24The answers/markschemes are below each question in italics. You can reorganize the document so that you do not see the answer/markschemes when you answer the questions.

1.Foraminifera are small protozoans found in the sediment of all marine ecosystems. Several thousand species of foraminifera live in the Earths oceans. Because a large number of individuals can be found in a small amount of sediment and because they exist worldwide, foraminifera are useful in examining the distribution of species. The bar graph below summarizes data gathered from five coastal regions around North America. Those species occurring in all five regions are considered to be ubiquitous and those species occurring in only one area are considered to be endemic. The species of foraminifera were placed into three classes based on the number of times each species occurred at the five coastal regions.

[Source: Buzas and Culver, BioScience (1991), 41, pages 483489] (a)Calculate the percentage of endemic species occurring in the Pacific region...........................................................................................................................................................................................................................................................................(1) (b)Among the five regions, deduce the region where it would be easiest to find most of the ubiquitous species......................................................................................................................................(1)

(c)Compare the occurrence of endemic species in the Pacific and Caribbean regions.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (d)Suggest, giving a reason, which of the Pacific, Atlantic or Caribbean regions will have a greater extinction rate.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (e)Identify which region has the lowest species diversity......................................................................................................................................(1)(Total 7 marks)

(a)79% 2%1 (b)Gulf of Mexico / Atlantic1 (c)total number of Caribbean endemic species is greaterthan in the Pacific / 425 and 450;no Caribbean endemic species occur in great numbers / >32 compared to the Pacific / which has about 45;the number of Caribbean endemic species occurringin small numbers / 12 is more than twice that in the Pacific / about 280 and 120;2 max

(d)the Caribbean region will have a greater extinction rate;because of the great number of endemic speciesoccurring in small numbers;small numbers of a species are more vulnerableto extinction than high numbers;for Caribbean ubiquitous species the percentage ofspecies occurring in high numbers / >32 is lower than in the Pacific;2 max (e)the Arctic;1[7]

3.On a field trip a group of students was asked to estimate the size of the population of a small, nocturnal ground dwelling mammal, the long-nosed bandicoot (Perameles nasuta). The bandicoot feeds on invertebrates and plant material found by digging pits 5 cm deep in the ground with its front legs.

[Source: J Smith & P Smith, Fauna of the Blue Mountains, Kangaroo Press, Sydney, 1990] (a)(i)State the name of an appropriate technique to estimate the population sizeof P. nasuta............................................................................................................................(1)

(ii)Describe this method of estimating the population size of P. nasuta..............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3) (b)Deduce, with reasons, the trophic level of P. nasuta in food chains.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 6 marks)

(a)(i)capturemarkreleasecapture / capturerecapture / cohort method;1(ii)To receive full marks there must be reference to the use of Lincoln index / similar equation. capture animals;mark / tag animals;release again;recapture after an appropriate time period eg next night, a few nights later;use of Lincoln Index equation / similar type of equation;orcount the number of pits made by a bandicoot in a night;count the total number of pits made in a night;estimate the number of bandicoots based on number of pits made in a night;3 max

(b)primary consumer / second trophic level; feeds on plant material;secondary consumer / third trophic level;feeds on invertebrates;2 max[6]

5.Explain how energy and nutrients enter, move through, and exit a food chain in an ecosystem.(Total 8 marks)

energy enters from (sun)light;chloroplasts / plants / producers / autotrophs capture (sun)light;energy flows through the trophic levels / stages in food chain;energy transfer is (approximately) 10% from one level to the next;heat energy is lost through (cell) respiration;energy loss due to material not consumed / assimilated / egested / excreted;labelled diagram of energy pyramid;energy passes to decomposers / detritivores / saprotrophs in dead organic matter; nutrient cycles within ecosystem / nutrients are recycled;example of nutrient cycle with three or more links;nutrients absorbed by producers / plants / roots;nutrients move through (food chain) by digestion of other organisms;nutrients recycled from decomposition of dead organisms;nutrients from weathering of rocks enter ecosystem;nutrients lost by leaching / sedimentation (eg shells sinking to sea bed);8 max(Plus up to [2] for quality)[8]

7.The Kluane boreal forest ecosystem project was a large scale ten year experimental manipulation of food and predators on arctic ground squirrel population (Spermophilus parryii plesius).Three areas were set up:a food addition areaa predator exclusion areaa food addition area enclosed within a predator exclusion area.

The areas were monitored from 1986 to 1996. In spring 1996 all fences were dismantled and food addition was stopped.As a further experiment, spring and summer mark-recapture population estimates of the squirrels were conducted from spring 1996 to spring 1998. The results for these two years are shown below. The areas are labelled according to the conditions imposed during the previous ten years.

