IB Biology SL C4.2 Transfers of Energy and Matter Questions

Practise IB Biology SL C4.2 by tracing energy flow, nutrient cycling, biomass transfer and ecological data across trophic levels.

Exam points

Define ecosystems as open systems exchanging energy and matter, and explain sunlight as the initial source converted to chemical energy by autotrophs.
Trace chemical energy through producers, consumers and decomposers, and construct or interpret food chains and food webs with arrows showing transfer.
Classify autotrophs, heterotrophs, detritivores, decomposers and saprotrophs by carbon source, energy source and digestion, including photo- versus chemoautotrophy.
Explain respiration as chemical-energy release producing ATP and CO2 with heat loss, and deduce trophic levels including omnivory or parasitism.
Construct, calculate and interpret energy pyramids and transfer efficiency using energy units, trophic labels, respiration, heat, uneaten biomass, egestion and excretion.
Explain why respiratory heat cannot be recycled and how inefficient energy transfer limits food-chain length and higher-level biomass.
Distinguish gross and net primary production, calculate productivity with units, and evaluate secondary production, feed conversion and biomass gain.
Construct and interpret carbon-cycle and carbon-budget evidence, identifying stores, fluxes, sinks, sources and CO2 release from biomass or fossil-fuel combustion.
Analyse Keeling-curve data to distinguish long-term atmospheric CO2 rise from seasonal photosynthesis and respiration oscillations.
Trace recycling of carbon and other elements through decomposers, inorganic nutrients and producer uptake, distinguishing matter recycling from one-way energy flow.

Covered syllabus points

C4.2.1—Ecosystems as open systems C4.2.2—Sunlight as principal energy source C4.2.3—Chemical energy flow C4.2.4—Food chains and food webs C4.2.5—Supply to decomposers C4.2.6—Autotrophs as self-feeders C4.2.7—Energy sources C4.2.8—Heterotrophs C4.2.9—Energy release C4.2.10—Trophic levels C4.2.11—Energy pyramids C4.2.12—Energy reductions C4.2.13—Heat loss C4.2.14—Restrictions on trophic levels C4.2.15—Primary production C4.2.16—Secondary production C4.2.17—Carbon cycle diagrams C4.2.18—Carbon sinks and sources C4.2.19—CO₂ release during combustion C4.2.20—Keeling Curve analysis C4.2.21—Dependence between respiration and photosynthesis C4.2.22—Recycling of all chemical elements

[Maximum number: 6]

Describe the movement of energy and nutrients in an ecosystem.

[Maximum number: 7]

Compounds of carbon, hydrogen and oxygen are used to supply and store energy.

Explain how the energy supply in an ecosystem is dependent on sunlight.

[Maximum number: 4]

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.

Crustacean and jellyfish silhouettes compare wet mass in grey with carbon mass in black. Each organism has a grey wet-mass silhouette and a smaller black carbon-mass silhouette; the jellyfish has a much larger grey silhouette.

(a)

State one process that results in the loss of carbon dioxide from a marine organism such as a crustacean or a jellyfish.

[ 1 ]

(b)

Explain how energy enters, flows through and is lost from marine food chains.

[ 3 ]

[Maximum number: 3]

Explain how energy enters, flows through and is lost from marine food chains.

[Maximum number: 2]

The sea snail Nucella ostrina and the sea star Pisaster ochraceus are predators of the mussel Mytilus trossulus. The mussels live on rocks at the edge of the sea and feed on phytoplankton and zooplankton. The zooplankton feed on the phytoplankton.

Nucella ostrina

Pisaster ochraceus

Mytilus trossulus

Groups of 50 mussels were transplanted to an experimental area and protected from predation until the start of the experiment. Researchers then investigated the effect of the predators on the population of the mussels over a period of 60 days.

The sea star also eats the sea snails. Construct a food web to show the feeding relationships between these five organisms in the ecosystem.

[Maximum number: 2]

Food chains combine to form food webs in an ecosystem.

Describe the role of decomposers in ecosystems.

[Maximum number: 1]

Food chains combine to form food webs in an ecosystem.

Define the term autotroph.

