Required Practical 12- Distribution of species

Question 1

Explain why it is important to use a statistical test in analysing the results of an investigation

Answer 1

-results may be due too chance
-confirm difference is significant
-in order to accept or reject null hypothesis

Question 2

Describe how you would place quadrats at random

Answer 2

random number generator on calculator
- to determine coordinates to place quadrat in a gridded area

Question 3

Describe how you would decide the number of quadrats to use in order to collect representative data

Answer 3

-enough to carry out a statistical test
-large enough to be reliable and collect in available time
-calculate running mean

Question 4

Explain why biologists collect data randomly

Answer 4

-avoid bias
-to collect representative data
-so statistical tests can be calculated

Question 5

Explain why it is important to check the repeatability of measurements

Answer 5

increases reliability of measurements
- differences less likely to be due to measurement error / anomalies

Question 6

Describe how you could use a scatter diagram to check the repeatability of measurements made by two observers

Answer 6

plot one set of results against the other
expect to see points lying close to line
OR
plot both sets against variable
look for overlapping/ corresponding points

Question 7

Suggest precautions taken when carrying out sampling

Answer 7

allow sufficient time to elapse before taking further samples so vegetation can recover from trampling
study organisms in situ or take minimum number and return

Question 8

Evaluate density in measuring abundance of a species

Answer 8

-most accurate
-time consuming
-not suitable when there are too many individuals / individuals are difficult to identify

Question 9

Evaluate percentage cover (% area of quadrat) in measuring abundance of a species

Answer 9

-more accurate than frequency but less time consuming compared to density
-subjective so unreliable
-does not consider overlapping individuals

Question 10

Evaluate frequency (% squares in quadrat) in measuring abundance of a species

Answer 10

-quick, basic overview
-inaccurate
-does not consider overlapping individuals

Question 11

Draw a conclusion using data provided

Answer 11

Give BALANCED Argument

-correlation data shows
-state if correlation is weak or strong
-give anomalous examples
-sample size small so unreliable
-other factors not considered
-cannot be sure since no statistical analysis

Question 12

Suggest precautions taken when sampling

Answer 12

-avoid trampling on vegetation
-allow sufficient time to elapse before further studies
-study organisms in situ / remove and return and minimum amount

Question 13

State when to use quadrats and transects

Answer 13

Quadrats - uniform distribution

Transects - distribution changes over an area

Question 14

Suggest why a certain number of samples is taken

Answer 14

too many would be too time-consuming
- too few would be unreliable and insufficient to eliminate anomalies