20. Human influences on ecosystems
A section of Biology, 0610
Listing 10 of 393 questions
Rain forests are the natural vegetation in areas with high rainfall. Tropical rain forest is being cut down in many parts of the world to clear land for agriculture. The soil of the rain forest allows water to drain through it very rapidly. Table 3.1 shows the yield of cotton crops, grown under three different conditions, on land cleared of rain forest. Table 3.1 yield of cotton / kg per hectare years since the forest was cleared no fertiliser added to the soil fertiliser added to soil during year 1 chopped grass added to the soil during year 1 What happened to the yield of cotton over the three years if no fertiliser was added to the soil? For Examiner's Use Suggest possible reasons for this change in the yield of cotton. What happened to the yield of cotton when fertiliser was added to the soil in year 1? Suggest why excessive quantities of fertiliser should not be added to the soil. Chopped grass added to the soil has little effect on the crop yield in year 1. Suggest why it has much greater effect on the yield in years 2 and 3.
0610_s10_qp_21
THEORY
2010
Paper 2, Variant 1
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For Examiner's Use The Food and Agriculture Organization (FAO) collects data on food supplies worldwide. The FAO classifies the causes of severe food shortages as either by natural disasters or as the result of human action. Natural disasters are divided into those that occur suddenly and those that take a long time to develop. Human actions are divided into those that are caused by economic factors and those that are caused by wars and other conflicts. shows the changes in the number of severe food shortages between 1981 and 2007. 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003 2005 2007 total natural disasters result of human action year number of severe food shortages For Examiner's Use shows the causes of severe food shortages in the 1980s, 1990s and 2000s. natural disasters result of human action key sudden onset economic factors slow onset war and conflict 1980s 1990s 2000s 86 % 80 % 73 % 14 % 20 % 27 % 14 % 2 % 20 % 27 % 11 % 98 % 89 % 73 % 27 % 11 % 27 % 98 % 89 % 73 % State two types of natural disaster that occur suddenly and may lead to severe food shortages. 1. 2. State one type of natural disaster that may take several years to develop. For Examiner's Use Use the information in and to describe the changes in food shortages between 1981 and 2007. Explain how the increase in the human population may contribute to severe food shortages. For Examiner's Use The quality and quantity of food available worldwide has been improved by artificial selection (selective breeding) and genetic engineering. Use a named example to outline how artificial selection is used to improve the quantity or quality of food. Define the term genetic engineering.
0610_s10_qp_31
THEORY
2010
Paper 3, Variant 1
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For Examiner's Use The highest yields of potatoes are obtained in the USA. In Bangladesh they are very much lower. Scientists investigated the effects of improving soil fertility on the growth and yields of potatoes in Bangladesh. They carried out an investigation by dividing a field into four plots, E to H. The potatoes in each plot received different treatments: E – no fertiliser or manure F – manure only G – chemical fertiliser only H – manure and chemical fertiliser The scientists measured different aspects of growth and final yield of the potato plants. Their results are shown in Table 3.1. Table 3.1 plot treatment mean plant height at maturity / cm mean fresh mass of potato tubers per plant / g yield of potato tubers / tonnes per hectare E no fertiliser or manure 46.2 190.0 12.6 F manure only 59.3 285.0 19.3 G chemical fertiliser only 66.1 320.5 21.2 H manure and chemical fertiliser 71.5 365.0 24.3 The yield of potato tubers was greater in plot H than in plot E. Calculate the difference in yield as a percentage of the yield in plot E. Show your working. Answer = % Suggest and explain the importance of increased plant height in the production of tubers. For Examiner's Use Describe the effect of adding manure and chemical fertilisers on the yield of potato tubers. Manure and chemical fertilisers provide plants with nitrate ions. Explain how extra nitrate ions in the soil may have increased the yield of the potatoes. State why plot E was included in this investigation. Discuss the advantages and disadvantages of adding chemical fertilisers to crops.
0610_s10_qp_32
THEORY
2010
Paper 3, Variant 2
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For Examiner's Use The highest yields of potatoes are obtained in the USA. In Bangladesh they are very much lower. Scientists investigated the effects of improving soil fertility on the growth and yields of potatoes in Bangladesh. They carried out an investigation by dividing a field into four plots, E to H. The potatoes in each plot received different treatments: E – no fertiliser or manure F – manure only G – chemical fertiliser only H – manure and chemical fertiliser The scientists measured different aspects of growth and final yield of the potato plants. Their results are shown in Table 3.1. Table 3.1 plot treatment mean plant height at maturity / cm mean fresh mass of potato tubers per plant / g yield of potato tubers / tonnes per hectare E no fertiliser or manure 46.2 190.0 12.6 F manure only 59.3 285.0 19.3 G chemical fertiliser only 66.1 320.5 21.2 H manure and chemical fertiliser 71.5 365.0 24.3 The yield of potato tubers was greater in plot H than in plot E. Calculate the difference in yield as a percentage of the yield in plot E. Show your working. Answer = % Suggest and explain the importance of increased plant height in the production of tubers. For Examiner's Use Describe the effect of adding manure and chemical fertilisers on the yield of potato tubers. Manure and chemical fertilisers provide plants with nitrate ions. Explain how extra nitrate ions in the soil may have increased the yield of the potatoes. State why plot E was included in this investigation. Discuss the advantages and disadvantages of adding chemical fertilisers to crops.
0610_s10_qp_33
THEORY
2010
Paper 3, Variant 3
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Questions Discovered
393