1.
The graph below shows variation in the concentration of CO2 in the atmosphere as measured at Mauna
Loa in Hawai’i. The small inset graph shows the variations in CO2 during a one year period.
[Source: adapted from Dr P Tans, NOAA Earth System Research Laboratory]
Why does the amount of CO2 fall between April and August?
A.
Seasonal increase in the rate of photosynthesis in the northern hemisphere forests
B.
Seasonal decrease in the rate of photosynthesis in the northern hemisphere forests
C.
Seasonal decrease in the rate of fossil fuel consumption
D.
Seasonal increase in the amount of CO2 dissolved in the oceans
(Total 1 mark)
2.
Which group of organisms in the carbon cycle converts carbon into a form that is available to primary
consumers?
A.
Decomposers
B.
Saprotrophs
C.
Detritus feeders
D.
Producers
(Total 1 mark)
3.
What are the main sources of carbon dioxide on earth?
A.
Cellular respiration of consumers, producers and combustion of fossil fuels
B.
Photosynthesis and cellular respiration of consumers
C.
Cellular respiration of producers and combustion of fossil fuels
D.
Photosynthesis and combustion of fossil fuels
(Total 1 mark)
IB Questionbank Biology
1
4.
The diagram below shows a simplified version of the carbon cycle.
CO2 in atmosphere
I
II
Fuels
Plants
Secondary
Consumer
Primary
Consumer
What processes are involved in the transfer of carbon at stages I and II?
I
II
A.
combustion
photosynthesis
B.
photosynthesis
respiration
C.
combustion
respiration
D.
fossilization
respiration
(Total 1 mark)
5.
The diagram below shows some of the links in the carbon cycle.
What processes are taking place at I, II and III?
I
II
III
A.
photosynthesis
fossilization
combustion
B.
cell respiration
fossilization
greenhouse effect
C.
photosynthesis
decomposition
combustion
D.
cell respiration
decomposition
greenhouse effect
(Total 1 mark)
IB Questionbank Biology
2
6.
Outline the habitat of methanogens.
anaerobic habitats;
marshes / guts of mammals / oxygen depleted soils;
(2)
7.
Living organisms at every trophic level are part of the carbon cycle. Draw a labelled diagram of the
carbon cycle to show the processes involved.
(9)
Award [1] for each of the following shown on a diagram of the
carbon cycle.
Award [5 max] for points not shown on a diagram.
The following show carbon which is static within the cycle at this
point in time.
carbon dioxide in air/water;
(sugars/carbon compounds in) plants/producers;
(carbon compounds in) animals/consumers;
(carbon trapped in) coal/oil/gas/fossil fuels;
The following should show arrows in direction of carbon flow.
carbon dioxide absorbed by plants/producers and used in
photosynthesis;
carbon dioxide released by (cell) respiration in plants/producers;
plants/producers eaten by animals/primary consumers/herbivores;
primary consumers eaten by secondary consumers;
carbon dioxide released by (cell) respiration in animals/consumers;
plants/animals die and are decomposed by (saprotrophic) bacteria/fungi;
carbon dioxide released by combustion of coal/oil/gas/fossil fuels;
carbon dioxide released by (cell) respiration in bacteria/fungi/
decomposers;
forest fires/combustion releases carbon dioxide from trees/plants;
carbon dioxide emitted by volcanoes;
IB Questionbank Biology
9 max
3
8.
During aerobic cell respiration, oxygen is consumed and carbon dioxide is produced inside cells. This
generates concentration gradients between respiring cells and the environment, which cause diffusion of oxygen
and carbon dioxide. Both oxygen and carbon dioxide are soluble in water. As the temperature rises, water
becomes saturated at a lower concentration of the gas.
The world’s oceans can absorb large amounts of carbon dioxide. This process has been studied in
the Pacific Ocean near Hawaii, by measuring carbon dioxide concentrations in the atmosphere and
in surface water every month, from October 1988 onwards. The graph below shows the carbon
dioxide concentration expressed as partial pressures (Pco2).
[Source: Nature by Nature Publishing Group. Reproduced with permission of Nature Publishing Group in the format Journal via
Copyright Clearance Centre.]
(c)
(i)
Describe the trends in atmospheric carbon dioxide concentration, shown in the graph.
rising trend overall;
annual rise and fall / fluctuations;
(2)
(ii)
Suggest two reasons for the trends that you have described.
(CO2 emissions from) increased burning of fossil fuels/deforestation/ other anthropogenic factor;
variation in photosynthesis rates during the year / variations in CO2 uptake in the oceans;
(2)
(d)
(i)
Diffusion of carbon dioxide only occurs when there is a concentration gradient.
Deduce the pattern of carbon dioxide diffusion, between water and atmosphere, from 1988
to 2002.
diffusion in both directions during each year;
diffusion from atmosphere to water during most of the year;
IB Questionbank Biology
4
diffusion from water to atmosphere for part of year/autumn/fall/seasonal;
increasing diffusion from water to atmosphere in later years; (2)
(ii)
The graph provides evidence for the hypothesis that there will be no net diffusion of carbon
dioxide between water and atmosphere by 2020. Explain this evidence.
(no net diffusion because) concentrations will become equal / there will be no gradient;
water concentration higher than atmospheric concentration as often as atmospheric
concentration higher than water concentration; (1)
The concentration of carbon dioxide in the atmosphere is currently 385 ppm (parts per million).
Variations in the concentration of carbon dioxide in the atmosphere can be studied using ice-cores. An ice-core
record covering the last 400 000 years has been obtained from Vostok in the Antarctic. The graph below shows
the carbon dioxide concentrations that were measured at different depths in the ice. Atmospheric temperatures
are also shown on the graph. These were deduced from ratios of oxygen isotopes. The upper line on the graph
shows CO2 concentrations and the lower line shows temperature.
(e)
(i)
State the highest carbon dioxide concentration shown on the graph.
300 ppm (Allow answers in the range 295–305 ppm) unit must be included to earn mark. (1)
(ii) State the highest temperature shown on the graph.
3.3°C (Allow answers in the range 3.0–3.3°C) unit must be included to earn mark.
N.B. A maximum of [1] per exam can be deducted for a missing unit. (1)
(f)
Using the data in the graph, deduce the relationship between atmospheric carbon dioxide
concentration and temperature.
positive correlation / higher temperature with higher CO2 concentration
(1)
9. There has been a significant increase in the concentration of carbon dioxide in the Earth’s atmosphere
during the last fifty years.
(a)
Suggest two reasons for this increase in atmospheric carbon dioxide concentration.
burning / use of fossil fuels / example;
burning forests;
destruction of autotrophs that fix carbon dioxide / deforestation;
2 max
Do not accept “pollution” unqualified.
IB Questionbank Biology
5
..........................................................................................................................
(2)
(b)
Suggest one effect of an increase in carbon dioxide concentration on organisms in a pond.
Include in your answer the reason for the effect and the type of organisms that are affected.
increased growth / photosynthesis by plants / pond weeds / algae / autotrophs / producer /eutrophication;
carbon dioxide used in photosynthesis / photosynthesis provides raw materials for growth;
effect of lower pH of water on a named type of organism (eg some
plants cannot grow in acidic water);
increased carbon dioxide concentration makes water more acidic;
For those candidates who have interpreted increase in carbon dioxide
concentration to mean atmospheric carbon dioxide, include these marks:
increased atmospheric carbon dioxide leads to global warming;
global warming causes pond warming;
pond warming may promote growth of aquatic vegetation;
pond warming may kill intolerant plant / animal species;
(2)
IB Questionbank Biology
6