Feversham College
A-level Biology (7401/7402)
Name:
Class:
Section 5 Practical Skills
Author:
Date:
Time:
141
Marks:
109
Comments:
Page 1
Feversham College
Q1.
S
The diagram shows apparatus used to measure the oxygen uptake of snails that live on the
seashore. The apparatus was kept at a constant temperature.
(a)
(i)
Explain the purpose of the strip of filter paper in the potassium hydroxide solution.
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(1)
(ii)
The level of liquid in the right-hand side of the manometer went down during the
experiment. Explain why.
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(2)
(iii)
What measurements are needed to calculate the rate of oxygen uptake by the
snails in mm3 g–1 h–1?
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(3)
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(b)
Two experiments were carried out using the apparatus shown in the diagram.
1
The oxygen uptake of batches of 10 seashore snails kept in moist air was measured
at temperatures between 5 °C and 35 °C.
2
Experiment 1 was repeated but with batches of 10 seashore snails covered by
aerated seawater.
The experiments were repeated several times and means and standard deviations
calculated. The results are shown in the table. The values given are means plus or minus
one standard deviation.
Temperature / °C
Oxygen uptake of
snails kept in moist
air / mm3 g–1 h–1
Oxygen uptake of
snails kept in
seawater / mm3 g–1 h–1
5
35 ± 2
28 ± 8
10
34 ± 6
32 ± 3
15
36 ± 3
35 ± 3
20
86 ± 8
52 ± 10
25
141 ± 13
96 ± 15
30
132 ± 14
108 ± 9
35
120 ± 16
79 ± 21
(i)
Describe one similarity and one difference between the pattern of mean oxygen
uptake of the snails kept in moist air and those covered by seawater.
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(2)
(ii)
Explain why valid conclusions cannot be drawn about the trends in oxygen uptake at
temperatures of 25 °C and above.
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(2)
(Total 10 marks)
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Q2.In some countries, pigs are reared in intensive units in which the temperature is controlled.
Agricultural
scientists investigated the effect of temperature on pig growth and on the efficiency with which the
pigs
converted food to biomass.
(a)
(i)
In the investigation, the scientists used pigs of the same breed, with similar
genotypes.
Explain why.
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(2)
(ii)
The pigs were allowed to eat as much food as they wanted.
How could this have decreased the reliability of any conclusions drawn from the
investigation?
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(2)
The table shows the results of this investigation.
Temperature / °C
Mean growth rate /
kg per day
Efficiency of conversion of
food to biomass /%
0
0.54
19
10
0.80
42
20
0.85
48
30
0.45
37
35
0.31
37
(b)
(i)
Describe the effect of temperature on mean growth rate.
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(1)
(ii)
A student concluded from these data that the mean growth rate of the pigs was
fastest at 20 °C.
Do you agree with this conclusion? Explain your answer.
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(2)
(c)
(i)
Pigs can survive at temperatures above 35 °C. Use the data to suggest why
scientists did not
carry out any investigations at temperatures higher than 35 °C.
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(2)
(ii)
The efficiency of conversion of food to biomass is lower at 0 °C than it is at 20 °C.
Suggest an explanation for the lower efficiency.
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(2)
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Feversham College
(d)
Pigs require a mixture of fibre and protein in their food. The greater the ratio of fibre to
protein, the less
the food costs.
Scientists took five large groups of pigs. They fed each group a different high-fibre food.
Each of the foods contained fibre from different plant species, but they all had the same
energy content. The scientists fed a control group of pigs a low-fibre food with the same
energy content. After 10 days, the scientists compared
the masses of the pigs fed on high-fibre food to those fed on low-fibre food.
The graph shows the results of the investigation. The bars represent ±2 standard errors of
the mean.
A farmer saw these results and concluded that he should replace his pigs’ usual food with
food B.
Evaluate this conclusion.
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(Extra space) .................................................................................................
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(4)
(Total 15 marks)
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Q3.
Gas exchange in an aquatic plant was investigated by placing shoots in tubes containing
bromothymol blue indicator solution. Bromothymol blue indicator is yellow below pH 6, green
between pH 6.1 and 7.5, and blue at pH 7.6 and above. Into each of four tubes, A, B, C and D,
10 cm3 of bromothymol blue solution were placed. Each tube was closed with a bung and left for
10 minutes. Similar-sized shoots of an aquatic plant were then placed into each of tubes A, B and
C. The tubes were treated as shown in the diagram.
They were then placed at equal distances from a 60 watt lamp and left for one hour.
