1. Study the passage and data below and then answer the questions that follow. Grazing in the Serengeti grassland The Serengeti is a huge area of tropical grassland in Tanzania. Herds of grazing mammals, such as wildebeest, gazelle and zebra, roam freely. Every year, these herds migrate across the Serengeti, in search of fresh grassland. The grazing mammals affect the primary productivity of the grassland. Long-term research has found that the rate of primary production is linked to both the rainfall and the numbers of grazing mammals. - Figure 1 Map of Africa showing the location of the Serengeti Figure 2 A wildebeast, one of the many types of grazing mammal found in the Serengeti Grazing can increase the growth rate of many grass species. This is called compensatory growth. The grazing mammals remove the upper parts of the grass leaves and this increases the amount of light reaching the rest of the plant. The smaller leaf area reduces transpiration and this decreases the uptake of water by the roots. Researchers investigated compensatory growth of grasses in a region of the Serengeti. They fenced off several areas to prevent mammals from grazing the grass. During the annual migration, thousands of wildebeest moved into the study region where they grazed intensively for 4 days and then moved on. The researchers recorded the changes in the fresh biomass of the grasses in the grazed and ungrazed areas over the next 32 days (Figure 3). A further investigation studied the effect of grazing intensity on primary productivity (Figure 4). 1
59764515 Unit 4 Ecology Evolution Ecoystems Global Warming Forensics Questions
Oct 02, 2014
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1. Study the passage and data below and then answer the questions that follow.
Grazing in the Serengeti grassland
The Serengeti is a huge area of tropical grassland in Tanzania. Herds of grazing mammals, such as wildebeest, gazelle and zebra, roam freely. Every year, these herds migrate across the Serengeti, in search of fresh grassland. The grazing mammals affect the primary productivity of the grassland. Long-term research has found that the rate of primary production is linked to both the rainfall and the numbers of grazing mammals.
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Figure 1Map of Africa showing
the location of the Serengeti
Figure 2A wildebeast, one of the manytypes of grazing mammal foundin the Serengeti
Grazing can increase the growth rate of many grass species. This is called compensatory growth. The grazing mammals remove the upper parts of the grass leaves and this increases the amount of light reaching the rest of the plant. The smaller leaf area reduces transpiration and this decreases the uptake of water by the roots. Researchers investigated compensatory growth of grasses in a region of the Serengeti. They fenced off several areas to prevent mammals from grazing the grass. During the annual migration, thousands of wildebeest moved into the study region where they grazed intensively for 4 days and then moved on. The researchers recorded the changes in the fresh biomass of the grasses in the grazed and ungrazed areas over the next 32 days (Figure 3). A further investigation studied the effect of grazing intensity on primary productivity (Figure 4).
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Figure 3
Table showing the fresh biomass over a 32 day period on grazed and ungrazed grassland. Day I is the first day after the wildebeest moved on.
D a yF r e s h b i o m a s s / g m
G r a z e d U n g r a z e d
1
8
1 6
2 4
3 2
5 0
5 5
1 0 0
1 2 0
2 0 0
4 3 0
4 2 0
3 8 0
3 5 0
3 0 0
– 2
Figure 4
Graph to show the effect of grazing intensityon the primary productivity of Serengeti grassland
9 0 0
8 0 0
7 0 0
6 0 0
5 0 0
4 0 0
3 0 0
2 0 0
1 0 0
00 . 0 0 . 1 0 . 2 0 . 3 0 . 4 0 . 5 0 . 6 0 . 7 0 . 8
G r a z i n g i n t e n s i t y / a r b i t r a r y u n i t s
P r o d u c t i v i t y / g m y e a r– 2 – 1
(a) Define the terms biomass and productivity.
Biomass
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Productivity
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(b) (i) Using the data in Figure 3, calculate the mean rate of change of fresh biomass per day, for both the grazed and ungrazed grassland, between days 1 and 32. Show your working.
Grazed grassland.........................................
Ungrazed grassland.....................................(4)
(ii) Suggest why the fresh biomass of grass in the ungrazed area decreased.
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(c) Study the information provided in Figure 4
(i) What is the optimum grazing intensity for Serengeti grassland?
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(ii) Suggest reasons for the very low levels of primary productivity at the highest grazing intensity (0.8 arbitrary units).
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(d) In the Serengeti, lions are the top consumers. Suggest and explain how a fall in the number of lions could affect the Serengeti food chain and grassland productivity.
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(e) The grazing mammals have an important role to play in the recycling of nutrients on the grassland. Their dung is rich in organic nitrogen-containing compounds. Describe how these compounds are converted to nitrates.
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(Total 20 marks)
2. Scientists estimate that the atmosphere holds 755 gigatonnes (Gt) of carbon, mostly as carbon dioxide. This value is increasing each year as a result of human activities, such as the burning of fossil fuels and of timber. The diagram below shows a simplified “balance sheet” of the carbon cycle for one year.
A t m o s p h e r i cc a r b o n ( 7 5 5 G t )
B u r n i n g o ff o s s i l f u e l s
V o l c a n i ce r u p t i o n s
B u r n i n go f t i m b e r
R e s p i r a t i o n
P h o t o s y n t h e s i s
O c e a n i cp r o c e s s e s
5 . 5 G t
0 . 1 G t
1 . 6 G t 1 2 0 G t1 2 1 G t
9 0 G t
9 3 G t
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(a) Calculate the increase in atmospheric carbon during this year. Show your working.
Answer ..............................................................(3)
(b) Describe and explain how carbon can be removed from the terrestrial (land based) part of the cycle for long lengths of time.
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(c) By reference to the information in the cycle, suggest reasons for the net effect of oceanic processes on the carbon content of the atmosphere.
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(d) Suggest how the quantities of carbon dioxide released by the combustion of fossil fuels could be reduced.
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(Total 14 marks)
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3. The table below shows the size of the populations, and the numbers and percentages of the population that are infected with HIV, in five southern African countries.
Country Population(thousands)
Populationaged 15–49(thousands)
HIVinfectedpeople
(thousands)
% of totalpopulationwith HIV
% of adultswith HIV
% of femaleadults
aged 15–49with HIV
South Africa 39 900 20 982 4 200 10.5 20.0 54.8
Botswana 1 597 786 290 18.2 35.8 51.2
Namibia 1 695 795 160 19.5 53.1
Lesotho 2 108 1 000 240 23.6 54.2
Swaziland 980 468 130 13.3 25.3 51.5
(a) Complete the table by calculating the percentage of the total population with HIV in Namibia and Lesotho.
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(b) Using the information in the table, explain the significance of the percentage of females aged 15 to 49 who are infected with HIV.
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(c) Suggest how the structure of the population of South Africa will change in the future. Explain your answer.
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(Total 5 marks)
4. Coral reefs are formed and maintained by very large numbers of simple animals called polyps. These polyps have single-celled algae (simple photosynthetic organisms) living inside their cells.
It is thought that when the sea is too warm the relationship between the coral polyps and the algae breaks down, and the reef begins to look white (becomes bleached). If the sea temperature falls again within a few weeks then the coral polyps and the algae reunite. If it does not, then the coral polyps die.
In 1998, 16% of the world’s coral reefs showed some bleaching. Half of these damaged reefs are now recovering.
The Great Barrier Reef off the east coast of Australia has been badly bleached in the last few years. The average sea temperature on the reef has increased by 0.3 °C in the last century. It is feared that southern and central sections of the Great Barrier Reef are likely to be severely affected by sea temperature rises in the next 20-40 years.
(a) Name a method by which global sea temperatures can be monitored.
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(b) Suggest how the algae normally help the coral polyps to survive.
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(c) Some recovery in the Great Barrier Reef may be taking place at present. Suggest a possible explanation for this, other than change in sea temperature.
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(Total 5 marks)
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5. The possible effects of global warming on the growth of Arctic shrubs were investigated using small portable greenhouses in which dwarf birch trees were grown.
(a) Suggest three factors, other than temperature, which would be affected by enclosing a plot of land inside one of these greenhouses.
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(b) The diagram below shows the wood of one of the dwarf birch trees used in the experiment, as seen in transverse section under a microscope. Inorganic ions (fertiliser) were added to the soil while the tree was growing. The white arrows indicate the wood that was formed just before the fertiliser was added.
(i) Name the method by which tree rings can be used to make deductions about the climate in the past.
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(ii) Describe the change in growth following the addition of the fertiliser.
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(c) Describe a technique which could be used to provide evidence that dwarf birch became more abundant 9000 years ago during an earlier period of global warming.
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(d) Explain why a large increase in growth of trees may help to reduce the amount of global warming in future.
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(e) Explain why an increase in the temperature of the soil (such as that due to global warming) would affect the decay of plant material in Arctic soils.
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(Total 12 marks)
6. The graph below shows changes in the biomass of trees during 240 years at a site undergoing
primary succession. Biomass was measured in tonnes per hectare (tonnes ha–1).
