Topic 1- Foundations
What is an ecosystem?
A community of organisms interacting with each other and their physical environment.
What is the term for an organism that produces its own organic compounds using an external energy source, such as sunlight?
An autotroph (producer).
What is biodiversity?
The variety of life, including genetic diversity, species diversity and ecosystem diversity.
What is the process by which liquid water changes into water vapour?
Evaporation.
What is soil erosion?
The removal and transport of topsoil by agents such as water, wind or human activities.
What is the difference between a biotic and an abiotic factor? Give one example of each.
Biotic factors are living components or biological influences, such as predators. Abiotic factors are non-living physical or chemical components, such as temperature.
What is the difference between a food chain and a food web?
A food chain shows one pathway of energy transfer; a food web shows interconnected feeding relationships within an ecosystem.
What is the difference between an endemic species and an endangered species?
An endemic species is native to and restricted to a particular geographic area. An endangered species faces a very high risk of extinction in the wild.
What is the difference between a water store and a water flow in the hydrological cycle? Give one example of each.
A store holds water, such as a lake or groundwater aquifer. A flow transfers water, such as precipitation, infiltration or runoff.
What is the difference between intensive and extensive agriculture?
Intensive agriculture uses high inputs of labour, capital or other resources per unit of land to maximise production. Extensive agriculture uses relatively lower inputs per unit of land and typically requires larger areas.
What is the difference between a system's inputs, outputs, storages and flows?
Inputs enter a system, outputs leave it, storages hold matter or energy, and flows transfer matter or energy between components or storages.
Explain why less energy is available at each successive trophic level.
Energy is lost through respiration and heat, movement, waste and uneaten or undigested material. Only a proportion is transferred to the next trophic level.
Explain how habitat fragmentation can reduce biodiversity, even if the total area of habitat remains unchanged.
Fragmentation isolates populations, restricts movement and gene flow, increases edge effects and can make small populations more vulnerable to local extinction.
Explain why fertiliser runoff into a lake can lead to fish deaths.
Excess nutrients can cause eutrophication and algal growth. When algae die, decomposers break them down and consume dissolved oxygen, potentially causing hypoxia and fish deaths.
Explain two ways that monoculture farming can reduce the long-term sustainability of food production.
It can reduce biodiversity, increase vulnerability to pests and diseases, deplete particular soil nutrients and increase reliance on fertilisers or pesticides. Any two explained points.
A rise in temperature causes ice to melt, reducing Earth's albedo and causing more solar energy to be absorbed. Identify the feedback mechanism and explain why it occurs.
Positive feedback. Melting reduces reflectivity, increasing energy absorption and causing further warming and melting.
A predator is removed from a food web. Explain how this could lead to a trophic cascade.
Prey populations may increase, putting greater pressure on their food sources. This can change the abundance of organisms at lower trophic levels and alter ecosystem structure.
Compare in situ and ex situ conservation, giving one example of each.
In situ conservation protects species in their natural habitats, such as through national parks. Ex situ conservation protects them outside their natural habitats, such as in zoos, seed banks or captive-breeding programs.
Explain how ocean acidification occurs and describe one potential impact on marine organisms.
The ocean absorbs atmospheric CO₂, which reacts with water to form carbonic acid and lowers ocean pH. This reduces the availability of carbonate ions, making it harder for organisms such as corals and shellfish to build and maintain calcium carbonate shells or skeletons.
Explain why converting tropical rainforest into agricultural land can contribute to both biodiversity loss and climate change.
Habitat destruction reduces species populations and can cause extinctions. Deforestation also releases stored carbon through burning and decomposition and reduces future carbon sequestration by trees.
A forest is cleared for agriculture. Explain how the same change could be viewed differently by an ecocentric environmental value system and an anthropocentric environmental value system.
An ecocentric perspective may oppose clearing because of the intrinsic value of ecosystems and biodiversity. An anthropocentric perspective may support or oppose it based on human needs, such as food production, livelihoods and long-term ecosystem services.
Two ecosystems have the same number of species, but one has a much more even distribution of individuals among species. Which ecosystem is likely to have greater species diversity, and why?
The ecosystem with greater evenness is likely to have higher diversity because its individuals are distributed more evenly among species. Species richness is equal, but evenness differs.
A conservation programme protects one large, connected forest, while another protects several smaller forest fragments. Explain two factors that could influence which strategy is more successful.
Relevant factors include habitat requirements and territory size, population viability, connectivity and migration, edge effects, habitat quality, and the distribution of endemic or threatened species. A well-justified comparison is required; neither strategy is always best.
A city replaces natural vegetation with roads and buildings. Explain how this can affect both the quantity and quality of water entering a nearby river.
Impermeable surfaces reduce infiltration and groundwater recharge while increasing surface runoff, peak discharge and flood risk. Runoff can carry pollutants, sediment, oils and nutrients into the river, reducing water quality.
A country wants to increase food production to feed a growing population. Evaluate the trade-offs between expanding agricultural land and increasing yields on existing farmland.
Expansion may increase production but can cause deforestation, habitat loss, carbon emissions and soil degradation. Increasing yields can reduce pressure to clear new land, but intensive methods may increase fertiliser and pesticide use, water demand and pollution. The strongest answers consider local conditions, long-term sustainability and the possibility of combining both approaches.