1.

Photosynthesis is a complex metabolic process which can be influenced by many different environmental factors. (a) Explain the term limiting factor with reference to photosynthesis. . . . .(2)

(b)

An investigation into the effect of light intensity and carbon dioxide concentration on photosynthesis was carried out using pond weed. The pond weed was placed in a test tube that contained pond water and a quantity of sodium hydrogencarbonate. The light was provided by a lamp. The oxygen bubbles produced by the pond weed were directed into a length of capillary tubing.

The graph below shows how the rate of oxygen production of the pond weed changed with light intensity when immersed in two different concentrations of sodium hydrogencarbonate. 0 .8 0 .7 R a te o f o x y g e n p r o d u c tio n 0 .6 / c m 3 m in 1 0 .5 0 .4 0 .3 0 .2 0 .1 0 0 50 100 150 200 250 300 350 400 L ig h t in te n s ity / a r b itra ry u n its 0 .1 m o l d m 3 s o d iu m h y d ro g e n c a rb o n a te 0 .5 m o l d m 3 s o d iu m h y d ro g e n c a rb o n a te

1

(i)

Explain the shape of the graph between a light intensity of 0 and 400 arbitrary units in the sodium hydrogencarbonate concentration of 0.5 mol dm3. ... ... ... ... ... ... ... ...(4)

(ii)

Describe and explain the effect of increasing the concentration of sodium hydrogencarbonate, on the rate of oxygen production. ... ... ... ... ... ...(3)

(iii)

A number of precautions would need to be taken while carrying out this investigation in order to obtain reliable data. Describe one precaution and explain why this precaution is necessary. ... ... ... ...(2)

(c)

During the light-dependent stage of photosynthesis, oxygen is produced by photolysis. Describe the process of photolysis and explain its role. . . . . . .(3) (Total 14 marks)

2.

(a)

The rate of photosynthesis can be limited by a number of factors.

Explain why temperature can be a limiting factor in photosynthesis. . . . .(2)

(b)

The diagram below shows the structure of a chloroplast.

3

Name the parts labelled A, B and C. A . B . C .(2)

(c)

The flow diagram below shows some of the processes which occur in the light independent reaction of photosynthesis. 5 c a rb o n c o m p o u n d + X

R e g e n e ra tio n

Y N A D PH + H ATP T rio s e p h o s p h a te+

G lu c o s e p h o s p h a te

(i)

Name the substances represented by the letters X and Y. X ... Y ...(2)

(ii)

State the origin of the NADPH + H+ and the ATP used in the light-independent reaction. ...(1)

(d)

Describe how the products of photosynthesis are transported in the plant. . . . . . . . . . .(5) (Total 12 marks)

3.

The diagram below shows an outline of the light-independent stage of photosynthesis, together with some of the products. C2O

X

Y N o t e T r i o s e k n o w n T p r i o s e h o s p h h o s e r y a t e l a t e d S u 6 C c r o s u s e g a r p h a s o G s p A h a t e L P i s o r a l s o P G A

P G

h

o l u

s p c o

5

(a)

Using the information provided in the diagram, identify substances X and Y and state the number of carbon atoms present in each. X ........................................................................................................................................ Y .....................................................................................................................................(2)

(b)

Explain how substance Y is converted to triose phosphate. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(2)

(c)

Triose phosphate is converted to a phosphorylated 6-carbon sugar which in turn can be converted to a number of products such as sucrose and glucose. Sucrose is translocated around the plant in phloem. Describe how phloem tissue is adapted for this function. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................(6) (Total 10 marks)

4.

The diagram below shows one pair of electrons being passed between the molecules of the electron carrier system (A, B, C and D) during part of the light-dependent reactions of photosynthesis.

7

(a)

(i) Explain how the pair of electrons move from chlorophyll to the electron carrier system. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

Explain how electrons lost from chlorophyll are replaced. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(iii)

Explain how ATP is synthesised when electrons pass between electron carriers B and C. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(b)

Describe the Calvin cycle. You should answer this question in continuous prose. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(6) (Total 12 marks)

5.