The table shows the initial and final colours of the indicator in the four tubes.
Tube
Treatment
Initial colour of
indicator
Colour of indicator
after one hour
A
Uncovered
Green
Blue
B
Covered with black paper
Green
Yellow
C
Covered with muslin
Green
Green
D
Uncovered
Green
Green
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(a)
Explain the results for
tube A;
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tube B;
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tube C.
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(4)
(b)
(i)
Explain how the results from tube D help to confirm that the explanations for the
other tubes are valid.
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(1)
(ii)
Explain why all the tubes were placed the same distance from the lamp.
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(1)
(Total 6 marks)
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Feversham College
Q4.
The percentage of light absorbed by an aquatic plant was measured when it was exposed to
different wavelengths. The rate of photosynthesis was also measured at each wavelength of light.
The results are shown in the graph.
(a)
Describe and explain the relationship between light absorption and the rate of
photosynthesis for the wavelengths of light between 410 nm and 500 nm.
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(2)
(b)
Give one dependent variable you could measure in order to determine the rate of
photosynthesis in an aquatic plant.
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(1)
(c)
Use the graph to identify the range of wavelengths of light that would be green in colour.
Give a reason for your answer.
Wavelengths ................... to ................... nm
Reason ........................................................................................................
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(2)
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Feversham College
(d)
A suspension of chloroplasts was isolated from an aquatic plant and a reagent was added.
The reagent is blue when oxidised and is colourless when reduced.
(i)
The suspension of chloroplasts in blue reagent was exposed to sunlight. The blue
colour disappeared. Use your knowledge of the light-dependent reactions of
photosynthesis to explain why.
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(2)
(ii)
Another suspension of chloroplasts was set up as before. Small quantities of ADP
and phosphate ions were added and then the tube was exposed to light. The blue
colour disappeared more quickly. Explain why.
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(2)
(Total 9 marks)
Q5.
Detritivorous insects feed on the dead remains of plants. Some students estimated the
numbers of detritivorous insects at two different sites in an ecosystem. They also obtained data
about the net primary production of the sites to see if this influenced the numbers of insects
present. Net primary production is a measure of plant biomass formed per year. The results are
shown in the table.
Site
Number of insects
per m2
Net primary production /
g m–2 y–1
A
316
1440
B
90
550
(a)
Explain how the students could use the mark-release-recapture technique to estimate the numbers of
insects.
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(4)
(b)
The students used the chi-squared (χ2) test to test the hypothesis that there was no
significant difference between the numbers of insects per square metre at sites A and B.
The value they obtained was 125.8. They checked this value in χ2 tables.
(i)
How many degrees of freedom should they check against?
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(1)
(ii)
What level of probability is normally used to judge whether a difference is statistically
significant?
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(1)
(iii)
The value of χ2 for the 0.001 level of probability for this number of degrees of
freedom is 10.8. What does the value obtained by the students suggest about the
difference in numbers of the insects per square metre between the two sites?
Explain your answer.
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(2)
(c)
(i)
Explain why the net primary production of an area does not represent the total
amount of plant biomass formed per year by photosynthesis.
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(2)
(ii)
Suggest how the difference in net primary production of sites A and B might explain
the difference in the number of insects between the sites.
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(1)
(Total 11 marks)
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Feversham College
Q6.
Ions of metals such as zinc often pollute rivers. The effect of zinc ions on gas exchange and
respiration in fish was investigated. Fish were kept in tanks of water in a laboratory.
The fish in one group (X) had a solution of a zinc compound injected directly into their blood and
were then put in a tank of zinc-free water. A second group (Y) was not injected but had the
solution of the zinc compound added to the water in the tank.
The partial pressure of oxygen in the blood of both groups of fish was then monitored. The results
are shown in the graph.
(a)
During this investigation, the water temperature in the tanks was kept constant. Explain
why changes in the water temperature might lead to the results of the investigation being
unreliable.
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(1)
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Feversham College
(b)
The results from the two groups were compared using a statistical test.
(i)
Suggest a null hypothesis that could be tested.
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(1)
(ii)
Explain why it is important to use a statistical test in analysing the results of this
investigation.
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(2)
(c)
Two suggestions were made to explain the results shown in the graph.
A
Zinc ions reduce the rate at which oxygen is taken up from the water and
passes into the blood.
B
Zinc ions reduce the ability of haemoglobin to transport oxygen.
