IB Questionbank Biology11.B[1]

2.B[1]

3.(a)food chains describe the feeding relationships between species;arrows show (one) path of energy flow in an ecosystem / energyflow described;food chain with arrows pointing in the correct direction;producer first step in chain;three other named organisms making a realistic food chain;4 maxAccept explicit common names exact enough to identify the foodsource e.g. Oak not tree, sparrow not bird, rye grass not just grass, etc. (b)global warming is an increase in temperature of the atmosphere/oceans/Earth;may result in climate change / changes in amount of precipitation /greater ranges in temperature;melting ice leads to rising of sea level;leading to loss of habitat / example of organism that would losehabitat;changes in salinity / changes in ocean currents change distributionof nutrients;changes in predator-prey relationships (due to ecosystem disruption);increased success of pest species;temperate species with bigger range of habitats as ice melts;increased rate of decomposition of detritus;5 max

(c)members of a population of the same species show variation;some organisms are more likely to survive due to selectiveadvantage / survival of the fittest;some organisms have a reproductive advantage;these variations may be genetically controlled/heritable;these genes are most likely to be passed on to offspring;this can change the characteristic of the population;bacteria can normally be killed with antibiotics;antibiotics impose a selection pressure;if a few bacteria have natural resistance to the antibioticthey will survive;if the resistance is heritable they will pass it on to their offspring;they will reproduce/evolve to form bacterial colonies resistantto the antibiotic;example of organism selected by use of antibiotic;(e.g. MRSA bacteria / resistant TB bacteria)9 max(Plus up to [2] for quality)[20]

4.(a)Highest probability: 0.58 (Allow answers from 0.570.59)Lowest probability: 0.25 (Allow answers from 0.240.26)1Both required for the mark. (b)different varieties from same lake / I1 (c)individuals are more likely to breed if they are the same variety /individuals of different varieties have a low probability of breeding;the probability of breeding between individuals of the samevariety shows a large range of values / narrow range if of different variety;the probability of breeding between any two individuals isalways less than 0.6/correct numerical value;2 max (d)data provides (strong) evidence for reproductive isolationbetween the varieties in each lake;different sizes/feeding habits/habitat (shore versus open water)seem to contribute (strongly) to low breeding probability;this could lead to speciation/formation of separate species ineach lake;same varieties from different lakes do not show strongreproductive isolation/geographical isolation is a weak factorin speciation / no evidence of allopatric speciation;sympatric speciation seems to be taking place because differentvarieties from the same lake have a low probability of breeding;3 max[7]

5.(a)simple molecules must polymerize/assemble into polymers;origin of self-replicating molecules / formation of self-replicatingmolecules;simple molecules must become isolated from the surroundings/enclosedin membranes;2 max (b)in water as organic reactions are aqueous;warm conditions/pools near geothermal vents/volcanic poolsallow high reaction rates;evaporation of water allows organic (precursor) molecules tobecome more concentrated;high temperatures not desirable as organic molecules becomeunstable;clay minerals/metal ions may act as catalysts / clay forms amatrix for monomers to attach;2 max (c)early atmosphere was oxygen free;some prokaryotes could carry out chemosynthesis;cyanobacteria (and other varieties) developed the ability tophotosynthesize;used water as hydrogen source so released oxygen;oxygen began to accumulate in the atmosphere;more photosynthesis than respiration;2 max[6]

6.(a)original concentration of the radioisotope must be established/estimated;rate of decay/half-life of the isotope must be known;in radiocarbon dating concentration of the surviving 14C in the fossilis measured;in potassium-argon dating ratio of 40K to 40Ar atoms are measured;2 max (b)10000 years 1(c)increased bipedalism;increased brain size/cranial capacity;reduction of sagittal crest;tooth size reduction;flattening of the facial bones;development of opposable thumb; 2 max[5]

7.(a)in flight1

(b);4.2 (%); (Allow answers from 4% to 4.2%)1 max (c)birds spend most of time active on the water;more or less the same time in flight, diving and resting in water;Need all three parts for the mark.2 (d)birds need to rest/sleep to recover energy/digest food / are inactiveat night;moulting makes them flightless;defending territory / protection of young / other example of socialbehaviour;2 max[6]

8.(a)(i)Pine Warblers/Dendroica pinus (of Delmarva)1 (ii)2.6 mm (accept answers in the range of 2.5 mm to 2.7 mm)1 (iii)Yellow-throated Warblers have a bigger range / greatervariation (of beak length) in Delmarva than in Midwest(accept numerical values)1Accept converse. (b)allows them to eat other foods / changes feeding behaviour;reduces competition with Pine Warblers;1 max (c)allopatric speciation occurs between populations that live indifferent areas;(when populations are geographically isolated) there is nointerbreeding;natural selection works on each population independently;competition with the Pine Warbler only occurs in Delmarva /the Pine Warbler acts as selective pressure on the Yellow-throatedWarbler in Delmarva;eventually Yellow-throated Warblers in the two areas couldbecome two species instead of one / OWTTE;3 maxAward [2 max] if no reference to Warbler.[7]

