A2 Science in Society – answers to chapter 1 questions
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A2 Science in Society
Answers to the questions
Chapter 1 Cells, Chemicals and the Mind
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included
which go beyond the direct requirements of the question.
1
The brain is very complex.
It is difficult to measure the small electrical changes in neurones as they happen.
There are no clear links between the activities of neurones and subjective
experience.
There are ethical issues relating to studying the brains of living mammals.
2
Brain research can improve our understanding of issues such as memory and
learning, aggression and warfare, mental disorders, neurodegenerative diseases
and the effects of drugs. All of these are of crucial importance to human welfare.
3
Infectious diseases are caused by bacteria, viruses, protoctista or fungi. These are
termed pathogens and are transmitted from person to person causing diseases
such as colds, flu, measles, meningitis, tuberculosis and malaria. Degenerative
diseases include multiple sclerosis, muscular dystrophy and arthritis. Body organs
or tissues become damaged and their function deteriorates. It is likely that some
degenerative diseases are triggered by pathogens, so there is not an absolute
distinction.
4
Levodopa reduces the symptoms of Parkinson’s disease but is not a cure.
5
A doctor would ask the patient to describe their symptoms, which might include
shaking and muscle stiffness. If these symptoms are improved by taking levodopa
(or a similar drug), the patient is likely to have Parkinson’s. There is a range of
different forms and types of the disease, together referred to as ‘Parkinsonism’,
and all responsive to levodopa.
6
Drug A slows the conversion of levodopa to dopamine outside the brain, allowing
more levodopa to enter the brain where it is converted to dopamine. Note that
dopamine itself is unable to enter the brain.
7 a) The mimic acts as a neurotransmitter, taking the place of dopamine in the brain.
b)
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It must be able to pass the blood-brain barrier.
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c)
The mimic is not converted to dopamine in the body – unlike levodopa. Dopamine
in the body causes nausea and other side effects.
8
The number of older people is increasing for demographic reasons. There is no
cure likely to be available in the near future.
9
A more even dose can be provided via a skin patch. There are also slow-release
pills.
10
DVLA relies on self-assessment. Patients in the early stages of Parkinson’s are
mentally healthy and able to judge their own abilities. They must declare a
condition such as Parkinson’s and DVLA may require a medical statement. Criteria
might include standards of muscular control and strength.
11
The procedure is risky, and only those with a severe condition are willing to
undergo the risks, since they may feel they have little to lose.
12 a) It is doubtful whether this technique would ever be suitable for general use.
b)
It might be justified for people with mental handicap or brain injury.
13
You need to know that there are more Lewy bodies in Parkinson’s brains than in
healthy brains. It is possible that Lewy bodies are present in the brains of many
old, but healthy, people.
14
Lewy bodies may be a sign that nerve cells are degenerating: they may be a
symptom rather than a cause. (Just as a red nose is not the cause of a cold).
15
It does not demonstrate a neuroprotective effect since levodopa may be
damaging substantia nigra cells, rather than the drug protecting them.
16
Drugs must fit the receptors in neurone membranes.
17
Research benefits from collaboration between neuroscientists and chemists.
Chemists develop drugs able to fit the receptors, then neuroscientists test them.
18
In vitro means in glass eg in a flask, dish or test-tube. In vivo means in life, ie in a
living organism.
19
Development and testing of new drugs is very expensive and time consuming.
Pharmaceutical companies need to protect their investment by patenting their
findings, so they can benefit commercially and reduce competition.
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20
Give pocket money, take to a show, give a present, verbal praise, high marks,
praise and prizes for school work etc!
21
Drugs stimulate the reward centres of the brain and this is very difficult to resist.
22
Use of nicotine patches or gum to substitute source of nicotine. Aversion therapy,
cognitive behavioural therapy.
23
Alcohol is readily available and affordable to young people. Outlets open 24 hours.
Culture of getting intoxicated. Problems of unruly behaviour, violence and drinkdriving.
24
Drugs which influence reward centres would have unwanted effects on general
behaviour and mood, so there is no easy biological solution.
Addiction is seen as a symptom of society rather than a biological problem.
Funding has gone into social strategies rather than scientific funding.
25
Some people more easily succumb to addiction than others, perhaps for genetic
reasons. To this extent addiction could be regarded as a mental illness. Yet not all
potential addicts become addicted and some addicts recover, so it is partly a social
problem.
26 a) Loss of job, self-esteem, harm to relationships, poor health, criminal record.
b)
Cost of treatment, police, legal profession, criminal behaviour, impairment of
workforce.
27 a) The first two apply to UK drugs policy with regard to illegal drugs. The third applies
more to the use of alcohol and tobacco.
b)
Legalisation of drugs could reduce the drugs trade and drug related crime. It is
uncertain whether it would lead to greater drug taking but that is a risk which
governments have been unwilling to take.
28
Scientists can provide information about the effects of drugs on human health,
including long term effects on organs such as the liver and brain. Some drugs may
affect memory or increase the risk of developing a mental illness. Scientists can
also give insights about the addictive properties of drugs, and advice on drug
substitutes to help addicts. Scientists can provide research evidence about a
drug’s effect on human performance, for example driving a vehicle. Psychologists
research the effectiveness of behavioural therapy and other non-drug treatments.
29
Drug use is affected by availability, cost, effects and deterrents. Cannabis is
relatively cheap and easily available and its use does not usually lead to
prosecution. Cocaine has a powerful effect and is fashionable in some circles.
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Governments do not want to be seen to be soft on drugs as this could lead to loss
of political support. This leads to some drugs being classified in a more
‘dangerous’ category than they merit. Alcohol and tobacco are at least as harmful
as some illegal drugs but it would be politically very difficult to ban them.
31 a) Clinical trials should involve informed consent and double blind protocols involving
a placebo or standard treatment as a control.
b)
The patients showed euphoria and this gave the scientists a clue about which
patients had the drug and which the placebo. This could have led to bias when
judging symptoms.
32
There are cannabinoid receptors in the brain so it is important to know what possibly harmful - side effects cannabis might have when it binds to these
receptors.
33
Cold turkey refers to the unpleasant symptoms experienced when an addict stops
taking a drug.
34
The person might find it difficult to gain employment, get insurance or financial
credit.
35
It suggests a genetic link, but there is also the possibility that family members
share a common environmental trigger.
36
Chicken pox and measles have characteristic symptoms not exactly matched by
any other disease. An infectious disease is (usually) all or nothing: you either have
it or you don’t. ADHD is diagnosed using a series of descriptors, and matching
behaviour to them is a matter of judgement. There are degrees of severity of
ADHD and many people are borderline.
37
Children are hyperactive for a variety of reasons other than ADHD, for example
being restrained for long periods in lessons or in the house. Some would argue
that ADHD is just an extreme of normal childhood behaviour. Diagnosing children
as having a mental condition leads parents to seek a medical cure.
