web viewways in which energy is lost between producers and ... what is the importance of decomposers...

1. Moose are large herbivorous animals.

(a) In a study of one population of moose, 72 animals were trapped and marked with ear tags. They were then released. One month later, fieldworkers examined 120 moose and found that 14 of these had ear tags.

Use these figures to calculate the size of the moose population. Show your working.

Answer:............................(2)

(b) Isle Royale is a large island in Lake Superior. Moose first colonised this island in 1900. At the time they had no predators on the island. Wolves, which are predators of moose, were introduced to the island in 1950. The graph shows the moose population from 1900.

Isla nd co lo n ise db y m o o se

W o lv e sin tro d u ced

3 00 0

2 00 0

1 00 0

019 0 0 1 9 1 0 1 9 2 0 1 9 3 0 1 9 4 0 1 9 50 1 9 6 0 1 9 7 0

D ate

M o o sep o p u la tio n

Woodford High School 1

(i) Suggest an explanation for the changes in the moose population before the introduction of the wolves.

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(ii) Describe the effect of introducing wolves on the moose population.

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(Total 5 marks)

2. The diagram represents annual energy flow, in kJ m–2 year–1, through an aquatic ecosystem.

D ec o m p o sers

H erb iv o re s

P ro d u cers

S u nlig h t7 1 4 0 0 0 0

1 4 1 5 0

8 7 4 0 0

7 2 5 0

1 7 80 0

lo s t9 5 0 0

lo s t7 0 5 2 6 0 0


(a) Give two ways in which energy is lost between producers and herbivores.

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(2)

(b) Calculate the percentage of available sunlight trapped by the producers.Show your working.

Answer..............................(1)

(c) What is the importance of decomposers to the producers?

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(Total 4 marks)


3. Heather is a woody plant found in many moorland areas on higher ground in Britain. Grouse are chicken-sized birds which feed on the young shoots of heather. On many moorlands, the heather is managed to produce better conditions for grouse. This involves burning large areas. After burning, heather goes through the cycle of growth described below.

Pioneer phase0-7 years

New plants grow either fromseed or from stem basesundamaged by fire.

Building phase7-15 years

Phase of rapid growthproducing dense cover ofheather plants.

Mature phase15 - 25 years

Plants still growing but gapsstart to appear in the canopy.

Degenerate phase25+ years

Branches break. Central partof plant dies although outerbranches may remain alive.

Table 1 summarises some data collected from a study of heather plants of different ages.

Age/years Totalbiomass/g m2

Biomass of greenshoots/g m–2

Percentage cover Light at ground levelas percentage of light

in open

5 287 78 10 84

10 1508 203 85 5

20 1924 208 76 22

30 1043 n/a 34 56

Table 1

Key:n/a = figures not available


(a) To determine the total biomass, quadrats were used to collect the heather samples.Describe the procedure you would have used to place these quadrats.

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(b) Describe how and explain why the diversity of plant species would be likely to change during the cycle of growth of the heather.

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(c) (i) Calculate the mean rate of increase in the biomass of green shoots between 10 and 20 years. Show your working.

Answer: ............................................(2)


(ii) Explain why the mean rate of increase in the biomass of green shoots decreases with age.

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(iii) Management of heather by burning allows an area of land to support a larger population of grouse than if the heather is unmanaged. Use the information in Table 1 to suggest why.

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Table 2 shows the nitrogen content of heather plants, leaf litter and the soil in plots of land at various stages after burning.

Time after Nitrogen content/kg ha–1

burning/years Heather plants Leaf litter Soil

3 59 28 5794

8 92 61 5952

15 192 58 5394

Table 2

(d) (i) Give one organic compound in which the nitrogen will be found in the heather plants.

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(ii) Give one ion in which the nitrogen will be found in the soil.

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(e) Explain how bacteria make nitrogen present in the leaf litter available to the heather plants.

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(f) It has been suggested that if heather moorland is to be managed by burning, this should take place before the heather is 15 years old. Use the information in Table 2 to suggest why.

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(Total 20 marks)


4. The diagram shows the arrangement of some of the proteins in a myofibril from a skeletal muscle. The myofibril is shown in the relaxed state.

Z lin e

A b a n d I b a n dH zo n e

S a rco m ere

(a) Name the protein found in the H zone.

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(b) When the muscle contracts, what happens to the width of

(i) the A band; .......................................................................................................

(ii) the I band? ........................................................................................................(2)


S (c) The distance between two Z lines in a myofibril is 1.6 m. Calculate the magnification of the diagram. Show your working.

Answer ........................................................................................................................(2)

(Total 5 marks)

5. Many athletes practise glycogen loading. They eat food high in carbohydrates for 3 – 4 days before an event. This produces an increase in the amount of glycogen stored in the liver and muscles.