9.few hominid fossils have been found/not often found/are very rare;most hominids/organisms not preserved/decompose;only teeth and bones remain / soft tissues do not fossilize;require certain conditions for preservation/dry/anaerobic/quickly covered/frozen;earlier cultures did not bury the dead / remains were scavenged/dispersed;acids break down/dissolve teeth/bones;many missing links/fossils of intermediate stages;difficult to get conclusive evidence / difficult to falsify theories;theories change radically with one/few discoveries;6 max[6]

10.(a)arthropoda/arthropods;jointed legs/limbs/appendages/(hard) exoskeleton;2Use error carried forward if incorrect phylum but correct observationsuch as anelida because it is segmented/has bristles. This answerwould earn one mark. (b)fossils show changes over time (in organisms);fossilized organisms are different from existing ones;(yet) share features with existing organisms / homologous structures;suggest common ancestry;show intermediate stages in evolution of groups / missing link fossils;2 max (c)natural selection;over time/generations;range/variation in size of eye (in the trilobite population);individuals with larger eyes are more likely to survive;example of selective advantage of large eyes e.g. can see predators /find food;surviving individuals reproduce and pass on their genes/large eyesto offspring;2 max[6]

11.(a)a group of related organisms sharing a common ancestor / agroup of organisms containing an ancestor and all of itsdescendants / OWTTE1 (b)homologous structures evolved from a common ancestor whileanalogous structures did not;example of homologous and example of analogous; (both needed)2e.g. an example of homologous is pentadactyl limb in mammalsand birds / mouth parts in house fly and mosquito/other validexample and an example of analogous is eye in vertebrates andsquid/octopus / wings of insect and bat / jointed legs of vertebratesand insects/other valid example (c)Two correct labels for [1].2 max (d)opposable thumbs (enable grabbing);flat fingernails (instead of claws/for scratching);forward-facing eyes for stereoscopic vision;rotatable shoulder joints (for tree-climbing adaptation);skull modified for upright posture;large brain to body/skull ratio enables higher levels of thinking;2 max[7]

12.eukaryotes evolved from prokaryotes;mitochondria/chloroplasts evolved from (independent) prokaryotic cells;taken in by larger (heterotrophic) cell by endocytosis;theory supported by characteristics of chloroplasts/mitochondria;[2 max] for mitochondria/chloroplast characteristics:mitochondria/chloroplasts have naked DNA;mitochondria/chloroplasts divide/carry out fission;mitochondria/chloroplasts have 70S ribosomes / synthezise own proteins;mitochondria/chloroplasts have double membranes;cristae similar to mesosomes / thylakoid have similar structures in prokaryotes;but theory cannot be falsified as it predicts something occurring in the past;theory does not explain the origins of cilia/flagella/linear chromosomes/meiosis;weaker evidence that cilia/flagella evolved from attached bacteria/spirochetes;6 max[6]

13.(a)(i)0.26 (arbitrary units) (units not required)1 (ii)123 km (accept answers in the range of 122 km and 124 km)1 (b)none / low correlation / non-significant / OWTTE;less data/fewer results/less variation at 60/70 km distance;1 max

(c)both show genetic differences (between all pairs of colonies);both have (highly) variable/wide range of genetic distance;similar mean/average genetic distance;V. maculifrons has a greater range than V. squamosa; (vice versa)2 max (d)no/little evolution / not evolving;allele frequencies remaining the same;no natural selection;uncertain because limited number of colonies/alleles/time;2 max[7]

14.(a)(i)transient when one allele gradually replaces another /directional selection;balanced when allele frequencies do not change / no/stabilizingselection;2 (ii)e.g. gradual increase in darker peppered moths due toenvironmental change/industrial melanism1Accept any other valid example. (b)name of type of barrier;description;2e.g. behavioural isolation;different courtship behaviour so no mating between two populations;Accept only the first type of barrier in the answer. Acceptgeographical separation, hybrid infertility, difference in chromosomenumber or breeding time. (c)variation due to random mutations / count numbers of differencein base sequence;can be used as evolutionary clock / estimate time since divergence/separation;amount of variation indicates how closely species are related/linked;differences can indicate ancestry/sequence in which groups diverged;2 max[7]

15.A[1]

