Populations in Ecosystems Flashcards
what do populations of different species form?
a community
what is an ecosytem?
the interaction between a community and the non-living components of its environment
how do ecosystems range in size?
very small to very large
within a habitat, a species occupies a …
niche governed by the adaptation of abiotic and biotic conditions
what is a niche?
the role of a population in a habitat, the sum of its interactions with the biotic and abiotic components
what is a carrying capacity?
an ecosystem supports a certain size of population of a species
what can the population size for a carrying capacity vary as a result of?
- effect of abiotic factors
- interactions between organisms: interspecific and intraspecific competition and predation
what happens at each stage of succession?
- new species colonise the area and these may change the environment
how may the species alter the environment(new species for succession)?
- less suitable for existing species, the new species out compete the existing one, so take over given area
- more suitable for other species with different adaptations, this species may be out competed by the better adapted species
what is the first stage of succession?
pioneer species, these make up a pioneer community
what are some features that make pioneer species suitable to colonisation?
- asexual reproduction so single organism can rapidly multiply to build up a population
- produce vast quantities of wind-dispersed seeds or spores
- repaid germination of seeds
- ability to photosynthesise
- ability to fix nitrogen from the atmosphere
- tolerance to extreme conditions
what shows that an organism is a part of the pioneer species?
the number of them increases then decreases
what is the final stage of succession?
climax community
what are features of a climax community?
- the community is stable
- the population size is stable at carrying capacity
- abiotic factors are constant over time
how does succession occur?
- colonisation by the pioneer species
- pioneer species change the environmental conditions
- the environment becomes more suitable for the new species
- there is a change in biodiversity
- to climax community
what are some examples of abiotic factors affecting population size?
- wind speed
- percentage water
- temperature
- oxygen concentration
- light intensity
- annual precipitation
what is intraspecific competition?
competition which occurs the same species
what is interspecific competition?
competition occurs in different species
how can population size be estimated?
- randomly placed quadrats
- quadrats along a belt transect
= used on organisms which are slow moving or non-motile - mark-release-recapture method for motile organisms
what are some assumptions made when using the mark-release-recapture method?
- deaths or births in organisms
- mark could be rubbed off during investigation
- no loss to predation
- marking does not affect survival
- no immigration
- birth rate and death rate are equal
what is the equation for the estimated population size?
total number of individuals in first sample x second sample / number of marked individuals recaptured
where does succession occur?
in natural ecosystems
what is the process of allopatric speciation?
- some members of population would be geographically isolated from the rest by physical barrier like mountains
- geographical separation means that parts of populations would experience different environmental pressures
- the reproductive barriers lead to reproductive isolation
- reproductive isolation prevents gene flow
what is the process of sympatric speciation?
- speciation takes place in same geographical location
- ecological or behavioural separation mechanisms(e.g. mate selection) leads to group being reproductively isolated
- reproductive isolation prevents gene flow
