3.7.4 populations in ecosystems Flashcards
what is sampling?
sampling is investigating a subset of a population or community.
> sampling techniques should be unbiased.
how do you work out abundance using sampling?
isolate a standard unit of area for study of the distribution of organisms over a large area.
what is used in systematic sampling?
sampling along a transect.
when is counting used in quadrats?
- if population is small.
- individuals are easy to identify.
when is percentage cover used in quadrats?
- appropriate for organisms which form continuous cover over a surface like lichen or grass.
when is t-tests used?
used when we have two sets of numerical data, which measure the same variable but in two different populations.
> used to determine if the means of two sets of data are significantly different.
what is a community?
a group of populations of different species living together in one habitat, at the same time.
what is an ecosystem?
a collection of communities and their non-living surroundings, which form a stable system in which there is energy flow and nutrients are recycled.
what is a population?
a group of members of the same species that interact with each other, occupying the same habitat at the same time.
what is a habitat?
place where an organism lives characterised by the physical conditions and other species present.
what is a niche?
how an organism fits into the environment.
only one species can occupy a specific niche.
what is the carrying capacity?
the maximum population size a habitat can support over an extended period of time.
> determined by limiting factors.
how does temperature affect growth?
- high temperatures can cause enzymes to denature > enzymes used in photosynthesis and respiration.
- low temperatures, slow reactions > less kinetic energy.
how does light affect growth?
- high light can cause an increase in photosynthesis.
- low light can cause a decrease in photosynthesis > less glucose, less biomass.
how does pH affect growth?
- changing/unstable pH can cause enzymes to denature.
how does water and humidity affect growth?
- a high humidity can cause a decrease in transpiration rate.
- low water will cause a decrease ion photosynthesis > less glucose, less biomass > used in reactions and support (turgidity of cells).
what biotic factors affect carrying capacity?
- intraspecific competition (same species).
- interspecific competition (different species).
- predication, predator prey cycles in population.
what is mark-release-capture?
- mark using friendly paint, shaving small section of fur and tagging.
total in sample 1 x total in sample 2 / number marked and recaptured
what are the limitations and assumptions of mark-release-recapture?
- no births or deaths.
- assume population mixes.
- no migration/immigration.
- mark isn’t lost.
- mark doesn’t cause harm.
- equally likely to be caught.
what is spearman’s rank?
> use when we have two sets of numerical data, that we believe is correlated.
values must be paired so that their ranks can be compared.
must be enough data to make a judgement about correlation and doesn’t need to be evenly distributed.
what is succession?
change over time of the species occupying a particular area.
what are the stages of succession?
1) bare rock/barren land = harsh and hostile.
2) pioneer species = able to survive and grow in harsh environments (moss/lichen).
3) lichen die and decompose = releasing nutrients = organic matter builds up = mosses/small ferns start to grow.
4) mosses/ferns die and decompose = making conditions less hostile.
5) top soil/humus becomes more fertile = enables other species to grow = these plants also die and decompose.
6) organic matter can retain water an provide anchorage for roots = abiotic conditions less hostile, greater variety of habitats/niches, increased biodiversity, more complex food webs and increased biomass.
7) until we reach stable CLIMAX COMMUNITY.
what are the two types of succession?
primary = from purely inorganic starting point (sand dune/bare rock).
secondary = from area cleared of organisms, but with soil present (land cleared after fire) > quicker, doesn’t require pioneer species.
what is a plagioclimax community?
a community that will not develop further as humans are influencing it.
