UNIT 4

Question 1

State whats meant by tissue

Answer 1

group of same cells with same structure

Question 2

Spongy mesophyll is a site of gas exchange. The arrows on the diagram show the direction of movement of carbon dioxide during the day. Using the information in the diagram and your own knowledge of the properties of gas exchange surfaces, suggest how spongy mesophyll is adapted for gas exchange.

Answer 2

1. the gas exchange surface is the cell wall (and membrane) 2. so the diffusion distance is small (between air space and cytoplasm) ; 3. idea that the carbon dioxide can { continuously enter the leaf /circulate around the cells } 4. maintains a concentration gradient (between air space and cell) ;

Question 3

Photosynthesis takes place in palisade mesophyll. Describe what happens to the carbon dioxide that enters this tissue.

Answer 3

1. the gas exchange surface is the cell wall (and membrane) 2. so the diffusion distance is small (between air space and cytoplasm) ; 3. idea that the carbon dioxide can { continuously enter the leaf /circulate around the cells } ; 4. maintains a concentration gradient (between air space and cell) ;

Question 4

Xylem transports ions and water molecules to the leaf. Describe the roles of these ions and water molecules in photosynthesis.

Answer 4

1.. CCEPT carbon dioxide is soluble (in moisture) 2. idea that carbon dioxide { diffuses / moves / enters } into the { chloroplasts / stroma } ; 3. idea that carbon dioxide binds to RuBP / reference to carbon fixation / { reduction of carbon dioxide / eq } ; 4. reference to { Calvin cycle / light-independent reaction } ; to produce gp

Question 5

Describe the roles of the thylakoid membranes in the production of ATP in the light-dependent reaction.

Answer 5

2. idea of {chlorophyll / photosystems / eq} in the (thylakoid) membrane ; 3. for the absorption of light (energy) ; 4. so that electrons are released (from chlorophyll) / eq ; 5. idea that there are electron carriers are in the (thylakoid) membrane ; 6. idea that electrons are {picked up by / passed down} electron {carriers / proteins / acceptors} ; 7. resulting in {hydrogen ions / H+ / protons} being {moved into / accumulated in} the thylakoid space / eq ;

Question 6

Xylem transports ions and water molecules to the leaf. Describe the roles of these ions and water molecules in photosynthesis.

Answer 6

water for photolysis 2. { phosphate / Pi / PO43- } for ATP synthesis / eq ; 3. magnesium (ions) for chlorophyll ; 4. nitrate for { ATP / electron carrier protein / RUBISCO / ATP ase / enzymes involved in photosynthesis / chlorophyll / eq } ;

Question 7

Describe how the membranes inside the chloroplast are involved in photosynthesis.

Answer 7

1. idea of compartmentalisation (from stroma) ; 2. site of light-dependent reaction ; 3. credit named molecules {within / on / eq} membrane ; 4. idea of {ATPase / eq } in (thylakoid) membranes ; 5. idea that (thylakoid) membranes provide a space for accumulation of H+ ; 6. reference to photophosphorylation

Question 8

Answer 8

bottom left box:
oxygen

2. top middle box:
   (inorganic) phosphate (ions) /
   3.top right box:
   GALP

Question 9

Answer 9

Molecule P - water /

Molecule Q - oxygen

Question 11

Answer 11

D ATP and reduced NADP

Question 12

Describe the role of RUBISCO in the production of GALP in the light-independent
reaction.

Answer 12

1. reference to RUBISCO as an {enzyme / catalyst} ;
2. in the Calvin cycle ;
3. involved in {carbon fixation / bonding of CO 2 to RuBP /
   reaction between CO 2 and RuBP / eq} ;
4. to form GP / eq ;
5. GP converted to GALP / eq ;
6. using ATP and {reduced NADP / NADPH} (CO 2 to
   GALP / GP to GALP) ;

Question 13

Answer 13

Stroma

Question 14

Using the information in the graph, describe the overall changes in the
population sizes of elk and grey wolves between 1995 and 2010.
Give explanations for these overall changes.

Answer 14

1. elk decrease and wolves increase / eq ;
2. . N
3. idea that elk decrease as they are { being
   killed / eaten / predated } by the wolves at a
   faster rate than they are reproducing ;

2.. GNORE hunted

3. idea that the number of wolves increase as
   they are reproducing faster than they are
   dying ;

Question 15

Suggest two reasons for the decrease in the population of grey wolves
between 2011 and 2012.

Answer 15

1. birth rate less than death rate / eq ;
   2.accept wolves will starve /
   competition for food
2. disease ;
3. idea that the wolves are being { shot / hunted } ;
4. movement of wolves out of the Park ;

Question 16

Explain why, since 1995, the areas of forest in Yellowstone National Park have
increased.

Answer 16

1. idea that there is less grazing (as there are fewer elk) ;
2. idea that (secondary) succession can now take place ;
3. resulting in a climax community ;

Question 17

Suggest how the populations of other animals in Yellowstone National Park
might be affected by the reintroduction of the grey wolves.
Give explanations for your answer.

Answer 17

1. idea that other animals (prey of wolves) might decrease
   in number ;
2. as they are also being {killed / eaten / predated} by the
   wolves / eq ;
3. idea that other {carnivores / predators of elk / eq }
   might decrease in number ;
4. as there are {fewer elk to eat / more competition for the
   elk} ;

Question 18

Answer 18

D

Question 19

State two variables, other than the food source, that should be controlled in
this investigation.