16.(a)as latitude increases so does wing size / direct relationship / positivecorrelationDo not accept directly proportional as line does not pass through origin.1 (b)(i)at higher latitudes/above 45 European species have larger wingsthan American species/largest wing sizes seen in European flies;European flies show more variation than American flies (steeper curve);at lower latitudes/below 45 North American flies have larger wingsthan European species;South American flies have smaller wing size than European/N. American flies;2 max (ii)American species show less variation because they have hadless time to diverge / evolve;size of American flies closer to that of flies recentlyintroduced/founder effect/European founder populationfrom low latitudes;American flies exposed to different selective pressures;1 max (c)isolated populations diverge (genetically) / separation of gene pools;may become a new species / allopatric speciation;wing size will follow same trend as in Europe as population spreads tohigher latitudes;because larger size favoured by higher latitudes;wing size may stay small due to smaller gene pool;2 max[6]

17.(a)the non-living synthesis of simple organic molecules/amino acids frominorganic molecules;the assembly of these molecules into polymers/polypeptides;the origin of self-replicating molecules that made inheritance possible;the packaging of these molecules into membranes with an internalchemistry different from their surroundings;2 max (b)self-replicating and catalytic activities of RNA;short sequences of RNA have been able to duplicate/copy other RNAmolecules accurately;RNA enzyme/ribozyme (able to synthesize other molecules);3-dimensional structure of ribosome catalytic sites (for peptide formation)are composed of RNA;able to store information in sequence of (4) nucleotides (similar to DNA);2 max[4]

18.(a)most carbon is 12C but there is small amount of (radioactive) 14C;organisms absorb the same ratio of 12C:14C as in the environment;after death, no more atoms accumulate;14C steadily breaks down so amount decreases/12C:14C increases withage / half-life (approx 5730 years) expresses rate of decay of 14C;the less 14C in a sample the older the fossil / 14C useful for dating samplesone thousand to one hundred thousand years old;2 max (b)Ardipithecus is an older genus (5.24.4 million years ago) thanAustralopithecus (42.5 million years ago);toe structure of Ardipithecus shows it was probably bipedal / earlyAustralopithecus at least partially bipedal;tooth structure changed as diet changed from soft fruits/leaves/seeds/nuts to omnivorous diet;large/primitive canines seen in Ardipithecus to smaller caninesin Australopithecus;increasing height Ardipithecus is smaller (the size of a chimpanzee);change in face from projecting to flat face / from tall to small lowerjaw / development of high forehead / loss of brow ridges;3 max[5]

19.both explain similar structures in different organisms;Convergent evolutionDivergent evolutiondifferent ancestorcommon ancestor;converge to produce similar solutions/analogous structuresdiverge to suit different functions/homologous structures;e.g.wings in insects and birdse.g.vertebrate limb structure;species appearance becomes more similar over timespecies appearance becomes more different over time;unrelated species look similar but are genetically differentspecies look different but are closely related genetically;3 max[3]

20.(a)varied members of a single species occupy a variety of niches / migrationof a species to an area with a variety of niches;natural selection/selection pressure will be different in various nichescausing adaptation of groups to the varied niches;results in many species from one ancestral species;reproductive isolation enhances adaptive radiation;adaptive radiation results in speciation;3 max

(b)in gradualism evolution occurs at a constant pace;fossil records of gradual change with intermediate forms supportthis theory;evolution of modern horse/another suitable example seems tosupport this view;in punctuated equilibrium evolution proceeds rapidly for shortperiods of time intermittent with long periods of little change/stability;gaps in the fossil record/lack of intermediate forms support the idea ofpunctuated equilibrium;strata in the fossil record with appearance of many new species followinga mass extinction supports the idea of punctuated equilibrium;4 max[7]

21.(a)Australopithecus afarensis/A. afarensis had a relatively small skullwith a low forehead/moderate sized brow ridges;A. africanus/A. robustus evolved from A. afarensis with increasesin cranial capacity/larger brow ridges/low forehead;Homo habilis/H. habilis had a small cranial capacity/small browridges/increased forehead;H. erectus/H. neanderthalensis/H. sapiens followed H. habilisand show increased cranial capacity;(as the Homo sp evolved) the forehead increased;(as the Homo sp evolved) the orbital ridges decreased;3 max (b)improved diet quality correlated (positively) with hominid skulldevelopment/size;improved diet quality provides energy to support a greaterbrain function;change of habitat (in Africa) 2.5 mya may have promptedemergence of Homo sp;change in diet to include meat increased brain size (of hominids);cooking food enabled hominids to eat a wider variety of food;2 max[5]

22.A[1]