[Source: Karels et al., Nature, (2000), 408, Pages 460463)] (a)State the squirrel population in the food addition plus predator exclusion area in spring 1996......................................................................................................................................(1) (b)Describe the effect of ending food addition on the squirrel population..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)

(c)Scientists believed that the number of ground squirrels in the boreal forests was limited by an interaction between food and predators that acted primarily through changes in reproduction. Using the data, discuss this hypothesis....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)(Total 6 marks)

(a)30 ( 1) squirrels hectare1;1(b)population decreases from 12 ( 1) squirrels hectare1 to 2 ( 1) in foodaddition area; in food addition plus predator exclusion area decreases from 30 ( 1) to 2 ( 1);reaches same level as control (in 2 years);other numerical comparison;2 max(c)addition of food and exclusion of predators results in more squirrels as conditions are ideal;squirrels can feed well and are not predated / higher reproduction rate;food addition alone also results in more squirrels;because food affects population growth more than predator exclusion(squirrels climb, hide);no additional food but predator excluded does not confirm the hypothesis;3 max[6]

9.The diagram below is a simplified version of a food web from Chesapeake Bay. The arrows indicate the direction of energy flow and the numbers indicate species within the food web.

At which trophic level or levels does species II function?A.2nd and 3rd consumerB.3rd consumerC.3rd and 4th consumerD.Producer(Total 1 mark)

A[1]

11.Conservationists noticed that the number of red squirrels (Sciurus vulgaris) in Wales was declining, and the number of a newly introduced species, the North American grey squirrel (Sciurus carolinensis), was increasing. In 1998, a project was started to reduce the number of grey squirrels in 244 hectares of woodland in Wales. The graph below shows the number of grey squirrels in 1998 and the number of red squirrels in 1999, 2000 and 2002. The data was collected at eight different sites (AH).

[Source: Craig Shuttleworth, (2003), Biologist, 50, (5), page 231, Institute of Biologists] (a)Identify the year in which the greatest number of red squirrels was found in site E.....................................................................................................................................(1) (b)State the number of sites that had a greater density of red squirrels in 2002 compared with the density of grey squirrels in 1998.....................................................................................................................................(1)

(c)Discuss the hypothesis that decreasing the density of grey squirrels after 1999 led to an increase in the density of red squirrels in the following years.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3) (d)Outline the relationship between grey squirrels and red squirrels assuming that they occupy the same niche.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(3)(Total 8 marks)

(a)20021 (b)6 / A B E F G H1 (c)hypothesis seems to be supported;in most / five sites the red squirrel density has increased since 1999;some sites decreased in density from 2000 to 2002;may be other factors controlling squirrel density;however there is no information about red squirrels in 1998 / more datais required starting with same density of grey squirrels in 1998 anddifferent densities of red squirrels;3 max

(d)(principle of) competitive exclusion;competition occurs between them;most successful of the two increases in numbers;displaces the other from the population;3 max[8]

13.(a)Outline why the transparency of water is important to organisms living in an aquatic habitat..........................................................................................................................................................................................................................................................................................................................................................................................................(2) (b)The diagram below shows a simplified food web for a lake.

[Source: Water on the Web (2004), Monitoring Minnesota Lakes on the Internet and Training Water ScienceTechnicians for the Future A National On-line Curriculum using Advanced Technologies and Real-Time Data,www.waterontheweb.org/under/lakeecology/11_foodweb.html,reprinted with the permission of Water on the Web project, University of Minnesota, Duluth, MN 55812]

(i)State the initial energy source for the above food web..........................................................................................................................(1) (ii)Define the term trophic level...................................................................................................................................................................................................................................................(1) (iii)Deduce the trophic level of the immature game fish..........................................................................................................................(1) (iv)In the food web shown, identify one heterotroph and one autotroph.heterotroph:....................................................................................................autotroph:....................................................................................................(1)(Total 6 marks)

(a)light penetration is required for photosynthesis;plants / phytoplankton / photosynthetic organisms are the base of many aquaticfood chains;allows interacting organisms to find one another (eg predator-prey relationship, courtship);allows interaction with the physical environment (eg finding shelter);2 max (b)(i)light / sunlight1(ii)the feeding level / position an organism occupies in a food chain1(iii)secondary consumer1(iv)heterotroph: immature game fish / trout / pike / shad / zooplankton;1 maxautotroph: phytoplankton;Two correct answers needed for [1].[6]

15.(a)The diagram below represents a pyramid of energy for a community of organisms. State what the bars labelled I and II indicate.

