Question 1
1
The micrograph shows a buttercup (Ranunculus bulbosus) stem in transverse section. Region T has been highlighted to show more detail.
Data Response0 marks
Question 1(d)
1(d)
Explain two adaptations of leaves that allow plants to live in hot deserts.
Mediumstructured2 marks
Answer
a. (thick) waxy cuticle to avoid water loss by evaporation/transpiration; b. small leaves / spines to reduce surface area for evaporation/transpiration; c. sunken stomata / hairs to keep moisture near the surface and reduce transpiration rate; d. rolled leaves keep moisture near the surface and reduce transpiration rate; e. succulent leaves with water storage tissue; f. some (CAM) plants open stomata only at night when temperature is cooler to decrease water loss; Adaptation + explanation needed for a mark. 2 max
Question 1
1
Beavers are large rodents that live in waterways throughout the northern hemisphere. Dams made by beavers change the temperature of the streams and affect the mayfly, Baetis bicaudatus. In the summer of 2008, beaver ponds in West Brush Creek and Cement Creek, Colorado, were studied to evaluate their impacts on mayflies. The study sites included streams flowing into (upstream) and out of (downstream) each beaver pond. Mayflies, including the species B. bicaudatus, are aquatic insects that hatch and spend their larval stages in water emerging from the water as adults. Larger females produce an increased number of better quality eggs.
12 marks
Question 1(b)
1(b)
Describe the effect dams have on water temperature.
Mediumstructured2 marks
Answer
a. height of dam affects the temperature b. high dams tend to cool the water c. low dams tend to warm the water d. pond 5 /one pond shows no change/stays the same 2 max
Question 1(c)
1(c)
The graph shows the mean dry mass of mayflies relative to the water temperature in their habitats. Using the graph, discuss evidence for the hypothesis that mayflies grow to greater dry mass in cooler water.
Mediumstructured2 marks
Answer
a. trend lines support «the hypothesis» OR trend shows a negative correlation shown «between increased temperature and size» b. the trend line is shallow / small slope OR there is a large amount of scatter at higher temperatures (reducing the certainty) OR wide/overlapping ranges so no significant difference «(at» \(9^{\circ} \mathrm{C}\) ) c. (hypothesis not supported because) females in water over \(10^{\circ} \mathrm{C}\) have the highest «mean dry» mass Do not credit answers with just numbers. Accept "line of best fit" wtte. Note that it is only the trend line that indicates support. Words other than "hypothesis not supported" may be used: "as opposed to", "whereas", to express deviation from support. 2 max
Question 1
1
Coral reefs are among the most spectacular ecosystems on Earth. They support a rich diversity of life and provide economic benefits to the people who use them. In Papua New Guinea in the Pacific Ocean north of Australia the following data were collected. Coral cover is the percentage of the reef surface covered by live hard coral.
13 marks
Question 1(b)
1(b)
Describe the evidence that the ocean temperature has an effect on coral cover.
Mediumstructured2 marks
Answer
a. coral cover decreases as temperature rises (between 1996 and 1998/2000 and 2002) / negative correlation between temperature and coral cover / coral cover highest when temperature is lowest/vice versa b. coral cover remains constant when temperature drops (between 1998/1999 and 2000)/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 if other parts of the answer give one of the alternative parts of the mark point. 2 max
Question 1
1
Pinnipeds are marine mammals with fins or flippers and include fur seals and sea lions. Some pinnipeds forage for prey near the surface (epipelagic) while others forage on the bottom of the sea (benthic). The graph shows the foraging behaviour and the relative time spent diving while at sea for five pinniped species.
18 marks
Question 1(a)
1(a)
State the relative time the Australian fur seal spent diving while at sea. \%
Easydata_response1 marks
Answer
42 (\%) (units not required) [1]
Question 1(b)
1(b)
Using the data in the bar chart, deduce which factor has the most significant effect on the relative time spent diving while at sea.