Which of these suggestions is the more likely? Explain the evidence from the graph
that supports your answer.
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(2)
(d)
During the investigation, the pH of the blood was also monitored. It decreased in group Y.
Suggest an explanation for this decrease in pH.
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(3)
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Feversham College
(e)
Leaves were collected from sycamore trees growing in a polluted wood and the
concentration of some metal ions in samples of these leaves was measured. Woodlice
were then fed with the leaves. After 20 weeks, the concentration of the ions in the bodies of
the woodlice was measured. Some of the results are shown in the table.
Concentration of ions / µg g–1
Leaves
Woodlice
(i)
Copper
Cadmium
Zinc
Lead
52
26
1430
908
1130
525
1370
132
Which of the elements shown in the table is concentrated most by the woodlice? Use
suitable calculations to support your answer.
(2)
(ii)
Suggest what happens to most of the lead ions in the leaves eaten by the woodlice.
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(1)
(iii)
Explain the difference in the copper ion concentration between the leaves and the
woodlice.
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(2)
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Feversham College
(f)
Yorkshire fog is a species of grass. Two varieties of Yorkshire fog were studied. One
variety was tolerant to arsenic, while the other variety was not. In a series of investigations,
it was found that
•
Arsenic-tolerant plants grow in soil which contains a high concentration of arsenic.
•
Arsenic-tolerant plants growing in soil containing high concentrations of arsenic and
phosphorus-containing compounds have very low concentrations of arsenic in their
cells. They also have low concentrations of phosphates in their cells. Arsenic and
phosphorus are chemically similar.
•
Plants that are not tolerant to arsenic grow poorly on soil which has a high
concentration of both arsenic and phosphorus-containing compounds.
•
Tolerance to arsenic in Yorkshire fog is caused by a single gene with the allele, a, for
tolerance recessive to the allele, A, for non-tolerance.
(i)
What caused the allele for tolerance to first arise?
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(ii)
Give two functions of phosphates in plant cells.
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(2)
(iii)
Arsenic-tolerant Yorkshire fog plants are very rare in areas with low concentrations
of arsenic in the soil, even where the soil has a high concentration of phosphate.
Explain why they are unable to compete in these conditions with plants that are not
tolerant to arsenic.
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(3)
(Total 20 marks)
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Feversham College
Q7.
A scientist investigated the uptake of radioactively labelled carbon dioxide in chloroplasts.
She used three tubes, each containing different components of chloroplasts. She measured the
uptake of carbon dioxide in each of these tubes.
Her results are shown in the table.
Tube
Contents of tube
Uptake of radioactively
labelled CO2 /
counts per minute
A
Stroma and grana
96 000
B
Stroma, ATP and reduced NADP
97 000
C
Stroma
4 000
(a)
Name the substance which combines with carbon dioxide in a chloroplast.
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(1)
(b)
Explain why the results in tube B are similar to those in tube A.
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(1)
(c)
Use the information in the table to predict the uptake of radioactively labelled carbon
dioxide if tube A was placed in the dark. Explain your answer.
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(2)
(d)
Use your knowledge of the light-independent reaction to explain why the uptake of carbon
dioxide in tube C was less than the uptake in tube B.
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(2)
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Feversham College
(e)
DCMU is used as a weed killer. It inhibits electron transfer during photosynthesis. The
addition of DCMU to tube A decreased the uptake of carbon dioxide. Explain why.
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(2)
(Total 8 marks)
Q8.A student investigated the effect of different wavelengths of light on the rate of photosynthesis. She
used the apparatus shown in Figure 1.
Figure 1
(a)
What measurements should the student have taken to determine the rate of
photosynthesis?
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(1)
(b)
Other than temperature and pH, give two factors which should be kept constant during
this investigation.
1 .....................................................................................................................
2 .....................................................................................................................
(2)
(c)
The student did not use a buffer to maintain the pH of the solution.
Explain what would happen to the pH of the solution during this investigation.
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(2)
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Feversham College
(d)
Figure 2 shows the student’s results.
Figure 2
Suggest and explain why the rate of photosynthesis was low between 525 nm and 575 nm
wavelengths of light.
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[Extra space] ................................................................................................
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(2)
(Total 7 marks)
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Feversham College
Q9.Plants have pigments that absorb light energy for photosynthesis. These pigments include two
types of chlorophyll and a group of pigments known as carotenoids. Different species of plant
contain different amounts of these pigments. The pigments that each plant species has are
adaptations to where and how they live; their ecological niche.