In an investigation into the effects of glycogen loading on performance, two groups of athletes followed different diets before exercising. All the athletes exercised at the same rate until they were exhausted. This time was recorded. The concentration of muscle glycogen was measured before and after exercise. Some results are shown in the graph.

M ix edd ie t

H ig hca rb o h y d ra te

d ie t

1 00 0

80 0

60 0

40 0

20 0

0

C o n cen tra tio no f m u sc leg ly c o ge n /m m o l k gd ry m a ss

– 1

K e yB efo re ex erc iseA fte r ex erc ise

F ig u res in b rack e tsin d ica te m ean tim eto e x h au s tio n inm in ute s

(1 2 6 )

(1 8 9 )


(a) (i) Calculate the percentage increase in mean time to exhaustion of the athletes following a high carbohydrate diet compared with those following a mixed diet.Show your working.

Answer ..............................................(2)

(ii) Explain this increase in mean time to exhaustion.

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S (b) What do the bars (I) on the graph indicate about the values?

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(Total 5 marks)


6. Like many insects, honeybees cannot survive in very cold conditions. Before an individual bee can fly, the temperature of its flight muscles must be above 15 °C. It achieves this with small, rapid contractions of the flight muscles, rather like shivering in a mammal.

Honeybees live as a colony in a hive. By clustering together in the centre of the hive they can keep the temperature of this area at a constant 34 to 35 °C. In this way the bees can survive in cold conditions.

In an investigation, the diameter of the cluster formed by one colony of bees was measured at various environmental temperatures. None of the bees died during the investigation. The results are shown in Figure 1.

3 6

3 3

3 0

2 7

2 4– 6 – 5 0 5 1 0 15

D iam eter o f th ec lu s te r / cm

E n v iro n m e nta l tem p era tu re / °C

Figure 1

(a) Describe and explain the relationship between the environmental temperature and the diameter of the cluster.

(2)


The table shows the results of a further investigation. It shows the relationship between the temperature in the centre of the cluster of bees and the sugar consumption of the bees.

Temperaturein the centre of cluster/°C

Mean sugar consumptionper bee/mg day–1

19 49

23 32

27 24

30 12

33 15

36 18

(b) Plot the data in the table as a suitable graph on the graph paper provided.(4)

(c) Explain the relationship between cluster temperature and sugar consumption:

(i) between 30 °C and 36 °C;

(ii) between 19 °C and 30 °C.(4)

(d) Use the data in the table to predict the effect of cluster temperature on carbon dioxide production by the bees. Explain your answer.

(2)


The graphs in Figures 2 and 3 show some aspects of the behaviour of bees.

Figure 2 shows the effect of an increase in carbon dioxide concentration in the hive on the number of bees which can be seen facing into the hive and fanning their wings vigorously.Figure 3 shows how the number of bees collecting water varies over the course of a day. These bees return to the hive and spread the water in tiny droplets over the internal surface of the hive.

1 5 0

1 2 0

9 0

6 0

3 0

00 1 2 3 4 5 6 7 8 9 1 0

C a rb o n d io x id e co n c en tra tio n / %

N u m b er o fbe es fan n in g

w in g s

Figure 2

4 0

3 6

3 2

2 8

2 4

2 0

1 6

1 2

8

4

0

4 0

3 5

3 0

2 5

2 0

Tem p era tu re / °C

N um b er o f b ees co llec tin g w a te r

N u m b er o fb ee s co llec tin g

w ater

Te m p e ra tu re

Tim e of d ay9 .0 0 1 0 .0 0 11 .0 0 1 2 .0 0 1 3 .0 0 1 4 .0 0

Figure 3


(e) Use information from these graphs to explain how the internal temperature of the hive is prevented from rising on a hot day.

(3)

(f) Although all honeybees belong to the same species, there are many different varieties. One variety called the mountain bee is found at high altitudes in East Africa. It has longer ‘hair’ on its body than other African varieties of bee.

(i) Suggest why this longer ‘hair’ may be an advantage to bees living at high altitude.(2)

(ii) Explain how natural selection could have resulted in bees with longer ‘hair’.(3)

(Total 20 marks)

7. The graph shows changes in the concentration of some hormones during the oestrous cycle of a cow.

1 2

1 0

8

6

4

2

00 2 4 6 8 1 0 1 2 1 4 1 6 1 8 2 0 2 2

C o n ce n tra tio no f h o rm o n e/

a rb itra ry u n its

T im e /da y s

P ro g e stero n e

O es tro g en

L H

(a) Between which days is fertilisation most likely to be successful? Explain your answer.

Days ............................................................................................................................

Explanation .................................................................................................................