38
A doctor might explain that ADHD is not a reflection of bad parenting. It has
genetic components, is treatable and may even have some beneficial aspects.
They could explain the evidence for abnormal brain activity in children with the
diagnosis.
39
A child might not fully understand ADHD or the implications of Ritalin treatment.
However it is desirable that the condition is explained and the child’s cooperation
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sought in addition to obtaining parental consent. Some might argue that a child
should have the final decision since it is the child who is taking the drug and
experiencing any side effects.
40
Doctors have differing views about the diagnosis and treatment of ADHD, and
prescribe accordingly. There may also be different levels of awareness among
parents, teachers and psychiatrists in different regions as well as differing levels of
funding, and different heath service guidelines.
41
There could be more reuptake molecules or a higher concentration of breakdown
enzymes, causing dopamine to be reabsorbed or broken down more rapidly from
the synapse after release. [A given level of dopamine would have a reduced effect
if the number of receptors on the receiving neurone were reduced].
42
Levodopa raises dopamine levels in the brain as does Ritalin so their side effects
can be similar.
43
Stigma means social disapproval, shame or disgrace.
44
Partly lack of research, but mainly because diagnosis of depression depends on
clinical judgement, so there can be no absolute distinction between being very
unhappy and having clinical depression.
45
Women may be more likely to admit to being depressed or to classify themselves
as more depressed than men, leading to higher reported incidence in women.
46
People may hide their depression and put on a brave face for the sake of family,
friends and work colleagues. Doctors might misdiagnose depression as having a
physical cause, such as exhaustion or a blood disorder.
47
Shorter day-length, lower light intensity, lower temperatures, low levels of vitamin
D, other dietary changes, possibly less socialising and greater alcohol
consumption.
48
The twin comparison suggests that there is not a causal link between depression
and exercise. There is likely to be a third factor which affects both depression and
exercise – increasing depression as it decreases the tendency to exercise.
49
Anything unrelated that increases/decreases in tandem. e.g. incidence of TB and
sales of mobile phones in the UK (positive correlation), consumption of organic
food and summer arctic ice cover (negative correlation).
50
The gene might disrupt sleep patterns leading to depression. It could also disrupt
other circadian physiological rhythms affecting mood, such as hormone levels.
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51
Serotonin has an important role as a neurotransmitter in the brain. If its action
were widely disrupted it would impair brain function, so there would be severe
side effects of the antidepressant drug.
52
No it does not: the drug could raise their mood above the norm. Alcohol can
change a person’s mood but that does not indicate that the person was suffering
from alcohol deficiency or depression.
53 a) Questions might include: is the drug addictive or might it lead to dependence?
What are the side effects? For how long will it need to be taken? What other nondrug treatments are available, and how does their efficacy compare?
b)
Drugs always have side effects. These might affect a person’s ability to work, or
affect relationships. The drugs might be expensive. There might be better
alternatives.
54
Lithium is often prescribed for bipolar disorder but is not suitable for all types of
depression. Depression has different causes in different people and there are
many different types of depression. The drug prescribed must be appropriate for
the condition. Lithium may only be effective if the cause of depression is linked to
a lack of serotonin.
55
Possible answers include: there are many depressed people, there is overdiagnosis of depression, doctors may have a vested interest in prescribing antidepressants, people without depression abuse anti-depressant drugs.
56 a) CBT tackles causes of depression rather than symptoms.
Patient develops new attitudes and behaviour which are long-lasting.
b)
Effects of drugs wear off and patient may develop drug tolerance.
57
Royal College of Physicians members feel they have enough experience to judge
when patients would benefit from ECT. They would like to test the effectiveness of
the treatment further without restrictions being imposed.
58
Caffeine.
59
Any answer acceptable with reasoned argument.
60 b) Is the drug legal? What are the side-effects? Is it addictive? Would it have a longterm effect (positive or negative)?
61
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Mental puzzles, strategic games.
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62 a) Therapy compensates for a deficiency or injury e.g.: muscle relaxants, pain killers,
anti-inflammatory injections, bandages and supports, physiotherapy, diet and
dietary supplements. Enhancement takes a healthy individual beyond their normal
range of achievement/abiltiy: erythropoietin injections, growth hormone, blood
transfusions, steroids, dietary supplements, potentially designer babies.
b)
Erythropoietin stimulates the body to make more haemoglobin than normal, and
is illegal in sport. However it is legal to provide iron supplements or train at
altitude both of which enhance haemoglobin.
c)
Some drugs are considered to give an unfair advantage, and ethical issues include
potential long-term harm to users.
63
The idea of a level playing field could be used here. It all students have access to
the same calculator the test is fair, and this is easy to verify. If students take brain
enhancing drugs it is very difficult to monitor and to know what has been taken
and when. Even if all students are provided with the same cognitive enhancement
treatment, its effects will vary.
64
The distinction could be drawn between compensating for a deficiency (causing
the brain disorder) and enhancing healthy function.
65
There may be a market for brain enhancing drugs for healthy people.
The research may offer clues about how the brain works.
The drugs may help mentally ill people.
Some mentally ill people can not give informed consent for research.
66
This depends on the meaning of normal. Everyone’s abilities vary over time and a
drug might allow them to perform at their best at all times.
67
To allow service personnel to stay awake and perform at their peak during long
periods of combat. Possible side effects are outweighed by the imperative for
effective action.
68
The study should include the following: use of controls, large representative
sample, statistically significant results, long term effectiveness, peer reviewed
paper.
69 a) It is cheating if it is done without the knowledge and approval of those setting and
marking the exams.
b)
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It could be argued that they should. It could be seen as equivalent to
plagiarism.
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70 a) The sample size is small and all male.
b)
Donepezil improved the retention of skills and information measured at the end of
a 30 day training course.
71
Cognitive enhancing drugs could improve examination performance and job
performance, increasing the prospects for university places, employment and
promotion. If they are available people will be tempted to try them.
72 a) Less dependence on notes, lists, reminders. Less wasted time. More interesting
and effective conversations and discussions. b) Able to achieve a better
understanding of the world and our place in it. Quicker at calculating figures. c)
Better able to come up with new ideas, mend equipment and machines and devise
strategies for complex activities.
73
Young people tend not to worry about long term side effects. They may think that
the benefits are so great that it is worth the risk. There may be considerable
pressure to achieve.
74
The risks from rock climbing etc can be quantified and controlled. The risks from
new drugs are much less well understood and measured.
75
It might be justifiable, for example, to help a person with mental degeneration or
injury who is unable to understand the benefits of the drug.
76 a) Drugs could, in principle, raise everyone’s IQ to a standard (high) level - though
this is very unlikely to be achievable.
b)
Cognitive enhancing drugs, if effective, are likely to be taken by those with social
and financial advantages and denied to others.
77
This depends on whether society and government accept cognitive enhancement
for healthy people or whether such drugs will be considered to be best reserved
for treatment of those with mental impairment.
