SL Paper 2
Honeybees (Apis mellifera) are key pollinators in most ecosystems. The worldwide use of neonicotinoid pesticides has caused concern because they may be contributing to the decline of honeybee populations.
Scientists measured the concentration of five neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) in honey samples from 198 different locations across the world. Each pie chart shows the relative frequency of neonicotinoids in honey samples from a continent.
[Source: Republished with permission of American Association for the Advancement of Science, from A worldwide survey of neonicotinoids in honey, Mitchell, E.A., et al., Science, Volume 358, Issue 6359, 2017. Permission conveyed through Copyright Clearance Center, Inc. https://science.sciencemag.org/content/358/6359/109.full.]
The neonicotinoids can be used alone or together with other neonicotinoids. The percentage of honey samples with 0, 1, 2, 3, 4 or 5 different neonicotinoids in each continent are shown in the stacked bar chart.
[Source: Republished with permission of American Association for the Advancement of Science, from A worldwide survey of neonicotinoids in honey, Mitchell, E.A., et al., Science, Volume 358, Issue 6359, 2017. Permission conveyed through Copyright Clearance Center, Inc. https://science.sciencemag.org/content/358/6359/109.full.]
In order to grow, honeybee larvae are fed royal jelly, a high energy food with very high acetylcholine concentrations.
In an experiment, larvae were bred artificially on a diet with reduced acetylcholine content in the royal jelly. The graph shows the mean survival rate of these larvae compared to control larvae fed on a normal diet.
[Source: Wessler I, Gärtner H-A, Michel-Schmidt R, Brochhausen C, Schmitz L, Anspach L, et al. (2016) Honeybees Produce Millimolar Concentrations of Non-Neuronal Acetylcholine for Breeding: Possible Adverse Effects of Neonicotinoids. PLOS ONE 11(6):e0156886. doi:10.1371/journal.pone.0156886 Copyright: © 2016 Wessler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.]
The concentration of acetylcholine was measured in royal jelly produced by honeybees that had never been exposed to neonicotinoids (control) and honeybees that had been exposed for three weeks to two neonicotinoids; clothianidin and thiacloprid.
Wessler I, Gärtner H-A, Michel-Schmidt R, Brochhausen C, Schmitz L, Anspach L, et al. (2016) Honeybees Produce Millimolar Concentrations of Non-Neuronal Acetylcholine for Breeding: Possible Adverse Effects of Neonicotinoids. PLOS ONE 11(6):e0156886. doi:10.1371/journal.pone.0156886 Copyright: © 2016 Wessler et al. This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Identify in which continent the fewest types of neonicotinoid were detected in honey samples.
Using the data, outline the different use of thiamethoxam in North and South America.
Identify the total percentage of honey samples contaminated with neonicotinoid pesticides in the continent with the lowest overall levels of contamination.
. . . . . . . . . . . . %
Deduce the conclusions that can be drawn from the data in the graph.
Suggest a reason for the effect of a diet reduced in acetylcholine on the larval survival rate.
Compare and contrast the effect of clothianidin and thiacloprid treatments on the concentration of acetylcholine in royal jelly.
Explain how neonicotinoids affect synaptic transmission in insects.
Companies that manufacture neonicotinoid pesticides have argued that they do not cause significant harm to honeybees. Construct an argument, based on the data in this question, for serious concern about the manufacture and use of neonicotinoid pesticides.
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.
The table shows the mean temperature differences (downstream – upstream) and mean dry mass for female and male mayflies.
The bat, Pipistrellus nathusii, feeds on insects including mayflies. A study was undertaken in Poland to see the effect of European beavers (Castor fiber) on the activity of bats. Beaver activity can affect forests that are covered by trees and meadows that are covered by grasses and have no trees. The following habitats were studied:
- forest (F)
- flooded forest with canopy gaps created by beavers and flooding due to the presence of beaver dams (FFG)
- forest with canopy gaps created by beavers but no flooding (FG)
- meadow (M)
- meadow with flooding due to the presence of beaver dams (MF).
As bats feed they fly through the air catching insects. The number of feeding passes made by bats was counted. The graph shows differences in the bat activity between particular habitats.
Calculate the difference in the mean dry mass of mayflies upstream and downstream of Cement Creek pond 9 for female and male mayflies.
Describe the effect dams have on water temperature.
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.
Analyse the data to find the effect of flooding and tree felling by beavers on the activity of bats.
The trout, Oncorhynchus mykiss, that live in West Brush Creek and Cement Creek also feed on the mayflies. Fishermen come to Colorado to catch and eat trout. Draw a diagram of part of a food web for the creeks in Colorado, including mayflies, humans, trout and bats.
