investigation population Flashcards
(20 cards)
how do you study a habitat
you need to count the number of individual of a species in a given space - abundance
why do we use samples
because it is impossible to count every organism and in doing so would damge the habitats
what is a point quadrat
a horizontal bar supported by two lefs
at set intervals are ten holes which a pin may be droped and the species that touches the pin is recorded
what is a frame quadrat
square frame divided by string or wire into equal subdivisions , the quadrat is placed in different areas with the abundance of each species within a quadrat then recorded
why doe we need to think about the size of the quadrat being used
this will depend on the size of plant or animal being counted and their distribution larger species require larger quadrats
what do we need if the population is unevenly disribulted
large number of small quadrat samples
what does a larger number of sampkle quadrat mean
the more reliable the results will be
as the nuber of different species increase what needs to be increase
the nuber of quadrats used
what must the position of the quadrat be
random sampling to produce statistically significant results
how to set out random sampling of two different field
choose fields that are close together to avoid, differnet soil conditions and tempo and water ect
lay two tapes at right angle
obtain a series of coordinates from generator
place quadrate on intersect of coordinates and record the species
why do we use systematic sampling
it is more informative especially wen there is gradual chanfe along a line of succession
how to do a belt transect
stretch a string ot tape across the ground in a straight line ,
a frame quadrat is laid alongside the tape and species recorderd
the quadrat is then moved across it length and recorded
what is abundance
the number of individuals of species living in a certain area at a given time
how do we measure frequency
it is the likelihood that a particular species will appear in a quadrat eg if a bee appeared in 15/ 30 of the quadrats the frequency is 50%
what is percentage cover
estimate of the area within a quadrat that a species covers , useful when a species is particulary abundant
what is the benfit of using these techniques
data can be collected rapidly and individual plants do not need to be counted
why cant we use quadrats for motile organisms
they move when they are approached they are often hidden and are difficult to find and identify
how do we measure the abundance of animals
known number of animals are caught
marked in some way
release
some time later a given number of organisms are captured and the number of marked individuals are counted and recorded
the size of the population is counted by
total individuals in first x total individuals in second sample/ number of marked individuals
what does capture and recapture rely on
the proportion of marked to unmarked is ame first and second time round
no new deaths no new birth
no immigration or emigration
mark not rubbed off