23.(a)self-replicating and catalytic activities of RNA;short sequences of RNA have been able to duplicate/copy other RNAmolecules accurately;RNA enzyme/ribozyme (able to synthesize other molecules);3-dimensional structure of ribosome catalytic sites (for peptide formation)are composed of RNA;able to store information in sequence of (4) nucleotides (similar to DNA);2 max (b)all living organisms use DNA as genetic/hereditary material;genetic code is (almost) universal;idea that mutations accumulate gradually in DNA;2 max (c)A is most similar to B;A is equally similar to C and D;A is least similar to both C and D;2 max (d)methods used to prepare cladograms use a different approach fromtraditional classification/taxonomy;show ancestral relationships;reflect how recently two groups shared a common ancestry;cladograms are (objective/accurate because they are usually) basedon molecular differences;they should be considered as a good complement to traditionalclassification;2 max[8]

24.cultural evolution based on skills / information passed from onegeneration to another;new methods can be transmitted between different groups;cultural evolution is learned/taught/language dependent;large brains of Homo species allow more learning;cultural evolution allows more rapid evolution / most recent changes arecultural;genetic evolution is dependent on/controlled by genes;genetic evolution is limited by the genetic composition/genotypes of thepopulations;e.g. of human genetic evolution (such as increase in cranial capacity);e.g. of human cultural evolution (such as tool making/religion/art);6 max[6]

25.(a)synthesis of simple organic molecules/nucleotides/amino acids;assembly of these molecules into polymers/DNA/protein;origin of self-regulating molecules that made inheritance possible;packaging of molecules into membranes (with internal chemistrydifferent from surroundings);2 max (b)gradualism is the slow change from one form to another / stable conditionslead to low levels of natural selection making it a long, gradual process;punctuated equilibrium implies long periods without much change andshort periods of fast changes / mass extinction promotes rapidchange/new species;2

(c)(i)a group including an ancestral species and all the descendents fromthat species / a group of organisms that evolved from acommon ancestor1 (ii)all four organisms have vertebrae;shark is the oldest/furthest from human/other examplesof relationships between the four organisms;human only one with all four characteristics;appearance of legs separated others from shark;appearance of mammary glands, separated kangaroo and human frombullfrog;appearance of placenta, separated human from kangaroo;both kangaroo and human are mammals;3 max[8]

26.DNA/genetic code is universal;

always pairing of AT and GC;same structure of double helix of complementary strands;use the same 20 amino acids in their proteins;all left-handed;same/similar enzymes in processes of replication/transcription/translation;small differences in DNA/proteins show closer relationships;e.g. hemoglobin/cytochrome C/gene structures show relationships amongorganisms;humans have the same biochemistry as all organisms so part of sameevolution/common ancestry;mitochondrial DNA used to determine maternal lines / y chromosome usedto determine paternal lines;endosymbiotic theory/mitochondria/chloroplast structures indicate commonlines of evolution;6 max[6]

27.C[1]

28.D[1]

29.(a)time taken for the radioactivity/% parental isotope to fall to half of its originallevel/for half of the atoms in a given mass to decay;after 28 years there is 50% of previous reading of strontium-90 isotopes;2 (b)4 to 2.5 million years ago;in East Africa;most complete skeleton Lucy;Lucy dated to 3.2/3.6 million years ago; (accept any date within this range)other part-fossils found;2 max[4]

30.(a)two alleles in a gene pool/polymorphic;one allele gradually replacing another;due to strong selection pressure;example; (e.g. melanic moths/industrial melanism)3 max (b)periods of stability/little evolution/stasis, followed by periods of suddenmajor change/lot of evolution/rapid speciation;in periods of stability organisms become well-adapted to environment;natural selection acts to maintain characteristics;equilibrium punctuated by rapid environmental change;such as volcanic eruption / meteor impact / change in sea level;directional selection leads to rapid evolution;4 max[7]

31.(a)111 (b)Ile and Glu (both needed to award the mark)1 (c)share 17 (out of 29) amino acids in common / more amino acidssimilar than different;both have Mn in the enzyme (as cofactor);greatest difference between them is from amino acid 18 to 22;mitochondrial has Gly (position 12) while E. coli (Mn) never has Gly;Leu is most common amino acid in both appearing four times / othervalid comparison;2 max (d)divergent (evolution) as the cytoplasmic dismutase shows a greaternumber of differences (than the other three enzymes);divergent as convergent (evolution) implies existence of analogousstructures and there are none here;1 max

(e)endosymbiotic theory states bacteria were engulfed by organisms tobecome mitochondria;sequence comparison between mitochondrial and bacterial dismutasesupports this hypothesis;more similarity in the amino acid sequence between mitochondrialand bacterial dismutase than between mitochondrial and cytoplasmicdismutase;2 max[7]

