Biodiversity and natural resourcesEdexcel A-Level Biology A: Topic test

1. 1
   A survey of a woodland recorded four species of millipede. The numbers of individuals found were 8, 6, 4 and 2.

   (a)

   One of the millipede species is found naturally only in this woodland and nowhere else. Which term describes this?

   [1 mark]

   • ASpecies richness
   • BEndemism
   • CGenetic diversity
   • DHeterozygosity

   (b)

   The index of diversity is D = N(N − 1) ÷ Σn(n − 1). What is the index of diversity for the millipedes in the woodland?

   [1 mark]

   • A3.2
   • B4.0
   • C0.26
   • D3.8

   (c)

   A gene for body colour in one millipede species was studied. Of the 56 millipedes of this species that were collected, 14 were heterozygous for the gene. Calculate the heterozygosity index and state what it shows.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   The base sequences of the same gene in four species of bird, P, Q, R and S, were compared. The sequences from P and Q differ at 3 of 500 positions, those from P and R at 20 positions and those from P and S at 55 positions.

   (a)

   Which species is most closely related to P?

   [1 mark]

   • AS
   • BR
   • CQ
   • DThe relationship cannot be deduced from DNA

   (b)

   On what evidence were the Archaea placed in a separate domain from the Bacteria?

   [1 mark]

   • ADifferences in the base sequences of their ribosomal RNA, and other molecular differences
   • BThey have a nucleus
   • CThey are multicellular
   • DThey live only in extreme environments

   (c)

   Explain why the scientific community critically evaluates new data before a new taxonomic group is accepted.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Bamboo stems are strong enough to be used as scaffolding in parts of Asia. A bamboo stem contains bundles of xylem vessels and sclerenchyma fibres, and all of its cells have walls made of cellulose.

   (a)

   Explain how the structure of cellulose makes the cell walls strong.

   [3 marks]

   (b)

   Compare the structure and function of xylem vessels and sclerenchyma fibres in the bamboo stem.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   In a large population of bank voles, the allele for black fur (b) is recessive to the allele for brown fur (B). 16% of the voles are black. A new motorway later divides the population into two groups that cannot meet or interbreed.

   (a)

   Use the Hardy-Weinberg equation to calculate the frequency of each allele and the percentage of voles that are heterozygous, and state two conditions that must apply for the principle to hold.

   [6 marks]

   (b)

   Explain how the isolation of the two groups of voles by the motorway could eventually lead to the formation of two new species.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   A student grows duckweed, a small floating plant, in four solutions: a complete nutrient solution, and solutions each lacking only nitrate ions, only magnesium ions or only calcium ions.

   (a)

   Which symptom would be expected in the duckweed grown without magnesium ions?

   [1 mark]

   • AYellowing of the leaves because chlorophyll cannot be made
   • BWeak cells that separate from each other because the middle lamella is poorly formed
   • CStunted growth because amino acids cannot be made
   • DWilting because water cannot be absorbed

   (b)

   Which substances does a plant make using nitrate ions?

   [1 mark]

   • AChlorophyll only
   • BCellulose
   • CAmino acids and nucleotides
   • DCalcium pectate

   (c)

   The duckweed lacking calcium ions grew poorly and its tissues were weak. Explain why.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   Before a new drug is given to patients, it is tested in a clinical trial. 400 volunteers with the condition are assigned at random to receive either the drug or a placebo, and neither the volunteers nor the doctors know who has received which until the end of the trial.

   (a)

   What is the purpose of the placebo?

   [1 mark]

   • ATo increase the dose that patients receive
   • BTo kill any bacteria in the patients
   • CTo make sure that every patient eventually receives the drug
   • DTo separate the effect of the drug from the effect of the patients' expectations

   (b)

   Why is the trial double blind?

   [1 mark]

   • ATo check that the drug is safe at every dose
   • BTo prevent the expectations of both the volunteers and the doctors from biasing the results
   • CTo reduce the number of volunteers needed
   • DTo make the drug and the placebo look identical

   (c)

   Describe what is tested in Phase 1 and in Phase 3 of the testing of a new drug.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A government environment department is planning how to protect endangered species and how to reduce the country's use of non-renewable resources.

   (a)

   The Arabian oryx became extinct in the wild in the 1970s. Animals bred in zoos were later reintroduced to protected desert reserves. Evaluate the contribution of zoos to the conservation of species such as the oryx.

   [3 marks]

   (b)

   Explain how the use of plant fibres and starch to make plastic-like products can contribute to sustainability.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   Two woodlands, X and Y, of the same area were surveyed for birds. In woodland X the numbers of individuals of five species were 12, 9, 5, 3 and 1. In woodland Y the numbers of individuals of four species were 22, 5, 2 and 1. Woodland X also contains two species of tit: one feeds on insects in the tops of the trees and the other feeds on seeds on the ground.

   (a)

   Calculate the index of diversity for each woodland and use your values to compare their biodiversity.

   [6 marks]

   (b)

   Explain the concept of a niche and why the two species of tit can live in the same woodland, and explain how natural selection could lead to the adaptation of one of the tit species to its niche.

   [6 marks]

   Total for question 8: 12 marks

End of questions