ecosystems

• what are the different levels of an ecosystem's organisation?

  1. individual: a single organism
  2. population: all the organism's of one species in a habitat
  3. community: all the organism's of different species living in a habitat.
  4. ecosystem: a community of organisms along with all non-living (abiotic) conditions.
• what is interdependence?

  organisms depend on each other for things like food and shelter in order to survive and reproduce.
• what can happen as a result of interdependence?

  a change in the population of one species can have huge knock-on effects for other species in the same community.
• what is mutualism?

  a relationship between 2 organisms from which both organisms benefit.
• what is an example of mutualism?

  bees and flowering plants. when bees visit flowers to get nectar, pollen is transferred to their bodies. The bees then spread the pollen to other plants when they land on their flowers. The bees get food and the plants get help reproducing.
• what isn't an example of mutualism?

  parasites live very closely with a host species, they take what they need to survive but the host doesn't benefit. For example, fleas are parasites to mammals such as dogs.
• what are changes in the environment caused by?


  abiotic (non-living) and biotic (living) factors affect communities in different ways.
• how do abiotic factors affect communities?

  • temperature
  • amount of water
  • light intensity
  • levels of pollutants
• how is temperature an example of how abiotic factors affect communities?

  the distribution of bird species in Germany is probably changing because of a rise in average temperature. For instance, the European Bee-eater bird is a Mediterranean species but it's now present in Germany.
• how is amount of water an example of how abiotic factors affect communities?

  daisies grow best in soils that are slightly damp. If the soil becomes waterlogged or too dry, the population of daisies will decrease.
• how is light intensity an example of how abiotic factors affect communities?

  as trees grow and provide more shade, grasses may be replaced by fungi (or mosses) which are better to cope with the lower light intensity.
• how is levels of pollutants an example of how abiotic factors affect communities?

  lichen are unable to survive if the concentration of sulfur dioxide (an air pollutant) is too high.
• how do biotic factors affect communities?

  • competition
  • predation
• how is competition (biotic factor) affect communities?


  organisms compete with other species (and members of their own species).
• how is competition an example of how biotic factors affect communities?

  red and grey squirrels live in the same habitat and eat the same food. Competition with the grey squirrels for these resources means there's not enough food for the reds. The population of red squirrels is decreasing as a result.
• how is predation an example of how biotic factors affect communities?


  if the number of lions (predators) decreases then the number of gazelles (their prey) might increase because fewer of them will be eaten by the lions.
• what do plants compete for?

  • water and mineral ions (from the soil)
  • light
  • space
• what do animals compete for?

  • food
  • mates
  • territory
• what might species depend on each other for?

  • shelter
  • seed dispersal
  • pollination
  • food
• when is a community stable?

  • environmental factors are balanced
  • species are balanced
  • population sizes stay constant
• what are the 5 levels of a food chain?

  1. producer
  2. primary consumer
  3. secondary consumer
  4. tertiary consumer
  5. apex predator
• what type of organisms are always at the bottom of the food chain?

  green plants and algae.
• producers use light energy from the sun to synthesise their own food.
• what type of organisms are usually primary consumers in the food chain?

  herbivores
• what type of organisms are usually secondary consumers in the food chain?

  carnivores that eat the herbivores.
• what type of organisms are usually tertiary consumers in the food chain?

  carnivores that eat carnivores
• what is parasitism?

  one organism benefits from the relationship, but the other is harmed.
• what is an example of parasitism?

  there are many parasitic worms that live in the human gut. They recieve food and shelter, but the human loses nutrients and may suffer illness.
• what is mutualism?

  both species in this relationship benefit.
• what is an example of mutualism?

  lichen (often found on tree trunks) is formed by both algae and fungi together; they provide structure and food for each other.
• what has to happen to water for the water cycle to be completed?

  it has to change state.
• what happens to carbon when organisms die?

  it is recycled so that it can be used by future generations.
• nitrogen moves through food chains.
• why is the recycling of materials essential?

  they provide the building blocks for future organisms.
• what removes carbon from the atmosphere?

  producers (algae for example) who use it in photosythesis.
• how do animals contain carbon compounds?

  by consuming plant matter.
• how is carbon put back into the atmosphere?

  (as carbon dioxide) due to the respiration that happens in plant and animal cells.
• when animals die, how is carbon put back into the atmosphere?

  decomposers return the carbon locked in their bodies back into the atmosphere via decay.
• what is the carbon cycle?

  • carbon is removed from the atmosphere by producers who use it in photosynthesis.
  • by consuming plant matter, animals obtain carbon compounds.
  • carbon is returned to the atmosphere (as CO2) because of the respiration that happens in plant and animal cells.
  • when animals and plants die, decomposers return the carbon locked in their bodies back into the atmosphere via decay.
• other than the carbon cycle, what is another source of carbon entry into the atmosphere?

  combustion of fossil fuels.