Adaptations, interdependence and competition:


  • An ecosystem is the interaction between the community of living organisms and their environment.
  • A community is two or more populations of organisms.
  • A population is all the organisms of the same or closely-related species in an ecosystem.
  • Interdependence means that all the organisms in an ecosystem are dependent upon each other.

Abiotic and biotic factors:

  • The abundance and distribution of organisms in an ecosystem are affected by biotic and abiotic factors.
  • Abiotic factors are non-living and include light intensity, temperature, moisture levels, soil pH and mineral content, wind intensity, direction, carbon dioxide levels and oxygen levels.
  • Biotic factors are living and include availability of food, the arrival of new preadtors and pathogens and being out-competed by other species.

Competition in plants and animals:

  • Competition can be between individuals of the same species which is called intraspecific or between different species which is called interspecific.
  • Plants compete for light, water and minerals from the soil and for space.
  • Animals compete for food, mates and territory.
  • Individuals within a species that cannot effectively compete are likely to die.
  • Whole species that cannot effectively compete are likely to become extinct.

Adaptations in plants and animals:

  • All adaptations make organisms better suited to their ecosystem and provide them with a better chance at survival and reproduction.
  • Examples of structural adaptations in plants are spines and in animals are sharp teeth and claws.
  • Examples of behavioural adaptations in plants are growing towards the light and courtship in animals.
  • An example of physiological adaptations in animals and plants is the production of venom or poisons.


  • An extremophile is an organism that lives in an extreme environment.
  • An extreme environment is one in which most organisms would find it difficult or impossible to survive such as polar regions, deserts and the deep ocean bed.
  • Deep sea volcanic vents are places on the ocean floor where the volcanic gases of underground magma chambers bubble through.
  • The organisms that live in these places have highly specialised adaptations.

Organisation of an ecosystem:

Levels of organisation:

  • 1. Feeding relationships show the levels of organisation in an ecosystem.
  • 2. Feeding relationships can be shown in food chains, which add together to make food webs for a habitat.
  • 3. At the base of almost every food chain is a producer, which is usually a plant or algae which photosynthesises.
  • 4. All the animals above the producer are called consumers.
  • 5. Decomposers are bacteria and fungi which breakdown dead organisms and help them rot.

Predators and Prey:

  • In a healthy, balanced ecosystem the numbers of predators remain fairly constant.
  • The numbers of predators and prey can be seen in repeating predator-prey cycles.
  • When the number of prey increases so does the number of predators because there is more food.
  • The number of prey reduces when there are more predators eating them.
  • Finally the number of predators decreases because there is less prey.

The Carbon Cycle:

  • Carbon is an important element that can exist in different


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