Biodiversity

Question 1

How do you work out the modal value of species richness from a graph?

Answer 1

It’s the one with the most dots on the row of species richness

Question 2

68% of all the fish caught in this investigation came from sample A.
A student thought this showed that sample A had a greater index of diversity than any of the other samples.

It is not possible to draw this conclusion from the given data.
Give reason why

3 marks

Answer 2

1. Number of individuals of each species not known;
2. Almost all (of sample A / the 68%) could be of the same species;
3. Two / other samples have a higher number of species / higher species richness but a lower number of individuals / fish;
4. Other samples may have more individuals of each species;

Question 3

The student wanted to use the data from plot 1 to estimate the total number of the beetle species in the meadow.
Suggest how the student should use the data from plot 1 and other information provided to estimate the total number of the beetle species in the meadow.
4 marks

Answer 3

1. Determine the area of plot 1.
2. Calculate (total) area of meadow;
3. Divide area of meadow by area of plot;
4. Multiply by number of beetles (per plot)/41;
   Accept multiply by incorrect figure taken from figure (eg 43)

Question 4

Explain why it is more useful to calculate an index of diversity than to
record species richness.
2 marks

Answer 4

1.
(Index of diversity also) measures abundance / number / population (size) of each species;
Ignore “total number of species” unqualified
Accept: every species for each species.

2.
(So useful because) may be many of some species
OR
(So useful because) may be few of other species;

Question 5

The scientists decided to collect animals from the soil samples for 40 minutes.

Suggest how the scientists decided that 40 minutes was an appropriate
time.

2 marks

Answer 5

1.
Repeat soil sorting for different times and record number of species collected;

2
Find optimum time / time beyond which further sorting does not lead to increase in animal species found

Question 6

Suggest an explanation for the effect size when non-native species were introduced to communities
2 marks

Answer 6

1. Non-native species out-competes / kills / eats / is a disease of native
2. Some (populations of) native species become extinct (in the
   community);

Question 7

Describe how you would investigate the effect of an invasion by a non-native species of plant (a biotic environmental factor) over many years on the abundance of a native species of plant in a community.

3 marks

Answer 7

1. Set up grid system with coordinates;
2. Place large number of quadrats (at coordinates) selected at random;
3. Count number of / estimate percentage cover of native plant in quadrats;
4. Repeat at same time each year (for many years);

Same answer if you were asked this question:
Outline a method the ecologists could have used to determine the plant species richness at one site.

Question 8

Suggest how this student would obtain data to give a more precise value for the index of diversity of this habitat.

2 marks

Answer 8

1. Take more samples and find mean
2. Method for randomised samples described

All larger area = 1 mark