[Maximum number: 1]

What is the energy source of photoautotrophs and chemoautotrophs?

They both use light only.

They both use oxidation reactions only as an external energy source.

Photoautotrophs use oxidation reactions, while chemoautotrophs use light.

Photoautotrophs use light, while chemoautotrophs use oxidation reactions.

[Maximum number: 1]

Which of the following trophic groups include fungi?

Detritivores

Autotrophs

Saprotrophs

Producers

[Maximum number: 1]

State one process that results in the loss of carbon dioxide from a marine organism such as a crustacean or a jellyfish.

[Maximum number: 1]

A terrestrial food web is shown.

How many species in the food web are only primary consumers?

[Maximum number: 3]

The following table shows the approximate production of organisms living in a salt marsh in the USA.

Construct a pyramid of energy showing the trophic levels for this salt marsh.

Figure for Answer to Question 12 — IB Biology SL

Correct shape of pyramid with base larger than primary consumer and secondary consumer smaller than the rest.
Pyramid proportions very close to 80:10:1 / correctly labelled values with units: 24000, 3000 and $300\ \mathrm{kJm}^{-2}\mathrm{y}^{-1}$ .
Correctly labelled levels.

[Maximum number: 3]

Food chains combine to form food webs in an ecosystem.

The efficiency of energy transfer along the various food chains in a food web varies. Suggest reasons for the differences.

[Maximum number: 1]

What is lost between trophic levels in ecosystems and cannot be recycled?

Heat

Nitrogen

Carbon compounds

Biomass

[Maximum number: 3]

The image shows an example of a soil food web.

Explain the reasons for food chains rarely containing more than four or five trophic levels.

[Maximum number: 1]

Calculate the gross production of an aquatic ecosystem that has a net primary production of $96 \mathrm{~kJ} \mathrm{~m}^{-2} \mathrm{y}^{-1}$ and a respiration rate of $45 \mathrm{~kJ} \mathrm{~m}^{-2} \mathrm{y}^{-1}$ , giving the units.

$\quad(=96+45)=141 \mathrm{~kJ} \mathrm{~m}^{-2} \mathrm{yr}^{-1}$

[Maximum number: 2]

The food conversion ratio (FCR) is the ratio between the mass of food given to a farmed animal and its corresponding increase in mass. The first bar chart shows the FCR for four farmed animals. The second bar chart shows the percentage yield of edible meat provided by each whole animal.

(a)

Calculate the increase in mass of a cow given 6 kg of food.

kg

[ 1 ]

(b)

Calculate how much food would be required to produce 20 kg of boar meat.

kg

[ 1 ]

[Maximum number: 1]

The diagram represents the carbon cycle.

Which arrows represent respiration?

R and V

T and Y

U and Z

W and X

[Maximum number: 1]

Carbon sinks are any reservoirs that absorb and store carbon dioxide from the atmosphere. Which process increases the size of the carbon sink in oceans?

Photosynthesis

Respiration

Ocean acidification

Decomposition

[Maximum number: 4]

There were widespread and intense wildfires in Southeast Australia during the summer season from November 2019 to January 2020. Estimates have been made of carbon dioxide emissions from these fires based on satellite monitoring data. The bar chart shows estimates made by five different research programmes: GFED, GFAS, QFED, FEER and FINN.

Bar chart of estimated CO₂ emissions from southeastern Australian wildfires in teragrams, comparing GFED, GFAS, QFED, FEER and FINN research programmes; patterns distinguish the five bars.

The table shows other statistics for comparison.

CO₂ comparison table in Tg: mean annual Australian wildfire emissions 410; annual Australian fossil-fuel emissions 402; previous mean November–January southeastern Australian wildfire emissions 9; mean of five November 2019–January 2020 wildfire estimates 715.

2019-2020 constrained by satellite. Nature (597), pp. 366-369. https://doi.org/10.1038/s41586-021-03712-y.]

(a)

The highest estimate of $\mathrm{CO}_{2}$ emitted from wildfires in Southeast Australia between November 2019 and January 2020 is 820 Tg , from the FEER research programme. State the lowest estimate.