32.(a)allele frequency: measurement of how often an allele appears (i.e. A or a);gene pool: total sum of all the genetic information available for reproductionwithin the population;Both responses are needed to award the mark.1 max (b)large population;random mating;no migration / immigration / emigration;no mutations;no natural selection;1 max (c)phylogeny is the evolutionary line of descent;

the greater the differences, the longer the time span since the two specieshad a common ancestor;variation can be due to mutations;mutations are chance events so caution must be taken when interpretingthese;3 max (d)organization of data helps to identify organisms;suggests evolutionary links;suggests the closeness of a relationship the more similar thecharacteristics are;allows prediction of characteristics shared by members of a group;2 max[7]

33.fossils being formed is a rare event;

fossils being preserved is a rare event;fossils being found is a rare event; (e.g. due to geographical locations)chances of finding fossils is improved by searching in the right geologicalstrata / OWTTE;poor data / fragmented remains / very small sample size;more prone to paradigm shifts/changes in theory when data is limited /discovery of a small amount of fossils can lead to a huge change in theories;paleoanthropology can still be considered a science e.g. Dmanisi, Georgia(falsification of earlier positions held);6 max[6]

34.A[1]

35.(a) 100; = 39% (units required)(Accept answers between 3741% with the corresponding correctcalculation.No marks if just difference (790570) calculated.)2 (b)from earlier periods less fossil evidence available;because of more niches available at lower sea temperature / speciesspreading over greater depth / they evolved so more species/moretime for adaptive radiation (speciation);modern classification methods recognize more species than previousmethods;more research done at greater depths;2 max (c)valve length increases over time while average sea temperature decreases /there is an inverse/negative correlation between shell size and seatemperature;evolution of new species was slow up to approx. 5 million years agowhen sea temperature was highest / evolution of new species wasfaster in last 5 million years when sea temperature was lower;depth of habitat not assessed for extinct species;conclusions unreliable because of lack of data from earlier timeperiods / conclusions unreliable because temperature relativelyconstant between 30 and 10 million years ago but the range ofvalves varies by about 100 m;3 max[7]

36.(a)non-living synthesis of simple organic molecules;from mixture of any three of methane, ammonia, water vapourand hydrogen;assembly of these organic molecules into polymers;the origin of self-replicating molecules that made inheritance possible;the packaging of these molecules into membranes with an internalchemistry different from their surroundings;binary fission of cell;3 max (b)endosymbiosis theory states that eukaryotes are formed from prokaryotes;symbiosis is an association between two or more species;mitochondria of eukaryotes evolved from aerobic bacteria;chloroplasts evolved from primitive autotrophic prokaryotes;taken into larger heterotrophic cells by endocytosis;eukaryotes formed membranes that could contain the prokaryotes;mitochondria/chloroplasts have DNA/RNA similar to prokaryotes;mitochondria/chloroplasts have double membrane;3 max[6]

37.(a)forward facing eyes/binocular vision;large brains;flexible shoulder joints / shoulder blades on the dorsal side of the thorax;manual dexterity / power grip / opposable thumb / grasping limbs;finger pads / nails not claws;skull adapted for upright posture;pronation / rotating hand;2 max (b)fossilization is an exceptionally rare occurrence;most components of formerly living things tend to decompose relativelyquickly following death;fossilization tends to favour hard body parts;fossilization favours species that were widespread/lived for a long time;paleoanthropology is an inductive/data-poor science (a relatively smallamount of data is used to draw conclusions);many of the conclusions that have been drawn on limited datahave not stood for long;exposed fossils are soon destroyed/weathered, reducing the chanceof them being found;new discoveries regularly come to light, leading scientists tore-interpret previous assumptions in the light of the new data;examples e.g. the Dmansi site, Georgia, discoveries have led to are-evaluation of previous theories of human evolution;3 max[5]

38.(a)RNA can replicate;can act as a catalyst;can code for information;2 max (b)simulated conditions of pre-biotic earth (in closed container);water vapour;mixture of ammonia, methane, hydrogen / reducing atmosphere;sparks/electric (discharge to simulate lightning);condenser / cooling of mixture;obtained amino acids;3 max[5]

39.(a)all the genes in an (interbreeding) population1 (b)both involve the formation of new species;by the isolation of its genetic pool (in both cases);both provide conditions for natural selection;sympatric in same geographical area, allopatric in different;sympatric could be reproductive/behavioural isolation while allopatricphysical isolation;example of each; (e.g. allopatric speciation of Galapagos finches andsympatric speciation due to polyploidy)Award mark only where comparison is clear.4 max (c)growth in brain requires more protein;increased brain correlates with change of diet from plants/leaves tofruit/meat (higher quality diet);eating meat provides more protein;larger brain implies more evolution as learning capacities increase;2 max[7]

