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2806/01
ADVANCED GCE
BIOLOGY
Unifying Concepts in Biology
WEDNESDAY 24 JANUARY 2007
Morning
Time: 1 hour 15 minutes
Additional materials:
Electronic calculator
Ruler (cm/mm)
INSTRUCTIONS TO CANDIDATES
•
•
•
•
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Write your name, Centre Number and Candidate Number in the boxes above.
Answer all the questions.
Use blue or black ink. Pencil may be used for graphs and diagrams only.
Read each question carefully and make sure you know what you have to do before starting your answer.
Do not write in the bar code.
Do not write outside the box bordering each page.
WRITE YOUR ANSWER TO EACH QUESTION IN THE SPACE PROVIDED. ANSWERS WRITTEN
ELSEWHERE WILL NOT BE MARKED.
FOR EXAMINER’S USE
INFORMATION FOR CANDIDATES
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•
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The number of marks for each question is given in brackets [ ] at the end of
each question or part question.
You will be awarded marks for the quality of written communication where
this is indicated in the question.
You may use an electronic calculator.
You are advised to show all the steps in any calculations.
Qu.
Max.
1
11
2
16
3
13
4
8
5
12
TOTAL
60
Mark
This document consists of 15 printed pages, 1 blank page and an insert.
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Answer all the questions.
1
(a) Fig. 1.1 shows the percentage of deaths from cancer in the UK attributed to some environmental
and behavioural factors.
30
25
20
percentage of
deaths from cancer
15
30
25
15
10
6
5
5
5
2
2
1
0
factor
Fig. 1.1
(i)
Calculate the percentage of deaths from cancer that are attributed to environmental and
behavioural factors.
Answer = ..................................................... % [1]
(ii)
Suggest and comment on another risk factor that may account for the remaining
percentage of deaths from cancer.
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..................................................................................................................................... [2]
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The effect of diet on cancer mortality is partly due to its effect on obesity. Obesity is defined as
having a Body Mass Index (BMI) over 24.9. BMI is calculated by the following formula.
BMI =
body mass (kg)
height (m)2
Fig. 1.2 shows the effect of BMI on the relative risk of dying from cancer. Non-obese people with a
BMI of 18.5–24.9 are assigned a baseline risk of 1.
2.0
men
women
relative
risk
of death
from cancer
1.5
1.0
0.5
0.0
18.5-24.9
25.0-29.9 30.0-34.9 35.0-39.9
≥40.0
BMI
Fig. 1.2
(b) (i)
Calculate the BMI of a woman 1.7 m tall with a mass of 105 kg.
Answer = ......................................................... [2]
(ii)
Use Fig. 1.2 to explain the likelihood of this woman dying from cancer.
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(c) One type of cancer that has a link to obesity is breast cancer. Increased concentration of
the hormone oestrogen increases the likelihood of developing breast cancer. Oestrogen is
secreted by the ovaries and by cells that store fat. Oestrogen concentration drops at the time
of the menopause.
(i)
Predict the relationship between age at onset of menopause and the incidence of breast
cancer.
...........................................................................................................................................
...........................................................................................................................................
..................................................................................................................................... [1]
(ii)
After the menopause, the ovaries of women stop producing oestrogen. However, cells
that store fat continue to produce low quantities of oestrogen.
Sketch on the axes provided a straight line to predict the relationship between BMI and
the risk of developing breast cancer after the menopause.
[1]
risk of
breast cancer
in women after
the menopause
BMI
(d) The low concentration of oestrogen after the menopause causes some problems however,
including an increased risk of osteoporosis. Hormone Replacement Therapy (HRT) is one
way of preventing this. A patch fixed to the skin releases oestrogen into the blood. Oestrogen
is a steroid hormone that is classified as a lipid.
Explain how oestrogen is able to travel from the skin patch into the blood.
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[Total: 11]
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2
All organisms can be classified according to where they get their energy and the element carbon.
Table 2.1 shows the four forms of nutrition (photoautotrophic, photoheterotrophic, chemoautotrophic,
chemoheterotrophic) that are possible. A number of different bacteria (kingdom Prokaryotes) are
shown in the table to identify their forms of nutrition.
Table 2.1
CARBON SOURCE
light
(phototrophic)
carbon dioxide
(autotrophic)
organic carbon
(heterotrophic)
photoautotrophic
photoheterotrophic
................................
ENERGY
SOURCE
purple non-sulphur
bacteria
cyanobacteria
chemical reactions
(chemotrophic)
chemoautotrophic
nitrifying bacteria
chemoheterotrophic
................................
saprophytic bacteria
(a) Complete Table 2.1 with the names of two other kingdoms. Write your answers on the
dotted lines in the shaded boxes.
[2]
(b) Explain why organisms need to obtain energy and carbon.
energy .......................................................................................................................................