Simazine is a herbicide that kills plants by disrupting the flow of electrons in the membranes of chloroplasts. An investigation was carried out into the effects of Simazine on photosynthesis. Two samples of plants were grown under the same controlled conditions. One sample was treated with water and the other with a solution of Simazine. Both samples were supplied with radioactive carbon dioxide (14CO2) in a well lit, sealed chamber for an hour. The plants were removed from the chamber and killed immediately. The mass of radioactive carbon fixed in the plants was measured.

9

(a)

Suggest one condition which should have been controlled while the plants were growing. ..................................................................................................................................... .....................................................................................................................................(1)

(b)

Explain why the plants were killed immediately after they were removed from the chamber. ..................................................................................................................................... .....................................................................................................................................(1)

(c)

The results of the experiment are given in the table below. Radioactive carbon fixed / mg Plants treated with water 10.6 Plants treated with Simazine 1.4

Suggest an explanation for the effect of Simazine on the mass of radioactive carbon fixed in the plants. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(5) (Total 7 marks)

6.

The carbohydrates in green plants are formed during the light-independent stage of photosynthesis. They are synthesised from glycerate 3-phosphate (GP). (a) State precisely where the synthesis of carbohydrates takes place during the lightindependent stage of photosynthesis. ......................................................................................................................................(1)

(b)

Name the products of the light-dependent stage of photosynthesis used during the synthesis of carbohydrates. ...................................................................................................................................... ......................................................................................................................................(2)

(c)

Describe the role of ribulose bisphosphate (RuBP) in the light-independent stage of photosynthesis. ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ...................................................................................................................................... ......................................................................................................................................(2)

11

(d)

An investigation of photosynthesis in cells taken from a green alga was carried out. Samples of the algal cells were taken at 1 minute intervals over a period of 6 minutes. The quantities of GP and RuBP in these cell samples were measured. At the start of the investigation, the algal cells were kept in an atmosphere with 1% carbon dioxide. After 3 minutes, the concentration of carbon dioxide was decreased to 0.003%. The graph below shows the results of this investigation. C a r b o n d i o x i d e d e c r e a s e d

1

%

c a r b

o

n

d

i o

x0 i . d0 e0

3

%

c a r b

o

n

d

i o

x

i d

e

Q u a n t i t i e s o f R u B P a n d G P / a r b i t r a r y u n i t s

R

u

B

P

G 0 1 Time / minutes 2

P 3

(i)

Describe the effects of the decrease in the concentration of carbon dioxide on the quantities of GP and RuBP. ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(2)

(ii)

Suggest explanations for the effects you have described in part (i). ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ............................................................................................................................... ...............................................................................................................................(2) (Total 9 marks)

7.

An experiment was carried out to investigate the effect of light intensity on the rate of photosynthesis of an aquatic plant, using the apparatus shown below. S c a l e i n m m

L

i g

h

t

C G

a p a s

i l l a r y b u b b

t u b e S y r i n l e s t b i n e

g

e

A q u a t i c p l a n p e r f o r a t e d t u

T w

e s t i t h

t u w

b e f i l l e d a t e r

13

(a)

Explain what is meant by the term limiting factor. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(b)

State two environmental conditions, other than light intensity, which would need to be controlled. Describe how each of these environmental conditions could be controlled. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(c)

The aquatic plant was allowed to carry out photosynthesis for 10 minutes. Describe how 3 this apparatus could be used to determine the rate of oxygen production (mm min 1). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(d)

Describe how you could modify this apparatus to determine the effect of different wavelengths of light on photosynthesis. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 12 marks)

15

8.

