1 154 ii The aquatic plants and the reeds both

1 154 ii the aquatic plants and the reeds both

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Sciencemathsmaster.weebly.com 154 (ii) The aquatic plants and the reeds both contribute to the formation of soil. Suggest how the aquatic plants and reeds contribute to raising the soil level. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) S (iii) The sedges are rooted in waterlogged soil. Their stems contain a spongy tissue through which air can reach the roots. Explain how this is important for the absorption of mineral ions by the sedges. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (3) (b) Explain why the ecosystem is likely to have more species in the later stages than in the earlier stages of succession. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (2) (Total 8 marks)
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Sciencemathsmaster.weebly.com 155 84. Chalk grassland is an important habitat for butterflies. Conservation of butterflies living in grassland depends on controlling the height of the grass by managing grazing by sheep. Table 1 shows the effects of grazing on the population of the meadow brown butterfly in three different areas of a nature reserve, X , Y and Z . Management scheme Population of meadow brown butterflies 1976 1983 Area Grazed by sheep in summer X Area Grazed by sheep in winter Y Area Not grazed by sheep Z 435 522 287 415 595 239 0.47 4.77 4.38 x 2 Table 1 Table 2 shows part of a chi-squared table Probability Degrees of freedom 1 2 0.50 0.45 1.39 0.25 1.32 2.77 0.10 2.71 4.61 0.05 3.84 5.99 0.02 5.41 7.82 0.01 6.64 9.21 Table 2
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Sciencemathsmaster.weebly.com 156 (a) Are there any significant differences in the population sizes in areas X , Y and Z between 1976 and 1983? Explain your answer. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (3) (b) Which type of grazing would you recommend in order to conserve the meadow brown butterfly? Explain your answer. ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (1)
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Sciencemathsmaster.weebly.com 157 S (c) The butterfly lays its eggs on vetch plants. The graph shows the number of eggs found on vetch plants in different heights of grass. 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 1 2 3 4 5 6 7 8 9 10 Height of grass where vetch plants are found / cm Mean number of eggs per vetch plant Use the information in the graph to explain the results shown in Table 1 . ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... ................................................................................................................................... (3) (Total 7 marks)
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Sciencemathsmaster.weebly.com 158 85. Small clearings in woods may occur when large trees die or are blown down. This allows herbaceous plants to grow for a few years. One plant species that commonly colonises woodland clearings is the foxglove. (a) Name and describe the ecological process which will result in the disappearance of foxgloves from a clearing after a few years. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (3) S (b) The foxglove is a biennial plant, which means that it lives for two years. In the first year it produces leaves but no flowers. In the second year it flowers and each plant releases about 300 000 very small seeds. (i) Suggest how being a biennial enables a foxglove plant to produce very large numbers of seeds. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2) (ii) Suggest how producing large numbers of very small seeds adapts the foxglove for colonising woodland clearings. .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... .......................................................................................................................... (2)
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Sciencemathsmaster.weebly.com 159 S (c) The leaves of foxgloves contain a poisonous substance, called digitalis. In high concentrations, digitalis slows down the rate at which impulses pass across the atria of the heart.
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