Mock Paper 2 [102 marks]

1a.

Coral reefs are among the most spectacular ecosystems on Earth. They support a rich diversityof life and provide economic benefits to the people who use them. In Papua New Guinea in thePacific Ocean north of Australia the following data were collected. Coral cover is the percentageof the reef surface covered by live hard coral.

Calculate the difference in coral cover in 1996 and 2002. No working required.

Markscheme60 (%)

1b. Describe the evidence that the ocean temperature has an effect on coral cover.

Markschemea. coral cover decreases as temperature rises (between 1996 and 1998/2000 and 2002) /negative correlation between temperature and coral cover / coral cover highest whentemperature is lowest/vice versa

b. coral cover remains constant when temperature drops (between 1998/1999 and2000)/remains (nearly) constant when temperature stops rising (between 2002 and 2003)

c. no proof of causation / only a correlation / other factors could be affecting the coral

Do not award this mark for “inversely proportional”, but the mark can still be awarded ifother parts of the answer give one of the alternative parts of the mark point.

[1 mark]

[2 marks]

1c. Suggest causes for the changes in ocean temperature.

Markschemea. increased carbon dioxide/methane in the atmosphere / carbon dioxide emissions fromburning of fossil fuels / other specific source of a named greenhouse gas

b. increased greenhouse effect / more heat/long wave radiation trapped in the atmosphere

c. heat transfer from atmosphere to ocean / ocean absorbs heat from atmosphere

No marks for increased CO in the oceans, global warming or climate change.The idea of an increase must be included, not just greenhouse effect or heat trapping .

2

1d.

In order to test the effect of temperature, live samples of a species of coral, Pocilloporadamicornis, were placed in an experimental chamber at a constant pH, water depth and lowlight. All the coral samples were started at 26°C and half of them were rapidly increased to30°C.

The pie charts show the percentage of live and dead tissues at the end of the experiment.

Identify one advantage of conducting this experiment in the laboratory rather than in theocean.

Markschemecontrol of variables/pH/light/temperature / no predators of coral

Acidification of the world’s oceans is an increasing threat to the health of oceanic life including

[2 marks]

[1 mark]

1e.

Acidification of the world’s oceans is an increasing threat to the health of oceanic life includingcoral reefs. Corals perform calcification to create their calcium carbonate exteriors. Anexperiment was conducted on Heron Island, Southern Great Barrier Reef, Australia. For theexperiment the pH was altered by dissolving carbon dioxide in the water. Three different coralspecies were used, with each test group at two different temperature ranges and three differentpH values. The white line in each photograph represents 5 cm.

(i) Describe the trend in calcification when the pH is decreased at 25 –26°C.

(ii) In environmental studies, a critical value is the level at which a population declines or showssigns of poor health. Suggest a critical pH for P. onkodes.

(iii) Using all of the data, comment on the hypothesis that ocean acidification in warming seaswill have the same effect on all species of coral.

[3 marks]

Markscheme(i) less calcification in all three/each species (as pH decreased)

(ii) 7.6 / 7.7 / 7.8

Accept any pH that is 7.6 or higher, but lower than 7.9 .

(iii)

a. greater reduction in calcification as pH drops at the higher temperature in P. onkodesthan on the other two species (so hypothesis not supported)

This answer is based on the larger drop in calcification between 8.2 and 7.6 at bothtemperatures in onkodes than the other two species.

b. net loss in calcification at lowest pH and highest temperature in P. onkodes whereasthere is still calcification in the other two species (so hypothesis not supported)

This answer is based only on whether there are positive values for calcification or negative.

c. warming reduces calcification at all pH levels in A. intermedia but not in the other twospecies (so hypothesis not supported)

This answer is based on the drop in calcification at each pH when the temperature rises inintermedia, whereas in the other species there is a rise at one or more of the pHs.

d. combined effect of acidification and warming is a larger reduction inncalcification in A.intermedia than in the other two species (so hypothesis not supported)

This answer is based on the larger overall drop in calcification between pH 8.2 at 25/26°Cand 7.6 at 28/29°C.

e. more calcification as temperature rises at lower pH/pH 7.9 and 7.6 in P. lobata whereasthere is less in the other two species (so hypothesis not supported)

The answer must either state pHs 7.9 and 7.6 or specify lower pH or greater acidification.

f. more calcification as pH drops from 8.2 to 7.9 at higher temperature in P. lobata whereasthere is a drop/no rise in the other two species (so hypothesis not supported)

The answer must state the two pH values and state higher temperature or 28-29°C .

1f. Suggest another marine animal that has parts made of calcium carbonate and maytherefore be damaged due to ocean acidification.