I..........................................................................................................................II..........................................................................................................................(2) (b)Define the term biomass.......................................................................................................................................................................................................................................................................(1)(Total 3 marks)

(a)I.energy ingested by tertiary consumers / energy flowing through tertiaryconsumers;II.gross primary productivity / energy flowing through producers;2 (b)(net dry mass) of organic matter in living organisms / environment (in a givenarea usually per square kilometre)1[3]

17.What is an ecosystem?A.A species and its abiotic environmentB.A community and its abiotic environmentC.The habitat where a species livesD.A population of organisms in a specific habitat(Total 1 mark)

B[1]

19.What name is given to an organism that is able to manufacture its own food from simple chemical materials?A.HeterotrophB.SaprotrophC.AutotrophD.Detritivore(Total 1 mark)

C[1]

21.What is a community?A.A group of producers and consumers living and interacting in an area.B.A group of species living and interacting in an area.C.A group of organisms living and interacting in an area.D.A group of populations living and interacting in an area.(Total 1 mark)

D[1]

23.The food web below shows a community in central France 24 000 years ago.

Which statement is a correct description of Ursus spelaeus?A.It is an omnivore which feeds on Lemmus lemmus.B.It is a producer preyed upon by Vaccinium oxycoccos.C.It is a top carnivore and a primary consumer.D.It is a decomposer and it competes with Rangifer tarandus.(Total 1 mark)

C[1]

25.Which diagram shows the flow of energy through a community with three trophic levels?

(Total 1 mark)

D[1]

27.Which graph correctly shows the increase in the size of a population during the exponential growth phase?

(Total 1 mark)

C[1]

29.(a)Define the term random sample...........................................................................................................................................................................................................................................................................(1) (b)Draw and label a graph showing the sigmoid (S-shaped) population growth curve.

(3) (c)The masses of two different populations of sparrows (Passer domesticus) are shown in the table below.Population 1:mass of birds / gPopulation 2:mass of birds / g24.526.925.023.224.023.625.031.024.527.924.828.3

(i)Calculate the mean value of the mass of birds for population 1.......................................................................................................................................................................................................................................................(1) (ii)With reference to the data shown, explain what is meant by the term standard deviation. No calculation is expected........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 7 marks)

(a)a sample where every member of a population has an equalchance of being selected / sample selected without bias1 (b)axes correctly labeled (x = time, y = number of individuals / population size);carrying capacity / plateau correctly labelled;transitional / lag phase correctly labelled;exponential growth phase / stage correctly labelled;3 max(c)(i)24.6 g / 24.63 g (units needed)Award [0] for 25 g or significant figure errors.1 (ii)standard deviation is a measure of variability / degree of spread around the mean;a small standard deviation indicates the data is spreadclosely around the mean value / a large standard deviation indicates a wider spread around the mean;population 2 has greater variability, therefore, it has a greaterstandard deviation / vice versa;. 1 standard deviation from the mean represents68% of the data / . 2 standard deviations from the mean represent95% of the data;2 max[7]

31.Which factors can limit population growth?I.Shortage of foodII.Increased genetic variation in the populationIII.Increase in predatorsIV.Increase in diseases and parasitesA.I and II onlyB.I and III onlyC.I, III and IV onlyD.I, II, III and IV(Total 1 mark)

C[1]

33.The mosquito (Wyeomyia smithii) uses daylength as a guide to either continue development of its larvae or to begin hibernation. This response to daylength is genetically controlled. Longer daylengths maintain development whereas shorter daylengths induce hibernation. In the northern regions of the northern hemisphere, even though daylengths are longer, winter arrives earlier than in regions closer to the equator. The following data is from an experiment to determine if W. smithii has adapted to later onsets of winter as a consequence of global warming. In 1972 and 1996, larvae were collected at various locations in the United States at latitudes 3050 North. The larvae were examined to determine what daylength induced hibernation. Each circle on the following graph represents one larval population.

