the right kind of food to eat and shelter to live
  • The organisms (plants and animals) depend on each other and on their surroundings
  • The surroundings usually act as a source of energy
  • The plants and animals that are interdependent under a given set of conditions form the ecosystem
  • Zimbabwe has a variety of ecosystems for example forest, lake, river and grassland ecosystems
Energy transfer in an ecosystem

Energy transfer in an ecosystem

  • Every ecosystem depends on the energy from the sun
  • The plants use solar energy to create food using the photosynthesis process
  • The energy is stored/trapped in the plants until they are eaten by the animals
  • Thus energy flows in an ecosystem as it is transferred from the plants to the animals for example
  • The flow of energy is critical as it ensures a balanced ecosystem is maintained
  • There must be adequate transfer of energy from the sun, to the plants and to the animals
  • This balance can be easily upset by the interference of humans
  • Typically the environmental conditions in an ecosystem include the air, water, light and heat energy
  • The soil also has some physical properties such as its texture
  • Soils have living organisms in them as well as organic matter
  • These are biological components of an ecosystem
  • The biological components of an ecosystem (plants and animals) interact with one another

To access more topics go to the Combined Science Notes page.