Biotic factorsSpec 4.7.1.3
In short
Biotic factors are the living factors that can change a community. The four you need to know are the availability of food, new predators arriving, new pathogens, and one species outcompeting another so that its numbers are no longer sufficient to breed. A change in one population affects others, for example when a new predator reduces the number of prey.
Biotic (living) factors can also change a community. The four you need to know are:
| Biotic factor | How a change could affect a community |
|---|---|
| Availability of food | Less food means more competition, so animal numbers fall. More food means numbers can rise |
| New predators arriving | Prey are eaten, so the prey population falls. Anything the prey ate may then increase |
| New pathogens | Disease can kill or weaken many organisms of a species, so the population falls |
| One species outcompeting another | The weaker competitor gets less of the food, light or space it needs. Its numbers may become no longer sufficient to breed, so the species can die out in that area |
A change in one population affects others. If a new predator reduces the number of prey, the predator's other food sources and the prey's food source are all affected.
Do not say that a population 'adapts' to a new predator or pathogen in the short term. Describe what happens to numbers: they rise or fall, and why.
You may be asked to interpret a graph of two populations over time. Describe how each changes, then link the changes, for example prey falling when predators rise.
Written and checked against the AQA GCSE Combined Science (8464) specification · Updated October 2026