Answer 19

1. { age / time of laying / batch } of eggs ;
2. { species / type } (of butterfly / caterpillar / egg) ;

Question 20

Describe how the growth rates of the caterpillars could be determined in this
investigation.

Answer 20

1. measure { length / mass / eq } of caterpillar ;
2. idea of measuring several caterpillars to calculate the
   mean (change in growth measurement) ;
3. idea of taking measurements over a period of time ;
4. growth rate = change in { length / mass } divided by
   time / eq ;

Question 21

Suggest why the food source of the caterpillars could affect their growth rate.

Answer 21

1.. CCEPT a different content of
a named nutrient / energy

2. idea different {carbohydrate / lipid / eq} content will
provide different yields of energy ;
3. idea that {respiration / metabolism / production of ATP}
is affected (by energy content / carbohydrate / lipid) ;
4. idea that the (ATP) energy used for {synthesis of new
molecules / cell division} ;

5. idea that protein content will affect (rate of) {protein /
   enzyme / named example} synthesis ;

Question 22

Question 23

Explain the meaning of the term net primary productivity.

Answer 23

1. (rate of) {production of / energy incorporated into / eq}
   {biomass / organic material / eq} ;

by plants ;

2. ACCEPT autotrophs / producers
3. (NPP) = GPP – R / eq ;

Question 24

Name two inorganic ions and explain why each of these ions will affect the net
primary productivity.

Answer 24

1. e.g. {calcium / magnesium}
   ions, nitrates , phosphates
   IGNORE incorrect formulae
2. idea that calcium ions used in synthesis of {calcium
   pectate / middle lamella / cell wall / eq} ;
3. when cells are {dividing / growing / eq} ;
4. idea that nitrates are used in synthesis of {nucleic acids
   / DNA / RNA / amino acids / protein / enzymes /
   chlorophyll / eq} ;
5. credit appropriate link with NPP
6. e.g. enzymes used in Calvin
   cycle, DNA for synthesis before
   mitosis, RNA for translation,
   proteins for enzymes,
7. idea that magnesium ions needed to produce chlorophyll ;
8. chlorophyll used for {photosynthesis / light absorption /
   synthesise glucose / eq } ;
9. idea that phosphates are used in synthesis of {nucleic acids /
   DNA / RNA / ADP / ATP / NADP / eq} ;
10. credit appropriate link with NPP
    (4)

Question 25

Describe the differences in net primary productivity in these environments.
Suggest reasons for the differences.

Answer 25

1. ACCEPT from a description of all
   three environments
   Piece together
2. e.g. Tropical forest is 1200 gm2
   yr-1 more than savannah
   IGNORE answers without correct
   units
3. {tropical forest has best combination of factors / desert has
   worst combination of factors / eq} ;
4. ACCEPT ideal conditions
   IGNORE optimum conditions
5. idea that {rain / water} is needed for {photolysis / lightdependent reaction / eq} ;
6. ACCEPT idea of {transpiration /
   translocation} if qualified
7. idea that temperature affects rate of enzyme action ;

Question 26

Describe how the oxygen concentration of water could be measured.

Answer 26

1. idea of using an (oxygen) {probe / meter / sensor /
   titration method / chemical test / eq} ;
2. idea of {removing a sample (of water) to analyse /
   holding probe in the water} ;

Question 27

Answer 27

C 96.7%

Question 28

Suggest why the oxygen concentration of the water may increase again
further downstream.

Answer 28

idea that there is less {pollution

Question 30

Suggest why bloodworms can survive in polluted water but the freshwater
shrimps cannot.

Answer 30

1. idea of {taking sample of water / kick sampling};
2. credit details of sampling method ;
3. idea of sampling at (regular)intervals along the river /
   eq ;
4. idea of counting the numbers of shrimp and bloodworm ;

Question 31

Suggest why bloodworms can survive in polluted water but the freshwater
shrimps cannot.

Answer 31

1. ACCEPT stone washing, using
   a net / coring
2. e.g. same volume of water, kick
   sampling for same length of time,
   how stones are washed ; same
   volume of core

Question 32

Explain the meaning of the term net primary productivity (NPP).

Answer 32

1. (rate of) {production of / energy incorporated into / eq}
   {biomass / organic material / eq} ;
2. reference to {losses in respiration / GPP – respiration / eq}
3. in {producers / plants};

Question 33

Using the information in the table, calculate the percentage of patients with
TB in 2008 who were HIV positive. Show your working.

Answer 33

1. idea that NPP depends on photosynthesis ;
2. higher the temperature the more NPP ;
3. enzymes in {photosynthesis / (anabolic) chemical
   reactions / eq} {can work faster / have more kinetic
   energy / eq} ;
4. increase in rainfall increases NPP ;
5. idea of water needed for light-dependent reaction ;

Question 35

Describe the appearance of a graph showing the relationship between gross
primary productivity (GPP) and rainfall, in ecosystems. Give a reason for your
answer.

Answer 35

1. idea that shape would be similar / credit a {description /
   sketch} of the graph;
2. idea that the {line would be higher / increase in GPP would
   be greater}(than NPP) ;
3. idea that GPP has to be higher than NPP as respiration
   has to be subtracted from GPP;

Question 36

Answer 36

1. correct subtraction (2800-1750 / 1050) ;
2. 1050 x 100 / 5300 (= 19.8 / 19.81 / 20) ;

Question 37

Answer 37