3 5 0 –
3 0 0 –
2 5 0 –
2 0 0 –
1 5 0 –
1 0 0 –
5 0 –
0 –0 4 0 8 0 1 2 0 1 6 0 2 0 0 2 4 0
B i o m a s s /t o n n e s h a
H e m l o c k s p r u c e
S p r u c e
W i l l o w
A l d e r
T i m e s i n c e s u c c e s s i o n b e g a n / y e a r s
(a) Using the information in the graph, explain the meaning of the term succession.
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(b) Describe the changes in the total biomass of the trees between 0 and 240 years.
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(c) Suggest why hemlock spruce is not present until 160 years after the start of the succession.
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(Total 7 marks)
7. (a) Describe a technique for determining the abundance of a named organism in a habitat that you have studied.
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(b) Mussels are animals found on rocky seashores. They are enclosed in two hard shells that can be clamped together very tightly. Adult mussels attach themselves firmly to the rocks and do not move around.
Ecoscene/Kevin King
A study was carried out to investigate the distribution of mussels on a rocky shore that has a freshwater stream running across it into the sea. The sea level rises and falls twice every day, between low water level A and high water level B. The sketch map below shows the shore between the low water level and the high water level, the freshwater stream and the six sites where the adult mussels were sampled.
The numbers of mussels found at each of the sites are shown in the table below.
Site 1 2 3 4 5 6
Number of mussels
3 5 15 22 20 2
(i) Describe how the freshwater stream affects the distribution of the mussels.
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(ii) Suggest two possible reasons for this distribution.
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(c) Mussels are preyed upon by marine snails called dog whelks. A dog whelk crawls on to a mussel and takes one or two days to make a hole in the shell before it can eat the mussel inside.
Life size
Ecoscene/Chinch Gryniewicz
The numbers of dog whelks found at each of the sites are shown in the table below.
Site 1 2 3 4 5 6
Number of dog whelks
7 8 1 0 0 4
Suggest how the abiotic and biotic factors referred to in this question determine the distribution of the dog whelks on this seashore.
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(Total 11 marks)
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8. Measurements were made of the rate of energy flow in an ecosystem. The results are shown in the table below.
Energy/ kJ m–2 yr–1
Energy fixed by photosynthesis 1.9 × 104
Energy used in plant respiration 1.1 × 104
Energy in new biomass of primary consumers 0.1 × 104
(a) (i) Calculate the net primary productivity in this ecosystem. Show your working.
Answer ...............................(2)
(ii) Use the information in the table and your answer from (a)(i) to calculate the percentage efficiency of energy transfer from the plants to the primary consumers. Show your working.
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(b) Give two reasons why not all of the energy fixed by the plants can be used to form biomass in the consumers.
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(Total 6 marks)
9. Wiithin Lake Washington, two distinct populations of salmon are evolving. The populations live in different areas of the lake and breed at different times of the year.
(a) Explain why there is likely to be little transfer of genes between the two populations.
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(b) Explain how natural selection could result in the two populations becoming separate species. You should answer this question in continuous prose.
(Allow one lined page).(7)
(c) Suggest reasons why some people might not accept that species have arisen by the process of evolution.
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(Total 10 marks)
10. The digestive processes of ruminant animals produce the gases methane and carbon dioxide. A study was carried out in Virginia, USA, to determine the methane and carbon dioxide emissions from cattle and sheep. The results of this study are shown in Figure 1 below.
Figure 1 – Table showing the emissions of methane and carbon dioxidefrom cattle and sheep in 1990 and 1996.
Methane emissions
/tonnes year–1Carbon dioxide
emissions/tonnes year–1
1990 1996 1990 1996
Beef cattle 45 897 52 626 126 217 144 723
Dairy cattle 11 537 10 108 31 727 29 144
Sheep 976 672 2 628 1 848
Total 58 410 63 406 160 572 175 715
% Increase — 8.6 —
Both methane and carbon dioxide are greenhouse gases. Greenhouse gases vary in their potential warming effect. Figure 2 shows the global warming potential (GWP) of greenhouse gases relative to carbon dioxide.
Figure 2 – Table comparing the global warming potential of four greenhouse gases.
Greenhouse gas Global Warming Potential (GWP)
Carbon dioxide 1
Methane 21
Nitrous oxide 206
CFC-11 3400
The percentage contribution of the different greenhouse gases to global warming has changed since 1880. These changes are shown in Figure 3.
Figure 3 – Pie charts showing the percentage contribution of different greenhousegases to global warming.
O t h e r O t h e r
C F C s
C F C sM e t h a n e
M e t h a n eC a r b o nd i o x i d e
C a r b o nd i o x i d e
N i t r o u so x i d e s N i t r o u s
o x i d e s
( a ) 1 8 8 0 – 1 9 7 9 ( b ) 1 9 8 0 – 1 9 8 9
(a) Describe how cellulose in grass is digested in a ruminant animal.
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(b) Using the data in Figure 1, calculate the percentage increase in the carbon dioxide emissions between 1990 and 1996. Show your working.
Answer ..............................(2)
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(c) Describe the changes in the emissions of methane and carbon dioxide between 1990 and 1996 as shown in Figure 1. Suggest reasons for these changes.
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(d) The digestive processes of ruminant animals are not the only sources of methane and carbon dioxide in the atmosphere. State one other source of each of these gases in the atmosphere.
Methane ........................................................................................................................
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(e) Explain the importance of greenhouse gases in the atmosphere and explain how a change in the concentration of these gases can lead to global warming.
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(f) Using the information provided in Figure 2, explain how an increase in methane concentration in the atmosphere can have more effect than the same increase in carbon dioxide concentration.
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(g) Carbon dioxide emissions increased after 1980.
(i) Explain why the percentage contribution of carbon dioxide to global warming decreased as shown in Figure 3.
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(ii) Explain how human activities could have been responsible for the changes since 1980 in methane, CFCs and nitrous oxides, as shown in Figure 3.
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(Total 19 marks)
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11. (a) Explain the meaning of the term speciation.
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(b) Using suitable examples, explain how sympatric speciation differs from allopatric speciation.
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(Total 6 marks)
12. There is widespread concern about the possible effects of human activities on global warming.
(a) State two sources of evidence that global warming has been increasing over the past 150 years.
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(b) Dinosaurs became extinct about 65 million years ago, possibly because of climate change resulting from the impact of a meteorite with the Earth.
(i) Suggest how this impact might have caused the extinction of the dinosaurs.
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(ii) Give one alternative explanation that has been proposed by reputable biologists to explain the mass extinction of the dinosaurs.
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(c) Climate change could mean extinction for many of Britain’s rare species of plants and animals.
Suggest how rare species which do not become extinct may be affected by global warming.
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(d) Recent global warming might be the result of an increase in greenhouse gases in the atmosphere, related to the burning of fossil fuels by human activity since the Industrial Revolution.
(i) Name two greenhouse gases other than carbon dioxide.
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(ii) Give one explanation for recent global warming other than burning fossil fuel.
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(Total 11 marks)
13. A student investigated the decomposition of leaves from a sweet chestnut tree. In November 1988, she placed an equal number of leaves in nylon bags with three different mesh sizes. The bags were then buried in garden soil. A fourth sample was placed in a mesh bag and suspended in the air. She examined the bags at intervals of six months and made estimates of the percentage of leaves that remained before reburying the bags. Her results are shown in Figure 1.
Figure 1 – The percentage of sweet chestnut leaves remaining in nylon bags of differingmesh size over a period of two and a half years.
Percentage of sweet chestnut leaves remaining in the bags
SampleNovember
1988May1989
November1989
May1990
November1990
May1991
0.05 mm meshbag in soil
100 62 60 51 42 38
1 mm meshbag in soil
100 62 38 30 30 29
5 mm meshbag in soil
100 33 10 10 10 10
0.05 mm meshbag in air
100 96 92 88 84 80
In another investigation, the nitrogen content of leaves from six species of tree was measured. Some fresh leaves from these trees were then placed in separate nylon bags with a 5 mm mesh and buried in garden soil in July. The bags were examined after four months and the percentage of the leaves remaining was recorded. The results of this investigation are shown in Figure 2.
Figure 2 – A scattergraph showing the relationship between the percentage of leaves remaining after four months and the nitrogen content of the leaves.
P i n eC h e r r y
O a k
S y c a m o r eB i r c h S w e e t C h e s t n u t
1 0 09 08 07 06 05 04 03 02 01 0
00 0 . 5 1 1 . 5 2
N i t r o g e n c o n t e n t o f l e a v e s / %
P e r c e n t a g eo f l e a v e sr e m a i n i n g a f t e rf o u r m o n t h s
(a) (i) Using the information in Figure 1, compare the breakdown of the sweet chestnut leaves in the four bags between November 1988 and May 1991.
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(ii) Suggest an explanation for the differences that you have described in (a)(i).
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(b) Using the information in Figure 2, describe the relationship between the nitrogen content of the leaves and the decomposition of the leaves. Suggest a reason for this relationship.