Review questions
78 a) Helps in diagnosing and developing treatments for people with mental illnesses
(such as Parkinson’s disease, Alzheimer’s disease, depression, ADHD or
schizophrenia) or brain injuries.
Helps in understanding and treatment of drug addiction and predicting the long
term effects of drugs on the brain.
Important for pure research into how the brain works.
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b)
Examples might include levodopa/dopamine and Parkinson’s disease, acetyl
choline mimics and Alzheimer’s, SSRIs and schizophrenia/depression,
Ritalin/serotonin and ADHD. Drug either mimics the neurotransmitter or prevents
breakdown or re-uptake.
c)
Examples include: ritalin for ADHD used as memory enhancer, cholinergic drugs
for Alzheimer’s used as memory enhancers, drugs for narcolepsy used to keep
alert/awake.
d)
Synapses outside the brain use similar or identical transmitters to those found in
the brain. Drugs enter blood stream and pass around body before entering brain,
affecting synapses and causing side effects. In addition, drugs may have nonintended effects on brain synapses.
79 a) Wide differences between European countries in use of cocaine despite all sharing
common EU laws and policies on drugs. Spain and UK highest.
b)
Reasons could include fashion, culture, availability, law enforcement (lack of),
availability of alternative drugs, cost, local drug policies, policing, penalties.
80 a) Depression affects a person’s ability to cope with daily life, and includes both
mental and physical symptoms, and sometimes psychosis.
b)
Multifactorial means that there is more than one cause of the condition. A
combination of factors adds up to cause the effect. This is likely to be true of many
mental disorders, which usually have a genetic component and several
environmental ones. Factors may have a synergistic action i.e. the effect can be
greater than the sum of the separate factors – the factors reinforce each other.
81 a) Mental disorders are diagnosed using self reports of a patient’s moods, behaviour
and thought processes. These symptoms are scored against a list of criteria agreed
by psychiatrists to characterise a condition, such as depression or ADHD. It is a
matter of clinical judgement as to how well any patient’s symptoms match the
criteria of a condition. No patient will show all the symptoms on a list and each
symptom will be experienced to differing degrees. There is therefore no clear
dividing line between having or not having the condition and different
psychiatrists may reach different conclusions.
b)
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Social factors include economic factors, family circumstances, schooling, access to
medical help, education level. Conditions such as dyslexia and ADHD are more
likely to be recognised by more wealthy and better educated parents and in
children attending schools with more individual attention.
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c)
E.g. depression: diagnosis has disadvantages such as social stigma and difficulties
with finding employment, as well as possible side effects of any drug treatment.
But without diagnosis a patient is unlikely to receive the necessary help and may
be unable to work or socialise.
82
For: improved brain function. Improved work, study, enjoyment of leisure, ability
to concentrate, remember, reason etc. Against: unknown side effects, unfair
advantage over those not able or willing to take drug, possible development of
tolerance to pills leading to dependence. Cost.
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A2 Science in Society
Answers to the questions
Chapter 2 Nature and Nurture
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included
which go beyond the direct requirements of the question.
1
Embargos may benefit the private publishing companies rather than disseminating
the outcomes of research as it becomes available.
2
It is an interaction between the two. Journalists benefit from sensational stories
which consumers like to view/read.
3
The MMR vaccine and autism story received a lot of attention because:
The story is difficult to disprove.
If true it would have major consequences with possible compensation issues.
There are several case studies where children have developed problems
coincindentally with having the vaccination.
A scientist purporting to have demonstrated a link between MMR and autism has
been discredited. There is always public interest in a personal story, especially
when two views are pitted against each other.
4
It is simpler to understand than the reality, which is an interaction between nature
and nurture. It implies that people are under genetic control to an extent which is
unrealistic but exciting to consider.
5
Journalists may be specialists in their field, but headline writers are not and are
therefore likely to sensationalise a headline at the expense of accuracy, either by
mistake or by design.
6
Potentially useful applications of research help to relate the ideas to everyday life.
The scientists involved may promote potential uses as this helps to justify,
advertise and fund their research.
7
Human nature is probably similar the world over and across time. All people have
a propensity to violence and anger given the right circumstances. People may
differ in the thresholds which give rise to such behaviour. [In times of war or
protecting others, such qualities might be seen as positive].
8
Graph c) shows a discontinuous distribution: the characteristics are in categories
with no intermediates, controlled largely by genes. Graph d) shows a continuous
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distribution: the characteristic show all possible intermediate values across the
range, controlled by many genes interacting with the environment.
9
The project could only be managed by sharing the funding, scientific expertise and
facilities of several countries/organisations.
10
DNA is the material of genes. Genes control the structure and function of cells.
Knowledge of the genome allows scientists to discover the function of each gene.
11
An adopted child may not be aware the fact, or the possibility it has siblings.
Genetic problems in the genetic family of an adopted child may be found and a
decision made about whether to inform the child and/or its adoptive parents.
12
Scientists try to alter just one (independent) variable at a time. By using fraternal
same-sex twins, the variables of being/not being a twin and same sex/different sex
are controlled.
13
Non-identical twins share 50% of their genes – the same as all siblings.
14
The policy is not helpful: the ideal is for the compared siblings to have the same
genes but experience contrasting environments. On the other hand, if
characteristics appear in adopted children but not the adoptive family, it may be
possible to suggest strong genetic effects.
15 a) Scientists cooperating on an area of research, each offering different knowledge
and skills. They may work in the same institution or different ones, perhaps in
different countries.
b)
A scientist who studies the molecular structure of genes - ie DNA - and the way it
controls the cell.
c)
Difficulties with speaking, understanding speech, reading or writing – possibly but
not necessarily attributable to a named condition such dyslexia.
d)
A longitudinal study follows the progress of the same individuals over a long
period of time (opposite to cross-sectional study).
e)
A single change in the base sequence means that one base is substituted for
another.
f)
Reading abilities are affected by many different genes, each having a very small
effect.
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16
The contribution of parents and family, availability of books, presence of siblings,
lack of other distractions such as television, good reading conditions such as
lighting, provision of spectacles if needed.
17
Any shared environmental condition experienced by the family to a greater extent
than by the general population.
18
An association with a genetic marker shows that the gene of interest is nearby on
the same chromosome. This focuses the area of search for the gene.
19
Research might show a person to be near the end of the range of normal
distribution for a trait (for example aggressiveness). An arbitrary cut-off could be
decided beyond which the person is assigned to a condition eg ‘aggression
syndrome’. Giving a person such a label could be used as justification for
intolerance and/or medical intervention.
20
Being at the extreme end of a normal distribution spectrum does not indicate the
extent to which the attribute is caused by genes or by the environment. Drug
treatment carries the assumption that the trait is genetic and biochemical in cause
and can be rectified by medical means.
