19.5 investigating populations

Question 1

factors

the size of the quadrat to use

Answer 1

depends on size of plan/animal being counted and how they are distributed

Question 2

factors

The number of sample quadrats to record within the study area

Answer 2

larger the number of sample quadrats the more reliable the results
balance between reliability of results and time available

Question 3

factors

The position of each quadrat within the study area

Answer 3

to produce statistically significant results random sampling must be used

Question 4

why do factors need to be considered when using a quadrat

Answer 4

to get the best representative results

Question 5

why is systematic sampling along belt transects useful

Answer 5

useful where some form of gradual change (transition) in communities of plants and animals takes place

Question 6

random sampling method (quadrats)

Answer 6

1. lay out 2 long tape measures at right angles long two sides of study area
2. obtain series of coordinates by using random numbers (computer generated
3. place quadrat at intersection of each pair of coordinates and record species within

Question 7

belt transect method

Answer 7

stretch string/tape across ground in a straight line
frame quadrat laid down beside line and species within it recorded
then moved its own length along line and process repeated

Question 8

ways to measure abundance of species

frequency

Answer 8

likelihood of a particular species occurring in a quadrat
e.g. species occure 15 out of 30 quadrats, abundance is 50%
+useful when species hard to count. quick idea of species in area and their distribution
-does not provide info on density and detailed sitribution of species

Question 9

ways to measure abundance of species

percentage cover

Answer 9

estimate of area within a quadrat that a particualar species covers
useful when a species in abundant or hard to count
+data can be collected rapidly. individual plants do not need to be counted
-less useful where organisms occur in overlapping layers

Question 10

mark-release-recapture method

Answer 10

known number of animals caught and marked
released back into community
some time later a given number of individuals is collected randomly
number of marked individuals is recorded

estimated population size= (total no. of individuals in 1st sample x total no. of individuals in 2nd sample) / number of marked individuals recaptured