Living organisms are interdependent and show adaptations to their…

The idea

Interdependence means organisms rely on each other for food, shelter, pollination, seed dispersal and nutrient cycling. A change in one population can ripple through a community. Adaptations are inherited features that improve survival and reproduction in a particular habitat. For example, a polar bear has thick fur, a white coat and a compact body shape that reduce heat loss and camouflage it against snow. A cactus has spines that deter herbivores and a thick stem that stores water. They should also interpret food webs and predator-prey cycles to show interdependence, and suggest how environmental change affects populations.

What earns the marks

• Define interdependence as the reliance of organisms on each other for resources such as food, shelter, pollination and seed dispersal.
• Explain that a change in one population, such as a fall in prey numbers, can affect predator numbers and then other species in the food web.
• Describe an adaptation as an inherited feature that increases an organism's chance of survival and reproduction in its habitat.
• Give a named example and link the feature to its advantage, such as thick fur reducing heat loss in cold environments.
• Distinguish between structural, behavioural and functional adaptations, using examples such as migration, hibernation and water storage.
• Interpret predator-prey graphs by describing the lag between peaks and explaining why predator numbers follow prey numbers.

Common mistakes and how to put them right

• Listing an adaptation without explaining its advantage.

  Put it right: State how the feature helps the organism survive or reproduce, for example 'white fur camouflages the bear against snow so it can stalk prey'.

• Treating interdependence as one-way, such as saying only predators depend on prey.

  Put it right: Describe two-way effects, for example prey numbers affect predator numbers and predator numbers affect prey numbers.

• Assuming individual organisms adapt during their lifetime.

  Put it right: Adaptations are inherited characteristics that become more common in a population over generations through natural selection.

Exam tips

• When asked about interdependence, refer to a specific food web or named species and describe the effect of a change on at least two other populations.
• For adaptation questions, use the structure 'feature → advantage → survival or reproduction' to make the link explicit.
• Read graph axes carefully in predator-prey questions; describe the pattern, then explain it using the idea that predator numbers rise after prey numbers rise.