← Biology syllabus

EnglandBiology

B4 Community level systems

5 dot points across 5 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

How are organisms organised into ecosystems, and what makes them depend on each other?

The levels of organisation (organism, population, community, ecosystem), abiotic and biotic factors, interdependence within a community, and competition between organisms for resources.
A focused answer to the OCR Gateway GCSE Biology A topic B4 on ecosystems, covering the levels of organisation, abiotic and biotic factors, interdependence within a community, and competition between organisms for resources.
9 min answer →

How does energy pass along a food chain, and why do predator and prey numbers rise and fall together?

Food chains and food webs, the roles of producers, consumers and decomposers, the transfer and loss of energy along a food chain, and predator-prey cycles.
A focused answer to the OCR Gateway GCSE Biology A topic B4 on feeding relationships, covering food chains and webs, producers, consumers and decomposers, the loss of energy along a food chain, and predator-prey cycles.
9 min answer →

How do ecologists estimate how many organisms live in an area without counting every one?

Using quadrats to estimate population size and to compare two areas, using transects to study how distribution changes across a habitat, random sampling to avoid bias, and improving the reliability of sampling.
A focused answer to the OCR Gateway GCSE Biology A topic B4 on sampling techniques, covering quadrats to estimate population size, transects to study distribution, random sampling to avoid bias, and how to improve reliability, with worked estimation.
9 min answer →

How are carbon and water recycled through living things and the environment?

The carbon cycle (photosynthesis, respiration, decomposition and combustion), the water cycle (evaporation, transpiration, condensation and precipitation), and how human activities such as burning fossil fuels affect the carbon cycle.
A focused answer to the OCR Gateway GCSE Biology A topic B4 on the carbon and water cycles, covering photosynthesis, respiration, decomposition and combustion in the carbon cycle, the stages of the water cycle, and the human impact of burning fossil fuels.
9 min answer →

How is nitrogen recycled by bacteria, and what controls how fast dead matter decays?

The nitrogen cycle and the roles of nitrogen-fixing, nitrifying, decomposing and denitrifying bacteria, the process of decomposition, and the factors affecting the rate of decay (temperature, water and oxygen).
A focused answer to the OCR Gateway GCSE Biology A topic B4 on the nitrogen cycle and decomposition, covering nitrogen-fixing, nitrifying, decomposing and denitrifying bacteria, the process of decay, and the factors affecting the rate of decomposition.
9 min answer →