Identify an example of competition between organisms in this food web.
The North American beaver (Castor canadensis) was introduced to islands adjacent to Argentina and Chile where they have become an invasive species. Discuss one ecological criterion (a basis for deciding) whether beavers are harmful or helpful to the ecosystems there.
Native oyster populations are decreasing where rivers meet the ocean along the northwest coast of North America. These oyster populations are being attacked by a gastropod.
It is known that oysters and gastropods have hard parts composed of calcium carbonate and that ocean acidification is increasing. Studies were carried out using juvenile oysters and gastropods to investigate the effects of acidification on the decrease in the population of oysters.
The first step was to raise oysters in two different mesocosms. One had seawater at a normal concentration of CO2 and the other had sea water with a high concentration of CO2. Gastropods were raised in two further mesocosms with normal and high CO2 concentrations respectively.
A juvenile gastropod will attack a juvenile oyster by using its tongue-like structure (radula) to drill a hole through the oyster shell. Once the hole has been drilled, the gastropod sucks out the soft flesh. Researchers investigated the shell thickness at the site of the drill hole in relation to the size of the oyster. The results are seen in this graph.
Equal numbers of oysters raised in seawater with a normal CO2 concentration and in seawater with a high CO2 concentration were then presented together to the gastropod predators in seawater with a normal CO2 concentration. The same numbers of oysters from the two groups were also presented together to the gastropods in seawater with a high CO2 concentration. The bar charts show how many of the oysters were drilled by the gastropods and the mean size of drilled oysters.
Outline how acidified sea water could affect the shells of the oyster.
Outline the trends shown in the data in the graph.
Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were than drilled oysters raised in seawater at a normal CO2 concentration.
Deduce from the data in the bar charts which factors were and were not correlated significantly with the number of oysters drilled by the gastropods.
Suggest reasons for the differences in the numbers of oysters drilled, as shown in the bar charts.
The radula in a gastropod is hard but not made of calcium carbonate. Outline how this statement is supported by the drilling success of the gastropods in seawater with normal or high CO2 concentrations.
Using all the data, evaluate how CO2 concentrations affect the development of oysters and their predation by gastropods.
The mass of an individual organism can affect its physiology and feeding ecology. The diagram shows the relative mass of carbon (black) and total wet mass (grey) of a marine crustacean, Calanus hyperboreus and a jellyfish, Bathocyroe fosteri.
[Source: Kristian McConville, Angus Atkinson, Elaine S. Fileman, John I. Spicer, Andrew G. Hirst. Disentangling the counteracting effects of water content and carbon mass on zooplankton growth. Journal of Plankton Research. 2017, Volume 39, Issue 2, Pages 246–256. https://doi.org/10.1093/plankt/fbw094. Adapted (and translated) by permission of Oxford University Press.]
State one process that results in the loss of carbon dioxide from a marine organism such as a crustacean or a jellyfish.
The crustacean and the jellyfish obtain carbon compounds by feeding. State one source of carbon for marine organisms, other than feeding.
Explain how energy enters, flows through and is lost from marine food chains.
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
State the immediate consequence of a species producing more offspring than the environment can support.
Explain the consequence of overpopulation on the survival and reproduction of better adapted individuals within a population.
The incidence of white syndrome, an infectious disease of coral, was investigated in a six-year study on Australia’s Great Barrier Reef. The map shows disease conditions on coral reefs at six study sites.
[Source: adapted from Bruno, J.F., Selig, E.R., Casey, K.S., Page, C.A., Willis, B.L., Harvell, C.D., Sweatman,
H. and Melendy, A.M., 2007. PLOS Biology, [e-journal] 5(6), e124. https://doi.org/10.1371/journal.pbio.0050124.]
Satellites were used to record sea surface temperatures. The temperatures each week above a reef were compared with mean temperatures for that week between 1985 and 2004. If the sea surface temperature was 1 °C or more above the mean, this was recorded as a weekly sea surface temperature anomaly (WSSTA). The number of WSSTAs was calculated for the twelve months preceding the date on which a reef was surveyed for white syndrome.
On each reef, the number of cases of white syndrome in a 1500 m2 sample area was surveyed once per year. The table shows these cases in relation to numbers of WSSTAs and coral cover on the reef. Low coral cover was 0–24 % and high coral cover was 50–75 %.