Programme:
Estimate:

[ 1 ]

(b)

Using the data in the table, comment on the magnitude of the wildfires in Southeast Australia from November 2019 to January 2020.

In addition to carbon dioxide, carbon monoxide and other gases, the wildfires emitted smoke. Smoke is an aerosol of solid particles and liquid droplets suspended in air. The complex mixture of chemicals in this aerosol includes black carbon (soot) and compounds of nitrogen, phosphorus and iron. This aerosol absorbs light, allowing its optical density and movement to be assessed by satellite monitoring.

Much of the smoke from the wildfires in Southeast Australia in 2019-2020 was carried eastwards across the South Pacific Ocean. The study area shown in the map was affected by the smoke.

Map from Australia across the South Pacific to South America, with smoke shading and a boxed study area near 40–50°S east of Australia.

Australian wildfires. Nature (597), pp. 370-375. https://doi.org/10.1038/s41586-021-03805-8.]

The graph shows the optical density of the air and the chlorophyll concentrations of the water in this study area. The concentration of chlorophyll is proportional to the density of phytoplankton (photosynthetic bacteria and algae) in the water.

Daily measures of aerosol optical density (AOD)
8-day mean chlorophyll concentration in 2019-2020

Time series from September 2019 to March 2020 compares daily aerosol optical density as bars, 2019–2020 eight-day mean chlorophyll as a stepped solid line and previous-year chlorophyll means as a dashed line. Chlorophyll and AOD use separate vertical scales.

Key:

[ 3 ]

a. larger than annual ( $\mathrm{CO}_{2}$ ) emissions for the whole of Australia;
b. larger than all fossil fuel emissions for the whole of Australia in a typical year;
c. extreme/intense/OWTTE;
d. (much) larger than the typical emissions of 9 Tg (for Nov to Jan) in SE Australia;

[Maximum number: 1]

What do records from the twentieth and twenty-first century show about the concentration of carbon dioxide in the atmosphere?

An upward trend with annual fluctuations

An upward trend with no annual fluctuations

Annual fluctuations but no overall trend

Random fluctuations and no overall trend

[Maximum number: 1]

Plants produce carbon dioxide in respiration and use carbon dioxide in photosynthesis. The graph shows the volume of carbon dioxide exchanged in a plant at different light intensities.

Carbon dioxide exchange plotted against light intensity. W lies below zero at zero light, X marks the zero crossing, Y marks the start of the plateau and Z lies farther along the plateau.

What is shown by the graph?

There is no photosynthesis between W and X .

There is no photosynthesis between Y and Z .

There is more respiration than photosynthesis between Y and Z .

There is more respiration than photosynthesis between W and X .

[Maximum number: 2]

The bar chart shows the mass of animal feed required to produce one kilogram of meat, egg or milk (kg dry matter in feed per kg of output).

Feed conversion ratio / kg dry matter in feed per kg of output

Outline two ways in which agricultural production of animals may change the cycling of nutrients (for example phosphorus or nitrogen) in ecological systems.

All question bank results loaded

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

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

a	energy is lost between the trophic levels;
b	transfer between levels is only usually 10% efficient OR energy transformations take place in living organisms / the process is never 100% efficient;
c	energy is lost by the organism/used in respiration/released as heat/movement;
d	energy is lost as waste/feces/urine/undigested food/uneaten parts;
e	as energy is lost between trophic levels, higher ones have less biomass / less biomass available for the next level;

a	animals remove nutrients from systems by feeding/being eaten;
b	nutrients added to systems by fertilizers/manure;
c	fertilizer/manure/organic matter run-off can affect other ecosystems;
d	deforestation results in leaching/loss of nutrients;
e	pesticides may affect decomposers;

a	(aerobic/cellular) respiration;
b	gas exchange / diffusion;

a	(aerobic/cellular) respiration;
b	gas exchange / diffusion;

Covered syllabus points

Question 1

Question 2

Question 3

Question (a)

Question (b)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14

Question 15

Question 16

Question 17

Question (a)

Question (b)

Question 18

Question 19

Question 20

Question (a)

Question (b)

Question 21

Question 22

Question 23