[Source: Bradshaw and Holzapfel, Proceedings of the National Academy of Sciences of USA, (2001),98 (25), pages 1450914511]

(a)Outline the relationship between daylength and latitude for the larval populations in 1972...........................................................................................................................................................................................................................................................................(1) (b)Compare the data of 1972 with 1996.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2) (c)Explain how the data illustrates an evolutionary response to a longer growing season due to a later onset of winter.....................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 5 marks)

(a)as the latitude increases so the length of dayneeded to induce hibernation increases;there is a direct correlation betweendaylength and latitude;1 max (b)the shortest daylength to induce hibernation is the sameat the lowest latitude in 1972 and 1996;at higher latitudes, the daylength to induce hibernation isless in 1996 than 1972;for the same daylength, the latitude at which hibernation occurshas moved further north in 1996 compared to 1972;at lower latitudes the change in daylength is lessthan at higher latitudes;2 max

(c)colder areas / higher latitudes become warmer / resemble lower latitudes (with shorter daylength);warmer weather delays organisms from beginninghibernation / mosquitos stay active longer into winter;(the graphs show) that organisms at higher latitudes haveadapted to a shorter daylength (to begin hibernation);2 max[5]

35.Phenologists are biologists who study the timing of seasonal activities in animals and plants, such as the opening of tree leaves and the laying of eggs by birds. Data such as these can provide evidence of climate changes, including global warming.The date in the spring when new leaves open on horse chestnut trees (Aesculus hippocastaneum) has been recorded in Germany every year since 1951. The graph below shows the difference between each years date of leaf opening and the mean date of leaf opening between 1970 and 2000. Negative values indicate that the date of leaf opening was earlier than the mean. The graph also shows the difference between each years mean temperature during March and April and the overall mean temperature for these two months. The data for temperature was obtained from the records of thirty-five German climate stations.

[Source: Walther et al., Nature (2002), 416, pages 389395] (a)Identify the year in which there was the(i)earliest opening of horse chestnut leaves;...........................................................................................................................(1) (ii)lowest mean temperature in March and April............................................................................................................................(1) (b)Use the data in the graph to deduce the following.(i)The relationship between temperatures in March and April and the date of opening of leaves on horse chestnut trees.......................................................................................................................................................................................................................................................(1) (ii)Whether there is evidence of global warming towards the end of the twentieth century.............................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)

From 1973 onwards phenologists in the Netherlands have been studying a population of great tits (Parus major) in a forest on the Hoge Veluwe. Nest boxes are checked every week to find out when the great tits lay their eggs and how many eggs they lay. Young birds are ringed when they are seven days old, to allow the reproductive success of their parents to be monitored. Great tits feed on arthropods, especially caterpillars. The phenologists found that the date of maximum caterpillar biomass each year in the forest could be estimated accurately using temperature records. The graphs below show the mean date of egg laying and the estimated date of maximum caterpillar biomass for each year from 1973 to 1995.

[Source: Visser, Noordwijk, Tinbergen and Lessells, Proceedings of the Royal Society of London,(1998), 265, pages 18671870] (c)(i)Compare the date of egg laying with the date of maximum caterpillar biomass.......................................................................................................................................................................................................................................................(1)

(ii)Suggest an advantage to great tits of the difference in dates.......................................................................................................................................................................................................................................................(1) (d)State the trend, shown in the graph, for the date of maximum caterpillar biomass...........................................................................................................................................................................................................................................................................(1) There was no statistically significant change in the date of egg laying between 1973 and 1995, but the phenologists found evidence that natural selection will eventually cause a change in the date of egg laying.(e)Explain how natural selection could cause a change in the date of egg laying in the population of great tits in the forest on the Hoge Veluwe..........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................(2)(Total 10 marks)

(a)(i)19901(ii)19701 (b)(i)the higher the temperature the earlier the date of leaf opening1(ii)there is evidence of warming;at the end of the twentieth century most years are warmer than the mean;all but one of the last (12) years are warmer than the mean;6 colder than mean years in the first 15 years and only 2 in the second 15 years;2 max

(c)(i)date of egg laying is (always) earlier than the date of maximum caterpillar biomass / date of maximum caterpillar biomass is (always) later than the date of egg laying1(ii)many caterpillars available to feed the young when they have hatched1 (d)date of maximum caterpillar biomass has got earlier / reduced / decreased;1(e)birds that lay eggs earlier find more caterpillars / their young are better fed;offspring of early egg layers have a better chance of survival;these birds inherit the early egg laying characteristic / others eliminated;2 max[10]

37.What are the main sources of carbon dioxide on earth?A.Cellular respiration of consumers, producers and combustion of n fuelsB.Photosynthesis and cellular respiration of consumersC.Cellular respiration of producers and combustion of fossil fuelsD.Photosynthesis and combustion of fossil fuels(Total 1 mark)

A[1]

39.Up to two additional marks are available for the construction of your answers.(2)(a)Draw a labelled graph showing a typical sigmoid growth curve.(4)(b)Outline the consequences of an increased greenhouse effect on arctic ecosystems.(6)(c)Explain how natural selection leads to evolution.(8)(Total 20 marks)

(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 that 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]