[Source: adapted from Bruno, J.F., Selig, E.R., Casey, K.S., Page, C.A., Willis, B.L., Harvell, C.D., Sweatman,
H. and Melendy, A.M., 2007. PLOS Biology, [e-journal] 5(6), e124. https://doi.org/10.1371/journal.pbio.0050124.]
The graphs show the relationship between the weekly sea surface temperature anomalies (WSSTA) and coral cover during two twelve-month periods (1998–99 and 2002–03), which were the warmest in the six-year study. Each dot represents one studied reef.
[Source: adapted from Bruno, J.F., Selig, E.R., Casey, K.S., Page, C.A., Willis, B.L., Harvell, C.D., Sweatman,
H. and Melendy, A.M., 2007. PLOS Biology, [e-journal] 5(6), e124. https://doi.org/10.1371/journal.pbio.0050124.]
Identify the site with the highest incidence of diseased colonies.
Deduce whether there is a trend in the incidence of white syndrome over the north-south range of latitude.
Describe the evidence that is provided by the data in the table for the harmful effects of rising sea temperatures on corals.
The researchers concluded that there was a threshold coral cover percentage, below which infection rates tended to remain fairly low. Using the data in the table, identify this threshold level.
Suggest a reason for a larger percentage of corals being infected with white syndrome on reefs with a higher cover of corals.
Compare and contrast the data for 1998–1999 and 2002–2003.
Suggest a reason for the correlation between coral cover and WSSTA in 1998–1999.
Some scientists predict that, if humans continue to produce carbon dioxide at the current rate, the pH of the oceans will become more acidic. Suggest possible effects on the coral reefs.
This study was carried out over six years on the Australian Great Barrier Reef. State one advantage of field investigations compared with mesocosm experiments to study ecological processes.
The diploid number of chromosomes in horses (Equus ferus) is 64 and the diploid number in donkeys (Equus africanus) is 62. When a male donkey and a female horse are mated, the result is a mule which has 63 chromosomes.
State the haploid number for horses.
Explain reasons that mules cannot reproduce.
Discuss whether or not horses and donkeys should be placed in the same species.
A mule was born at the University of Idaho in the USA with 64 chromosomes. Suggest a mechanism by which this could happen.
The diagram shows the greenhouse effect.
State the type of wavelength of the radiation labelled X and Y.
X:
Y:
Outline reasons for the change occurring at Z.
The short-tailed albatross (Phoebastria albatrus) nests and breeds on remote low-lying coral islands in the Pacific Ocean. Predict how global warming may threaten the survival of such an ocean bird.
Compare and contrast the mode of nutrition of detritivores and saprotrophs.
The image shows an example of a soil food web.
[Source: Anon., n.d. The Soil Food Web. [image online] Available at: https://www.nrcs.usda.gov/wps/portal/nrcs/
photogallery/soils/health/biology/gallery/?cid=1788&position=Promo [Accessed 11 March 2020].]
Draw a food chain from this food web, showing at least three organisms.
Explain the reasons for food chains rarely containing more than four or five trophic levels.
The amount of food passing into food chains can be affected by the rate of photosynthesis. Explain the effect of one limiting factor on photosynthesis.
All of the leaves in the image are from Solanum, a wild genus of tomato.
[Source: Courtesy: National Science Foundation, Credit Leonie Moyle.]
State one cause of variation in a plant such as the tomato.
Methane can be the product of anaerobic respiration in some organisms.
Describe anaerobic respiration in humans and in yeast.
Distinguish between the thermal properties of water and methane.
Explain the role of methane in climate change.
The graph shows the mean annual changes in global temperatures between 1880 and 2014. The mean temperature from 1951 to 1980 was used as the value of zero change in temperature.
[Source: National Aeronautics and Space Administration, n.d. GISS Surface Temperature Analysis (v3). [online]
Available at: https://data.giss.nasa.gov/gistemp/graphs_v3/ [Accessed 20 August 2019].]
Calculate the increase in mean global temperature between 1880 and 2010.
.......... °C
Outline how changes in temperature over short time periods could give a misleading impression of changes to the Earth’s climate.
Explain how increased carbon dioxide in the air leads to the greenhouse effect.
Draw a labelled diagram to show the fluid mosaic model of the plasma membrane.
Unicellular and multicellular organisms share the same functions of life. Outline four functions of life.
The structure of organisms is based on organic molecules containing carbon. Explain the cycling of carbon in an ecosystem.
Three-toed sloths (Bradypus variegatus) are placental mammals that live in trees in Central and South America. They eat leaves and fruit and get almost all their water from succulent plants.