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(c) Coniferous forests in Northern Europe have long cold winters and short warm summers. Tropical rain forests are found in the hot and wet regions of the world. Coniferous forests have a thick layer of pine needles (leaves) lying on the forest floor. Tropical rain forests have relatively few leaves lying on the forest floor. Suggest reasons for this difference.
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(d) The organic nitrogen in fallen leaves is eventually converted into nitrates. Describe the role of soil microorganisms in this process.
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(Total 14 marks)
14. The diagram below shows a simplified carbon cycle.
(a) Each box represents a process. Write the name of the process in each of the boxes A, B, C and D.
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(b) With reference to an example, explain what is meant by the term carbon sink.
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(c) (i) The increase in the concentration of carbon dioxide in the atmosphere has been linked to global warming. Explain what is meant by the term global warming.
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(ii) Name two gases, other than carbon dioxide, which are thought to contribute to global warming.
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(Total 8 marks)
15. The Isthmus of Panama is a strip of land that separates the Pacific Ocean from the Atlantic Ocean in Central America. The map below shows the Isthmus of Panama.
The pictures below show two species of fish known as wrasse.
Blue-headed wrasse (Thallassoma bifasciatum)
Rainbow wrasse (Thallassoma lucasanum)
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The blue-headed wrasse is found in the coral reefs on the Atlantic side of the isthmus and the rainbow wrasse is found in the reefs on the Pacific side of the isthmus.
It has been shown that both of the species are descended from a common ancestral population that was split as the isthmus formed.
(a) Explain why the blue-headed wrasse and the rainbow wrasse are described as different species.
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(b) Suggest how analysis of DNA or proteins might be used to supply additional evidence that these species have descended from a common ancestor.
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(c) Explain how the splitting of the common ancestral population into an Atlantic population and a Pacific population have led to the formation of these two separate species.
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(Total 9 marks)
16. Changes in the global environment are investigated using remote sensing techniques.
(a) Describe and explain what is meant by remote sensing.
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(b) Describe two kinds of data commonly collected by remote sensing which can be used by scientists studying climate change and its effects.
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(c) Techniques such as remote sensing have been available only in recent times.Information from dendochronology is usually limited to the past 1000 years.
Apart from dendochronology, explain how scientists can investigate ecological changes over the past 12 000 years.
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(Total 9 marks)
17. The diagram below summarises the carbon cycle.
C a r b o n d i o x i d ei n t h e a t m o s p h e r e
D e c a y e d b ym i c r o b e sU s e d a s a f u e l
i n a p o w e r s t a t i o np r o d u c i n g e l e c t r i c i t yF o s s i l f u e l s
P l a n t b i o m a s s
B
A
B
C
(a) (i) Name the processes A, B and C.
A .......................................................................................................................
B .......................................................................................................................
C .......................................................................................................................(2)
(ii) Suggest a type of plant biomass that is used as a source of energy in some power stations as an alternative to fossil fuels.
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(b) The use of biomass is considered to be sustainable whereas using fossil fuels is not sustainable.
(i) State the meaning of sustainable.
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35
(ii) Suggest why using plant biomass to generate electricity is thought to be more sustainable than using fossil fuel.
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(c) The diagram below shows an experiment to test the hypothesis that carbon dioxide is a greenhouse gas.
E l e c t r i c a l c o n n e c t i o n s
T e m p e r a t u r ep r o b e s
A i r e n r i c h e d w i t hc a r b o n d i o x i d e f r o m as o d a - w a t e r s y p h o n r e f i l lG l a s s b o t t l e s
A t m o s p h e r i ca i r
Name two pieces of equipment not shown in the diagram that you would need to complete the experiment.
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(d) Some scientists think that global warming will increase the rate of decay of dead biomass.
(i) Suggest why global warming might increase the rate of decay.
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(ii) Explain one reason why an increase in the rate of decay might increase the rate of global warming even more.
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(Total 12 marks)
18. A model ecosystem was set up in an aquarium. Organisms from three trophic levels were introduced and left until their population sizes were fairly constant.
All of the organisms were then collected and the total biomass of each species was measured. The energy content per gram of the biomass was then measured.
The table below summarises the data collected.
Total biomass collected / g
Energy content per gram / kJ
Total energy from biomass / kJ
Species A 3000 0.5 1500
Species B 80 1.5
Species C 140 0.1
(a) (i) Complete the table by calculating the total energy from biomass of species B and C.
(1)
37
(ii) Calculate the total energy from biomass for species C as a percentage of that found for species B. Show your working.
Answer ....................................(2)
(b) Explain how the data above support the hypothesis that species C is a secondary consumer.
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(Total 6 marks)
19. A study of plant species near a sandy shore was carried out.
The table below shows some of the data collected. Sites were sampled at a range of distances inland from a reference point on the beach
Site number 1 2 3 4 5 6
Distance from reference point / m 20 80 250 500 650 1800
Dead organic matter in soil / % 0.4 0.5 0.9 2.8 6.4 23.4
Number of plant species found 1 1 8 16 7 2
Each site represents a stage in the succession from bare sand to a climax community.
(a) (i) Describe the changes in the percentage of dead organic matter and number of plant species as the distance from the reference point increases.
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(ii) Suggest how changes in the percentage of dead organic matter in the soil could account for the changes in the number of plant species.
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(b) Explain what is meant by a climax community.
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(c) Another way to study plant succession is to measure changes in the percentage cover of plant species. Describe how you could measure percentage cover of a plant species in a site you have studied.
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(Total 10 marks)
20. A group of students carried out an investigation to determine the energy flow in a rainforest food chain. They collected invertebrate animals from trees, identified them and placed them in the appropriate trophic level.
For each trophic level the animals were counted, weighed and the energy content determined. Using their data and other sources of information the students produced a diagram to show the energy flow along the food chain. The diagram is shown in Figure 1.
Figure 1
T e r t i a r y c o n s u m e r s
S e c o n d a r y c o n s u m e r s
P r i m a r y c o n s u m e r s
P r o d u c e r s
S u n l i g h t
2 0 0 × 1 0 k J m y– 23 – 1
1 4 0 × 1 0 k J m y– 23 – 1
2 4 × 1 0 k J m y– 23 – 1
R e s p i r a t i o n
D e c o m p o s e r s
7 0 0 0 k J m y– 2 – 1
7 0 0 k J m y– 2 – 1
7 0 k J m y– 2 – 1
Some farmers clear plots of rainforest to use for crops. The trees are felled and then burnt. This practice is called slash and burn. The soil is left covered in ash, which is rich in nutrients. However, the nutrients are soon used up by the growing crops. Within two or three years the plot is abandoned and the farmer moves on to a new plot.
41
The abandoned plot is colonised by tree species and eventually the land is covered by secondary rainforest. The sequence of events is shown in Figure 2. This figure also shows that the total biomass of the rainforest trees is made up of leaves, stems and branches, roots and leaf litter. These components of the biomass change as the rainforest is cleared, farmed and then abandoned.
Figure 2
P r i m a r yr a i n f o r e s t
S e c o n d a r yr a i n f o r e s tF a r m i n g
B i o m a s sc o m p o n e n t
L e a v e s
L e a f l i t t e r
B r a n c h e s
R o o t s
S l a s ha n d b u r n
P l o ta b a n d o n e d
1 0 y e a r s 2 5 y e a r s
5 0
4 0 0
5 0
2 0 0
1 0
5 0
1 0
5 0
5 0
2 0 0
5 0
5 0
5 0
3 0 0
5 0
7 5
The biomass components are shown in million tonnes per hectare.
(a) Define the term net primary production (NPP).
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(b) (i) Explain why only a small percentage of the light energy falling onto a leaf is converted into chemical energy.
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(ii) Explain why only 10% of the energy locked up in the secondary consumers is transferred to the tertiary consumers.
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(c) The energy shown entering the decomposers in Figure 1, is much greater than that entering all of the consumers. Suggest an explanation for this difference.
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43
(d) (i) Using Figure 2, compare the components of the biomass of the primary rainforest with those of the secondary rainforest after 25 years.
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(ii) Using all of the information provided, suggest why slash and burn farming is considered to be unsustainable.
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(e) Suggest how the biodiversity of the surrounding rainforest could be changed by the practice of slash and burn. Give reasons for your answer.
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(Total 18 marks)
21. An investigation was carried out into the effect of grazing by rabbits in an area of grassland. In 1954 and 1957, the mean height of the vegetation was measured.
In 1956 an outbreak of a disease greatly reduced the number of rabbits.
The results are shown in the table below.
1954 1957
Mean height of vegetation/cm 2.0 11.5
45
(a) Describe and explain the effect of the decrease in the number of rabbits on the mean height of the vegetation.
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(b) A grazed grassland is a plagioclimax community,
(i) Explain what is meant by the term plagioclimax.
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(ii) Describe how an area of grazed grassland could develop into a woodland community.
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(Total 8 marks)
22. Samuel Wilberforce, a bishop of Oxford in the 19th century, was a fierce critic of Darwin’s theory of evolution by natural selection.
