Question 21M.2.SL.TZ2.4
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.SL.TZ2.4 |
| Level | SL | Paper | 2 | Time zone | TZ2 |
| Command term | Deduce, Explain, State, Suggest | Question number | 4 | Adapted from | N/A |
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.
[1]
a. (aerobic/cellular) respiration ✔
b. gas exchange / diffusion ✔
Do not accept photosynthesis.
Do not accept breathing
Organism is taken to be a living thing.
In 4(a) most were able to state 'respiration' as the answer. 4(b) proved more difficult with fewer stating photosynthesis or absorption of dissolved CO2 or HCO3 from the seawater. Vague answers such as 'carbon in the water' were not credited. In 4(c) most knew that energy enters with sunlight, but did not state photosynthesis. They knew that it was transferred by feeding through the trophic levels and lost as heat due to respiration. A surprising number incorrectly stated that the energy was recycled and some drew diagrams of the energy flow showing this. In 4(d)(i) most were able to state that the crustacean was a richer source of carbon. An explanation using the data from the diagram was expected. In 4(d)(ii) most were able to present an argument for advantage or disadvantage.
The crustacean and the jellyfish obtain carbon compounds by feeding. State one source of carbon for marine organisms, other than feeding.
[1]
a. photosynthesis ✔
b. absorption of (dissolved) carbon dioxide / (hydrogen)carbonate directly from the oceans ✔
Accept reference to carbonate or hydrogencarbonate ions.
In 4(a) most were able to state 'respiration' as the answer. 4(b) proved more difficult with fewer stating photosynthesis or absorption of dissolved CO2 or HCO3 from the seawater. Vague answers such as 'carbon in the water' were not credited. In 4(c) most knew that energy enters with sunlight, but did not state photosynthesis. They knew that it was transferred by feeding through the trophic levels and lost as heat due to respiration. A surprising number incorrectly stated that the energy was recycled and some drew diagrams of the energy flow showing this. In 4(d)(i) most were able to state that the crustacean was a richer source of carbon. An explanation using the data from the diagram was expected. In 4(d)(ii) most were able to present an argument for advantage or disadvantage.
Explain how energy enters, flows through and is lost from marine food chains.
[3]
a. light energy is converted to chemical energy (in carbon compounds/sugars) by photosynthesis ✔
b. (chemical) energy (in carbon compounds) flows by means of feeding/through food chains/webs ✔
c. only (approximately) 10 % of energy is passed to the next trophic level ✔
d. energy released as heat (by respiration) ✔
e. energy is not recycled ✔
f. after death, energy may remain trapped as undigested detritus/fossils/fossil fuels ✔
In 4(a) most were able to state 'respiration' as the answer. 4(b) proved more difficult with fewer stating photosynthesis or absorption of dissolved CO2 or HCO3 from the seawater. Vague answers such as 'carbon in the water' were not credited. In 4(c) most knew that energy enters with sunlight, but did not state photosynthesis. They knew that it was transferred by feeding through the trophic levels and lost as heat due to respiration. A surprising number incorrectly stated that the energy was recycled and some drew diagrams of the energy flow showing this. In 4(d)(i) most were able to state that the crustacean was a richer source of carbon. An explanation using the data from the diagram was expected. In 4(d)(ii) most were able to present an argument for advantage or disadvantage.
Deduce whether jellyfish or crustacea are a richer source of carbon in a food chain.
[1]
crustacean as they have more carbon per unit volume
OR
crustacean as jellyfish has little carbon per total body size ✔
OWTTE.
The conclusion must be supported from the information given.
In 4(a) most were able to state 'respiration' as the answer. 4(b) proved more difficult with fewer stating photosynthesis or absorption of dissolved CO2 or HCO3 from the seawater. Vague answers such as 'carbon in the water' were not credited. In 4(c) most knew that energy enters with sunlight, but did not state photosynthesis. They knew that it was transferred by feeding through the trophic levels and lost as heat due to respiration. A surprising number incorrectly stated that the energy was recycled and some drew diagrams of the energy flow showing this. In 4(d)(i) most were able to state that the crustacean was a richer source of carbon. An explanation using the data from the diagram was expected. In 4(d)(ii) most were able to present an argument for advantage or disadvantage.
Suggest with a reason whether having a large body mass is an advantage or disadvantage for jellyfish.
[1]
a. advantage of large size is ability to eat /catch large prey ✔
b. (advantage as) lower rates of predation of large jellyfish ✔
c. (advantage as) can produce more reproductive cells ✔
d. (disadvantage as) can move slower to escape from predators/capture prey ✔
e. (disadvantage as) needs more energy/nutrients to maintain structure/move/grow ✔
f. (disadvantage as) low surface area to volume ratio and thus possibly difficulty with materials/gas/nutrient exchange ✔
g. (disadvantage as) more prone to mechanical damage during storms ✔
Accept other reasonable answer.
Must say advantage or disadvantage.
In 4(a) most were able to state 'respiration' as the answer. 4(b) proved more difficult with fewer stating photosynthesis or absorption of dissolved CO2 or HCO3 from the seawater. Vague answers such as 'carbon in the water' were not credited. In 4(c) most knew that energy enters with sunlight, but did not state photosynthesis. They knew that it was transferred by feeding through the trophic levels and lost as heat due to respiration. A surprising number incorrectly stated that the energy was recycled and some drew diagrams of the energy flow showing this. In 4(d)(i) most were able to state that the crustacean was a richer source of carbon. An explanation using the data from the diagram was expected. In 4(d)(ii) most were able to present an argument for advantage or disadvantage.