investigating biodiversity

Question 1

How can genetic diversity within or between species be measured?

Answer 1

● Comparing frequency of measurable/observable characteristics
● Comparing base sequence of DNA/mRNA
● Comparing amino acid sequence of a specific protein encoded by DNA and mRNA

Question 2

Explain how comparing DNA, mRNA and amino acid sequences can indicate relationships between organisms within a species and between species.

Answer 2

More differences in sequences → more distantly related
● As mutations (change in DNA base sequences) build up over time

Question 3

Explain the change in methods of investigating genetic diversity over time

Answer 3

● Early estimates made by inferring DNA difference from measurable or observable characteristics
○ Many coded for by more than one gene → difficult to distinguish one from another
○ Many influenced by environment → differences due to environment not genes
● Gene technologies allowed this to be replaced by direct investigation of DNA sequences

Question 4

Explain the key considerations in quantitative investigations of variation
within a species

Answer 4

● Collect data from random samples (use a random number generator) → removes bias
● Use large sample size→representative of whole population

● Ethical sampling → must not harm organism / allow release unchanged.

Maths:
● Calc mean value of collected data+standard deviation of that mean
● Interpret mean values and their SD
● Use [named] statistical test → analyse whether there is a significant difference between populations

Question 5

Describe how you would determine the mean percentage cover for beach grass on a sand dune.

Answer 5

1. Method of randomly determining position (of quadrats) e.g. random numbers table/generator;
2. Large number/sample of quadrats;
3. Divide total percentage by number of
   quadrats/samples/readings;

Question 6

The mark-release-recapture method can be used to estimate the size of a fish
population (lines 13–14).
Explain how

Answer 6

Capture/collect sample, mark and release;
2. Ensure marking is not harmful (to fish)
3. Allow (time for) fish to (randomly) distribute before collecting a second sample;
4. (Population =) number in first sample ×
number in second sample divided by
number of marked fish in second
sample/number recaptured;

Question 7

Suggest why the mark-release-recapture method can produce unreliable results in
very large lakes (lines 14–15).

Answer 7

. Less chance of recapturing fish
OR
Unlikely fish distribute randomly/evenly;