Identify and describe What Are Biotic Factors?, Food Availability as a Biotic Factor and Predators as Biotic Factors in the context of biotic factors.
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GCSE Biology Revision
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GCSE Biology revision
Biotic factors
Adaptations, interdependence and competition
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Explain the relationships between What Are Biotic Factors?, Food Availability as a Biotic Factor and Predators as Biotic Factors and how they contribute to biotic factors.
Apply and analyse knowledge of What Are Biotic Factors?, Food Availability as a Biotic Factor and Predators as Biotic Factors to interpret unfamiliar information about biotic factors.
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Key knowledge
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What Are Biotic Factors?
- A biotic factor is any living factor that can affect an organism or ecosystem.
- Examples of biotic factors include mice, plants, frogs, predators, pathogens, and competing species.
- Biotic factors differ from abiotic factors, which are non-living factors such as temperature, light, or rocks.
Food Availability as a Biotic Factor
- Organisms require food for survival, making food availability a key biotic factor influencing population size.
- Areas rich in food, such as rainforests, support a greater abundance and diversity of organisms.
- Regions with scarce food, such as tundra areas like Siberia, support fewer organisms due to limited resources.
Predators as Biotic Factors
- When a new predator enters a stable ecosystem, it increases competition at its trophic level.
- An increase in predation causes prey populations to decline dramatically, which can destabilise the entire food web.
- A reduced prey population can also cause existing predators to lose their food supply, potentially wiping them out.
Pathogens as Biotic Factors
- Pathogens introduced into an ecosystem can have a devastating effect on populations lacking immunity to them.
- When Europeans colonised Australia, smallpox devastated the Aboriginal population because they had not developed the required immunity.
- Pathogens can also be used for biological control, for example introducing pathogens and parasites to control ash borer populations.
New Species and Interspecific Competition
- A newly introduced species can out-compete existing native species for resources such as food, space, and shelter.
- The cane toad, introduced to Australia, out-competed existing native species and caused its own population to increase dramatically.
- The introduction of grey squirrels to the UK is another example of a new species out- competing an existing one, in this case the native red squirrel.
Effects of Biotic Factors on Ecosystems
- Biotic factors can cause population numbers to rise or fall, altering the balance of an entire ecosystem.
- Competition between species at the same trophic level is a key mechanism through which biotic factors drive change.
- The introduction of non-native species or pathogens can have irreversible consequences for native biodiversity.
Distinguishing Biotic from Abiotic Factors
- Biotic factors are always living organisms or products of living organisms, such as pathogens, predators, or food sources.
- Abiotic factors are non-living environmental conditions, such as temperature, pH, light intensity, and water availability.
- Being able to name at least three examples of each type of factor is essential for GCSE exam success.
Biological Control Using Biotic Factors
- Biological control involves deliberately introducing a living organism, such as a pathogen or parasite, to manage a pest population.
- This method uses biotic factors intentionally to reduce the numbers of a harmful species without chemical pesticides.
- Ash borers, which are destructive tree pests, can be controlled by introducing specific pathogens and parasites into their population.
Key Exam Tips for Biotic Factors
- Exam questions on biotic and abiotic factors often require straightforward recall, so memorising clear examples is essential.
- Remember that pathogens can have both negative effects (e.g. disease) and positive uses (e.g. biological control) in ecosystems.
- Grey squirrels and cane toads are excellent named examples of introduced species that out- competed native organisms.