Figure 1 shows the absorption of light of different wavelengths by chlorophyll a, chlorophyll b and
carotenoids.
Figure 1
A scientist investigated the energy in light of different wavelengths reaching the ground in a
forest. She measured the energy in
•
•
direct sunlight
sunlight that had passed through the leaves of trees.
Figure 2 shows her results.
Figure 2
Beech trees have two types of leaves called sun leaves and shade leaves. Sun leaves grow on
branches exposed to direct sunlight, shade leaves grow on branches exposed to light that has
passed through leaves. An ecologist collected sun leaves and shade leaves from beech trees and
determined the mean mass of each photosynthetic pigment in both types of leaf. His results are
shown in Figure 3.
Figure 3
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Feversham College
Mean mass of each pigment per m2 of leaf
area / μg (± standard deviation)
Photosynthetic pigment
Sun leaves
Shade leaves
Chlorophyll a
299.3 (± 2.1)
288.9 (± 0.1)
Chlorophyll b
90.7 (± 2.1)
111.1 (± 0.1)
Carotenoids
(a)
0.10 (± 0.01)
0.07 (± 0.01)
It is an advantage to beech trees to produce more chlorophyll b in the shade leaves.
Suggest and explain why.
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(2)
(b)
There are two hypotheses about the advantage to plants of producing carotenoids.
Hypothesis 1
Carotenoids help shade leaves to absorb more light of wavelengths 480 nm to 520nm for
photosynthesis.
Hypothesis 2
Carotenoids prevent damage to chlorophyll from very bright light.
(i)
Which hypothesis do the data provided on the resource sheet support?
Explain your answer.
Hypothesis ....................................
Explanation ............................................................................................
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(2)
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(ii)
Suggest one other piece of experimental evidence you would need in order to be
more confident about drawing your conclusion in (b)(i).
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(1)
(Total 5 marks)
Q10.The figure below shows the apparatus used for measuring the rate of oxygen consumption in
aerobic respiration by seeds.
(a)
For the first 10 minutes, the tap attached to tube A was left open and the syringe from tube
B was removed.
Suggest three reasons why the apparatus was left for 10 minutes.
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(3)
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Feversham College
(b)
Suggest and explain why the chosen temperature was 20 °C for this experiment.
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(2)
After 10 minutes, the tap attached to tube A was closed and the syringe was attached to
tube B. Every minute, the syringe plunger was moved until the levels in the U-tube were the
same. The reading on the syringe volume scale was then recorded.
The results are shown in the table below.
(c)
Time / minutes
Reading on syringe
volume scale / cm3
0
0.84
1
0.81
2
0.79
3
0.76
4
0.73
5
0.70
6
0.68
7
0.66
8
0.63
9
0.62
10
0.58
During the experiment, the coloured liquid in the tubing moved towards tube B.
Explain what caused this.
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Feversham College
(Extra space) ................................................................................................
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(3)
(d)
The mass of the seeds was 1.6 g. Use the information in the table above to calculate the
rate of oxygen consumption in cm3 g–1 hour–1 by the seeds.
Show your working.
Rate = .................................................................................. cm3 g–1 hour–1
(2)
(Total 10 marks)
Q11.A student investigated the rate of anaerobic respiration in yeast. She put 5 g of yeast into a
glucose solution and placed this mixture in the apparatus shown in the figure below.
She then recorded the total volume of gas collected every 10 minutes for 1 hour.
(a)
Explain why a layer of oil is required in this investigation.
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(1)
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Feversham College
(b)
The student’s results are shown in the following table.
(i)
Time / minutes
Total volume of gas
collected / cm3
10
0.3
20
0.9
30
1.9
40
3.1
50
5.0
60
5.2
Calculate the rate of gas production in cm3 g–1 min–1 during the first 40 minutes of this
investigation. Show your working.
Answer = ................... cm3 g–1 min–1
(2)
(ii)
Suggest why the rate of gas production decreased between 50 and 60 minutes.
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(1)
(iii)
Yeast can also respire aerobically. The student repeated the investigation with a fresh
sample of yeast in glucose solution, but without the oil. All other conditions remained
the same.
Explain what would happen to the volume of gas in the syringe if the yeast were only
respiring aerobically.
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(2)
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(c)
Respiration produces more ATP per molecule of glucose in the presence of oxygen than it
does when oxygen is absent. Explain why.
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(2)
(Total 8 marks)
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