(a) Explain why Wilberforce might have been so strongly opposed to the theory of evolution by natural selection.
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47
One argument that Wilberforce used was that no new species had been seen to arise. Even breeds of dog that had been prevented from cross breeding for many generations remained the same species. If two breeds of dog are allowed to interbreed they produce fertile offspring showing a variety of intermediate characteristics (mongrels).
(b) Describe how interbreeding of dog breeds can result in mongrel dogs.
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(c) Explain why Wilberforce’s example of dog breeds does not show that Darwin’s theory of evolution by natural selection is incorrect.
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(Total 7 marks)
23. (a) The table below shows some data obtained from studies on seaweed on a rocky shore.The species are listed in the order down the shore that they are normally found.Seaweeds on the upper shore may be out of the sea, and exposed to the air for many days at a time.
Some scientists suggested that seaweeds on the upper shore retain water better than seaweeds on the lower shore.
Cell wallthickness /μm
Water loss ondrying out forfixed time / %
Recovery of normalmetabolism after drying outand then rewetting / %
Upper Shore Pelvetiacanaliculata
1.2 85 95
Fucusspiralis
1.47 70 49
Fucusvesiculosus
0.69 80 20
Fucusserratus
0.42 83 0
Lower Shore(near sea)
Laminariadigitata
0.28 88 0
(i) Explain why these data do not support the hypothesis that seaweed species growing high on the shore will retain water better than seaweed species growing lower on the shore.
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(ii) Suggest an explanation, supported by the data, that could account for this distribution of seaweeds.
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The upper shore experiences a wider range of temperatures since it spends time exposed to the air, and it can reach much higher temperatures than seawater.
Another study was carried out to investigate the effects of temperature on the activity of rocky shore snails. The temperature at which 50% became inactive was measured for 5 species of snail and the data are given below. The rate of water loss on exposure to the air was also measured
Littorinalittorea
Littorinasaxatilis
CalliostomaLittorinaobtusata
Littorinaneritoides
Temperatureof inactivity /°C
46.0 45.0 34.5 44.0 46.3
Water loss /% body massper day
5.35 5.6 10.1 8.35 3.7
(b) Suggest one species that you would expect to find more frequently on the upper shore, and one species that you would expect to be limited to the lower shore, giving a reason for each of your answers.
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(c) Suggest two biotic factors that might affect the distribution of organisms in the rocky shore studied above.
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(Total 11 marks)
24. The periwinkle (Littorina littorea) is a small marine snail that feeds on algae (seaweeds) as shown in Figure 1 below. It prefers to eat fast-growing, short-lived green algae such as Enteromorpha rather than tough, long-lived red algae such as Chondrus.
Figure 1Periwinkle (Littorina littorea) feeding on algae.
If these two algae are growing in the same rock pool, the more rapid growth of Enteromorpha reduces the growth of Chondrus. However, periwinkles grazing on the Enteromorpha help to keep it under control and this allows Chondrus to grow.
51
A study was made of the feeding preferences of the periwinkle on rocky shores and how these affected the growth of Enteromorpha and Chondrus. An ecologist studied the percentage cover of algae in three rock pools.
The density of periwinkles in the three rock pools was:
• Rock pool A 100 per m2
• Rock pool B 200 per m2
• Rock pool C 0 per m2
At the start of the study she removed all of the periwinkles from Rock pool B and placed them in Rock pool C which had none. She monitored the changes in the percentage cover of algae over a period of 28 months. Her results are shown in Figure 2. The effect of the density of the periwinkles on the diversity of the algae was also studied. The results are shown in Figure 3.
Figure 2
1 0 08 06 04 02 0
00 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8
T i m e / m o n t h s
Per
cent
age
cove
r of
alg
ae (
%)
R o c k p o o l A
E n t e r o m o r p h a
C h o n d r u s
1 0 08 06 04 02 0
00 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8
T i m e / m o n t h s
Per
cent
age
cove
r of
alg
ae (
%)
R o c k p o o l B
1 0 08 06 04 02 0
00 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8
T i m e / m o n t h s
Per
cent
age
cove
r of
alg
ae (
%)
R o c k p o o l C
53
Figure 3
Graph showing the change in the number of algal species with the increase in thedensity of periwinkles in rock pools
1 41 21 0
86420
0 5 0 1 0 0 1 5 0 2 0 0 2 5 0 3 0 0
D e n s i t y o f p e r i w i n k l e s /n u m b e r p e r m2
Num
ber
of a
lgal
spe
cies
(a) State the terms that are used to describe the roles of the algae and periwinkles in a food chain.
Algae ...........................................................................................................................
Periwinkles ..................................................................................................................(2)
(b) (i) Using Figure 2, describe the percentage cover of Enteromorpha and Chondrus in Rock pools B and C at the start of the study (Month 0).
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(ii) Describe the changes in the percentage cover of Enteromorpha in Rock pools A, B and C.
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(iii) Suggest reasons for these changes described in (b)(ii).
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(iv) Suggest a reason for the sudden fall in the percentage cover of Chondrus in rock pool C after 18 months.
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(c) Using Figure 3, describe and explain the effect of periwinkle density on the number of algal species.
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(d) Rock pools can be polluted by excess nutrients.
(i) Give two sources of excess nutrients.
1 ........................................................................................................................
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(ii) Describe the effect of excess nutrients on aquatic habitats.
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(Total 18 marks)
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25. The fox (Vulpes vulpes) is a common mammal living in both rural (country) and urban (town) areas of the United Kingdom. Foxes eat a variety of foods including berries, rabbits, small birds and rodents such as rats and mice.
(a) The photograph below shows the skull of the fox. Describe two features of the teeth of this fox that are an adaptation for feeding on small mammals.
Magnification ×0.5Source: www.nhc.ed.ac.uk
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(b) A number of studies have investigated the differences between the diets of rural foxes and foxes living in urban areas. The results of one study are shown below.
6 0
5 0
4 0
3 0
2 0
1 0
0O t h e rS m a l l
p e t sH u m a n
f o o dB e r r i e sS m a l l
r o d e n t sL a r g e
r o d e n t s
% o
f di
et
R u r a l f o xU r b a n f o x
F o o d t y p e
(i) Compare the diet of the rural fox with the diet of the urban fox.
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(ii) Human food was found to have a high content of carbohydrates and fats. Suggest how this could affect the time spent looking for food and the quantity of food eaten by the urban foxes.
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(c) It has been suggested that the teeth of the urban fox are changing as their diet changes. Describe how the rural and urban foxes could evolve into separate species.
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(Total 10 marks)
26. During the last Ice Age, England was joined to France by an area of land (land bridge).About 12 000 years ago the air temperature started to rise and the ice melted. By about 8000 years ago the rising sea levels flooded the land bridge and England became part of an island.
S C O T L A N D
F R A N C E
E N G L A N D
1 0 0 k m
S C O T L A N D
F R A N C E
E N G L A N D
1 0 0 k m
North West Europe 12 000 years ago North West Europe 8000 years ago
As the ice melted and the climate became warmer, tree species such as pine, hazel and oak probably spread from France across the land bridge and then, over several hundred years, spread north to Scotland.
(a) Suggest how tree species may have spread across the land bridge and north to Scotland.
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(b) Suggest why it took many years for these tree species to spread from France to Scotland.
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(c) Using pollen analysis scientists have found that, in what we now call England, pine trees were growing before oak trees.
(i) Explain how pollen analysis is carried out.
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(ii) Explain the evidence that would show that in a particular place, pine came before oak.
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(d) Computer models can be used to predict the extent of global warming in Scotland over the next 100 years. Explain why these predictions may be inaccurate.
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(Total 11 marks)
27. The diagram below shows energy flow measured during a study of a grassland ecosystem.
The values shown are kJ m–2 year–1 × 104. Values of energy lost through respiration (R) and other means (L) are shown for some organisms. The biomass of the organisms in the ecosystem remained unchanged during the study.
O t h e ro r g a n i s m s
S e e d e a t i n g b i r d s
G r a s s e s 0 . 0 7
L = 2 5 . 4
L = 3 . 7
R = 1 2 . 5
R = 2
1 9 8 0
R = 3 6 0 0
1 1 . 6
4 4 . 4
6
G r a s s h o p p e r s S p i d e r s
F i e l d m i c e
(a) Name one primary consumer and one secondary consumer shown in this diagram.
Primary consumer .......................................................................................................
Secondary consumer ...................................................................................................(2)
(b) (i) Calculate the gross primary productivity (GPP) for the grasses in this system.Show your working.
.................................... kJ m–2 year–1 × 104
(2)
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(ii) Describe how this figure could be used to calculate the net primary productivity (NPP) of the grasses.
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(c) (i) Calculate the percentage of the energy taken in by the grasshoppers that is converted into new grasshopper biomass. Show your working.
Answer ..............................................(3)
(ii) Give two ways in which energy is lost by the grasshoppers other than in respiration.
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(d) Use your calculated figures from parts (b)(i) and (c)(i) to explain why food chains are of limited length.