The diagram below shows some of the stages in the Calvin cycle. C R u B P2O

F

B

P

a s e

P

G

A

G

l u

c o

s e

P

G

A

L

S

u

c r o

s e

(a)

Some stages of the Calvin cycle require energy from ATP. Describe in outline how ATP is made available by reactions in the chloroplast. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(5)

FBPase is an enzyme involved in one step of the pathway used to re-form the CO2 acceptor molecule RuBP. In an investigation, plants were modified by introducing a gene which reduces the activity of FBPase. The graph below shows the effect of this treatment on the sucrose content of the leaves of treated and untreated plants. 2 % o f n s u c r o s e c o n t e n t1 5 0 2 o 1 5 0 a l

0 0 r m 5 0 0 0 U p 0

n

t r eT a r t e e a d t e d l a n tp s l a n t s

(b)

Describe the effect of reduced FBPase activity on the sucrose content of leaves. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

(c)

Suggest an explanation for the difference in sucrose content of the leaves of treated and untreated plants. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2)

17

(d)

Suggest potential benefits of plants modified in this way. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 11 marks)

9.

The diagram below shows a root hair cell.

(a)

Describe how the shape of a root hair cell increases the efficiency of absorption of water and mineral ions from the soil solution. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(1)

(b)

Mineral ions can be taken up by root hair cells and may accumulate at higher concentrations than in the soil solution. Explain how mineral ions are taken up by root hair cells. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(c)

Phosphate ions are required for the synthesis of many important molecules in plants. Name two products of the light-dependent stage of photosynthesis that require phosphate ions in their molecular structure. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(1)

19

(d)

Describe a simple procedure by which you could use mineral culture solutions to find the effect of a lack of phosphate ions on plant growth. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3) (Total 9 marks)

10.

(a) In the space below, draw a diagram of a chloroplast showing the main features of this organelle. On your diagram indicate the location of the light-dependent reactions and the lightindependent reactions.

(4)

21

(b)

Describe the process of non-cyclic photophosphorylation. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(c)

Describe what happens to the products of non-cyclic photophosphorylation. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 10 marks)

11.

The diagram below shows a chloroplast. A B C

D

(a)

(i)

Name the parts labelled A, B, C and D.

A ........................................ B ......................................... C ........................................ D ........................................(2)

(ii)

State the part of the chloroplast, shown on the diagram, where oxygen is produced. ...........................................................................................................................(1)

23

(iii)

Explain how oxygen is produced in chloroplasts during photosynthesis. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(b)

Oxygen inhibits the enzyme that catalyses the fixing of carbon dioxide. High concentrations of oxygen, within a chloroplast, can reduce the rate of photosynthesis. Describe and explain the effect of high concentrations of oxygen on the rate of carbohydrate production in a chloroplast. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)

(c)

Suggest two environmental conditions which could increase the rate of oxygen production by plants. 1 .................................................................................................................................. 2 ..................................................................................................................................(2) (Total 11 marks)

12.

One of the reactions of photosynthesis can be summarised as shown below. hydrogen ions + oxygen gas + electrons water

(a)

Name the reaction shown. .....................................................................................................................................(1)

(b)

Give one other factor, not shown above, that would be required for this reaction to occur in a chloroplast. .....................................................................................................................................(1)

(c)

Describe the role of the electrons in the light dependent reaction of photosynthesis. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

25

(d)

Describe and explain how the products of the light dependent reaction are involved in the production of glyceraldehyde-3-phosphate (GALP). ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(e)

GALP does not accumulate in a chloroplast during photosynthesis. Explain how GALP is used following its production. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 12 marks)

13.

The diagrams below show the absorption spectra and the action spectrum that were produced in an investigation of photosynthesis in a flowering plant. A b s o r p t i o n s p e c t r a c a r o A b s o r p t i o / a r b i t r a r y n u n i t s c h l o r bo p t e n o c h h i d l o y s r ao l l p h y l l

4

0

0

5 W

0

0 a v

6 e l e n

0 g

0 t h

7 0 0 / n m

A

c t i o n

s p

e c t r u

m

R a t e o f p h o t o s y n t h e s i s / a r b i t r a r y u n i t s

4

0 b

0 l u e

5

0 6 0 0 W a v e l e n g t h l i g h t r e d

0

7 0 0 / n m l i g h t

27

(a)

Using the information in the two graphs, explain the relationship between the absorption and action spectra for this flowering plant. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(3)

(b)

State precisely where the chlorophyll pigments would be found in a chloroplast of a flowering plant. .....................................................................................................................................(1)

(c)

Describe how chromatography could be used to identify the chloroplast pigments from the leaves of a flowering plant. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(d)

Explain why flowering plants grown in soil which is deficient in magnesium ions often have leaves with pale yellow patches between the veins. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(2) (Total 10 marks)

14.

