Biodiversity — AQA GCSE Combined Science
Test yourself on Biodiversity with AQA GCSE practice questions.
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Biodiversity explained
Biodiversity means the variety of all the different species of organisms on earth, or within an ecosystem.
Read the full explanation
It includes the number of different species present and the range of variation within each species. A woodland with many plant, insect, bird and fungal species has high biodiversity, while a field growing only one crop has low biodiversity. Biodiversity can be considered at different scales: the whole earth, a biome, or a single ecosystem such as a pond. High biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment, so the loss of one species has less impact.
A great biodiversity ensures the stability of ecosystems by reducing the dependence of one species on another for food, shelter and the maintenance of the physical environment.
Biodiversity is the variety of species in an ecosystem. When many species are present, each one tends to rely less on any single other species for food, shelter and the maintenance of the physical environment, such as nutrient cycling, soil formation and water regulation. In a species-poor system, losing one species can remove a food source or shelter for others, so the whole community may collapse. In a species-rich system, alternative food sources and habitats exist, so the ecosystem can absorb change and remain stable. For example, a hedgerow with many plant species supports many herbivores, and predators can switch prey if one species declines. This reduces the dependence of one species on another and helps the ecosystem resist disturbance.
The future of the human species on Earth relies on us maintaining a good level of biodiversity. Many human activities are reducing biodiversity and only recently have measures been taken to try to stop this reduction.
Humans depend on biodiversity for food, clean water, medicines, raw materials and a stable climate. If biodiversity falls too far, ecosystems may provide fewer of these services, threatening human survival and wellbeing. Many human activities reduce biodiversity: clearing land for farming or building, pollution, overfishing, hunting, introducing invasive species and contributing to climate change. These activities destroy habitats, reduce population sizes and can drive species to extinction. Only recently have large-scale measures been introduced to slow or stop this loss, such as protected areas, breeding programmes, seed banks, recycling, reducing pollution and international agreements. These measures aim to protect species and habitats so that ecosystems, and the human species, can continue to function.
Your focus
- State that biodiversity is the variety of all the different species of organisms.
- Apply the concept of biodiversity to the whole earth or to a named ecosystem.
- Explain how high biodiversity contributes to ecosystem stability by reducing species dependence.
Show all 9 objectives
- Describe what biodiversity is and give examples of species variety in an ecosystem.
- Explain how greater biodiversity reduces the dependence of one species on another for food and shelter.
- Apply the idea of stability to predict the effect of losing a species from a species-rich and a species-poor ecosystem.
- Describe how human activities such as deforestation and pollution reduce biodiversity.
- Explain why maintaining biodiversity is important for the future of the human species.
- Evaluate the effectiveness of recent measures taken to stop the reduction in biodiversity.
Biodiversity exam tips
Marking Points
- Biodiversity is the variety of all the different species of organisms.
- It can be measured on earth as a whole or within a single ecosystem.
- It includes the number of different species and the range of variation within species.
- High biodiversity ensures ecosystem stability by reducing the dependence of one species on another.
- Human activities such as deforestation and pollution can reduce biodiversity.
- Biodiversity means the variety of different species living in an ecosystem.
- Greater biodiversity means species have alternative food sources, so a decline in one prey species does not cause starvation of a predator.
- Greater biodiversity provides a range of shelter and habitat types, so loss of one plant or structure does not remove all shelter.
- A diverse community maintains physical environmental processes such as nutrient cycling, decomposition and soil stability through the activities of many species.
- Stability means the ecosystem can resist or recover from change, such as disease, drought or the removal of one species.
- Reduced dependence on one species means the food web has many interconnections rather than a single critical link.
- Humans rely on biodiversity for resources such as food, medicine, clean water and fertile soil.
- Human activities that reduce biodiversity include deforestation, pollution, overexploitation, urbanisation and introduction of invasive species.
- Reducing biodiversity can destabilise ecosystems and reduce the ecosystem services on which humans depend.
- Conservation measures include protected areas, legal protection, captive breeding, seed banks, habitat restoration and international agreements.
- These measures are recent compared with the long history of human impact, and their effectiveness varies.
- Maintaining biodiversity is linked to the long-term survival and wellbeing of the human species.
Examiner Tips
- 💡Use the phrase 'variety of all the different species' to secure the definition mark.
- 💡When explaining stability, explicitly state that high biodiversity reduces the dependence of one species on another.
- 💡Link each clause of the statement to a named example, such as a food web where a predator can switch prey.
- 💡Use the phrase reduced dependence when explaining why a species-rich ecosystem is more stable.
- 💡When asked to explain, give a cause and effect chain: many species → alternative food or shelter → less impact if one species declines → stable ecosystem.
- 💡Name specific human activities and link each to a clear effect on biodiversity.
- 💡Give named conservation measures and state how each protects species or habitats.
- 💡Use the phrase ecosystem services when explaining why human survival depends on biodiversity.
Common Mistakes
- Defining biodiversity as simply the number of organisms; correction: it is the variety of different species, not the total count of individuals.
- Thinking biodiversity applies only to the whole earth; correction: it can also describe a single ecosystem such as a pond or woodland.
- Stating that high biodiversity increases species dependence; correction: high biodiversity actually reduces the dependence of one species on another, increasing stability.
- Thinking biodiversity only means the number of individuals, not the number of species. Correction: biodiversity is the variety of species, and often the range of habitats and genetic variation too.
- Assuming a stable ecosystem never changes. Correction: stability means the ecosystem can resist or recover from change, not that it is static.
- Believing one species can maintain the whole physical environment alone. Correction: many species together contribute to processes such as nutrient cycling and soil maintenance.
- Thinking biodiversity loss only affects wild species and not humans. Correction: humans depend on ecosystem services such as food, water and medicine.
- Believing all human activities reduce biodiversity equally. Correction: some activities have a much greater impact, and some, such as habitat restoration, can increase biodiversity.
- Assuming conservation measures are old and universal. Correction: many large-scale measures are recent and not yet applied everywhere.