40.D[1]

41.(a)non-living synthesis of simple organic molecules;assembly of (simple organic) molecules into polymers;origin of self-replicating molecules that made inheritance possible;packaging of molecules into membranes with an internal chemistrydifferent from their surroundings;1 max (b)initial atmosphere contained no free oxygen / anaerobic bacteria perhapsthe first organisms on Earth;some prokaryotes were chloroplast-like/photosynthetic/cyanobacteria;oxygen is by-product of photosynthesis/oxygen produced byphotolysis of water;2 max[3]

42.(a)speciation is the formation of a new species by the splitting of anexisting species;allopatric speciation caused by geographical separation;sympatric speciation occurring within the same habitat causedby different niches / caused by courtship/feeding differences/behavioural differences;both processes lead to isolation of sub-populations;isolation favours certain genetic variations (within a species);over time this leads to genetic barriers/speciation;Both allopatric and sympatric speciation must be mentioned. [3 max]if only one mentioned.4 max (b)all organisms have DNA as the genetic material;all organisms use (approx.) 20 different (L) amino acids;genetic code is (nearly) universal;mechanism for protein synthesis is similar;metabolic pathways are similar;if parts of DNA (genes) are shared between organisms then itdenotes (close) relationship;the greater the percentage of genes shared, the closer the geneticrelationship;mitochondrial DNA is maternally inherited in most organisms/phospolipid membranes/ATP common in most (all) organisms;conserved genes have similar function;6 max[10]

43.(a)2 (%) (units not required)Allow answers in the range of 2.0 to 2.1.1 (b)17.5% (allow answers in the range of 17.3 to 17.7%)1 (c)both show range variation;

greater range of genetic variation in nDNA than mtDNA / 18% in nDNAand 6.5% in mtDNA;three of mtDNA have less than 1% genetic divergence while none ofnDNA have less than 5%;the highest divergence of mtDNA is similar to the lowest of nDNA;mtDNA3 and nDNA8 have no (known) species with the same sequencedivergence;3 max

(d)mtDNA (appears to be) more stable (due to less genetic divergence) /converse;mtDNA (likely) has fewer genes which could be a limit on theaccumulation of mutations / converse;mtDNA more stable as no meiosis/cross-over/chromosomere-assortment;smaller range of genetic divergence may indicate that theyhad a common ancestor/are more closely related;natural selection could put more pressure on nDNA / moreevolutionary change;problem in using mutations as an evolutionary clock / differentgenetic divergence / different rates of mutation depending on thegenes examined;the high rates of nDNA6 divergence could be neutral substitutions /no effect / intronic;insufficient data to know the effects of these mutations;3 max[8]

44.(a)cultural evolution involves passing of technology/language/customsfrom one generation to the next / does not affect the gene pool/changethe genetic makeup while genetic evolution involves passing ofgenes/genetic mutations from one generation to another / OWTTE;cultural evolution allows for faster changes than genetic evolution;Accept any other valid difference.1 max (b)long stable periods / little change;short periods of sudden/rapid evolution;e.g. volcanic evolution/meteor impact causing sudden climatic/environmental changes / other valid examples;2 max[3]

45.(a)analogous: [2 max]similar structures but different (evolutionary) origins / different basicstructure but same function;e.g. vertebrate and invertebrate eyes / insect and human legs;Accept any other valid example.homologous: [2 max]structures are of similar origin / same basic structure but different functions;e.g. pentadactyl limbs in vertebrates;Accept any other valid example.4

(b) predicts frequencies of dominant and recessive alleles of a given gene;homozygous for each allele and heterozygous;frequency of dominant allele = p, recessive/albino allele = q;total frequency of both alleles = 1 or p + q = 1;random mating, probability of receiving two dominant alleles is p p or p2;probability of receiving two recessive alleles is q q or q2;expected frequency of heterozygous genotype is 2pq;p2 + 2pq + q2 = 1;assumes no mutations / large population / random mating / no selectivepressure / no immigration nor emigration;explains why recessive alleles do not disappear over several generations;q2 = or q = 0.007 (frequency of recessive);p = 1 0.007 or 0.993;frequency of dominant p2 = 0.986 or 98.6%;frequency of heterozygotes 2pq = 0.014 or 1.4%;Accept values with more significant figures.5 max[9]

46.A[1]

47.(a)(under the hypothesized conditions) on the pre-biotic Earth, simpleorganic molecules could have been created1 (b)smaller/70S ribosomes in mitochondria/chloroplasts (as in prokaryotes);circular DNA in mitochondria/chloroplasts (as in prokaryotes);mitochondria/chloroplasts have double membrane;similar size/shape of mitochondria/chloroplasts to prokaryotes;2 max[3]