[1 mark]

MarkschemeMollusca/named marine mollusc with a shell/crustacean/named marinecrustacean/Porifera/sponges/named calcareous marine sponge

Reject terrestrial examples. Reject sea shells, shellfish. Specific named examples must beverified if it is uncertain whether they have calcified parts.

1g. Outline causes of ocean acidification.

Markschemea. carbon dioxide makes an acid/carbonic acid in water

b. (carbon dioxide from) burning fossil fuels/forest fires

c. carbon dioxide forms solution with/dissolves into water/oceans/rain

Do not award a mark for stating only that carbon dioxide causes ocean acidification.

Do not award marks for methane sources or sources of unspecified greenhouse gases orstatements about increased carbon dioxide in the atmosphere.

1h. Discuss the need for international cooperation to solve the problems of declining coralpopulations.

Markschemea. international cooperation needed to reduce carbon dioxide emission/concentrations

b. carbon dioxide produced anywhere increases the greenhouse effect/globalwarming/ocean acidification/health of coral everywhere

c. ocean currents/tides/wind move carbon dioxide/acid/heat around the world / oceans ofthe world are interconnected/part of one overall system

d. (some) coral reefs are in international waters (or words to that effect) / coral reefs cannotbe protected by single national governments alone

e. the more groups of people/nations/corporations that reduce their carbon emissions, thelower the impact on coral will become / not enough for one country/group/corporation toreduce carbon dioxide emissions

f. sharing of technology/research/information/resources

g. aid to poorer/developing countries (to help with coral conservation)

h. reference to an economic/ecological benefit of conserving coral reefs

2a.

In the pea plant (Pisum sativum), the allele for tall plants is A and the allele for short plants is a.The allele for green plants is B and the allele for yellow plants is b.

Determine the phenotype of Aabb.

[2 marks]

[3 marks]

[1 mark]

Markschemetall and yellow

2b. Compare the information that could be deduced when the genotypes are presented asAaBb or

Markscheme

2c.Deduce one possible recombinant offspring of individual after a test cross.

Markscheme

3. Define saprotroph.

Markschemean organism that lives on/in non-living/dead (organic) matter and secretes digestiveenzymes/digestive juices into it / OWTTE

The image is an electron micrograph of the lining of the small intestine.

[2 marks]

[1 mark]

[1 mark]

4a. The image is an electron micrograph of the lining of the small intestine.

(i) Label the microvilli using the letter M and a nucleus using the letter N.

(ii) State the function of the goblet cell.

(iii) Deduce, with a reason, whether or not the goblet cell is likely to divide.

[3 marks]

Markscheme(i)

Award [1] for one microvillus labelled M and one nucleus labelled N.

Both are essential for the mark.

Do not award the mark if any structure is labelled incorrectly.

(ii)

secretion/exocytosis / produce mucous

Candidates are not required to have studied goblet cells, so are just expected to deducefrom the vesicles that the function is secretion; allow enzyme secretion but reject answerssuggesting secretion of something that is clearly incorrect such as secretion of bile.

(iii)

not likely to divide as specialized/differentiatedORnot likely to divide (as nucleus) is in interphase/not in mitosis

Do not award a mark for stating that the goblet cell lacks a nucleus.

4b. Explain how the cell cycle is controlled. [4 marks]

Markschemea. cell cycle is a sequence of stages / cell cycle is G , S, G and mitosis

b. (control of the cell cycle) by cyclins/cyclin

c. levels of cyclins rise (and fall)/fluctuate during the cell cycle/surge at different times/haveto reach a certain concentration

d. conditions inside as well as outside the cell affect regulation

e. four cyclins/different cyclins to enter different stages of/events in the cell cycle / cyclinsregulate the sequence/timing of the cell cycle / cyclins trigger the next stages

The idea of different cyclins acting at different phases must be clear .

f. cyclin-dependent kinases / cyclins bind to kinases and activate them

g. kinases phosphorylate other proteins

h. phosphorylated proteins perform specific functions in the cell cycle

1 2

5a. State the role of four named minerals needed by living organisms.

Markschemesulfur – part of amino acids / proteins;calcium – strengthening/formation of bones / muscle contraction / synaptic transmission;phosphorus – formation of nucleic acids / ATP / GTP / NADP / phospholipids;iron – formation of hemoglobin / transport of oxygen;sodium – nerve impulse / sodium-potassium pump / osmoregulation;potassium – nerve transmission / sodium-potassium pump / osmoregulation;magnesium – part of chlorophyll molecule;

5b. Explain the processes by which minerals are absorbed from the soil into the roots.