[Source: Adapted from Laube, S., 2003. Three-toed-sloth (Bradypus variegatus), Lake Gatun, Republic of Panama. [image online] Available at: https://meta.wikimedia.org/wiki/User:Bradipus#/media/File:Bradypus.jpg]
Three-toed sloths change their body posture in response to the temperature of their environment (ambient temperature). Researchers assessed posture on a scale from 1 to 6, with 1 being when the sloth was curled into a tight ball and 6 when it had all limbs spread. The percentage of time the sloths were observed in each position was recorded at ambient temperatures from 22 °C to 34 °C. The researchers also measured the body temperature of the sloths over the same range of ambient temperatures.
[Source: Adapted from Cliffe, R.N., Scantlebury, D.M., Kennedy, S.J., Avey-Arroyo, J., Mindich, D. and Wilson, R.P., 2018. The metabolic response of the Bradypus sloth to temperature. PeerJ, [e-journal] 6: e5600. http://dx.doi.org/10.7717/peerj.5600. Licensed under a Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/.]
The daily food intake of three-toed sloths and daily ambient temperatures were monitored over a 160-day period from February to early July. The graphs show the mean results.
[Source: Cliffe et al. (2015), Sloths like it hot: ambient temperature modulates food intake in the brown-throated sloth (Bradypus variegatus). PeerJ 3:e875; DOI 10.7717/peerj.875 Licensed under a Creative Commons Attribution 4.0 International License https://creativecommons.org/licenses/by/4.0/.]
State the relationship between sloth body temperature and ambient temperature.
Explain how this relationship differs from that in humans.
Describe the trend in body posture as ambient temperature rises from 22 to 34 °C.
Suggest reasons for this trend.
The mean daily food intake fluctuated from day to day. State the month that contains the day on which the mean intake of food was highest.
Outline the relationship between ambient daily temperature and food intake in March.
Suggest, with a reason, how the activity of the sloth varies with ambient temperature.
State one feature of the sloth that would indicate it is a mammal.
Cultivated rice, Oryza sativa, is one of the most important human foods. The two main sub-species of cultivated rice are O. sativa indica and O. sativa japonica. O. rufipogon is a wild species from which they probably evolved.
To investigate whether the sub-species of cultivated rice evolved independently from the wild species, scientists analysed their chromosomes to find areas with similar DNA base sequences. Wild species tend to have many different alleles of genes present on each chromosome, but during the development of a crop plant by artificial selection from a wild species, this diversity drops considerably, increasing the base sequence similarity.
The number of different alleles of the genes on a chromosome can be represented by a diversity index. The following graph of part of chromosome 7 shows the diversity index of O. rufipogon and two varieties of cultivated rice, O. sativa indica and O. sativa japonica. The gene PROG1 allows the plant to stand upright, which is typical of cultivated rice. Its position is indicated by the vertical arrow on the graph.
[Source: He Z, Zhai W, Wen H, Tang T, Wang Y, Lu X, et al. (2011) Two Evolutionary Histories in the Genome of Rice:
the Roles of Domestication Genes. PLoS Genet 7(6): e1002100. https://doi.org/10.1371/journal.pgen.1002100]
In another experiment, scientists retrieved genome sequences of the wild rice O. rufipogon taken from a wide range of geographical sites (I, II and III) and those of the two sub-species of O. sativa from gene banks.
The pie charts, presented along with a cladogram, show the proportion of alleles for three genes which confer specific characteristics to O. sativa. Mutations can produce derived alleles that are different from the original ancestral alleles. The control group represents wild rice species other than O. rufipogon.
[Source: reprinted by permission from Springer Nature: Nature, Huang, X., Kurata, N., Wei, X. et al. A map of rice
genome variation reveals the origin of cultivated rice. Nature 490, 497–501 (2012) doi:10.1038/nature11532]
State the reason that O. sativa and O. rufipogon are classified as different species.
Determine which type of rice has the lowest overall diversity index.
Compare and contrast the trends for O. rufipogon and O. sativa indica.
State the proportion of the ancestral allele for the gene GS3 in the O. rufipogon-III population.
Distinguish between the proportion of ancestral and derived alleles for all three genes in O. sativa indica and O. sativa japonica.
State one reason for having a control group.
Using all of the data, discuss whether there is evidence that the two sub-species of O. sativa might have evolved independently from O. rufipogon.
The diagram shows a leaf from Dryopteris arguta.
[https://commons.wikimedia.org/wiki/File:E20161208-0001%E2%80%94Dryopteris_arguta_(Reverse)%E2%80%94RPBG_(30698925004).jpg, E20161208-0001—Dryopteris arguta (Reverse)—RPBG Source: https://www.flickr.com/photos/john_d_rusk/30698925004/ Author: John Rusk from Berkeley, CA, United States of America, licensed under Creative Commons licence: https://creativecommons.org/licenses/by/4.0/legalcode]
State the phylum of this plant.
