| Date | November 2016 | Marks available | 4 | Reference code | 16N.2.HL.TZ0.8 |
| Level | Higher level | Paper | Paper 2 | Time zone | TZ0 / no time zone |
| Command term | Describe | Question number | 8 | Adapted from | N/A |
Question
In ecosystems, energy is used to convert inorganic compounds into organic matter. Energy enters ecosystems through producers.
Explain the processes by which light energy is converted into chemical energy.
Describe how energy flows through and is used by organisms in ecosystems.
Markscheme
a. plants/producers/autotrophs convert light to chemical energy by photosynthesis
b. chlorophyll/photosynthetic pigments absorb light
c. electrons are excited/raised to higher energy level
d. excited electrons pass along chain of electron carriers
e. energy from electrons used to pump protons across thylakoid membrane/into thylakoid space
f. chemiosmosis/proton gradient used to make ATP
g. ATP synthase generates ATP
h. pigments arranged in photosystems
i. electrons from Photosystem II flow via the electron chain to Photosystem I
j. electrons from Photosystem I are used to reduce NADP
k. ATP and reduced NADP used in the light independent reactions/Calvin cycle
l. carbohydrate/glucose/carbon compounds produced containing energy
Award marking points for any point made on a clearly annotated diagram.
a. producers/plants/autotrophs obtain energy from light/sun/inorganic sources
b. food contains energy / energy passed in the form of food/carbon compounds (along food chains/between trophic levels)
c. consumers obtain energy from other organisms/from previous trophic level
This mark point distinguishes consumers from producers.
d. energy released (in organisms) by (cell) respiration
Reject energy used in respiration.
e. ATP produced
f. energy/ATP used for biosynthesis/movement/active transport/other valid use of ATP
g. less energy available / energy lost at each trophic level
Examiners report
Syllabus sections
- 16N.1.SL.TZ0.18: What restricts the length of a food chain? A. Energy losses between the trophic levelsB. A...
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21M.2.SL.TZ2.4d.i:
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
- 17M.2.HL.TZ2.4a.ii: Using the food web, identify a saprotroph.
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20N.2.HL.TZ0.4a:
Distinguish between the transfers of energy and inorganic nutrients in ecosystems.
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19M.1.HL.TZ1.14:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.
[Source: © International Baccalaureate Organization 2019]
Which organism is a tertiary consumer?
A. Organism T
B. Organism U
C. Organism W
D. Organism Y
- 17M.2.HL.TZ2.4c: Outline the energy flow through this food web.
- 17N.2.SL.TZ0.04b: Outline why the number of trophic levels is limited in a food chain.
- 22M.2.SL.TZ1.1g: Outline the relationship between ambient daily temperature and food intake in March.
- 18N.1.SL.TZ0.17: The diagram shows interactions between food chains in an ecosystem in the African...
- 18M.1.HL.TZ2.22: Which processes occur in an ecosystem? I. Biomass increases in each successive trophic...
- 16N.2.SL.TZ0.1f: Identify an example of competition between organisms in this food web.
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19M.1.SL.TZ1.18:
The diagram shows the food web for an aquatic ecosystem in which letters R–Z represent individual species.
[Source: © International Baccalaureate Organization 2019]
Which organism is a tertiary consumer?
A. Organism T
B. Organism U
C. Organism W
D. Organism Y
- 17M.1.SL.TZ2.17: What is lost between trophic levels in ecosystems and cannot be recycled? A. Heat B....
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21N.2.SL.TZ0.3b.i:
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.
- 17M.1.SL.TZ2.27: The bacterium Neisseria gonorrhoeae causes infections related to the human reproductive...
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16N.2.SL.TZ0.1e:
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.
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16N.2.SL.TZ0.7c:
Draw a labelled diagram of a pyramid of energy.
- 17M.1.SL.TZ1.21: Cladograms can be created by comparing DNA or protein sequences. The cladogram on the left is...
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19N.2.HL.TZ0.8c:
Explain the movement of energy and inorganic nutrients in an ecosystem.
- 22M.2.SL.TZ1.1h: Suggest, with a reason, how the activity of the sloth varies with ambient temperature.
- 22M.1.SL.TZ2.18: The diagram shows part of a food chain. The left box represents producers and the right box...
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22M.2.SL.TZ2.7a:
Outline energy flow through a community in a natural ecosystem.
- 21N.1.SL.TZ0.18: In a woodland ecosystem, each tree provides food for numerous aphids which feed on the sap of...
- 22M.1.SL.TZ1.18: The table contains information about the diet of some animals. Which pyramid of energy...
- 17M.3.HL.TZ1.13c: Distinguish between mutualism and parasitism, providing another example of mutualism and...
- 20N.1.HL.TZ0.16: Plankton are major producers in marine ecosystems. Only a small proportion of the energy...
- 22M.2.SL.TZ1.1f: The mean daily food intake fluctuated from day to day. State the month that contains the day...
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21N.2.HL.TZ0.1b:
Compare and contrast the effects of temperature on the biomass of autotrophs and heterotrophs with added nutrients.
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21N.2.HL.TZ0.1d:
Suggest reasons for the decreases in biomass of autotrophs as temperature rises, despite the increases in photosynthesis.
- 19M.2.HL.TZ2.8a: Outline energy flow through a food chain.
- 18M.1.SL.TZ1.17: Animals in the highest trophic level of a food chain will often be the largest in body size...
- 17M.2.HL.TZ1.1f.ii: Suggest a reason for the greater expression of the gene for the urea transporter after an...
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20N.2.HL.TZ0.8a:
Outline the criteria that should be used to assess whether a group of organisms is a species.
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21M.1.SL.TZ2.18:
The diagram shows the flow of energy through an ecosystem in
[Source: “Energy flow: Figure 3,” (https://cnx.org/contents/24nI-KJ8@24.18:fbNheNoN@8/Energy-Flow) by OpenStax College, Biology CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).]
What percentage of the energy passed from primary producers to primary consumers is lost to cellular respiration by tertiary consumers?
A. 0.001%
B. 0.08%
C. 0.2%
D. 0.4%
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21M.2.SL.TZ2.4c:
Explain how energy enters, flows through and is lost from marine food chains.
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21M.2.SL.TZ2.4d.ii:
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
- 18M.2.HL.TZ2.6c: Describe the reasons for the shape of a pyramid of energy.
- 17M.2.SL.TZ1.1c: Estimate how much smaller drilled oysters raised in seawater at a high CO2 concentration were...
- 18M.2.SL.TZ2.3c: Explain how energy and nutrients are transferred in ecosystems.
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16N.2.SL.TZ0.7a:
Explain the processes by which energy enters and flows through ecosystems.
- 19N.2.SL.TZ0.5c: Explain the movement of energy and inorganic nutrients in an ecosystem.
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19M.2.SL.TZ2.3a.i:
State two causes of the decrease of biomass along food chains in terrestrial ecosystems.
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17M.2.SL.TZ1.2d:
Explain the role of decomposers in an ecosystem.
- 21M.1.SL.TZ1.21: The diagram shows the energy flow between five “sinks” in a terrestrial ecosystem. In a...
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21N.2.SL.TZ0.3b.ii:
Explain the reasons for food chains rarely containing more than four or five trophic levels.
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19M.1.SL.TZ2.18:
The Silver Springs feed into the Silver River in Florida. The diagram shows a pyramid of energy for the Silver Springs ecosystem. The units are kJ m–2 y–1.
[Source: © International Baccalaureate Organization 2019]
What do level I and level III represent in the pyramid of energy?