The diagram below summarises the light dependent reactions of photosynthesis.L I G H T P r o d u c t A

C

h

l o

r o

p

h

e l e c t r o y l l

n s E l e c t r o

n

e l e c t r o n s c a r r i e r s P r o

d

u

c t

B

(a)

Give the precise location within a chloroplast where this sequence of reactions occurs. .....................................................................................................................................(2)

(b)

Give the names of product A and product B. Product A .................................................................................................................... Product B ....................................................................................................................(2)

(c)

Give the name of the process that provides electrons to replace those lost by chlorophyll. .....................................................................................................................................(1)

(d)

A chemical called atrazine prevents the flow of electrons to the electron carriers. Describe and explain the likely effect of atrazine on the production of carbohydrate in a29

chloroplast. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................(4)

(e)

Atrazine can be used as a weedkiller. (i) Explain how the presence of weeds can reduce the yield of crop plants. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

(ii)

A change in a single gene can alter the electron carriers so that atrazine is ineffective. Suggest how crop plants unaffected by atrazine could be used to increase crop yields. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 13 marks)

15.

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 worlds primary productivity.

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.

31

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. period. 3 3 P rim a ry p ro d u c tiv ity / g C m m o n th ly to ta l2

Productivity due to phytoplankton in North Sea over a twelve month 5 0 5 0 5 0

2 2 1 1 5 0

J

F

M

A

M

J M o

J n

A t h

S

O

N

D

Figure 5. period. 2 1 1 M e a n m o n th ly s e a te m p e ra tu re d e g re e s C 1 1 1 8 6 4 2 0 0 8 6 4 2 0

Mean sea surface temperature of the North Sea over a twelve month

J

F

M

A

M

J M

J o n

A t h

S

O

N

D

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 2 T o ta l b re e d in g b io m a s s / to n n e s 1 1 5 , 5 , 0 , 5 , 0 0 0 1 0 0 0 0 0 0 0 0 0 C H o d e r r i n

g

9

61 39

6 1 99

7 1 5 9 Y

81 19 e a r

8 1 7 9

91 39

9 2 90

0

5

33

Figure 7. Location map.

N S U K

o r t h e a

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: 169182. 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=UTF8&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

No rw

ay

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

(b)

(i) Suggest two advantages to the phytoplankton of being concentrated just below the sea surface (Figures 1 and 4). ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)

35

(ii)

Like land plants, phytoplankton require mineral salts. Suggest why phosphates are essential for the growth of phytoplankton. ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(1)

(c)

(i) In Figure 4, the units used to express primary productivity are abbreviated as gCm2. Given that C stands for organic carbon and the other letters are common 2 metric units, suggest what gCm stands for by writing it out in full. ...........................................................................................................................(1)

(ii)

With reference to Figures 4 and 5, discuss the extent to which mean sea surface temperature controls the primary productivity of phytoplankton. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

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

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

37

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

(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. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 20 marks)

16.

(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 Photophosphorylation Stores non-carbohydrate organic material Carbon fixation(3)

Label letter

Name of structure

(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. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2)+

39

(ii)

The electrons are later involved in the reduction of NADP. Explain the importance of reduced NADP in the light-independent reactions of photosynthesis. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(3)

(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. Ecosystem Tropical rainforest Temperate forest Boreal forest Polar tundra Net primary productivity 2 1 / kJ m year 37 800 25 200 14 700 2 400

(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 year

2

1

(2)

(ii)

Suggest two reasons for the differences in the net primary productivity as the distance from the equator increases. ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ........................................................................................................................... ...........................................................................................................................(2) (Total 13 marks)

41