Measuring biodiversityAQA A-Level Biology: Subtopic test

1. 1
   Two ponds were each surveyed with the same sampling effort. Each pond contained four species and 100 individuals in total. In pond A the individuals were shared equally between the four species. In pond B, one species made up 97 of the individuals and each of the other three species was represented by a single individual.

   (a)

   Which statement defines species richness?

   [1 mark]

   • AThe number of individuals of the commonest species in a community
   • BThe number of different species in a community
   • CThe total number of individuals of all species in a community
   • DThe relationship between the number of species and the number of individuals in each species

   (b)

   Which pond has the higher index of diversity, and why?

   [1 mark]

   • APond A, because the individuals are spread evenly between the species
   • BPond B, because it contains a very large population of one species
   • CBoth ponds have the same value because they have the same number of species
   • DPond B, because three of its species are rare

   (c)

   Explain why species richness alone is not a sufficient measure of the biodiversity of the two ponds.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   An ecologist calculated the index of diversity (d) for ground beetles in two habitats. The value for a hedgerow was 1.8 and the value for an area of ancient woodland was 14.5.

   (a)

   Which conclusion is best supported by these values?

   [1 mark]

   • AThe hedgerow is more diverse, because a lower value shows individuals are spread more evenly
   • BThe woodland must contain more individuals than the hedgerow
   • CThe woodland community is more diverse, with more species and/or a more even spread of individuals between them
   • DThe woodland contains exactly eight times as many species as the hedgerow

   (b)

   A community containing only a single species, with more than one individual, would give a value of d equal to which of the following?

   [1 mark]

   • A0
   • B0.5
   • CThe total number of individuals, N
   • D1

   (c)

   Suggest why the community in the woodland is likely to be more stable than the community in the hedgerow when the environment changes.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A survey of ground beetles in a woodland used randomly placed pitfall traps and recorded five species, with 12, 8, 5, 3 and 2 individuals of each. A sample collected in the same way in a neighbouring conifer plantation contained three species, with 25, 4 and 1 individuals of each.

   (a)

   Calculate the index of diversity (d) for the woodland sample, using $d = \frac{N(N-1)}{\sum n(n-1)}$. Show your working.

   [3 marks]

   (b)

   Calculate the index of diversity for the conifer plantation sample and use both values to compare the two habitats.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   An ecologist compared two meadows in the same county. Each was sampled once in June using the same number of randomly placed quadrats. In meadow X, 12 plant species were recorded but a single grass species made up about 90% of all the plants counted. In meadow Y, 7 plant species were recorded, with roughly equal numbers of each.

   (a)

   Evaluate which meadow has the greater biodiversity, referring to species richness and to an index of diversity.

   [6 marks]

   (b)

   The county council wants to use these results to describe the biodiversity of all meadows in the county. Evaluate how reliable this conclusion would be, and explain how the investigation could be improved.

   [6 marks]

   Total for question 4: 12 marks

End of questions