sampling Flashcards
what does abundance mean?
the number of individuals of once species in a particular area
what is distribution?
where a particular species is within the area youre investigating.
what is a quadrat?
a square frame placed randomly on the ground to count number of species. moved to different random locations and repeated
quadrat key point
large number of quadrats need to be sampled for accuracy
quadrats placed randomly to avoid bias
area sampled divided up into grid and cooridnates generated using random number generator
what is a transect?
tape measure placed along varied stretch of habitat and use quadrat to record species at regular intervals along the line.
what are transects used for?
to see how the distribution of species changes as the habitat changes.
transect key point
2 types of transect: belt and interrupted
belt: quadrats placed next to each other along transect to work out species frequency
interrupted: take measurements along quadrat placed at regular intervals
what is percentage frequency?
the probability that a species will be found within a single quadrat
how is percentage frequency calculated?
number of quadrats in which species is found / number of quadrats x 100
what is percentage cover?
faster but more subjective
estimate what percentage of the area enclosed by quadrat is occupied by each species
what is a disadvantage of percentage cover?
plants in flowers tend to be over estimated and low growing plants are under estimated
mark release recapture method?
take a sample from population and count them
mark the population
release back into their habitat
wait for marked population to mix with the rest of the population
take a second sample in the same way
record the total number of animals in the second sample and the number of marked animals
how to calculate estimate population size?
number caught in first sample X number caught in second sample / number marked in 2nd sample