Markschemeplants absorb minerals in ionic form/mineral ions;nitrate / phosphate / potassium / other example of mineral;minerals can be absorbed by (facilitated) diffusion;(diffusion is) movement of ions from high to low concentration/down concentration gradient;root hair cells provide a large surface area for absorption;fungal hyphae help to absorb minerals/phosphate;minerals absorbed by active transport;as mineral ion concentration is smaller outside the root than inside / absorbed against aconcentration gradient;active transport requires energy/ATP;occurs through pump/carrier proteins;proton pump transports hydrogen ions/H out of cell (allowing mineral movement in);+

In anaerobic conditions, plants release energy by glycolysis. Outline the process of

[4 marks]

[8 marks]

5c. In anaerobic conditions, plants release energy by glycolysis. Outline the process ofglycolysis.

Markschemeoccurs in cytoplasm (of cell);substrate is hexose/glucose/fructose;phosphorylation of glucose/fructose/hexose;to form hexose diphosphate/glucose 6-phosphate;requires ATP;glucose/fructose/hexose (diphosphate) converted into (two) pyruvates/three carboncompounds;oxidation;to produce (two) NADH + H / (two) reduced NADs;net gain of two ATP (per glucose);

+

6a.

In ecosystems, energy is used to convert inorganic compounds into organic matter. Energyenters ecosystems through producers.

Explain the processes by which light energy is converted into chemical energy.

Markschemea. plants/producers/autotrophs convert light to chemical energy by photosynthesis

b. chlorophyll/photosynthetic pigments absorb light

c. electrons are excited/raised to higher energy level

d. excited electrons pass along chain of electron carriers

e. energy from electrons used to pump protons across thylakoid membrane/into thylakoidspace

f. chemiosmosis/proton gradient used to make ATP

g. ATP synthase generates ATP

h. pigments arranged in photosystems

i. electrons from Photosystem II flow via the electron chain to Photosystem I

j. electrons from Photosystem I are used to reduce NADP

k. ATP and reduced NADP used in the light independent reactions/Calvin cycle

l. carbohydrate/glucose/carbon compounds produced containing energy

Award marking points for any point made on a clearly annotated diagram.

6b. Describe how energy flows through and is used by organisms in ecosystems.

[6 marks]

[8 marks]

[4 marks]

Markschemea. producers/plants/autotrophs obtain energy from light/sun/inorganic sources

b. food contains energy / energy passed in the form of food/carbon compounds (along foodchains/between trophic levels)

c. consumers obtain energy from other organisms/from previous trophic level

This mark point distinguishes consumers from producers.

d. energy released (in organisms) by (cell) respiration

Reject energy used in respiration.

e. ATP produced

f. energy/ATP used for biosynthesis/movement/active transport/other valid use of ATP

g. less energy available / energy lost at each trophic level

7a. Nitrogen is part of many important substances in living organisms.

Draw labelled diagrams to show a condensation reaction between two amino acids.

Markschemea. at least one of the amino acid structures completely correct

b. peptide bond shown with N–C and C=O and N–H correct

c. release of water clearly shown

7b. Nitrogen is part of many important substances in living organisms.

Distinguish between transcription and translation.

[3 marks]

[4 marks]

Markschemea. DNA is transcribed AND mRNA is translated

Disallow the first mark, if a candidate gets transcription and translation the wrong wayround, but allow marksafter that up to [3 max]

b. transcription produces RNA AND translation produces polypeptide/protein

c. RNA polymerase used in only in transcription and ribosomes only in translation

d. transcription in the nucleus «of eukaryotes» and translation in the cytoplasm

e. tRNA needed for translation but not transcription

f. nucleotides linked in transcription and amino acids in translation

OR

sugar-phosphate/phosphodiester bonds in transcription and peptide bonds in translation

[Max 4 Marks]

7c. Nitrogen is part of many important substances in living organisms.

Explain how insects excrete nitrogenous wastes.

[8 marks]

Markschemea. excreted as uric acid

b. excretion by Malpighian tubules

c. nitrogenous waste/ammonia «accumulates» in hemolymph

d. nitrogenous waste/ammonia absorbed by Malpighian tubules

e. ammonia converted to uric acid

f. conversion to uric acid requires energy/ATP

g. high solute concentration in Malpighian tubules

OR

active transport of ions/Na+/K+ into Malpighian tubules

h. water absorbed by osmosis flushes uric acid/nitrogenous waste to «hind» gut

i. water/ions reabsorbed from the feces and returned to hemolymph

j. uric acid precipitates/becomes solid/forms a paste so can pass out with little water

k. uric acid excreted/egested with the feces

l. water conservation/osmoregulation

OR

reduces mass of water «in body»

m. uric acid is non-toxic

[Max 8 Marks]

8a. Draw a labelled diagram that shows the positions of proteins within the cell membrane.

MarkschemePhospholipid bilayer drawn and labelled with at least one protein labelled and drawnembedded either in one or both halves of the bilayer

Reject if only peripheral proteins are shown.

