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strand 7 (part 2) - Coggle Diagram
strand 7 (part 2)
populations
random sampling ~ random sampling is used to avoid any bias in collecting data. avoiding bias ensures that the data obtained is valid.
systematic sampling ~ samples are taken at regular intervals within a set sampling area. importance when some form of gradual change occurs in the communities.
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frequency ~ the likelihood of a particular species occurring in a quadrat. it gives a quick idea of the species present and their general distribution within an area. however it does not provide information on the density and detailed distribution of species.
percentage cover ~is an estimate of the area within a quadrat that a particular plant species covers. advantage – data be collected rapidly & individual plants do not need be counted disadvantage – less useful organisms occur in several overlapping layers.
mark capture release ~ known number animals caught, marked and released. some time later given number of individuals are collected randomly and mark recorded.
isolation and speciation
species ~ organisms that can breed together to reproduce living fertile offspring when the gametes fuse together
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genetic drift ~ when allele frequencies change by chance. in small reproductively isolated populations circumstances exist that can produce rapid changes in allele frequencies without mutation, the smaller the population the more susceptible to these changes
types of speciation
allopatric
involves a population becoming geographically separated, conditions either side of the barrier vary, natural selection occurs and populations adapt (adaptive radiation) over time this leads to reproductive separation.
sympatric
involves reproductive isolation within a randomly mating population. members of a population become reproductively isolated, caused by mutation which can influence many factors to cause isolation and leads to disruptive selection
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competition
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types of competition
intraspecific
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the larger the availability of resources, the larger the population.
interspecific
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individuals of different species occupying the same niche will have a competitive advantage over one another.
one population size will grow, the other shrink.
populations (2)
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mark capture release
estimated population size = total num of indiv in 1st sample x total number in 2nd sample/ number of marked recaptured
how do we catch them?
sweep nets, beating trays, pitfall traps, longworth traps
how do we mark them?
spot of paint for invertebrates, leg rings for birds, shaved hair for mammals, small disks for fish, blood sample to make a dna fingerprint for larger animals
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