4.6 - Biodiversity within a community

Question 1

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

Answer 1

• (Index of diversity also) measures abundance / number / population (size) of each species
• (So useful because) may be many of some species / (So useful because) may be few of other species

Question 2

What data would the students need to collect to calculate their index of diversity in each habitat? Do not include apparatus used for species sampling in your answer. (1)

Answer 2

• (Number of species and) number of individuals in each species (in each habitat)
• (Number of species and) population of each species (in each habitat)

Question 3

Give two ways the students would have ensured their index of diversity was representative of each habitat. (2)

Answer 3

• Random samples
• Large number (of samples) / (Continue sampling) until stable running mean

Question 4

Farmers are now being encouraged to replant hedges on their land. Suggest and explain one advantage and one disadvantage to a farmer of replanting hedges on her farmland. (2)

Answer 4

Advantage:
- Greater (bio)diversity so increase in predators of pests
- Increase in predators of pests so more yield/income/less pesticides/less damage to crops
- Increase in pollinators so more yield/income
- May attract more tourists/subsidies to their farm so more income (from diversification)

Disadvantage:
- Reduced land area for crop growth/income
- Greater (bio)diversity so increase pest population
- Increase pest population so less yield/less income/(more) need for pesticides/(more) damage to crops
- Increased (interspecific) competition so less yield/income
- More difficult to farm so less income

Question 5

What is meant by ‘species richness’? (1)

Answer 5

• (A measure of) the number of (different) species in a community

Question 6

Three of the bee species collected in the farmland areas were Peponapis pruinosa, Andrena chlorogaster and Andrena piperi. What do these names suggest about the evolutionary relationships between these bee species? Explain your answer. (2)

Answer 6

• A. chlorogaster and A. piperi are more closely related (to each other than to P. pruinosa)
• Because they are in the same genus

Question 7

Define each of the following terms:
- Species
- Species richness (2)

Answer 7

• Species = (A group of) organisms that are able to produce fertile offspring
• Species richness = the number of (different) species in a community

Question 8

The UK government pays farmers to leave grassy strips around the edges of fields of crops. These grassy strips contain a variety of plant species. Leaving the strips is an attempt to encourage biodiversity of animals. Give two reasons why the grassy strips increase the biodiversity of animals. (2)

Answer 8

• Increase in plant diversity leads to more types of food for animals
• Increase in variety of animals leads to increase in predator species
• Increase in niche / habitat

Question 9

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

Answer 9

• Non-native species out-competes / kills / eats / is a disease of native plants
• Some (populations of) native species become extinct (in the community)

Question 10

Suggest how this student would obtain data to give a more precise value for the index of diversity of this habitat. (2)

Answer 10

• Take more samples and find mean
• Method for randomised samples described

Question 11

Species richness and an index of diversity can be used to measure biodiversity within a community. What is the difference between these two measures of biodiversity? (1)

Answer 11

• Species richness measures only number of (different) species / does not measure number of individuals