Mediumdata_response2 marks
Answer
(all) epipelagic species spend less time diving / benthic spend more time; (thus) foraging behavior/feeding location affects diving time more than species;
Question 1(c)
1(c)
Different species are able to store different amounts of oxygen in their muscle tissues in preparation for diving. The graph shows the relationship between typical dive duration and oxygen storage in tissues in the same five species. State the oxygen stores for a New Zealand sea lion for a dive of 3.4 minutes. \(\mathrm{cm}^{3} \mathrm{~kg}^{-1}\)
Easydata_response1 marks
Answer
\(46\left(\mathrm{~cm}^{3} \mathrm{~kg}^{-1}\right)\) (accept answers in the range of \(45.5\left(\mathrm{~cm}^{3} \mathrm{~kg}^{-1}\right)\) to \(47\left(\mathrm{~cm}^{3} \mathrm{~kg}^{-1}\right)\) )
Question 1(d)
1(d)
Using the data in the graph, analyse the correlation between dive duration and oxygen stores in the different species.
Mediumdata_response2 marks
Answer
benthic (species) dive for longer (than epipelagic species); the longer the dive, the greater the oxygen stores / overall relationship is positive between dive duration and oxygen stores; oxygen store is variable in dives of same duration (in benthic)/per minute of dive; Award any other sensible point.
Question 1(e)
1(e)
In another study on the Antarctic fur seal (epipelagic), scientists measured the temperature difference between the skin of diving seals and the water at all depths of the dives. The data shown is for one fur seal during one period of dives. Describe the variations in the
4 marks
Question 1(e)(i)
1(e)(i)
characteristics of each successive dive during the period investigated.
Mediumdata_response2 marks
Answer
the depth of the dives decreases (slightly) over time; the length/duration of the dive increases (slightly) over time; the frequency of the dives increases over time / time spent on surface decreases;
Question 1(e)(ii)
1(e)(ii)
difference between the temperature of the skin and the water during the period investigated.
Mediumdata_response2 marks
Answer
in each dive the temperature difference decreases as the seals dive down and increases (slowly) after they rise; temperature difference decreases over time; but in a variable, regular fashion;
Question 1(h)
1(h)
Using the data, discuss reasons for pinnipeds diving for less than 3.5 minutes.
Mediumdata_response3 marks
Answer
oxygen reserves used up after 3.5 minutes; need to replenish oxygen reserves on surface; too cold after 3.5 minutes; need to remain on surface to raise body temperature; have caught prey by 3.5 minutes / return to surface to eat prey;
Question 1
1
Increasing carbon dioxide concentration in the atmosphere leads to acidification of the ocean. This in turn reduces the amount of dissolved calcium carbonate. A study was undertaken to investigate the effect of increasing the concentration of atmospheric carbon dioxide on the calcification rate of marine organisms. Calcification is the uptake of calcium into the bodies and shells of marine organisms. The study was undertaken inside Biosphere-2, a large-scale closed mesocosm. The graph shows the results of the data collection.
0 marks
Question 1(c)
1(c)
Outline one way in which reef-building corals are affected by increasing atmospheric carbon dioxide.
Easystructured2 marks
Answer
Alternative 1 a. corals have parts/shells/«exo»skeleton made of calcium carbonate b. calcium carbonate «shells» dissolve in acid conditions c. acid/high \(\mathrm{CO}_{2}\) conditions reduces availability of calcium carbonate «for forming shells» OR negatively affects enzymes involved in calcification Alternative 2 d. \(\mathrm{CO}_{2}\) is «significant» greenhouse gas causing rise in ocean temperatures e. higher ocean temperatures/acidification leads to rejection of zooxanthellae OR higher ocean temperatures/acidification leads to coral bleaching 2 max
Question 1
1
White-nose syndrome (WNS) is a disease caused by the fungus Geomyces destructans. This kills bats from many species during their winter hibernation. Scientists used echolocation to record the number of bat flights over a station in 10 minute sample periods during the summers of 2007 to 2009. The graph shows the mean number of flights and number of recording samples for little brown bats (Myotis lucifugus), a species affected by the fungus, along with those of hoary bats (Lasiurus cinereus), which are not affected.