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carbon .......................................................................................................................................
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(c) Nitrifying bacteria are chemoautotrophs. Some nitrifying bacteria gain energy from converting
nitrite ions (NO2–) to nitrate ions (NO3–).
Explain how the activity of these bacteria affects the growth of plants in an ecosystem.
...................................................................................................................................................
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............................................................................................................................................. [2]
Bacteria are metabolically very diverse and show all four forms of nutrition identified in Table 2.1.
This diversity can be shown in a simple piece of apparatus called a Winogradsky column.
A glass tube, 30 cm tall and 5 cm in diameter, is set up with the lower third containing river mud,
some shredded newspaper as a source of cellulose, and the minerals sodium sulphate and
calcium carbonate. The top two-thirds of the column is filled with river water and the tube is sealed
and placed under a bright light source. After three months different types of bacteria establish
themselves in zones.
Fig. 2.1, on an insert, shows some chemical changes occurring in a Winogradsky column containing
six types of bacteria.
Fig. 2.2, also on the insert, gives more details of the metabolic activities of the six types of
bacteria.
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(d) Use the information given in Figs. 2.1 and 2.2, and in Table 2.1 (on page 5) to identify the forms
of nutrition of
(i)
Clostridium and Desulfovibrio ...................................................................................... [1]
(ii)
green sulphur bacteria ................................................................................................ [1]
(e) (i)
Name the element that is being recycled in Fig. 2.2.
..................................................................................................................................... [1]
(ii)
Use Fig. 2.1 to describe how two named types of bacteria recycle sulphur in the
Winogradsky column.
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...........................................................................................................................................
..................................................................................................................................... [2]
(f)
Unusual communities of animals are found deep in the ocean in warm, sulphur-rich water.
Use the information given in Figs. 2.1 and 2.2 to suggest which type of bacteria is the producer
at the base of food chains in these communities.
............................................................................................................................................. [1]
(g) Gas gangrene is a condition caused by the bacterium Clostridium perfringens.
Suggest why gas gangrene only occurs in severely damaged tissue where blood supply is
restricted.
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[Total: 16]
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BLANK PAGE
PLEASE DO NOT WRITE ON THIS PAGE
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3
Hummingbirds are very small. Typically their mass is between 3 and 5 g. They are able to hover at
a fixed point in the air by beating their wings very rapidly. The rufous hummingbird, Selasphorus
rufus, is a migratory species. It breeds in Canada and Alaska in the summer, migrates south to
Mexico in the autumn and returns to high latitudes in spring after completing its annual moult (loss
of feathers, which are then re-grown).
(a) Suggest why the rufous hummingbird has a very high requirement for energy.
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In order to save energy, rufous hummingbirds can enter a state called torpor during the night. This
is when their metabolic rate and body temperature both drop to a very low level. An investigation
into how rufous hummingbirds use, save and store energy at different times of year was carried
out. Key findings of the study are given in Figs. 3.1, 3.2 and 3.3 on page 10.
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resting at
normal body
temperature
resting in a
state of torpor
100
20
80
18
16
60
percentage
of nights on
which torpor
occurred 40
14
12
mean oxygen
consumption 10
/ cm3 g–1 h–1
8
6
20
4
2
0
0
autumn spring summer
autumn
season
Fig. 3.1
spring summer
season
Fig. 3.2
5.0
4.5
x
x
mean
body
mass / g
4.0
x
x
x
x
x
x
3.5
x
x
x
x
x
3.0
migration
moulting
autumn
spring
summer
2.5
Aug Sept Oct Nov Dec Jan Feb Mar
month
Fig. 3.3
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Jul
Aug
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•
Fig. 3.1 shows how use of torpor by the birds varies according to season.
•
Fig. 3.2 compares the oxygen consumption of birds resting at normal body temperature with
that of birds resting in a state of torpor.
•
Fig. 3.3 shows how body mass of the birds changes over the course of a year.
(b) Use Figs. 3.1, 3.2 and 3.3 to describe and explain the results for the birds in the
September-October (autumn) period.
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(c) Suggest how the low body mass of the birds in spring may be related to enhancing the birds’
survival during the moulting period, when the feathers are lost and regrown.
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(d) It is suggested that smaller birds, which have a larger surface area to volume ratio when
compared to larger birds, require more oxygen per gram of their body mass.
Discuss whether the data given in Figs. 3.1, 3.2 and 3.3 support this hypothesis.
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[Total: 13]
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4
In this question, one mark is available for the quality of spelling, punctuation and grammar.
Some of the key physiological areas of a mammal are the:
•
blood
•
alveoli
•
gut
•
kidney.