21
For: employers could take account of the potential strengths and weaknesses of
an employee when assigning them work. Against: knowledge of a person’s
genotype might be used to discriminate against them. The employer might
wrongly assume the genetic test to be totally predictive of the person’s
capabilities.
22
Allele 3.
23
The allele either causes the condition or is closely linked to the allele causing the
condition.
24
Yellow, this gene is close to the gene for schizophrenia, so is most likely to be
inherited along with the schizophrenia gene.
25
The identical twin of a schizophrenic and the offspring of two schizophrenics do
not always have schizophrenia. Heritability is 48% and 46% respectively, not 100%.
Whether or not you have schizophrenia if you have this gene depends on your
environment.
26 a) High heritability would indicate to the scientist that possessing the allele is likely to
cause an effect (and will not be masked by environmental effects). Commercially,
this means that people with the gene are a potential market for a drug which
counteracts its effects.
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b)
The size of the effect on body mass will show the scientist whether the allele has a
significant effect on a person’s overall body mass. The size of this effect will affect
whether or not people think it is worth taking a drug to counter the gene’s effects.
27
Val/val
28
Cannabis is implicated as one of many possible causal factors and its effects are
influenced by a person’s genotype.
29
Genotyping is likely to be expensive and difficult logistically. Having the genotype
indicates risk but is not predictive. Advice can more easily be provided. Risk for
non-cannabis users is significantly lower for val/val genotypes. However, potential
cannabis users may have no understanding or knowledge of their risk of
schizophrenia.
30
Presence of the protein in the brain shows a correlation with symptoms. The
protein may be a symptom of the disease but not its cause. The causal factor may
produce the protein and cause the disease.
31
Ideally they should be selected randomly, but in practice the most obvious or
severe cases are more likely to come to attention, particularly when the disease is
rare.
32
Each member of the control group should be matched to an individual with
Alzheimer’s disease for age, sex, socio-economic category, race and geographical
location (to control for environmental factors).
33
New research findings and the experience of psychiatrists continually modify the
understanding of mental disorders. Experience may show that a disorder has been
over, under or mis-diagnosed so the criteria are adjusted accordingly.
34
Many diseases are characterised by symptoms which are merely the extreme end
of a continuous distribution. The dividing line between normality and disease is a
matter of judgement and not everyone will agree where this should fall.
35
Scientists can have a vested interest in increasing the diagnosis of mental
disorders since they may benefit financially from the medical treatments involved.
They may be tempted to adjust the criteria so as to increase positive diagnoses.
36
Answers might include: causes of asthma, allergies, autism, hyperactivity/ADHD,
dyslexia, eczema, schizophrenia, drug addiction, criminal behaviour etc.
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37
Sample attrition: ie people dropping out of the study: those dropping out may not
be a representative (random) sample of the cohort. Attrition can also reduce
sample size to a critical level where a few individuals can influence the results
significantly. A cohort selected from a particular region may not show the full
range of genetic variation of the national population, or may possess atypical
genes which influence the expression of genes identified as significant. A local
cohort could also share an environmental factor – lacking elsewhere - which
influences genetic expression, invalidating generalisation to the wider population.
38
An infrequent condition may not occur in a cohort with sufficient frequency to
yield statistically significant results.
39 a) The gene may be expressed differently in the environment of Northern Canada
from elsewhere. The gene might not cause alcoholism but be linked (ie positioned
closely on the chromosome) to a gene which does: in other populations the
relevant gene may not be so closely linked because of chromosomal changes [see
also answer to q. 37] b) The scientists could sequence the gene, discover the
protein it codes for and investigate the actions of the protein with relation to
alcohol metabolism/addiction. Alternatively, they could investigate whether there
is a genetic link in a different population.
40
It is unrealistic for scientists to keep their findings confidential until treatments
and cures are perfected. It is important that scientists emphasise the preliminary
and incomplete nature of their findings, and discourage the media from
exaggerating them.
41
Cab drivers form more dendrites and synaptic connections as they learn the
routes, enlarging the hippocampus.
42
Reduced corpus callosum in abused children.
43
Were the children who spent more time in nursery matched with the group that
spent less time – for factors such as age, sex, parenting style, socio-economic
background etc.
44
Is there a threshold of time in nursery above which antisocial behaviour rapidly
rises? Are there ways in which parents and carers can ameliorate any negative
effects of long hours in a nursery?
Are boys and girls equally affected?
What effect has the age of the child?
Were the effects seen in all nurseries: if not what is the explanation?
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45
If long hours in nursery care are harmful, there is a case for the government
providing support for young parents to stay at home with their babies in the early
years.
46
Education should target the teaching of each skill at the time when it can be
acquired most easily – and give extra help for those that miss the window.
47
It is unlikely that all television is bad. It depends what is watched and for how long.
Some television may be highly beneficial.
48
No, because correlation does not signify cause. Even if TV were shown to cause
ADHD it might be only certain types of programme which are responsible.
49
Good state nursery schools can provide reading, playing and other support that
some parents do not provide at home.
50
There is a strong argument for removing a child from an environment where the
child’s full academic potential is compromised. However, this argument could be
used to justify the removal of any child from below average parenting. Any such
action would need to demonstrate a serious disadvantage or risk to the child
remaining with its parents, and there will be many borderline cases where
decisions are difficult to make.
51
For: knowing a child has potential difficulties enables the child to receive
appropriate extra help from an early stage. Against: the presence of particular
genes is not predictive of difficulty – it merely makes difficulties more probable.
Having a label can lead to discrimination and stigmatisation. It may also lead to the
child having low self-esteem and low expectations.
52
Monoamine oxidase (MAOA) breaks down the family of neurotransmitters which
include dopamine and serotonin, in the synaptic gap (Fig.1.4 p.3). This means that
the neurotransmitters are quickly inactivated. MAOA inhibitors prevent the
breakdown of neurotransmitters, causing more frequent/stronger signals to be
passed across the synapse. Depression can be caused by a lack of dopamine
and/or serotonin in synapses. MAOA inhibitors – in tiny quantities – bring the
levels of the neurotransmitters back to ‘normal’, improving the mood of the
patient.
53
There may be other peculiarities about the Dutch family which make them
aggressive, and the low levels of MAOA are simply a coincidence.
54
Men show more physical aggression than women.
Studying one sex removed an extraneous variable from the study.
It could be argued that a separate study of women should be done.
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55
Maoris have a different racial origin from later settlers and may differ in
aggressiveness.
This would add another extraneous variable which could make the results less
clear-cut.
As an isolated indigenous population, they may have evolved some traits
separately from populations outside New Zealand. In fact, a higher than average
incidence of MAOA resistance has been found in the MAORI population, and this
particular variant has been dubbed the ‘warrior’ gene.
56
Social services might be able to provide extra guidance and help (e.g. behavioural
therapy) to people with low MAOA activity – though this would assume that an
easy test for this genotype was available.
57
Middle and right hand columns for low MAOA activity.
58
The two right hand columns (severe maltreatment low and severe maltreatment
high).