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(b) Did the cow become pregnant during this cycle? Give the evidence from the graph for your answer.

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(Total 3 marks)

8. The island of Surtsey was formed in 1963 by a series of volcanic eruptions. Biologists have studied the colonisation of this new island by plants and animals.

(a) The graph shows the number of species of plants found on the island each year for the first seven years of its existence.

1 6

1 4

1 2

1 0

8

6

4

2

0

N u m b ero f sp ec ie s

19 6 3 1 96 4 1 96 5 1 9 6 6 19 6 7 1 9 6 8 1 9 6 9 1 9 7 0Year


The development of the plant community on Surtsey illustrates the process of succession. Explain why:

(i) very few species could grow on the island in the first few years after it was formed;

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(ii) once some plants were growing, the rate at which new species could establish themselves increased rapidly.

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(b) Animals also colonised Surtsey. One conclusion drawn from studying them was that particular species of animals found here had broader ecological niches than they did on the nearby mainland. Suggest why.

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(Total 4 marks)


9. The graph shows the effect of applying different amounts of nitrogen fertiliser on the yield of wheat.

5 .0

4 .0

3 .0

2 .00 .0

0 2 0 40 6 0 8 0 1 0 0 12 0 1 4 0 1 6 0 1 8 0 2 0 0

Yie ld /to n n e s h a– 1

–1N itro g en fe r ti lise r ap p lie d /k g h a

(i) Calculate the percentage increase in yield obtained when the amount of nitrogen fertiliser is increased from 50 to 100 kg ha–1. Show your working.

(2)


(ii) It would not be advisable for a farmer to apply more than 160 kg ha–1 of fertiliser to this wheat crop. Use the graph to explain why.

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(iii) Give two advantages of using an inorganic nitrogen fertiliser, rather than an organic fertiliser.

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(Total 6 marks)

10. Wheat is a cereal crop grown mainly for grain. Wheat straw consists of dead leaves and stems. An investigation was carried out into the effect of adding nitrogen-containing fertiliser on the yield of wheat.

M a ss o f fe rtilise ra d d ed /g m – 2

– 2Y ie ld / g m

G ra in4 7 85 4 96 2 2

0 .06 .3

5 0 .0

S traw2 4 52 8 43 2 4


(a) Does adding 50 g m–2 of nitrogen-containing fertiliser have a greater effect on the grain or the straw? Use suitable calculations based on the figures in the table to support your answer.

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(b) (i) When 6.3 g m–2 of nitrogen-containing fertiliser was added, the ratio of straw to grain was 0.517. Calculate the ratio of straw to grain when 50 gm–2 of nitrogen-containing fertiliser was added. Show your working.

(2)

(ii) Suggest why the grain to straw ratio may be important to a farmer.

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(c) Farmers remove weeds from land on which wheat is growing. Suggest why the yield of wheat grain is higher if weeds are removed at the beginning of the growing season than if they are removed later in the growing season.

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(Total 8 marks)

11. The diagram shows the annual transfer of energy in a forest ecosystem. The figures are inkJ m–2.

A bso rb e dby p ro d u cers

4 .6 × 1 0

O rg an icm o lec u le s

4 4 0 9 0

H eat lo ss inresp ira tio n

2 0 0 0 0

P r im aryco n su m e rs

D e tr itu s1 5 3 3 0

S u n lig h t7 .1 × 1 0

M a te ria ls n o tc on su m ed

5 8 4 0

6

6

(a) Although the producers absorb 4.6 106 kJm–2, only about 1% of this is transferred to organic molecules. Suggest one reason for this.

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(b) Calculate the energy transferred to primary consumers in this ecosystem.

................................................... kJm–2

(1) (c) Nitrogen compounds in the detritus are broken down by bacteria to ammonium ions

)NH( 4

. Describe how ammonium ions are converted into a form that can be readilyabsorbed by the producers.

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(Total 5 marks)


12. The graph shows the blood glucose and glucagon concentrations in a healthy person during and after eating a meal.

1 2 0

1 0 0

8 0

1 2 0

11 0

1 0 0

9 0

M e a l

G lu co se

G lu ca g o n

O neh ou r

b efo rem eal

M e alb eg in s

Tw o h o u rsa fte r m ea l

B lo o d g lu co sec o nc en tra tio n /

m g 1 0 0 cm

B lo o d g lu ca g o nco n ce ntra tio n /a rb itra ty u n its

– 3

(a) (i) From where is glucagon secreted?

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(ii) Explain the changes that occur in the glucagon concentration over the period on the graph.

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(b) Explain how the information shown in the graph provides an example of negative feedback.

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(Total 5 marks)


web viewways in which energy is lost between producers and ... what is the importance of decomposers...

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