0 marks
Question 1(d)
1(d)
Distinguish between the patterns of hibernation of the uninfected and infected bats.
Mediumstructured1 marks
Answer
a. more (frequent) interruptions/emergences from hibernation/shorter periods of hibernation/more spikes in temperature (indicating emergence) in infected bats b. more fluctuation in (body) temperature (during hibernation) in infected (than uninfected bats) c. emergences/interruptions become more frequent during the hibernation period in infected bats versus (about) about the same frequency in uninfected 1 max
Question 1
1
Ozone gas in the atmosphere helps to block high-energy ultraviolet light (UV) from reaching the Earth's surface. Over the past few decades, the ozone layer has been decreasing, thus allowing through more UV. The effect of this decrease in the ozone has been studied in different plants. An early study was undertaken on patience dock plants (Rumex patientia) to test the effect of atmospheric ozone levels decreasing by 38 %. The net photosynthesis (total photosynthesis minus total respiration) and respiration of the plants were measured during seven days of exposure to UV. The rates of photosynthesis and respiration are given in rates of carbon dioxide uptake per unit area of leaf.
10 marks
Question 1(g)
1(g)
Discuss where in the world plants will be harmed most by the effects shown in the graph, given that ozone depletion is greatest near the north and south poles and light intensity is highest near the equator.
Hardessay2 marks
Answer
plants affected most near the poles/have lowest photosynthesis; because more UV there (has greatest impact); because lowest light intensity (has greatest impact);
Question 1
1
Arabidopsis is a small flowering plant in the mustard family (Brassicaceae) that is widely used in basic research. It has a short life cycle, flowers quickly producing a large number of seeds and is easy to cultivate. It forms a circle of leaves known as a rosette that lies close to the soil. Flowers form at the end of short stems. A study was carried out of differences in development between Arabidopsis plants grown in long days ( 16 hours light, 8 hours dark) or short days ( 8 hours light, 16 hours dark). The sixth leaf (L6) to emerge in the rosette of each plant was used in all investigations. New leaves are initiated by the meristem and go through four stages as they develop. - Stage 1 (S1) - rapid cell division - Stage 2 (S2) - cell division has ceased, cell expansion continues - Stage 3 (S3) - decreasing cell expansion rate - Stage 4 (S4) - leaf growth complete The start of each stage of leaf development for plants grown in long days and short days is shown above the first graph.
0 marks
Question 1(b)
1(b)
Distinguish between plants grown in long days and short days in the mean number of leaves per rosette during the experimental period.
Mediumstructured2 marks
Answer
a. rosette of plant grown in long day has fewer leaves b. rosette leaf number of plant grown in long day plateaus/stays constant while the number continues to increase for plants grown in short days Accept vice versa. OWTTE. 2 max
Question 1(f)
1(f)
Using all relevant data in this question, deduce with reasons whether Arabidopsis is a long day plant or a short day plant in terms of flowering.
Hardstructured2 marks
Answer
a. long day plant b. flowering hormone metabolism gene over represented in long day exposure c. fewer leaves produced «rapidly» by plant in long day as energy shifted to flower formation d. plants grown in short days produce more leaves over longer period before beginning to flower/need to use light more efficiently to photosynthesize Accept other valid reasons from the data Allow ECF if student indicates short day plant. 2 max
Question 1
1
White clover (Trifolium repens) is native to Eurasia but is now a common plant found worldwide in lawns, next to roads, in pastures and similar habitats. Some T. repens plants are able to produce the toxin hydrogen cyanide (HCN) by cyanogenesis. A study at 128 sites ( 2509 plants) in Toronto (Canada) looked at the proportion of T. repens plants producing HCN. The sites were at regular intervals from the city centre towards rural areas.
9 marks
Question 1(d)
1(d)
The researchers then investigated a possible correlation between cyanogenesis and exposure to freezing conditions. It had been proposed that when a cyanogenic plant freezes, its cells burst, releasing HCN which is toxic to the plant. Snow can insulate the ground and plants from freezing temperatures. However, snow is more likely to melt in cities, which then exposes plants to freezing temperatures. All four of the cities studied receive below freezing temperatures and winter snowfall. Researchers looked at the number of days below freezing \(\left(0^{\circ} \mathrm{C}\right)\) that did not have snow cover in these cities.