59
Authors of scientific papers place their own findings in the context of previously
published work, to which they cite references. They may agree or disagree with
previous studies and this can modify accepted theories.
60
The Dunedin study shows that genes and environment do not have separate
additive effects – but that their effects interact to determine the phenotype
61
The possession of particular genes could be seen as legitimising
unacceptable/illegal behaviour. It could also be seen as an extenuating
circumstance in a court case, justifying more lenient treatment. [A determinist
would argue that all human behaviour is controlled by genes and environment (ie
we have no free will) in which case no-one is responsible for their actions].
62
Being genetically predisposed to commit a crime does not make criminal
behaviour inevitable, so an adverse genetic forensic profile would not in itself
make a person guilty. However, knowledge of such a profile might bias the
attitude of police and courts, making arrest and conviction more likely.
63
100 in each case.
64
15 units.
65
You can’t calculate the interquartile spread from the spread of the data, you need
to know how the values are distributed across this range.
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66
This helped to ensure that people from all races and backgrounds came to an
agreed version of the report, avoiding biased, polarised or politicised views.
67
The idea that IQ has a genetic component could be used to justify eugenics, in an
attempt to ‘improve’ the human race. [Eugenics has recently been used in the
form of embryo selection, in order to avoid genetic diseases or provide suitable
tissue for donation to a sick sibling. It is also a component of sperm, egg and
embryo donation in fertility treatment. This is, of course, very different from
controlling who breeds and who does not].
Acceptance of a genetic link could also influence educational policies.
68
Siblings reared apart and identical twins reared apart.
69
A maximum correlation score would be 1.0 so a correlation of 0.5 shows that
there is only a moderate correlation between these measures.
70
Research is likely to show the way these genes control the structure and function
of neurones, perhaps at synapses. Intelligence is determined by the nature of a
brain’s neuronal connections.
71
GG
72
There is an initial decline in intelligence score as the number of intelligence SNPs
rises from 2 to 3, then the graph reverses and there is a positive correlation
between 3 and 10 SNPs.
73
Epigenetic theory says that environmental factors can change DNA expression
with effects that can be transferred from one generation to the next. It was
previously thought that the DNA code was ‘wiped clean’ each generation.
[However, this is not the same as saying that acquired characteristics are
inherited: the DNA code itself is not changed, and transgenerational epigenetic
effects are likely to be limited in extent compared with genetic inheritance].
74 a) Parents should be aware that a child’s environment can alter gene expression,
perhaps for life.
b)
An individual’s lifestyle can change gene expression in their eggs or sperm,
potentially passing on environmental influences to their offspring (which might be
beneficial or harmful).
75
The same conclusions reached independently provide much stronger evidence
than a single study, whose authors may have reached invalid conclusions. It also
inspires confidence if the same findings are found in a variety of species from
different biological groups.
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76 a) If the environment changes genes (by ‘tagging’ them, thereby altering their
expression), this could be thought of as genes having a memory of past events –
especially if the tags are long-lasting.
b)
Bygren and Pembury claim that food shortage in a person’s grandparents’ time
can reduce life expectancy.
77a) Epigenetics is the study of the way environmental factors control gene expression.
b)
Experiencing severe food shortage can reduce the life expectancy of your
grandchildren.
78
Scientists may wish to follow their interests and ideas without constraint, whereas
commercial funders usually seek a (relatively) short term financial return.
79
By lobbying politicians and research organisations, contributing to funding
charities, writing articles, books and blogs, giving talks, being scientifically literate
and informed.
Review questions
80 a) Stage of development: e.g. genes for growth of neurones in unborn child, genes
predisposing to neurodegenerative diseases (e.g. Alzheimer’s) expressed in old
age. The growth of neurones (and other cells) and the development of Alzheimer’s
are both influenced by the environment.
Where cell is in body: e.g. genes for neurotransmitters are expressed only in
neurones, not other cells: genes for different transmitters expressed in different
neurones/brain regions.
The action of other genes: many genes can have small additive effects on the
phenotype, e.g. in height and intelligence; some genes act synergistically – their
combined effect is more than the sum of each individually e.g. some cancer genes.
b)
Environmental factors can add molecular tags to genes (DNA), affecting their
expression. These tags can sometimes be passed on in egg or sperm, meaning that
environmental factors can influence gene expression in the next generation. E.g.
rat pup’s anxiety altered by maternal licking which causes epigenetic chemical tags
to be added. Food supply of grandparents shown to affect life expectancy in
Swedish study.
81 a) Case control studies use participants that have already developed a condition, and
compare their background with those of matched controls without the condition.
b)
Case control studies are used when a condition is rare in the general population,
and a cohort study would not produce a big enough sample. However, case
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control studies pre-select people who already have a condition and these may not
be representative of the whole population. It is also very difficult to reconstruct
the environmental history of participants in a case control study, especially those
with a neurodegenerative disease.
c)
Circumstances would be where the condition is uncommon, for example a rare
genetic mutation, or a condition such as schizophrenia.
82 a) A longitudinal population based study (prospective cohort study) takes a large
sample of people (often several thousand) and follows their fortunes over many
months or years (e.g. ALSPAC study). The participants’ lives are documented in
great detail for the duration of the study, and they may also be analysed
genetically. The study then looks for any associations between the incidence of a
condition (eg heart disease, neurodegenerative disease) and environmental or
genetic factors.
b)
Advantages include the opportunity to document the participants’ environment in
great detail (see 81b) and the large sample size. Disadvantages include the
difficulties of obtaining a large enough sample size for rare conditions, and
attrition – the loss of participants from the study - which may be non-random.
c)
In complex situations it is difficult to separate the individual effects of each factor:
any factor is likely to be associated with several others (for example smoking and
drinking alcohol tend to occur together).
‘Reverse causality’ can imply a false positive eg those predisposed to developing
schizophrenia may be more likely to smoke cannabis.
It is hard to disprove that a larger sample would not demonstrate an effect.
Individual cases can lead people to jump to conclusions which are difficult to
dislodge (eg MMR vaccine and autism): people tend to use evidence selectively
when they have already come to an opinion.
83 a) Galton’s twin studies, study of Dutch family with low MAOA and Pembrey’s work
on epigenetics have all influenced the direction of research.
b)
Examples of peer reviewed studies in the chapter include: day care and antisocial
behaviour, ADHD and television, maltreatment/MAOA activity and violence. These
could be contrasted with claims made in the book ‘Bell Curve: Intelligence and
Class Structure in American Life’ which is not peer-reviewed and makes
unsubstantiated claims about race and intelligence.
c)
84
The prime example is the Human Genome Project.
The popular media tend to sensationalise research results, and pick out issues
which they think readers will find entertaining eg intelligence, criminality and
sexuality, sometimes at the expense of objective reporting. Science journalists are
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not always good scientists, but the best are very good and report scientific results
rigorously. The reader needs to select the highest quality writers and journals.
