Describe the different levels of organisation from individual organisms,…

The idea

Ecological organisation builds upward in a fixed order. One individual organism is a single living thing, such as one oak tree or one blackbird. A population is all the individuals of the same species living in the same area at the same time, for example all the blackbirds in one wood. A community is all the populations of different species living and interacting together in that area, so the blackbirds, insects, oaks and fungi together. The ecosystem adds the non-living surroundings: the physical factors such as light, temperature, water and soil, plus the community, forming a working system. So the sequence runs individual organism, then population, then community, then whole ecosystem. Each level includes everything below it, and the ecosystem is the largest, combining living community with its abiotic environment.

What earns the marks

• States the order: individual organism, population, community, ecosystem.
• Defines a population as all individuals of one species in the same area at the same time.
• Defines a community as all the different populations of species living and interacting in an area.
• Explains that an ecosystem includes the community together with the non-living (abiotic) surroundings.
• Recognises that each higher level includes the levels beneath it.

Common mistakes and how to put them right

• Calling a group of different species a population.

  Put it right: A population is one species only, while a community contains many species.

• Treating the ecosystem as just the living things.

  Put it right: The ecosystem also includes abiotic factors such as light, water and soil.

• Placing the community below the population in the order.

  Put it right: Population comes before community, which combines all populations.

Exam tips

• Learn the four levels as a fixed sequence so you can order them quickly.
• Check whether a term names one species (population) or many species (community).
• Remember to add the non-living environment when the question asks about an ecosystem.