19 populations in ecosystems Flashcards
what is ecology?
the study of inter-relationships between organisms and their environment
what are biotic factors?
living factors of an ecosystem
what is an ecosystem?
all the living and non living components of a particular area
what is a population?
organisms of the same species living in the same habitat
what is a community?
all the populations of different species in the same area at the same time
what is a habitat?
part of an ecosystem in which particular organisms live
what is a niche?
an organisms role within an ecosystem. their position on the food web and their habitat.
(each species occupies their own niche)
what is population size?
the number of individuals in a population
4 abiotic (nonliving) factors that influence the size of a population
- temperature
- light
- pH
- water and humidity
what is interspecific competition?
competition between organisms of different species for resources such as food, water, light etc
what is intraspecific variation?
competition between organisms of the same species for resources such as food, water, breeding sites etc.
what is carrying capacity?
the size of population that an ecosystem can support
what does population size vary as a result of?
- the effect of abiotic factors
- interactions between organisms: interspecific and intraspecific competition and predation
what is predation?
when one organism is consumed by another
what is the predator-prey relationship and what is its effect on population size?
1) predators eat there prey, thereby reducing population of prey
2) less prey available so more competition between predators
3) predator population decrease as some individuals unable to survive or reproduce
4) less predators so more prey survive and reproduce
5) prey population increases
6) more prey available so predators population increases
why is the predator-prey relationship often less severe?
organisms eat a range of foods so not dependent on only one population
what are the two types of quadrats?
point quadrat: horizontal bar through which a long pin is dropped, each species the pin touches is recorded
frame quadrat: frame divided into equally sized subdivisions, abundance of each species within the quadrat is recorded
3 factors to consider when using quadrats?
- size of quadrat used
- number of sample quadrats to record within the study area
- position of each quadrat within the study area
why is random sampling important?
to avoid bias so data is reliable
when should systematic sampling be used?
where some form of gradual change takes place, e.g the distribution of organisms along a line of succession (sand dunes)
what is abundance?
the number of individuals of a species within a given area
how to measure abundance in motile organisms?
mark-release-recapture - a known number of animals are caught, makes and release back into the community. later, a given number of individuals are collected randomly and number of marked individuals is recorded
equation for estimated population size
individuals in first sample x individuals in second sample / marked individuals recaptured
4 assumptions made when using mark-release-recapture technique
- proportion of marked to unmarked in second sample is the same as the whole population
- no immigration or emigration
- few deaths and births
- method of marking is not toxic to the individual