Media can influence the direction of research by drawing attention to issues such
as cannabis and schizophrenia, MMR vaccine and autism, upbringing and
antisocial behaviour. Public concern leads to government funding of relevant
research.
85
Points might include:
 Intelligence is not easy to measure.
 Intelligence has many dimensions/aspects and is not a unitary quality of the
brain.
 IQ tests measure only some aspects of intelligence.
 Evidence shows that many genes interact to control intelligence.
 Very little is yet known about which genes are important.
 The environment interacts with genes in a complex way in controlling
intelligence.
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A2 Science in Society
Answers to the questions
Chapter 3 Watching the Brain Working
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included
which go beyond the direct requirements of the question.
1
When we feel emotional the (autonomic) nervous system causes the heart to beat
faster and the breathing rate to increase. The emotion we experience depends on
the context. People noticed that their hearts beat more strongly when they had
strong feelings so came to the conclusion that it was the heart that gave them the
feelings.
2 a) Astrology, scientology, intelligent design, homeopathy.
b)
Pseudoscience can sound plausible and is often difficult to disprove. People like
clear definite answers and explanations rather than uncertainty. Pseudoscience is
often well funded and supported and can have political or religious dimensions.
3
Early scientists did not have the choice of using brain scans or electrophysiological
methods (placing fine electrodes in nerve cells). Even dissection of dead people
was not acceptable in some societies.
4
Case studies provide natural ‘experiments’ which can tell us a lot about which
parts of the brain have different functions. From a variety of case studies,
scientists can piece together a picture of the whole brain.
Large scale clinical trials avoid the difficulties of relying on just one case study. A
single person may be atypical.
5 a) The doctor might be biased towards seeing a favourable outcome.
b)
Patients may not be good judges of their own mental state since they were
mentally impaired before the operation and the surgery itself is likely to have
affected their judgment.
c)
Carers may be over-sensitive to both positive and negative signs as they will be
very anxious and know the patient well. They are likely to remember the patient’s
condition before illness began and could have over-optimistic expectations of
surgery.
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6 a) An animal model means that an animal substitutes for a human in medical
research. Species are chosen for their similarity to humans physiologically and
mentally. In some cases animals are selected or altered to model a particular
human disease or injury.
b)
Rats and mice have relatively smaller brains than primates. Primates are monkeys
and apes, including humans. Non-human primates are the closest animal brain
models to humans.
7
Human brains are relatively much larger than those of non-human primates and
there are many differences in structure and function. Chimpanzees and humans
shared a common ancestor 5-6 million years ago and since then have evolved
independently. Humans have a much larger cerebral cortex, and have developed
much greater intelligence and new abilities, such as language. There are even
greater differences between human brains and rodent brains.
8 a) Chimpanzees are highly intelligent and their behaviour and emotions share many
qualities with those of humans. It is accepted by ethics committees that
chimpanzees would suffer more from experimental procedures than other
mammals. [However, this could be a reflection of our greater ability to empathise
with our closer relatives, and there is increasing evidence that other mammals,
such as elephants, have very sophisticated emotions and social behaviour].
b)
In each case it would need to be demonstrated that a non-primate model was
inadequate. Research which is non-invasive – such as studies of learning - would
be easier to justify than research requiring brain surgery. There are good rodent
models of Parkinson’s disease. However, an ethics committee could be persuaded
that a new drug developed using rodents should be tested in non-human primates
before human clinical trials, since primates might react differently. Thinking and
reasoning could be argued on the basis of the much greater intelligence of
primates. Vision research could require the learning ability of primates in order to
demonstrate what the animal is seeing. Primates have colour vision similar to
humans whereas most other mammals do not. The specific impairments caused
by stroke are more likely to be mimicked in primates. Primates may show more
parallels in localization and lateralization of function. Primates would be sourced
from captive breeding and not from wild populations.
9
The hands, lips and tongue, because these parts contain many different muscles
and make complex movements.
10
Either: the brain has spare capacity and unused (or less important) regions can
take over the role of damaged areas or: damaged brain areas are able to repair
themselves. Both explanations require plasticity of the brain – an ability to make
new connections – and both probably occur.
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11
Chimpanzees have shown language learning by eg:
 using a symbol appropriately in a new context (eg using key sign when seeing a
closed door).
 Combining symbols to convey meaning eg ‘open, hurry’.
 Generalising to new situations eg using ‘more’ sign for tickling/food.
 Responding to human commands appropriately.
[However, scientists disagree about the conclusions to be drawn from ape
language studies].
12
Having a larger brain must have conveyed a selective advantage, allowing
individuals to survive and/or reproduce better. The context/habitat in which this
selection occurred is not fully known. High intelligence could have been important
in hunting, tool making, communicating, fighting or attracting a mate. Some
scientists think that the main selection pressure was social – high intelligence was
used for anticipating the behaviour of other humans and outwitting them.
13 a) 2,4,1,3
b)
The auditory cortex receives and analyses nerve impulses from the ears when the
question is spoken. The auditory cortex sends impulses to Wernicke’s area which
interprets the meaning of the words, and composes an answer (probably calling
on memory of past events). Wernicke’s area then sends impulses to Broca’s area,
which sorts out the pattern of nerve impulses to send to the motor area. The
motor area responds by sending impulses to the muscles used in speech, in the
correct way to form the words of the answer.
14
Different brain areas interact to carry out a function, and no area works in
isolation.
15
Taking an average gives an overview of the human brain. This can useful in
providing a simplified or generalised view. We might want an overview of this kind
when investigating child development, studying brain evolution or comparing
humans with other species. However, it overlooks individual differences and sex
differences which could be of great interest and may be of critical importance
when diagnosing or treating a patient.
16
Answers might include: learning music, art, dance, languages, sciences, sporting
skills, social learning, specialist knowledge of various kinds. Students might be able
to describe particular formative experiences which they think were important to
them.
17
A false positive means that someone is believed to be lying when they are telling
the truth.
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A false negative means that someone is believed to be telling the truth when they
are lying.
18
Polygraph evidence can be relied on too heavily. People may be anxious when
questioned by those in authority, even when they are innocent, leading to a false
positive. Conversely a guilty person might be good at hiding his/her emotions,
leading to a false negative.
19
Students should be able to recognize: cerebrum, cerebral cortex, corpus callosum,
cerebellum, brain stem, spinal cord.
20
Eg reading a clinical thermometer: a) the scale is incorrectly inscribed b) the
reader mistakes the 36 degree mark for the 37 degree mark in all measurements,
so all readings are 1 degree too low.
21
Systematic errors are either all above or all below the true value, so cannot
average out at the true value. Random errors are equally likely to be above or
below the true value.
22
During brain activity, blood oxygen levels dip then rise then dip again. If fMRI
scans are timed to occur too early or too late after brain activity begins, a
systematic error could occur whereby brain activity is underestimated by a fixed
amount.