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(Total 12 marks)
28. In an investigation, several leaves were removed from a Magnolia tree. These leaves were weighed and then placed on the surface of some moist compost in an incubator set at 25 °C. At two-day intervals for a period of 4 weeks, the leaves were weighed and then replaced on to the surface of the compost.
Figure 1 – Graph of mass of leaves against time after removal from the Magnolia tree
2 5 0
2 0 0
1 5 0
1 0 0
5 0
0
Mas
s of
leav
es /
g
0 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 6 2 8T i m e a f t e r r e m o v a l f r o m t r e e / d a y s
Figure 2 – Photograph of a freshly-picked Magnolia leaf compared with a Magnolia leaf that has been on the surface of the compost for 28 days Freshly-picked leaf Leaf after 28 days on compost
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(a) (i) Describe the changes in the mass of the leaves during the first 14 days of the investigation.
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(ii) Suggest why it is unlikely that the activity of saprobiontic microorganisms in the compost caused these changes in mass during the first 14 days.
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(iii) Suggest a possible reason for the changes in mass in the first four days.
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(b) State one difference in appearance of the two leaves in Figure 2, and suggest how saprobiontic microorganisms brought about this change.
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(c) When leaves are added to compost heaps, explain why it is important that the compost is not allowed to become waterlogged or compacted.
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(Total 11 marks)
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29. A transect can be used to study trends in the abundance and distribution of organisms.
(a) Describe one method you could use to estimate the abundance of an organism at intervals along a transect line.
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(b) State one biotic factor that could be measured at each interval.
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(c) (i) State one abiotic factor of soil that could determine the distribution of plants.
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(ii) Describe how you could measure this soil factor.
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(Total 7 marks)
30. The photograph below shows a herd of cattle on an area of dry grassland and scrub that is undergoing desertification in central Australia.
Wayne Lawler / Ecoscene
(a) Suggest two possible causes of the desertification of dry grassland in central Australia.
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(b) Describe and explain the processes that lead to desertification of dry grassland.
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(c) Suggest two ways of preventing desertification in the driest parts of the world such as Australia.
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(Total 10 marks)
71
31. Compost is usually produced from waste plant material by the action of aerobic microorganisms. It consists mainly of partly decomposed organic material that is rich in minerals such as nitrates. A variety of plant material, such as grass cuttings, fallen leaves and vegetable waste, can be used to produce compost.
The rate of production of compost depends on several factors such as temperature, moisture content and aeration.
The diagram below shows a container used for producing compost.
W a s t e p l a n tm a t e r i a l
S l a t t e d c o n t a i n e r t o a l l o w a i rt o e n t e r
(a) Explain how nitrates are produced from the waste plant material.
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(b) The compost can be added to soil to provide more nitrates. Explain how nitrates would be absorbed and used by plants during the growing season.
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(c) An investigation into the relationship between the temperature in a compost heap and the external air temperature was carried out. A container was filled with waste plant material. After 8 weeks, measurements of the temperature in the centre of the compost and the external air temperature were taken each week. The results of this investigation are shown on the graph below.
Tem
pera
ture
/C
5 0 –
4 0 –
3 0 –
2 0 –
1 0 –
0 –
T i m e / w e e k s
–
2
–
3
–
5
–
7
–
9
–
1
–
1 0
–
1 1
–
1 2
–
1 3
–
1 4
–
0
–
4
–
6
–
8
C o m p o s t h e a pE x t e r n a l a i r
– 1 0 –
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(i) Compare the temperature in the compost with the temperature of the external air in the first six weeks.
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(ii) Suggest reasons for the differences in the two temperatures in the first six weeks.
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(iii) The temperature of the compost falls between week 9 and week 14. Suggest how changes in factors, other than external air temperature, may have contributed to this fall in temperature.
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(Total 12 marks)
32. The distribution of organisms within a habitat or on a world-wide scale is influenced by both biotic and abiotic factors.
(a) Explain what is meant by the terms biotic and abiotic factors.
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(b) For a particular habitat that you have studied, describe one technique which you used to investigate how a specific abiotic factor affected the distribution of a named organism. (The results of your investigation are not required.)
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(Total 4 marks)
33. (a) Explain what is meant by the term global warming.
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(b) In 1976, a scheme was set up to record the distribution and abundance of butterflies in the United Kingdom. The records show that the abundance and distribution of many species of butterfly have changed. The graph below shows the changes in the abundance of two groups of butterflies. The generalists are butterflies found in a wide range of habitats, while the specialists are butterflies found only in certain types of habitat.
2 . 4
2 . 2
2
1 . 8
1 . 6
1 . 4
1 . 21 9 7 5 1 9 8 0 1 9 8 5 1 9 9 0 1 9 9 5 2 0 0 0 2 0 0 5
Y e a r
Col
late
d in
dex
of a
bund
ance
S
E±
G e n e r a l i s t s
S p e c i a l i s t s
(i) Compare the trends and patterns of the abundance of the two groups of butterflies shown in the graph.
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(ii) Suggest reasons for the changes that you have described in (b)(i).
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(c) The distribution of the Comma butterfly (shown below) has altered considerably since 1982. This butterfly has expanded its range northwards more than any other British species of butterfly.
The dots on the maps indicate places where the Comma butterfly was recorded.
Copyright © Ecoscene/Robin Williams
N
1 9 8 2
N
2 0 0 0
79
Suggest how global warming could affect the distribution of the Comma butterfly.
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(Total 11 marks)
34. (a) Name the processes described below, selecting the most appropriate answer from the following list:
absorption combustion decomposition
photosynthesis respiration transpiration
Description Process
(i) Carbon dioxide in the atmosphere is convertedinto wood by growing trees
(ii) Dead wood is converted to substances which canbe readily absorbed by fungi
(iii) Carbon dioxide is released from carbohydratesanimals have eaten
(iv) Carbon dioxide is released from wood in awood-fired power station
(4)
(b) (i) Explain why coal reserves represent a carbon sink.
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(ii) Explain why burning wood is described as ‘carbon neutral’, unlike the burning of fossil fuel.
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(c) The UK Forestry Commission has calculated that, in order to remove the carbon dioxide produced by an average family car during an average driver’s lifetime, it would be
necessary to plant 0.5 hectares (5000 m2) of new forest.
Suggest and explain one reason why planting extra forests may not be a complete long term solution to the problem of rising carbon dioxide levels in the atmosphere.
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(Total 9 marks)
81
35. (a) Explain the difference between the terms ‘global warming’ and ‘the greenhouse effect’.
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(b) The graph below shows the changes in mean global surface temperature between the years 1880 and 2000.
+ 1 . 6
+ 1 . 4
+ 1 . 2
+ 1 . 0
+ 0 . 8
+ 0 . 6
+ 0 . 4
+ 0 . 2
0
– 0 . 2
– 0 . 4
1880
1890
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
Y e a r
Dep
artu
re f
rom
long
term
mea
n (º
C)
(i) Draw the line of best fit on the above graph between 1940 and 2000.(1)
(ii) Using your line of best fit, estimate the increase in mean global surface temperature between 2000 and 2020. Indicate how you made your estimate on the graph and in the space below.
Estimated increase in temperature .............................................(3)
(iii) Using the graph to support your answer, suggest why the estimated increase in temperature might not be an accurate prediction of mean global surface temperature in 2020.
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(c) Suggest why a relatively small increase in temperature may have a large effect on the survival of particular species of plants and animals in particular places.
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(Total 12 marks)
83
36. Sunflower seedlings were planted and kept under controlled conditions for 20 days. The gross primary productivity (GPP) and the net primary productivity (NPP) were measured each day. The results are shown in the graph below.
G P P
N P P
P r i m a r y p r o d u c t i v i t y /
a r b i t r a r y u n i t s
3 5
3 0
2 5
2 0
1 5
1 0
5
00 5 1 0 1 5 2 0 2 5
T i m e s i n c e p l a n t i n g / d a y s
(a) (i) Compare the changes in GPP and NPP during the time period shown on the graph.
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(ii) Suggest an explanation for the changes you have described in (a)(i).
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(b) Explain the relationship between GPP, NPP and respiration.
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(Total 6 marks)
37. Answer the following essay question.
You are expected to answer in continuous prose. You should use examples from the biology course you have studied but need not restrict yourself to the course content.
You should spend approximately 45 minutes answering this question including planning time.
Marks will be awarded for the following areas:
Breadth: selection of a range of relevant examples (up to 6 marks)
Depth: Further description and discussion of the examples (up to 8 marks)
Balance: Have you answered the question asked; for example have you recognised the advantages and disadvantages or benefits and risks (up to 6 marks)
Style: Coherence, clarity and expression (up to 4 marks)
The effect of climate change on the world’s ecosystems is often seen as a potential catastrophe. Yet wild species and ecosystems are able to adapt to climate change and have done so many times in the past.
Write an essay on: ‘Biological effects that might be caused by climate change in the 21st Century: a catastrophe or a harmless change?’