Fig. 4.1 shows some of the pathways where biochemicals are exchanged between these areas,
the tissue fluid (extracellular fluid) and a liver cell.
gut
lumen
alveoli
blood
tissue fluid
liver
cell
tissue fluid
kidney
Fig. 4.1
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Use the diagram to describe how these exchange pathways function to maintain relatively constant
concentrations of biochemicals in the liver cell.
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Quality of Written Communication [1]
[Total: 8]
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5
The bulb of the onion plant, Allium cepa, is widely used in food preparation. It has a strong smell
and flavour when raw due to sulphur-containing chemicals that are released when an onion is cut.
The precursor of these flavour molecules is in the cytoplasm of the onion bulb cells. This precursor
is acted on by an enzyme called alliinase, which is stored in the cell vacuole. Alliinase breaks the
precursor molecule into two volatile flavour molecules, which enter the air, and into a third product,
pyruvate, which remains dissolved in the onion tissue.
(a) Explain why the strong smell of an onion is only released when the onion is cut or damaged.
...................................................................................................................................................
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The strength of an onion’s flavour can be estimated by measuring the concentration of pyruvate in
cut onions. Table 5.1 shows the pyruvate concentration of fresh onions, onions from the previous
season that have overwintered, and onions of a new variety called Supasweet.
Table 5.1
type of onion
pyruvate
concentration / mol g–1
fresh
7
overwintered
4
Supasweet
3
(b) Suggest why the concentration of pyruvate is lower in an overwintered onion.
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(c) The mild Supasweet onions were produced by a process of artificial selection. The growing
environment also needs to be manipulated to decrease the concentration of flavour
molecules.
(i)
Explain how artificial selection was used to produce the mild Supasweet onions.
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(ii)
Use the information given about the biochemistry of the onion smell and flavour to
suggest an environmental change that would enable a milder onion to be grown.
...........................................................................................................................................
..................................................................................................................................... [1]
(d) It is claimed that strong onions, with a more pungent smell and flavour, are able to resist
rotting over the winter better than milder onions.
Describe how you would test this claim.
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............................................................................................................................................. [3]
[Total: 12]
END OF QUESTION PAPER
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PLEASE DO NOT WRITE ON THIS PAGE
Copyright Acknowledgements:
Figs. 1.1 & 1.2
Figs. 3.1, 3.2 & 3.3
Fig. 4.1
Q.5 adapted text and
Fig. 5.1 adapted table
© National Obesity Forum, www.nationalobesityforum.org.uk Reproduced by kind permission of the National Obesity Forum
© Sara Hiebert, Hummingbird Torpor and Body Mass, from The Auk, vol. 110, October 1993.
Reproduced by kind permission of Sara Hiebert
© Pat Wilmer, Graham Stone, Ian Johnston, Environmental Physiology of Animals, Blackwell Science, 2000
© Dr Meriel Jones, Biological Sciences Review, Feb 2005. Reproduced by kind permission of Philip Allan Publishers Ltd
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every
reasonable effort has been made by the publisher (OCR) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the
publisher will be pleased to make amends at the earliest possible opportunity.
OCR is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES),
which is itself a department of the University of Cambridge.
© OCR 2007
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2806/01
ADVANCED GCE
BIOLOGY
Unifying Concepts in Biology
INSERT
WEDNESDAY 24 JANUARY 2007
Morning
Time: 1 hour 15 minutes
INSTRUCTIONS TO CANDIDATES
•
This insert contains Fig. 2.1 and Fig. 2.2.
This insert consists of 4 printed pages.
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*
cyanobacteria
6CO2 + 6H2O C6H12O6 + 6O2
AEROBIC
WATER
colourless sulphur bacteria
gain energy from oxidation of H2S
to convert CO2 C6H12O6
*
purple non-sulphur bacteria
ANAEROBIC
WATER
*
green sulphur bacteria
6CO2 + 6H2S C6H12O6 + 6S
Desulfovibrio
ANAEROBIC
SEDIMENT
Clostridium difficile
Arrows show flow of:
organic acids
hydrogen sulphide
sulphur
Bacteria marked
* depend on light for their metabolism.
Fig. 2.1
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3
cellulose
Clostridium difficile
glucose
colourless sulphur bacteria
green sulphur bacteria
cyanobacteria
*
*
Clostridium difficile
organic acids
CO2
Desulfovibrio
purple non-sulphur bacteria
*
Bacteria marked
* depend on light for their metabolism.
Fig. 2.2
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Copyright Acknowledgements:
Fig. 2.1 adapted diagram
© Jim Deacon, http://helios.bto.ed.ac.uk/bto/microbes/winograd.htm Reproduced by kind permission of the Institute of Cell and
Molecular Biology, University of Edinburgh.
Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every
reasonable effort has been made by the publisher (OCR) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the
publisher will be pleased to make amends at the earliest possible opportunity.
OCR is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES),
which is itself a department of the University of Cambridge.
© OCR 2007
2806/01 (Insert) Jan07