48.(a)both involve reproductive isolation / separation of gene pools;sympatric is speciation due to isolation of populations living in thesame geographic area whereas allopatric is speciation due togeographic isolation;2 (b)(i)e.g. A. afarensis / A. africanus / A. garhiAward [0] if species name has a capital letter.1 (ii)Award [1] for a value within date range and [1] forgeographic distribution.speciesdate rangegeographic distributionA. afarensis3.9 to 2.9 mya;eastern Africa;A. africanus2 to 3 mya;southern Africa;A. garhi2 to 3 mya;eastern Africa;2 max (c)long periods of stability;environmental change / sudden change;leads to rapid speciation/evolution;helps to explain absence of intermediate forms;competing theory is gradualism;3 max[8]

49.(a)both involve reproductive isolation / separation of gene pools;sympatric is speciation due to isolation of populations living in the samegeographic area whereas allopatric is speciation due to geographic isolation;2 (b)analogous structure similar in appearance/function but with differentevolutionary history e.g. wing of bat and wing of bird;1 (c)smaller/70S ribosomes in mitochondria/chloroplasts (as in prokaryotes);circular DNA in mitochondria/chloroplasts (as in prokaryotes);mitochondria/chloroplasts have double membrane;similar size/shape of mitochondria/chloroplasts to prokaryotes;2 max (d)opposable thumb;large range of shoulder movement;good vision / stereoscopic vision / overlapping field view;large brain relative to body size;tailless primate;Y-5 cusps of molars;2 max[7]

50.DNA/RNA found in all living organisms/genetic code is universal;amino acids all L- not D- isomerssame 20 amino acids/proteins found in all living organisms;involves comparing similarities and differences in the amino acid sequence of thesame molecule;e.g. hemoglobin;involves comparing base sequences of variable regions of DNA;e.g. mitochondrial DNA;the more similar the base/amino acid sequence, the more closely related;comparing amino acid sequences that result in the phenotype/comparing DNAsequences that result in the genotype;evidence for molecular evolution in drug resistance;6 max[6]

51.B[1]

52.(a)Award [1] for each of the following clearly drawn and correctly labelled.Simple shapes may be used but must have a key or be clearly labelled.two nucleotide strands (note that strands must be drawn antiparallelalthough it does not need to be labelled as such);alternating sugar-phosphate backbone;complementary base pairs shown, A-T and C-G;hydrogen bonds between base pairs;covalent bonds between sugar and phosphate groups / between sugar and bases;nucleotide including sugar, phosphate and base (with parts correctlyconnected);4 max (b)mutation is a change in the genetic make-up;base substitution mutation occurs when one (nitrogenous) base in DNA chain isreplaced by another;this is a gene mutation / change in the base sequence of a gene;effect of mutation ranges from no effect / no change in amino acid sequence todrastic changes;sickle-cell anaemia involves change in gene for one of polypeptides inhemoglobin / Hb / HBA;GAG has mutated to GTG (on DNA);adenine replaced by thymine in DNA;transcription of DNA produces the triplet GUG instead of GAG on mRNA;one codon is different in mRNA;new codon is for valine rather than glutamic acid;tRNA brings amino acid to ribosome during translation;different amino acid placed in polypeptide chain being formed by translation;the two amino acids differ in solubility / have different properties / valine causesHBS to be less soluble;causes red blood cells to become sickle shaped / carry oxygen less efficiently;HBS allele causes sickle-cell anaemia but gives resistance to malaria;8 max (c)comparative anatomy of groups of animals or plants shows certainstructural features are basically similar;homologous structures are those that are similar in shape in different typesof organisms;structural similarities imply a common ancestry;(homologous structures) used in different ways;example is pentadactyl limb in vertebrates / modification of ovary wall orpericarp to aid seed dispersal / other suitable example;adapted to different mode of locomotion in particular environment / example of two differences such as bats wing and human hand;illustrates adaptive radiation since basic plan adapted to different niches;the more exclusive the shared homologies the closer two organisms are related;certain homologous structures in some species with no apparent function such ashuman appendix (homologous with functional appendix in herbivores);6 max(Plus up to [2] for quality)[20]

53.(a)T. laboriosa1 (b)(i)Award [2] maxDefinition of convergent evolution: independent evolution of similartraits in response to similar environments;Evidence for: T. stelarobusta (Maui) and T. hawaiensis (Hawaii)produce the same type of web;T. filiciphilia (Maui) and eurylike (Oahu) also produce similar webs;(ii)Definition of adaptive evolution: rapid speciation to fill ecological niches;Evidence for: on Maui, all three T. species present produce three differentkinds of webs;3 max (c)on Maui T. stelarobusta and T. eurychasma are closely related based on thetree diagram (but they produce different webs);distantly related spiders, eg T. hawaiensis and T. stelarobusta producesimilar webs but are on different islands;suggesting island is better indicator for relatedness than webs;data inconclusive / more studies needed;2 max[6]

