Biodiversity and its measurementEdexcel A-Level Biology A: Subtopic test

1. 1
   A botanist surveys the forest on a remote island. She records 42 plant species in total. Nine of these grow naturally on the island and nowhere else in the world; the other 33 also occur on the nearby mainland.

   (a)

   Which term describes the nine species found only on the island?

   [1 mark]

   • ANative
   • BEndemic
   • CInvasive
   • DKeystone

   (b)

   What percentage of the plant species recorded in the forest are endemic to the island?

   [1 mark]

   • A9.0%
   • B27%
   • C21%
   • D79%

   (c)

   Suggest why endemic species are more at risk of extinction from human activity than species that also occur elsewhere.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A conservation geneticist studies one gene locus in two populations of a rare orchid. In population A, 35 of the 50 plants sampled are heterozygous at the locus. In population B, 6 of the 40 plants sampled are heterozygous at the locus.

   (a)

   What does the heterozygosity index measure?

   [1 mark]

   • AThe genetic diversity within a population of one species
   • BThe number of different species in a habitat
   • CThe number of alleles that are dominant
   • DThe proportion of a population that is homozygous

   (b)

   What is the heterozygosity index for population A?

   [1 mark]

   • A0.14
   • B0.30
   • C0.35
   • D0.70

   (c)

   Calculate the heterozygosity index for population B and state which population has the greater genetic diversity at this locus.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   A student compares the beetles living in two habitats using pitfall traps. In the meadow she catches 50 beetles belonging to 5 species, in numbers of 20, 15, 10, 4 and 1. In the hedge bank she catches 50 beetles belonging to 3 species, in numbers of 40, 8 and 2. She uses the index of diversity, D = N(N − 1) / Σn(n − 1), where N is the total number of individuals and n is the number of individuals of each species.

   (a)

   Calculate the index of diversity for the meadow. Show your working.

   [3 marks]

   (b)

   The index of diversity for the hedge bank is 1.5. The student concludes that the meadow has the greater biodiversity. Evaluate this conclusion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A tropical rainforest in South-East Asia is cleared and replaced by a plantation of a single crop. Before clearance a survey recorded 150 plant and animal species per hectare. Afterwards the plantation holds 12 species per hectare, and the crop makes up 95% of all individuals. Small patches of the original forest remain, isolated from one another by plantation.

   (a)

   Explain how the change in land use is likely to reduce biodiversity at the level of habitats, species and genetic diversity.

   [6 marks]

   (b)

   Biologists want to compare the biodiversity of the plantation with that of the original forest. Evaluate the use of species richness, the index of diversity (D) and the heterozygosity index (H) for this comparison.

   [6 marks]

   Total for question 4: 12 marks

End of questions