(Total 20 marks)
85
38. The carbon cycle involves many different organisms and processes. Figure 1 shows how carbon atoms in the organic waste in the faeces of a mammal may eventually be incorporated into the organic material forming the wood of a tree.
Figure 1
O r g a n i c w a s t e i n f a e c e s
P r o c e s s X
C a r b o n d i o x i d e i n a t m o s p h e r e
P r o c e s s Y
O r g a n i c m a t e r i a l i n t r e e
The formation of woody biomass in large forests acts as an important carbon sink. A study of northern hemisphere forests made estimates of the carbon stored in woody biomass (carbon pool) and the mean rate of carbon uptake, in the late 20th century. These estimates are shown below in Figure 2.
Figure 2
[t = tonnes, ha = hectare, yr = year]
CountryAverage
carbon pool
/t ha–1
Area offorest /
ha × 106
Total carbonpool in forest
/t × 106
Mean rate ofcarbon uptake
/t yr–1 × 106
Canada 44.09 239.5 10560 73.12
USA 57.91 215.5 12480 141.53
China 25.77 142.6 3675 38.62
Finland 34.88 17.2 600 5.56
Japan 47.35 19.0 900 11.92
Russia 37.98 24391 283.59
Sweden 39.86 26.5 1056 13.86
Others 59.40 117.4 6974 116.17
(a) With reference to a suitable type of organism, explain how the carbon in the organic waste in faeces may be converted to carbon dioxide in the atmosphere by process X in Figure 1.
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(b) (i) Name process Y, shown in Figure 1.
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(ii) Explain why only a proportion of the organic material, formed using carbon dioxide, will become plant tissues.
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(c) Explain the meaning of the term carbon sink.
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(d) Using the data in Figure 2, calculate the estimated area of forest in Russia. Show your working.
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(e) The data for the areas of forest and the carbon pools in Canada and the USA are fairly similar and yet the mean rate of carbon uptake per year in Canada is approximately half that in the USA. Suggest two reasons for this considerable difference in the mean rates of carbon uptake in the forests of these two countries.
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(f) Explain how deforestation could have an effect upon the mean temperature of the Earth’s surface.
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(Total 15 marks)
89
39. A river is an ecosystem which is influenced by the biotic and abiotic factors that are present within the river itself. The water in a river drains into it from its catchment area.Factors within the catchment area also have an effect on the river’s ecosystem.
In a river, there are two sources of plant material that contribute towards the net primary production. The first source is the living plants which grow within the river itself. Most of these are algae forming a surface covering on rocks near the surface or suspended in the upper layers of water. The second source is dead plant material, such as leaves, that is brought in from the surrounding land. This forms most of the layer of decomposing organic material (detritus) found on the bed of the river.
The relative quantities of these two types of plant material can determine the types of consumers in the dependent food chains. The grazing invertebrates that feed on algae tend to form the main food source for trout and other carnivorous river fish. Invertebrates that feed in the detritus layers are not easily seen and do not form a major part of the diet of most of these fish.
In New Zealand, the Wangapeka River and the Motupiko River meet to form the Motueka River which flows into the sea. A study of the Motueka River was carried out to estimate the influence of dead plant material from the catchment area on the ecosystem. Nine sampling sites between the sources of the rivers and the sea were selected. The three rivers and the sampling sites in the catchment area of the study are shown in Figure 1.
At each of the sampling sites, gross primary production (GPP) of algae was estimated by measuring the production of oxygen in the water over a 24 hour period. As oxygen is released, a proportion of it will be used during respiration of all organisms in the river community. This uptake of oxygen, which was also estimated, is known as community respiration (CR). The estimates were made during winter and summer. These results are shown in Figure 2 and Figure 3.
[Data adapted from Cawthron Research News September 2002]
Figure 1 – The Wangapeka, Motupiko and Motueka river system.
D i r e c t i o n o f w a t e r f o w
W A N G A P E K A R I V E R
N o r t h
M O T U E K A R I V E R
M O T U P I K O R I V E R
= S a m p l i n g s i t e
S E A
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Figure 2 – Gross primary production in the Motueka River catchment area.
1 6
1 4
1 2
1 0
8
6
4
2
01 5 01 2 51 0 07 55 02 50
= S u m m e r
= W i n t e r
D i s t a n c e f r o m t h e s o u r c e / k m
Gro
ss p
rim
ary
prod
ucti
on /
gO m
da
y2
–2–1
Figure 3 – Community respiration in the Motueka River catchment area.
1 5 01 2 51 0 07 55 02 50
3 0
2 5
2 0
1 5
1 0
5
0
D i s t a n c e f r o m t h e s o u r c e / k m
Com
mun
ity
resp
irat
ion
/ gO
m
day
–2–1
2
= S u m m e r
= W i n t e r
(a) (i) Explain what is meant by the term gross primary production.
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(ii) State two abiotic factors that can affect gross primary production in this river system.
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(b) If the input of dead plant material from the catchment area into a river increased, the uptake of oxygen would also increase. Give an explanation for this.
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(c) (i) With reference to Figure 3, compare the trend in community respiration in winter with that in summer for, the Motueka River catchment area.
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(ii) Suggest why community respiration shows this trend.
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(d) (i) The numbers of carnivorous fish, such as trout, are higher in the Motueka River than in the other two rivers. With reference to Figure 2, suggest reasons for this.
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(ii) With reference to Figure 3, suggest how the population of these carnivorous fish might change in the winter.
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(Total 17 marks)
40. An investigation was carried out to find the distribution of plant species on sand dunes.A transect was used which extended inland from a beach. Quadrats were used at nine positions along the transect. The percentage cover of selected species was recorded in each quadrat as well as the number of plant species in each quadrat. A sample of soil was taken from the area within each quadrat and used to measure the mass of organic material present.
Gary Skinner, Bioschool
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The results are shown in the two tables below.
Quadrat number 1 2 3 4 5 6 7 8 9
Distance from topof beach / metres
0 80 170 250 500 650 980 1600 1980
Number of speciesfound
1 1 5 11 18 7 5 2 2
Mass of organicmaterial / grams
0.4 0.3 0.3 0.9 2.8 6.4 25.1 23.4 32.8
Percentage cover
Quadrat number 1 2 3 4 5 6 7 8 9
Bare sand 80 30 30 8
Sea couch 20
Marram grass 70 50 20 5 5
Red Fescue 5 40 55 40
Sea buckthorn 80
Common heather 90
Corsica pine 100
(a) Explain why it is necessary to use a quadrat to estimate percentage cover.
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(b) Explain why a transect is more appropriate than random sampling in this study.
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(c) Use the information in both tables to compare the data collected from quadrat 1 and quadrat 5.
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(d) Differences in the variety and number of plant species found in the different quadrats can be explained by succession. Use the information in the table to suggest how the results of the study could be explained by succession.
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(Total 12 marks)
41. A new species of large cat, the clouded leopard (Neofelis diardi) has been identified on the island of Borneo. Neofelis diardi on Borneo is distinct from Neofelis nebulosa on the mainland.
(a) Explain why the clouded leopard and the mainland leopard share the name Neofelis.
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(b) There are 46 genetic differences between the two species of leopard. Explain how these differences may have arisen, assuming that the two species share a common ancestor.
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(c) The clouded leopards are found in regions of the island of Borneo that are governed by three different countries, Brunei, Indonesia and Malaysia.
Suggest reasons why this may make the conservation of leopard habitats difficult.
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(Total 6 marks)
42. Oil is a fossil fuel. It can be used as fuel in power stations and in engines. Figure 1 below shows oil production between 1960 and 2004.
When oil is burnt, some gases, including carbon dioxide, are released. Some processes by which carbon dioxide is added to, or removed from, the atmosphere are shown in Figure 2.
Carbon dioxide is a greenhouse gas, which has an influence upon the mean global temperature of the Earth’s surface. Changes in this temperature between 1960 and 2004 are shown in Figure 3.
Figure 1. Oil production in thousands of barrels per day between 1960 and 2004
8 0 0 0 0
7 0 0 0 0
6 0 0 0 0
5 0 0 0 0
4 0 0 0 0
3 0 0 0 0
2 0 0 0 0
1 0 0 0 0
0
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1962
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2002
2004
Y e a r
9 0 0 0 0O
il p
rodu
ctio
n/ 1
000
barr
els
per
day
Figure 2. Diagram showing part of the carbon cycle
C a r b o n d i o x i d e i n t h e a t m o s p h e r e
F u e l i n a p o w e r s t a t i o n
P r o c e s s B
P r o c e s s A
P r o c e s s C
P r o c e s s C
O i lP l a n t b i o m a s s
D e c a y i n g m a t e r i a l
101
Figure 3. Changes in the mean global temperature of the Earth’s surface between 1960 and 2004
1964
1960
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1972
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2000
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2004
Y e a r
1 4 . 8
1 4 . 6
1 4 . 4
1 4 . 2
1 4 . 0
1 3 . 8
1 3 . 6
1 3 . 4
1 3 . 2
1 3 . 0
Tem
pera
ture
/ C°
(a) Name the processes A, B and C shown in Figure 2.