23
A laboratory investigation lacks what psychologists call ‘ecological validity’. The
brain may respond differently in a real life situation, which is more stressful, and
has more serious consequences. Also, the range of subjects used in a laboratory
trial may be too narrow (university students are often used as volunteers). The
age, mental state, medical condition, drug status and sex of the subject could all
affect the response. However, laboratory studies have the advantage of being able
to control extraneous variables.
24
A base-line trial could show up differences in brain activity when the subject was
telling what is known to be the truth or a lie. The pattern of brain response made
by the subject in the base-line trial could then be compared with their response
when answering questions about the case.
25 a) Different brain areas become active when telling a lie and when telling the truth.
The prefrontal cortex is more active when telling a lie.
b)
There are many reasons for the prefrontal cortex to be active, as it is the part of
the brain controlling much of our thinking and decision making.
Individuals vary in their brain responses. A lie in one person’s brain may look like
the truth in another.
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26
Possible questions include:
 How reliable are scans in detecting lies, terrorist intent, etc?
 Can there be false positives and false negatives?
 Is it possible to deliberately modify one’s brain activity to manipulate a scan
image?
 Who would have access to scan data?
 Where/how would scan data be stored?
 What is the likelihood of data being lost or misidentified.
 Can other aspects of a person’s thought processes be detected eg political
views, sexual orientation, racial views?
27
Possible answers include: deliberate misinterpretation of a lie-detector scan to
direct the outcome, use of a scan to force a confession, use for political purposes,
development of unethical marketing techniques.
28 a) Left handed people may use different brain areas from right handed people, and
this might lead to more variable brain responses.
b)
It is justified in the interests of discovering clear differences between favourite
and non-favourite brand responses. But there is a grey area when rejecting data
from a set of results. There can be a temptation to reject data that do not support
the hypothesis being tested. Peer review of scientific papers helps to prevent the
massaging of data, though scientists may not own up to excluding data which do
not fit.
c)
Students may be unaware that their participation in academic research has
commercial implications. There should be fully informed consent.
29
Some considerations might include: Commercial Alert picks on the worst
outcomes of marketing and advertising, suggesting that diseases such as diabetes
arise because people are persuaded to eat unhealthy food by unscrupulous
companies. The alternative argument is that the commercial world helps people to
find and purchase good products which they enjoy using, including healthy food
and medicines. The worry with neuromarketing is that it could be more persuasive
and effective than current techniques. There are parallels with subliminal
advertising – an image shown so briefly in a film sequence that we do not notice it.
Subliminal images may change people’s perceptions, and they are banned by law.
Neuromarketing is not a form of advertising, but a method of researching better
advertising techniques, and some would consider this to be a legitimate
commercial enterprise, especially if it is kept under review by a respectable
professional body.
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30
In most drug trials a placebo is necessary in order to carry out a fair test of a drug’s
effects. In the MRI trials, brain images showing the typical progression of the
disease could be the control. However, there is still the danger that brain images
may be interpreted in a biased way by the researchers, exaggerating the effects of
the drug, especially if they are funded by the drug company concerned. Ideally a
placebo should be used in a double blind trial. A double blind trial means that
neither the patient nor the scientist analysing the data knows who took the drug
and who took the placebo.
31
There is an ethical issue over consent, since people with dementia may not
understand what they are being asked to do. In these circumstances a relative or
spouse could give permission for a person to take part in a drugs trial. There is a
downside of being in a trial for a new drug: the drug may be harmful and may also
require the subject to stop taking their existing medication. Also the subject may
be in the placebo group, in which case they receive no treatment at all and may
deteriorate more rapidly than if they were not in the trial. However, properly
controlled trials are the only way of assessing the merits of new drugs.
32 a) She means that parts of the brain become active and are detected by the scanner.
b)
FMRI has thee spatial dimensions plus the dimension of time.
33
A child’s brain is more plastic; it has more ability to grow and adapt by forming
new connections than an adult’s brain.
34
The right hemisphere receives visual signals from the left visual field. The right
hemisphere also controls the left hand so he could use this hand to select the
object he had seen, even though he could not name it. [In an intact brain, the right
hemisphere would be able to instruct the left hemisphere about the nature of the
object seen and the left hemisphere would be able to name it].
35
The patients all had severe epilepsy. This means that their brains may not have
been typical of the general population. They were also all male and right handed.
36
Criteria might included:
Who has constructed the website? Is it a reputable scientific source?
Does the website offer a commercial service?
Does the website use scientific terms correctly?
Does the site oversimplify by claiming to measure features such as the ‘maleness’
of your brain or whether you are ‘right-brained’ or ‘left-brained’?
37
Gazzaniga’s participants’ left hemisphere guessed the reason for the right
hemisphere’s actions, which it could not know directly because the corpus
callosum was cut. This sort of guessing is called confabulation.
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38
page 1
Lie detecting techniques assume that we know whether we are telling the truth or
not. If our brains confabulate (ie invent facts to make a complete or better story of
past events) without our being aware of it, then we may not always know whether
our memories are true or false.
39 a) Empathisers would be keen to play with others and would offer everyone a turn in
a game. They would help someone who was hurt. They might show more eye
contact and talk more
b)
Systemisers might be very keen to add the score in a game or to discuss the exact
rules that should be followed, but might prefer to play alone or with one or two
particular friends.
40
Men enjoy cars, mechanics, football, DIY. Women enjoy socializing, shopping,
design, fashion, cooking. These are, of course, stereotypes and not very politically
correct. There are no exclusive activities of either sex!
41 a) Showing different attention to pictures does not necessarily indicate that the
babies would prefer to play with these objects or liked them better. There could
be differences between the sexes in the aesthetic appeal or other qualities of the
pictures. Males and females may see colours or other features of objects slightly
differently.
b)
Babies of this age show no self-recognition, so presumably they don’t know if they
are a boy or a girl. However, girls and boys are likely to have been given different
types of toys to play with and to have received different treatment from their
parents and older siblings appropriate to their sex. Differences in preference for
looking at objects could be nurture rather than nature.
42
Women can better compensate for loss of language function in one hemisphere
by using their language function in the other.
43
As the authors concede, there may be other brain regions involved in language
processing that do not show sex differences. If this is true then sex differences in
lateralisation in language processing could be overestimated.
44 a) Not true. If there really is a difference in empathising ability between boys and
girls, it is only a slight difference in the average.
b)
Probably true, but not necessarily so. The boys and girls in the class are a small
sample: the boys may be good at empathising for their sex and the girls may be
poor.
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45
Answers might include reference to the feeling of being a living person, able to
sense the world and make choices about what we do. We might be considered to
be unconscious or less conscious while asleep or day-dreaming, but it is still
possible to be aroused quickly, unlike when a person is in a coma.
