BRAINCAKEPopulations in Ecosystems
Revision notes for Populations in Ecosystems in AQA Biology (7402). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Populations and CommunitiesEcology uses a few precise terms to describe groups of organisms.
- EcosystemsAn ecosystem is a community of organisms together with the non-living (abiotic) components of their environment, interacting as a system.
- NichesA niche is the role of a species within its habitat.
- Carrying CapacityThe carrying capacity is the maximum population size of a species that an ecosystem can support.
- Abiotic Factors and Population SizeAbiotic factors are the non-living conditions of an ecosystem.
- Biotic Factors and Population SizeBiotic factors are the effects of living organisms on a population.
- Intraspecific CompetitionIntraspecific competition is competition between individuals of the same species for the same resources, such as food, water, light, space, breeding…
- Interspecific CompetitionInterspecific competition is competition between individuals of different species for the same resources, such as food, light, water, nesting sites…
- Predator-Prey RelationshipsPredation is when one organism, the predator, kills and eats another, the prey.
- Estimating Population Size with QuadratsIt is rarely possible to count every organism in a habitat, so ecologists estimate population size by counting organisms in samples.
- Random Sampling with QuadratsRandom sampling means every part of the study area has an equal chance of being sampled.
- Systematic Sampling along TransectsWhen an abiotic factor changes gradually across an area, random sampling may miss the pattern.
- Mark-Release-RecaptureAnimals that move around, such as woodlice, beetles, snails, fish and small mammals, cannot be sampled with quadrats.
- Assumptions of Mark-Release-RecaptureThe mark-release-recapture formula only gives a valid estimate if certain assumptions are true.
- SuccessionSuccession is the change in the species composition of a community over time.
- Primary SuccessionPrimary succession starts on land that has never had soil or a community before.
- Secondary SuccessionSecondary succession happens on land where a community has been removed or destroyed but the soil remains.
- Climax CommunitiesA climax community is the final, stable community at the end of a succession.
- Conservation and SuccessionConservation is the management of ecosystems so that their biodiversity is maintained.
- Managing Succession in ConservationLeft alone, most land habitats in the UK would slowly undergo succession until they became a climax community, usually woodland.