State two characteristics of plants from the phylum you stated in (a)(i).
Outline why the number of trophic levels is limited in a food chain.
The electron micrograph shows a palisade mesophyll cell.
State the name of the structures labelled I and II.
Outline the function of the structure labelled III.
The plant from which this cell was taken is in the group angiospermophyta. State one characteristic that is unique to this group of plants.
Distinguish between autotrophic nutrition and heterotrophic nutrition.
Explain how energy and nutrients are transferred in ecosystems.
Describe how detritivores obtain nutrition and the effects they have in ecosystems.
Outline the role of amylase in digestion in humans.
Explain how plants capture and use light in photosynthesis.
Draw a section of the Singer-Nicolson model of an animal cell membrane.
Outline the principles used by scientists to classify organisms.
Explain the movement of energy and inorganic nutrients in an ecosystem.
Plants have widespread influences, from food chains to climate change.
Draw a diagram of a palisade mesophyll cell labelling only the structures that would not be present in a pancreatic cell.
Explain the process of photosynthesis.
Describe the process of peat formation.
The photomicrograph below shows the protozoan Paramecium caudatum.
[Source: Deuterostome, CC BY-SA 3.0
https://creativecommons.org/licenses/by-sa/3.0, via Wikimedia Commons.]
State the genus of this organism.
State the domain in which it is classified.
Outline the method of nutrition carried out by P. caudatum.
Outline one aspect of how P. caudatum carries out homeostasis.
Apart from the ribosomes, explain the evidence for the endosymbiotic theory of the origin of eukaryotic cells.
Life is based on carbon compounds.
Draw a molecular diagram of alpha-D-glucose.
Outline how carbon compounds are produced in cells using light energy.
Explain the transformations of carbon compounds in the carbon cycle.
Pictured below are Louis Pasteur’s original drawings of swan-necked flasks.
Describe how Pasteur’s experiments provided convincing evidence to falsify the concept of spontaneous generation.
State the function of life in Paramecium that is carried out by:
cilia.
State the function of life in Paramecium that is carried out by:
the contractile vacuole.
Discuss the advantages and disadvantages of the use of adult stem cells.
Explain the role of decomposers in an ecosystem.
In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.
Explain the processes by which energy enters and flows through ecosystems.
Producers extract phosphates and nitrates from soil. Outline how these ions are used in the synthesis of organic molecules.
Draw a labelled diagram of a pyramid of energy.
Outline the process of inhalation.
Explain the process of gas exchange taking place in the alveoli.
Discuss the relationship between atmospheric carbon dioxide concentration and global temperatures.
Although simple in structure, bacteria as a group show a wide range of diversity.
Outline the roles bacteria play in the carbon cycle.
Describe the evolution of antibiotic resistance in bacteria.
Explain the process of genetically modifying bacteria.
State two causes of the decrease of biomass along food chains in terrestrial ecosystems.
The table shows the global carbon budget over two decades; the years 1990 to 1999 and 2000 to 2009.
[Source: © International Baccalaureate Organization 2019]
Using the table, explain causes of the changes in carbon flux over the two decades.
Suggest how climate change can influence the natural selection of organisms that live in the Arctic oceans.
Describe the structure and function of starch in plants.
Outline the production of carbohydrates in photosynthesis.
Discuss the processes in the carbon cycle that affect concentrations of carbon dioxide and methane in the atmosphere and the consequences for climate change.
The growing human population has an increasing demand for energy derived from crop plants. At the same time, increasing droughts that are part of climate change make it difficult to grow crops in some parts of the world.
Outline energy flow through a community in a natural ecosystem.
Explain how natural selection can cause traits such as drought resistance to develop in wild plants.
Suggest possible benefits and risks of using genetic modification to develop varieties of crop plant with traits such as drought resistance.
Boreal forests stretch across Canada, Russia and Scandinavia. This northern ecosystem accounts for 29 % of the world’s forest areas. The long, cold winters favour tall evergreen trees with either needles or scale-like leaves. These trees are wind-pollinated and their seeds are not enclosed in a fruit. The photograph shows a typical boreal forest in winter.
Identify the dominant plant phylum in the boreal forest.
In some areas there are gaps in the boreal forest where trees fail to grow and peat tends to accumulate. Suggest reasons for this.
An increase in global temperatures poses a critical threat to boreal forests. Explain the consequences of climate change to this northern ecosystem.
The boreal forests are situated close to the north pole and even in summer the intensity of sunlight is lower than at the equator. Sketch a graph showing the effect of light on the rate of photosynthesis, labelling the axes.
