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neurologyYou need to know

• Biotic factors are living factors in an ecosystem, such as food availability, predators, pathogens and competition from other organisms.
• Abiotic factors are non-living physical or chemical factors in an ecosystem, such as light intensity, temperature, water availability, oxygen concentration, soil mineral content, pH and wind intensity.
• A community is all the populations of different species living and interacting in the same ecosystem.
• Changes in biotic or abiotic factors can change the size and distribution of populations because organisms may survive, reproduce, migrate or die at different rates.
• An adaptation is a feature that helps an organism survive and reproduce in its natural environment.
• Structural adaptations are physical features of an organism, behavioural adaptations are actions an organism performs, and functional adaptations are internal processes such as producing antifreeze proteins or conserving water.
• Extremophiles are organisms adapted to live in extreme conditions, such as very high temperature, high salt concentration or high pressure.
• Photosynthetic organisms, such as plants and algae, are producers because they make biomass by converting light energy into chemical energy in glucose.
• A food chain shows feeding relationships and energy transfer from a producer to consumers, and arrows point in the direction of biomass and energy transfer.
• A food web shows many interconnected food chains in a community and can be used to predict how changes in one population may affect others.
• Predator and prey populations usually cycle because more prey provides more food for predators, predator numbers then increase, prey numbers then decrease, and predator numbers then fall after a time lag.
• A quadrat is a square frame used to sample the abundance or percentage cover of organisms in a known area, and a transect is a line used to sample how organisms change across an environmental gradient.
• The mean is the total of the values divided by the number of values, the median is the middle value when data are in order, and the mode is the most common value.
• Materials such as water, carbon and minerals cycle between biotic components, such as organisms, and abiotic components, such as the atmosphere, water and soil.
• The water cycle supplies fresh water needed for living organisms and includes evaporation, condensation, precipitation, absorption by roots and transpiration from plants.
• Microorganisms decompose dead organisms and waste, returning mineral ions and carbon compounds to the environment so materials can be reused by plants and other organisms.
• Biodiversity is the variety of living organisms in an area, including the variety of species, genetic variation within species and different ecosystems.
• High biodiversity helps ecosystems remain stable because a wide range of species can maintain food webs, nutrient cycling and pollination if conditions change.
• Human activities reduce biodiversity through pollution, deforestation, peat bog destruction, overfishing, intensive farming, land use change and climate change.
• Conservation programmes can reduce biodiversity loss by breeding endangered species, protecting habitats, reintroducing species, reducing deforestation, recycling resources, managing fisheries and creating protected areas.

• Interpret food chains and food webs by identifying producers, consumers, predators and prey, and by predicting the effect of changing one population on other populations.
• Construct food chains and food webs from ecological information, using arrows to show the direction of biomass and energy transfer.
• Measure the distribution of organisms using quadrats placed randomly or along a transect, recording abundance or percentage cover and calculating reliable estimates from repeated samples.
• Plot ecological data on appropriate graphs by choosing a suitable graph type, labelling axes with units, selecting sensible scales and drawing points or bars accurately.
• Describe and explain predator-prey cycles using population data, including the time lag between changes in prey numbers and predator numbers.
• Construct pyramids of biomass with producers at the base and each trophic level drawn as a correctly ordered bar representing total biomass.
• Calculate biomass transfer efficiency using `\text{efficiency} = \frac{\text{biomass transferred to next trophic level}}{\text{biomass at previous trophic level}} \times 100` and use the result to explain energy loss.
• Evaluate food production methods by comparing yield, cost, animal welfare, environmental impact, sustainability and ability to feed a growing population.
• Explain how intensive farming, selective breeding, genetic modification, mycoprotein production and sustainable fisheries can increase or secure food supply while recognising their limitations.
• Use evidence about pollution, global warming or habitat change to explain likely biological consequences, such as altered species distributions, extinction risk, reduced biodiversity and disrupted food webs.