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(b) Describe the changes in the production of oil between 1960 and 2004 as shown in Figure 1.
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(c) Study the graphs in Figures 1 and 3. Do the graphs support the theory that the rise in oil production is linked to the rise in global temperature? Give reasons for your answer.
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(d) Carbon dioxide is a greenhouse gas. Explain the term greenhouse gas and give an example of another greenhouse gas.
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(e) Oil is one type of fossil fuel. Give one other example of a fossil fuel.
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(f) Energy crops are plants grown in large plantations to provide a sustainable source of energy. These energy crops, such as fast-growing willow, are likely to become far more common in the future. Explain the term sustainable.
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(g) There is some concern that the replacement of traditional crops, such as wheat, by energy crops could affect the distribution of some birds normally found on farmland.
A study was undertaken to investigate the effect of changing land use on the distribution of bird species. Bird surveys were carried out in four habitats: arable land, grassland, willow plantation on former arable land and willow plantation on former grassland. The numbers of lapwing, snipe and woodcock were recorded by walking through each survey area for one hour three times during one summer. The results of this study are shown in Figure 4.
Figure 4. Results of the bird surveys that were carried out on arable land and grassland and in willow plantations growing on former arable and grassland
l a p w i n gs n i p ew o o d c o c k
1 . 0
0 . 9
0 . 8
0 . 7
0 . 6
0 . 5
0 . 4
0 . 3
0 . 2
0 . 1
0Mea
n nu
mbe
r of
bir
ds r
ecor
ded
per
site
pe
r vi
sit
A r a b l e l a n d
W i l l o w o n
g r a s s l a n d
G r a s s l a n dW i l l o w o n a r a b l e
l a n d
Use the data in Figure 4 to describe the effect of planting willow on the distribution of these three species of bird.
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(Total 16 marks)
105
43. If a horse, Equus caballus, is mated with a donkey, Equus asinus, a hybrid known as a mule is produced.
H o r s e( E q u u s c a b a l l u s)
2 n = 6 4
M u l e
D o n k e y( E q u u s a s i n u s)
2 n = 6 2×
Mules are almost always sterile and produce no offspring. This phenomenon is an example of a post-zygotic isolating mechanism.
(a) State the diploid number of chromosomes in a mule and suggest why mules are unable to produce offspring.
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(b) State what is meant by the term isolating mechanism. Suggest why the production of a mule by mating a horse with a donkey is described as a post-zygotic isolating mechanism.
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(c) It has been suggested that the mule should be named as a new species, Equus mulus.Suggest why this might not be acceptable to some biologists.
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(Total 8 marks)
44. Write an essay on the following topic.
Energy flow and succession in ecosystems.
Marks will be awarded for scientific content, coverage of the topic, and the quality of written communication. You should include in your answer any relevant information from the whole of your course. You may include diagrams if you wish, but make sure that they are relevant to your essay and add extra information to it.
(Total 15 marks)
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45. The photograph below shows brine shrimps.
A student carried out an investigation to determine the effect of temperature on the hatching success of brine shrimp eggs. The results are shown below.
Temperature/ °C 22 24 26 28 30 32
% Eggs hatching 36 40 42 44 42 41
(a) Describe the pattern shown by the data in this table.
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(b) Suggest why brine shrimps are affected by temperature in the way shown by the data.
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(c) Suggest how global warming, directly or indirectly, might alter brine shrimp populations.
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(Total 7 marks)
46. Pollen grains buried in peat can be used to deduce what the climate was like in the past.
(a) (i) State how the age of a peat layer can be estimated.
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(ii) The presence of a large amount of alder tree pollen in a layer of peat is taken to mean that there was high rainfall when the layer was formed. Suggest why it is thought that the presence of alder pollen in peat indicates high rainfall.
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(b) The exoskeletons of many insect species are also found in peat. Exoskeletons are resistant to decay. Suggest how insect exoskeletons from peat could be used to show that the climate became warmer over a period of years.
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A r c t i c O c e a n
T u n d r a
No r w
a y
R u s s i a
S w e d e nF i n l a n d
(c) Certain arctic plants are adapted to growing in very cold conditions in the treeless tundra habitat of northern Norway, Sweden, Finland and Russia, near the coast of the Arctic Ocean.
(i) Suggest why the geographical location of arctic plants makes them especially vulnerable to extinction due to global warming.
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(ii) Increase in temperature increases the rate of respiration more than it increases the rate of photosynthesis. Suggest why this might be a problem for arctic plants affected by global warming.
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(Total 7 marks)
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47. An investigation was carried out into the mating preferences of cichlid fish from three populations (A, B and C) taken from Lake Malawi. The fish were all the same species, but the males of each population showed distinct physical differences.
Male fish were separated into different areas of a tank by transparent plastic sheets. The plastic sheets had holes which allowed any female to enter, but prevented the males from leaving.
The diagram below shows the arrangement of the tank.
T r a n s p a r e n t p l a s t i c s h e e t s
H o l e b i g e n o u g h f o r f e m a l e t o p a s s t h r o u g h
M a l e f i s h F e m a l e f i s h
A
B
C
G l a s s t a n k
Females from each population were allowed to choose one mate, and their offspring were collected. The male parent of the offspring was determined using DNA analysis.
The table below shows the number of times mating occurred between individuals of the different populations in a range of trials.
Female from population
Male from population A B C
A 29 0 0
B 0 26 4
C 0 1 8
(a) Explain how the DNA analysis provides reliable evidence for the identity of male parents.
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(b) (i) Calculate the percentage of the matings that were between individuals of the same population. Show your working.
(2)
(ii) Describe the mating preferences shown by the female fish in this investigation.
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(c) Suggest how the data support the hypothesis that population A is the most likely to become a separate species.
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(Total 11 marks)
48. Chimpanzees and humans share about 98.4% of their DNA and it is thought that they had a common ancestor about four million years ago. One gene that shows differences is ‘Fox P2’ which is involved in speech. All modern humans have the same allele for this gene which is different from that found in chimpanzees.
(a) Explain how the frequency of the Fox P2 allele could have increased as humans evolved.
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(b) (i) Until 1968 it was illegal to teach evolution in schools in a number of states in the USA. Suggest two reasons why it was thought necessary to make the teaching of evolution illegal in these schools.
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(ii) Suggest why the teaching of natural selection has less opposition than the teaching of evolution.
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(Total 7 marks)
49. Data for use with the questions that follow.
Figure 1. Microscopic phytoplankton.Phytoplankton are microscopic single-celled plant-like organisms which live in vast numbers in the sea floating just below the surface where they carry out photosynthesis.Marine phytoplankton account for over 50% of the world’s primary productivity.
115
Figure 2. Calanus is a herbivorous small animal which makes up most of the zooplankton of the North Sea and feeds on phytoplankton. Calanus appears in the North Sea in March and starts to breed, but its numbers do not reach a maximum until July. Between late August to early October they leave the North Sea and return to the deep waters of the North Atlantic Ocean to spend the winter. Calanus are the main food source of many small fish as well as the young of larger fish such as herring and cod.
Figure 3. Sandeels.Sandeels are small fish which make up almost a half of the mass of fish in the North Sea. They feed on zooplankton, particularly Calanus. They are an important part of the diet of many of the larger fish such as cod and herrings caught for human food. Sandeels are also important in the diet of many sea birds such as puffins and kittiwakes. Sandeels are caught in vast numbers to make fish-meal food used for farm animals.
Figure 4. Productivity due to phytoplankton in North Sea over a twelve month period.
J F M A M J J A S O N D
3 5
3 0
2 5
2 0
1 5
1 0
5
0
M o n t h
Pri
mar
y pr
oduc
tivi
ty /
g C
mm
onth
ly to
tal
–2
Figure 5. Mean sea surface temperature of the North Sea over a twelve month period.
J F M A M J J A S O N D
2 0
1 8
1 6
1 4
1 2
1 0
8
6
4
2
0
M o n t h
Mea
n m
onth
ly s
ea te
mpe
ratu
rede
gree
s C
117
Figure 6. Breeding stock biomass of two species of fish in the North Sea. Herring stocks fell so low that from 1978 until 1982, fishing for this species in the North Sea was banned. In 2000 the EU negotiated a reduction in fishing for cod but scientists believed that the ‘fishing quotas’ agreed by the EU were too high to allow cod to recover to a sustainable level.
2 , 5 0 0
2 , 0 0 0
1 , 5 0 0
1 , 0 0 0
5 0 0
0
Tot
albr
eedi
ngbi
omas
s/to
nnes
C o d
H e r r i n g
1 9 6 31 9 6 91 9 7 51 9 8 11 9 8 71 9 9 31 9 9 92 0 0 5
Y e a r
Figure 7. Location map.
N o r t hS e a
U K
No r w
a y
Acknowledgements
Based on data in ‘Phytoplankton, biomass and production in the southern North Sea’.Joint, I. and Pomroy, A. (1993) Marine Ecology Progress Series. 99: 169–182.