54.(a)the formation of new species by populations that inhabit the same oroverlapping geographic regions1

(b)a population colonizes a new habitat that involves unique selectionpressures / becomes geographically isolated;eg Darwins finches;polyploidy;eg some variants of wheat;4[5]

55.(a)time for radiation material to decay to half its original amount / activity / mass1 (b)gradualism: slow, continuous change over a long period of time;gradual accumulation of (neutral) mutations / variations;punctuated equilibrium: long periods of stability followed by sudden changes;fossil record supports this;natural selection can be intense and can cause rapid change / evolution;rapid evolution due to major environmental changes / volcanic eruptions / meteor impact / other example;only advantageous alleles ultimately survive;some mutations had no morphological effects so not visible in the fossil record;rate of evolution could have fluctuated over time;6 maxAward [4 max] if only one idea is discussed.[7]

56.(a)Award [1] for each of the following clearly drawn and correctly labelled.clear ruled axes, labelled time on the x- and population size on the y- axis;exponential phase annotated to indicate rapid population growth because ofabundant resources;transitional phase annotated to indicate a developing shortage of resources andincrease competition between members of the population;plateau phase annotated to indicate a population now constrained by resourceavailability / natality equals mortality;4 (b)melting of permafrost;increased detritus decomposition;expansion of temperate species / reduced range for arctic species;example of an affected species;examples of human activity;rise in sea levels;change in climatic patterns;loss of ice habitat;more pests / pathogens;disturbance to food chains / webs / trophic levels;6 max

(c)parents produce more offspring than required to keep numbers constant;more are produced than the environment can support;example of an environmental condition;these offspring show variation;some are better adapted than others to the environment;these tend to survive to breed themselves;characteristics are inheritable;so the new generation has these characters too;this leads to changes in the population as a whole;these changes constitute evolution;8 max(Plus up to [2] for quality)[20]

57.(a)on Maui T. stelarobusta and T. eurychasma are closely related basedon the cladogram (but they produce different webs);distantly related spiders, eg T. hawaiensis and T. stelarobustaproduce similar webs but are on different islands;suggesting island is better indicator for relatedness than webs;data inconclusive / more studies needed;2 max (b)(mt) DNA is isolated from organism / species;(mt) DNA is sequenced / order of bases determined;(mt) DNA sequence is compared between organisms / species;more similarities between sequences signify more closely related / recent divergence;fewer similarities between sequences signify less relatedness / moredistant divergence;cladograms are calculated by software that depicts the cladogram with thefewest number of branches;for rooting the cladogram an outgroup / distantly related species is used;3 max (c)(i)Award [2] maxDefinition of convergent evolution: independent evolution ofsimilar traits in response to similar environments;Evidence for: T. stelarobusta (Maui) and T. hawaiensis (Hawaii)produce the same type of web;T. filiciphilia (Maui) and eurylike (Oahu) also produce similar webs;(ii)Definition of adaptive evolution: rapid speciation to fillecological niches;Evidence for: on Maui, all three T. species present producethree different kinds of webs;3 max[8]

58.(a)autocatalytic / can function as an enzyme;can function as genetic material;can (self)replicate;2 max (b)Award [1] for any two of the following:CH4 / H2 / NH3 / H2O1 maxAccept symbol, chemical formulae or words. (c)describes the origin of eukaryotic cells;endosymbionts live within larger host cells;eukaryotic cells contain mitochondria and / or chloroplasts;mitochondria and chloroplasts have evolved from independent free livingorganisms (bacteria);these organisms were taken into a larger heterotrophic cell by endocytosis;not digested but cells were kept alive and continued to carry out aerobicrespiration and photosynthesis;4 max[7]

59.(a)tool making first associated with H. habilis;requires larger brain;brain requires vast amounts of energy / consumes 40% of energy intake;so larger brain size had an effect on diet requirements / created a demand forchanges in diet;food scarcity may lead to decrease in brain size;change to higher calorific diet may allow increase in brain size;more complex tool making / human society / language development requiredlarger brain size;larger brain / better cognitive skills allowed for better hunting and gathering;led to greater calorific intake;about 2.5 MYBP (million years before present) animal foods began tooccupy an increasingly prominent place in diet;animal tissues can provide the necessary structural lipid for human brainexpansion;changes in the dental fossil record are indirect evidence for such a changein diet;[5]