Integral/intrinsic/transmembrane/carrier/pump/channel/pore protein labelled and showncrossing the membrane

Extrinsic/peripheral protein labelled and shown on membrane surface/not embedded inbilayer

Glycoprotein labelled and shown integral and with a clear carbohydrate region projectingout on one side of the membrane

The carbohydrate should be shown differently from the protein but need not be labelledspecifically.The protein part can be embedded in one or both phospholipid layers.

8b. Outline the effects of putting plant tissue in a hypertonic solution.

[3 marks]

[4 marks]

MarkschemeHypertonic solution has more solutes/higher solute concentration «than thetissue/cells/cytoplasm»

Water moves out of the cells/tissue by osmosis «into the hypertonic solution»

Water moves from lower solute concentration to higher solute concentration/up the soluteconcentration gradient

Reject answers based on water concentrations.

Pressure inside cell dropsORcell no longer turgidORcell becomes flaccid

Reject cell decreases in size.Reject plant wilts and other answers about whole plants.

Volume of cytoplasm dropsOR«plasma» membrane retracts from the cell wallORcell is plasmolysed

Reject plant cells shrink or shrivel .

8c. Explain how the structure of the nephron and its associated blood vessels enable thekidney to carry out its functions.

[8 marks]

MarkschemeOsmoregulation/excretion of nitrogenous waste/urea «is a function of the» kidney

Ultrafiltration in the glomerulus/smaller molecules filtered out in the glomerulusORcapillary walls/glomerulus permeable to smaller molecules Reject ultrafiltration in the Bowman’s capsule.

Basement membrane/filtration slits/podocytes act as filter/prevent loss of «large»«proteins»/prevent loss of blood cells

High «blood» pressure in glomerulus due to larger afferent than efferent arteriole

«Selective» reabsorption of glucose/useful substances in proximal convoluted tubule

Microvilli/coiling/convolutions give large surface areaORpump proteins to reabsorb specific solutes «in proximal convoluted tubule»

Water reabsorbed in descending limb «of loop of Henle»ORdescending limb permeable to water

Active transport/active pumping of sodium ions/Na out of ascending limb «from filtrate tomedulla»

Ascending limb is impermeable to water

Loop of Henle creates solute gradient/high solute concentration/hypertonic conditions inmedulla

Distal convoluted tubule adjusts pH/adjusts concentration of Na /K /H

Water reabsorbed in collecting duct

Collecting duct permeability to water varies due to number of aquaporins/ADH

Osmoregulation by varying the amount of water reabsorbed «in the collecting duct»

+

+ + +

9a. Cell biologists play an important role in research into disease, fertility, evolution andmany other areas of science.

Describe the origin of eukaryotic cells according to the endosymbiotic theory.

[4 marks]

Markschemea. mitochondria and chloroplasts are similar to prokaryotes

b. «host» cell took in another cell by endocytosis/by engulfing «in a vesicle»

Allow “taking in” in place of “engulfing”

c. but did not digest the cell/kept the «ingested» cell alive

OR

symbiotic/mutualistic relationship «between engulfed and host cell»

d. chloroplasts and mitochondria were once independent/free-living «organisms»

e. DNA «loop» in chloroplast/mitochondrion

f. division/binary fission of chloroplast/mitochondrion

g. double membrane around chloroplast/mitochondrion

h. 70s ribosomes «in chloroplast/mitochondrion»

Award up to [2] for evidence from mpe to mph

[Max 4 Marks]

9b. Cell biologists play an important role in research into disease, fertility, evolution andmanyother areas of science.

Compare and contrast the processes of spermatogenesis and oogenesis.

[8 marks]

Markschemea. both result in haploid cells/gametes

b. both involve mitosis at the start/in the «germinal» epithelium

c. both have cell growth «before meiosis»

d. both involve «two divisions of» meiosis

e. both involve differentiation to produce a gamete

f. both are stimulated by hormones

OR

spermatogenesis stimulated by testosterone and oogenesis stimulated by FSH

A table is not required but both statements in one row of the table must either be explicitlystated or clearly implied to award the mark

[Max 8 Marks]

9c. Cell biologists play an important role in research into disease, fertility, evolution andmanyother areas of science.

Outline the evidence for evolution provided by selective breeding.

[3 marks]

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Markschemea. crop plants/domesticated animals/livestock produced by selective breeding

b. specific example of a domesticated animal/crop plant and the wild species from which itwas developed

OR

specific example of a domesticated animal/crop plant and the features in it which havebeen improved «compared with the wild species»

For example dogs have been developed from wolves

c. artificial selection/crossing selected varieties/eliminating undesirable varieties

d. «selective breeding/artificial selection can cause» significant/rapid change over time/fromthe original wild species

e. «changes due to selective breeding/artificial selection» shows natural selection cancause change/evolution «in a species»

[Max 3 Marks]