Based on Zhihong Li, Holt M. and Osborne, J. (2000) ‘A baroclinic model of the NW European shelf seas’. http://www.google.co.uk/search?sourceid=navclient&ie=UTF-8&rls=GGLG,GGLG:2006-16,GGLG:en&q=north+sea+temperature+annual+cycle
http://www.aslo.org/photopost/showphoto.php?photo=1007&papass=&sort=1&thecat=500
http://www.statistics.gov.uk/cci/nugget.asp?id=367
Read and use the data above, and your own knowledge, to answer the following questions.
(a) (i) Construct an appropriate food web diagram to show the feeding relationships between the organisms referred to in the data booklet and which shows the trophic levels each organism occupies.
(3)
(ii) Explain why the total biomass of cod in the North Sea is normally much less than the total biomass of sand eels.
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(b) (i) Suggest two advantages to the phytoplankton of being concentrated just below the sea surface (Figures 1 and 4).
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(ii) Like land plants, phytoplankton require mineral salts. Suggest why phosphates are essential for the growth of phytoplankton.
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(c) (i) In Figure 4, the units used to express primary productivity are abbreviated asgCm–2. Given that ‘C’ stands for organic carbon and the other letters are common
metric units, suggest what gCm–2 stands for by writing it out in full.
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(ii) With reference to Figures 4 and 5, discuss the extent to which mean sea surface temperature controls the primary productivity of phytoplankton.
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(iii) Measurements show that the mean light intensity for the months May and July is the same, but the mean sea surface temperature is 8oC higher in July than in May. Suggest why, in spite of this, primary productivity is similar in these two months.
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(d) The numbers of Calanus in the North Sea have been decreasing since 1960 and there is some evidence that this may be due to climate change. The distribution of Calanus finmarchicus, one of the most abundant species, seems to be shifting northwards, becoming more common off the coast of Norway. Suggest why Calanus may not succeed so well in warmer water.
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(e) (i) There are several reasons why commercially important stocks of fish, such as cod and herring, are under threat in the North Sea. Using information in Figure 6 explain why over-fishing by humans is almost certainly part of the problem.
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(ii) Nets used by fishermen in the North Sea are required to have a mesh size which catches larger fish but allows the smaller (younger) fish to escape. This acts as a selection pressure on the cod population. Explain the effects this selection pressure might have on the phenotypes of these cod in future generations.
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(Total 20 marks)
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50. (a) The electron microscope image below shows part of a chloroplast.
The table below gives one function of each of the three structures labelled A, B and C on the electron microscope image. Complete the table below by writing in the appropriate letter and the name of each structure.
Function Label letter Name of structure
Photophosphorylation
Stores non-carbohydrateorganic material
Carbon fixation
(3)
(b) The equation below summarises the process of photolysis of water.
2H2O → 4H+ + 4e– + O2
(i) Explain what happens to the electrons released by photolysis.
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(ii) The electrons are later involved in the reduction of NADP. Explain the importance of reduced NADP in the light-independent reactions of photosynthesis.
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(c) The rate at which plants produce carbohydrate by photosynthesis is known as gross primary productivity.
Put a cross in the box next to the equation that shows the relationship between gross primary productivity (GPP), net primary productivity (NPP) and respiration (R).
GPP + R = NPP
GPP + NPP = R
GPP = NPP + R
GPP = NPP – R(1)
(d) The table below shows the net primary productivity in four different ecosystems. The ecosystems in the table are listed in order of increasing distance from the equator, starting with tropical rainforest.
EcosystemNet primary productivity
/ kJ m–2 year–1
Tropical rainforest 37 800
Temperate forest 25 200
Boreal forest 14 700
Polar tundra 2 400
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(i) It is estimated that 85% of the energy available to primary consumers will not be available to secondary consumers. Calculate the energy that will be available to the secondary consumers in the tropical rainforest. Show your working.
Answer ................................. kJ m–2 year–1
(2)
(ii) Suggest two reasons for the differences in the net primary productivity as the distance from the equator increases.
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(Total 13 marks)
51. A study of the distribution and abundance of three different seaweeds was carried out in the intertidal region of a gently sloping rocky shore. The intertidal region is the area that will be covered by water as the tide comes in and uncovered by water as the tide goes out.
The abundance of each seaweed was found by estimating its percentage cover at regular intervals from the high water mark at the top of the shore to the low water mark lower down the shore.
The results of this study are shown on the graph below.
C h o n d r u s
F u c u sA s c o p h y l l u m
6 05 55 04 54 03 53 02 52 01 51 0
50
0 2 4 6 8 1 0 1 2 1 4
D i s t a n c e f r o m h i g h w a t e r m a r k / m e t r e s
Per
cen
tage
e co
ver
/ %
(a) (i) Put a cross in the box next to the statement that could form part of a valid conclusion from the data shown in the graph.
A – Ascophyllum grows only in regions that are uncovered by waterfor long periods of time
B – Fucus grows better in regions that are never uncovered by water
C – Chondrus may not be able to compete with Ascophyllum(1)
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(ii) With reference to the graph discuss the validity of statements A, B and C.
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(b) Suggest two abiotic factors, other than the length of time the seaweeds are out of water, that could affect the distribution of the seaweeds on this shore.
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(c) Describe a technique that you have used to study the distribution of a named organism within its habitat.
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(Total 10 marks)
52. A study of tree pollen grains in a peat bog in Finland was carried out. The number of pollen grains of different tree species was recorded at different depths in the peat.
The data for four of these trees are given as a percentage of the total tree pollen sample, in the table below. An estimate of the age of the sample at each depth was also made.
Depth of Age / Tree pollen grain / %
sample/ m
yearsLarch Spruce Pine Beech
0.5 2 850 0 0 53 43
1.0 3 770 0 0 55 40
1.5 5 600 0 0 31 47
2.0 6 390 0 12 15 53
2.5 8 170 5 36 4 48
3.0 8 700 38 36 6 35
3.5 8 780 27 40 3 32
4.0 10 000 10 22 2 40
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The diagram below shows the present-day distribution of the four tree species found in the main climatic zones of the northern hemisphere.
C l i m a t i c z o n e D i s t r i b u t i o n o f t r e e s
A r c t i c
B o r e a l
T e m p e r a t e
S u b - t r o p i c a l
L a r c h S p r u c e
P i n eB e e c h
(a) Suggest how pollen grains can provide evidence about which species of tree were growing successfully in Finland as the peat bog was forming.
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(b) (i) Put a cross in the box next to the species of tree that does not provide evidence about the changes in climate in Finland during the last 10 000 years.
A Larch
B Spruce
C Pine
D Beech(1)
(ii) Explain your answer to (b)(i).
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(c) With reference to the present-day distribution of the four tree species and the results of the pollen grain study, suggest in what way the climate in Finland has changed during the last 10 000 years. Give reasons for your answer.
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(d) Describe how dendrochronology can be used to provide evidence for climate change.
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(Total 12 marks)
53. In 1937, a population of sockeye salmon was released into Lake Washington in the USA.Since then, the original stock appears to have split into two different populations which do not interbreed. One group of salmon breeds in the shallow waters of the lake. The other group breeds in a fast-flowing river that flows into the lake.
These two populations of salmon have developed very different physical features. In the river, the male fish are more streamlined than those in the lake. This is thought to enable them to deal with the river’s strong current. The females in the river are larger and more muscular than those in the lake population. This allows them to bury their eggs deep into the gravel, which is necessary to stop the eggs being dislodged by the fast water flow.
In addition, scientists have found evidence that the two populations appear to have developed differences between their gene pools. It is suggested that the Lake Washington salmon populations may eventually evolve into two separate species.
(a) State the term used to describe
(i) the separation of one species into two populations that do not interbreed
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(ii) the formation of two new species from one species
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(iii) the relative proportion of different forms of a particular gene within a gene pool.
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(b) Suggest how the two populations of salmon developed differences in their gene pools.
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(c) Explain how new alleles might appear in the gene pool of a species.
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(Total 10 marks)
54. (a) Forensic entomology can be used to estimate the time of death of a mammal. Adult
female blowflies soon arrive to lay their eggs on the body and the blowfly life cycle follows a precise sequence. The diagram below shows the sequence and times (in hours) for each stage when the surrounding temperature is 21 °C.
(i) Using information in the diagram, calculate the total percentage of the life cycle that a blowfly spends as a larva when the surrounding temperature is 21°C.
Answer .............................. %(2)
(ii) Temperature has an effect on the length of the blowfly lifecycle. Suggest an explanation for the effect of temperature on the length of the blowfly lifecycle.
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(iii) Suggest two factors, other than temperature, that may affect the timing of the blowfly lifecycle and lead to an incorrect estimate of the time of death.
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(b) Time of death can also be estimated by studying the degree of rigor mortis in muscles.Describe how rigor mortis in muscles occurs.
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(c) The process of succession occurs in plant communities as well as in a dead body.Compare these two forms of succession.
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(Total 13 marks)
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