3 marks
Question 1(d)(i)
1(d)(i)
Identify with a reason the city where the plants were more insulated from freezing temperatures.
Mediumstructured1 marks
Answer
i Montreal because it has the lowest number of days below \(0^{\circ} \mathrm{C}\) without snow cover; Do not award the mark for Montreal if the reason is not given
Question 1(d)(ii)
1(d)(ii)
Using all of the data so far, suggest whether exposure to freezing temperatures in the four cities is supported as a reason for the differences in HCN production in T. repens.
Mediumstructured2 marks
Answer
a cities with more days without snow cover have positive correlation between distance from city center and HCN / vice versa for Montreal; b fewer plants with HCN within cities that have more days without snow cover/have more exposure to freezing temperatures / converse for Montreal which has fewer days without snow cover; \(c \quad \mathrm{HCN}\) is 0.2 (or less) HCN in cities that have more days without snow cover proportion whereas city with fewer days/Montreal it is 0.5 / more than 0.4 ; d in Toronto cyanogenic and non-cyanogenic plants show little difference in herbivory; e support for hypothesis/exposure to freezing temperatures as reason; Do not accept 'Yes' unqualified as an answer, but accept it if supported by reasoning 2 max e i hours of daylight/light intensity/soil pH/soil nutrients/mineral nutrients/watering regime/humidity/ /population plants came from/location plants were adapted to/duration of cold period/ /size of plant pot/size of plant/wind speed/carbon dioxide concentration; Mark the first answer given only. Reject nutrition and sunlight unqualified. Reject number of plants. e ii Lowest: non-cyanogenic and produces A; Highest: non-cyanogenic and produces neither (chemical); Do not accept genotypes e iii Comparing the first and second bar with the third and fourth: a higher survival with aa than Aa / allele/gene A lowers survival; b higher survival if substrate/chemical A not produced / substrate/chemical A lowers survival; Comparing the first bar with the second: c no significant difference between A_L_and A_II / if A is present L/I doesn't affect survival; d conversion of substrate/chemical A to cyanide does not affect survival; Comparing the fourth bar with the third: e higher survival with aall than aaL_ / if A is not present L reduces survival; f lowers survival if chemical L/enzyme produced even if substrate/chemical A not produced; Comparing the fourth bar with the other three: g highest survival with aall/homozygous recessive h chemicals A and L/substrate and enzyme both lower survival; Do not accept L decreases survival unqualified as it does not for plants with allele A. Do not accept lower survival in A_II than A_LI as the difference is unlikely to be significant. Do not accept ranking the four genotypes in order of survival probability without more analysis. Accept any of these points if given as the converse, for example for mph 'highest survival without either chemical. Accept 'withstand freezing' in place of 'survival' in any mark point. 3 max
Question 1
1
A community living in the water of an estuary was used to investigate how climate change may affect ecological systems. The food web in this community included phytoplankton (producers), zooplankton (consumers) and saprotrophic bacteria. Small plastic mesocosms were set up with water from the estuary containing only these three groups of organisms. The mesocosms were subjected to four different temperatures and two nutrient levels (control and nutrients added) to replicate local variations of the conditions in the estuary during springtime warming. The graph shows the biomass of the community for each of the eight mesocosms at the end of the experimental period. Biomass was measured in terms of the amount of carbon present. The horizontal line indicates the initial biomass.
15 marks
Question 1(f)
1(f)
Suggest two abiotic factors, other than temperature and nutrient supply, that may affect the production of biomass of the grasslands.
Easystructured2 marks
Answer
a water availability/rainfall/humidity; b light/sunlight (intensity) / daylength; c salinity of soil / high/low soil pH; d chemical pollution/herbicides/allelopathy/parasitic weeds; Mark the first two answers only. Do not accept carbon dioxide or weather conditions. 2 max