Plant Structure and Function, Biodiversity and ConservationEdexcel International A Level Biology: Topic test

1. 1
   In a mature plant cell, a large central vacuole pushes the cytoplasm against a strong cell wall. Neighbouring plant cells are held firmly together by a layer between their walls.

   (a)

   What is the function of the middle lamella?

   [1 mark]

   • AIt stores starch
   • BIt allows substances to pass between neighbouring cells
   • CIt cements the walls of adjacent cells together
   • DIt controls which substances enter the cytoplasm

   (b)

   Which structure is surrounded by the tonoplast?

   [1 mark]

   • AVacuole
   • BChloroplast
   • CNucleus
   • DAmyloplast

   (c)

   Explain why a plant cell does not burst when it is placed in distilled water.

   [2 marks]

   Total for question 1: 4 marks

2. 2
   A horse and a donkey can mate and produce a mule. Mules are almost always infertile.

   (a)

   Why are horses and donkeys classified as different species?

   [1 mark]

   • AThey live in different habitats
   • BThey cannot mate with one another to produce fertile offspring
   • CThey are able to mate with one another
   • DThey differ in appearance

   (b)

   Which two domains contain only prokaryotic organisms?

   [1 mark]

   • AArchaea and Eukarya
   • BBacteria and Eukarya
   • CAll three domains
   • DArchaea and Bacteria

   (c)

   Explain why comparing the base sequences of DNA gives a more reliable classification than comparing the appearance of organisms.

   [2 marks]

   Total for question 2: 4 marks

3. 3
   Students used pitfall traps to sample ground beetles in two habitats: a conifer plantation (A) and an area of broadleaf woodland (B). In habitat A they caught 15 beetles from 3 species, with 10, 4 and 1 individuals of each species. In habitat B they caught 15 beetles from 5 species, with 4, 4, 3, 2 and 2 individuals of each species.

   (a)

   Calculate the index of diversity, D = N(N - 1) / Σn(n - 1), for each habitat and state which habitat has the higher biodiversity.

   [3 marks]

   (b)

   A student concludes that broadleaf woodland always has a higher biodiversity than conifer plantation. Evaluate how far these data support the conclusion.

   [4 marks]

   Total for question 3: 7 marks

4. 4
   A rare orchid has a population of 4,000 plants growing on a hillside. Flower colour is controlled by one gene with two alleles: the allele for purple flowers (P) is dominant to the allele for white flowers (p). In the population, 160 plants have white flowers. Conservationists want to protect the orchid.

   (a)

   Assume that the population is in Hardy-Weinberg equilibrium. Calculate the frequencies of the two alleles and the number of heterozygous plants, and state two conditions needed for the equation to apply.

   [6 marks]

   (b)

   Evaluate the use of a seed bank to help to conserve this orchid.

   [6 marks]

   Total for question 4: 12 marks

5. 5
   Emperor penguins breed in the Antarctic winter. The males huddle together in large groups, taking turns to stand on the outside of the huddle. They also have a thick layer of blubber and dense, waterproof feathers.

   (a)

   Which of the following is a behavioural adaptation of emperor penguins?

   [1 mark]

   • AA thick layer of blubber
   • BHuddling together in large groups
   • CDense, waterproof feathers
   • DA layer of insulating fat under the skin

   (b)

   Which statement best describes the niche of a species?

   [1 mark]

   • AThe place where the organism lives
   • BThe number of individuals of the species in a habitat
   • CThe range of different species found in a habitat
   • DThe role of the species in its habitat, including its interactions with other species and with abiotic factors

   (c)

   Explain how huddling together increases the chance of survival of the male penguins.

   [2 marks]

   Total for question 5: 4 marks

6. 6
   A gardener grows lettuces in a compost. The young leaves of some of the plants are distorted and stunted, and their growing points are dying.

   (a)

   Which mineral ion is needed to form the calcium pectate of the middle lamella, and so is likely to be deficient in these plants?

   [1 mark]

   • ACalcium ions
   • BNitrate ions
   • CMagnesium ions
   • DPhosphate ions

   (b)

   Which molecules in a plant need nitrate ions for their synthesis?

   [1 mark]

   • ACellulose and starch
   • BChlorophyll and cellulose
   • CAmino acids and DNA
   • DTriglycerides and glucose

   (c)

   Explain why a shortage of magnesium ions causes the leaves of a plant to turn yellow and the plant to grow slowly.

   [2 marks]

   Total for question 6: 4 marks

7. 7
   A researcher tests extracts from two plants, X and Y, for antibacterial activity. She spreads bacteria over a sterile agar plate and places paper discs soaked in each extract, and a disc soaked in sterile water, on the surface. After incubation at 25 °C for 48 hours, there is a clear zone with no bacterial growth around each extract disc. The zone around the disc with extract X has a diameter of 14 mm and the zone around extract Y has a diameter of 22 mm. There is no clear zone around the water disc. Extract Y is selected for development as a medicine.

   (a)

   Calculate the area of the clear zone for each extract and the number of times larger the zone for Y is than the zone for X.

   [3 marks]

   (b)

   Describe how the medicine made from extract Y would be tested on patients, including the use of a double-blind trial, and explain why a double-blind trial is used.

   [4 marks]

   Total for question 7: 7 marks

8. 8
   A large oak tree supports a trunk and branches that weigh many tonnes. Water travels from the roots to leaves more than 20 m above the ground, and sugars made in the leaves are transported to the roots. The cell walls of some of its cells are strengthened with cellulose and lignin.

   (a)

   Compare the structures and functions of xylem vessels, phloem sieve tubes and sclerenchyma fibres.

   [6 marks]

   (b)

   Explain how the structure of cellulose, the way it is arranged in the cell wall, and the presence of lignin give strength to the walls of the tree's cells.

   [6 marks]

   Total for question 8: 12 marks

End of questions