46
The ambiguous words have two different meanings (and sometimes spellings), but
sound the same (creak/creek, beam of wood/light, ceiling/sealing). A listener has
to decide which word is being used by taking account of the context, and this
takes extra computation (by Wernicke’s area).
47
The scientists could tell the woman a brief story as they recorded brain images.
They could then ask her to imagine the same story and compare the images with
the recordings.
48
The woman was in a minimally conscious state because she showed high
wakefulness and some awareness of words spoken to her.
49
Brain activity involves small electrical signals in neurons. The brain’s electrical
signals cause small electrical changes on the surface of the scalp, which can be
detected by sensors (as in an EEG). The sensors are connected to a computer to
activate a cursor.
50
A paramedic will ask the person their name, ask where they are and where they
live, and ask questions about what they have been doing. S/he will ask the patient
to move various parts of the body to see if there is any damage to motor function
– though not if a neck injury is suspected.
51
Patients can recover from loss of cortical activity, but not from loss of brain stem
activity. The latter would have to be established with certainty before any
decisions were made about organ transplantation.
52 a) The second doctor would have an independent, fresh view of the evidence.
b)
This ensures that there can be no question of the doctor’s diagnosis being
influenced by the need to acquire organs for transplant.
53
If the paediatricians knew the extent of brain damage in the infants it might bias
their assessments, perhaps unconsciously. It is common to find ‘demand
characteristics’ where scientists bias their results in favour of the hypothesis being
tested.
54 a) Knowing about the nature and extent of brain damage can help doctors and
others provide the best treatment and intervention.
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b)
page 1
Giving treatment is likely to carry some risks. Uncertainty means that doctors will
be more cautious about giving treatment, perhaps missing opportunities to help
the baby. [There is urgent need for further research on the link between immature
births, brain damage and future health].
(Q55 missing in book)
56
Family and doctors may find it difficult to balance the rights of the family with
those of the patient. Family may be keen to rid themselves of a burden or,
alternatively, be too ready to make a self sacrifice on behalf of a relative who has
no chance of a better quality of life. A lawyer will be able to make an independent
judgment. At present a final decision must have legal agreement.
57
The patient may already have given their view about organ donation before the
brain damage occurred, or have carried a donor card. If there is no knowledge of
the patient’s intent, it could be argued that a utilitarian approach means that it is
for the greatest overall good for the patient’s organs to be used. The patient’s
religious and moral views should be taken into account, if known.
58 a) Parents, siblings, other relations. Doctors, religious or moral counselors,
psychiatrists.
b)
Depends on view of student. Most would probably say the mother since she has
given birth to the child.
(two questions numbered Q58 in book)
58
Persistent and permanent have different meanings, with the latter implying that
no recovery is expected. However, there can be reluctance to make such a final
diagnosis, so health workers can be tempted to use the word ‘persistent’. This
may not be helpful when there is really no hope of any improvement, as it leaves
families in doubt about the meaning of a diagnosis.
Review questions
59a) Scientists select samples for measurement. The sample could be unrepresentative
or too small. Errors can be related to equipment e.g. MRI scans: measure blood
flow which is an indirect measure of neuronal activity, or be human error, e.g. misreading a scale or recording a reading incorrectly. Error can be systematic or
random.
b)
Systematic methods mean that extraneous variables are controlled e.g. fMRI scans
control the activity of the subject and the time at which the scan is taken. The
effects of an independent variable (e.g. the effects of alcohol on the brain) require
the use of a matched control sample (e.g. which takes no alcohol but are matched
for age, sex and environmental history).
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c)
Interpretation of brain scans is subjective – though increasingly depends on
computer analysis. Different scientists interpret the same scan in different ways.
Brains differ in the localisation of functions and the relative size of parts. Not easy
to relate brain parts ‘lighting up’ with what the brain is actually doing.
d)
Commercial uses of scans, such as neuromarketing and lie detection, can lead to
unrealistic claims about the significance and reliability of scan information.
Scientists make claims about animal sign language abilities which may be
unrealistic, but which help to promote their research.
60 a) Ethical issues are raised by brain scans, such as fMRI, in the contexts of lie
detection, neuromarketing and decisions about brain damaged individuals and
those with neurodegenerative diseases.
b)
(i) There are ethical guidelines about using animals in research and using humans
in trials of new techniques or drugs.
(ii) Ethics committees advise on procedures such as: decisions about withdrawing
treatment to brain impaired people, organ transplants, the uses of animals in
research.
c)
When decisions are made about withdrawing treatment to brain-impaired people,
the rights of the patient are balanced against the welfare of carers and family.
Some expensive surgical techniques (eg deep brain stimulation for Parkinson’s
patients) need to be balanced against other potential uses of the funding.
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A2 Science in Society
Answers to the questions
Chapter 4 Responding to global climate change
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included which go
beyond the direct requirements of the question.
1
Radiation reaching the top of the atmosphere from the Sun is at its highest in June
and lowest in December/January. The longest day is at the summer solstice which
is on the 20/21 June and shortest day at the winter solstice is the 21/22nd
December.
2
At the time of the summer solstice the tilt of the Earth points the northern
hemisphere towards the Sun while at the winter solstice the northern hemisphere
is tilted away from the Sun.
3 a) Examples: water evaporates from the oceans and enters the atmosphere, rain
(and other kinds of precipitation) carry water from the atmosphere to the oceans;
wind blowing over the oceans creates waves transferring energy to the moving
water; gases from the atmosphere, such as carbon dioxide, dissolve in the oceans.
b)
Examples: melting ice gives rise to local currents of less salty, cold water than the
surrounding ocean; sea ice insulates the ocean from the cold polar atmosphere;
ice reflects a much higher proportion of the Sun’s radiation that open ocean.
c)
Examples: snow falls from the atmosphere and builds up the thickness of ice;
ocean currents carry icebergs away from where they break away from ice sheets.
4
The poles are covered with ice and snow which is white and has a very high
albedo. Forests, open water and soils absorb much more radiation and reflect
much less than ice and snow.
5
Water is a liquid at the temperature of the surface of the Earth. Also the Earth’s
atmosphere contains rather little carbon dioxide but (thanks to photosynthesis) it
is one-fifth oxygen.
6
Red is at the longer wavelength end of the visible spectrum, blue is at the shorter
wavelength end. On heating in a flame, a piece of metal first glows a dull red and
then as it gets hotter it becomes more orange and then yellower as the radiated
light shifts towards the shorter wavelength end of the spectrum. The colour of the
very hot filament of an incandescent light bulb is a yellowish-white and not red.
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7
Possible effects: the material gets hotter (microwaves, IR); electric currents flow in
the material if it is a conductor (radiowaves); chemical changes happen to the
material (UV and other ionising radiations).
8
The hotter the air the more moisture it can hold. This is why dew forms at night on
surfaces at the air cools. On even colder nights the water condensing from the air
forms frost.
9
Motor exhausts contain oxides of nitrogen if catalytic converters are not working
efficiently. In sunlight, these oxides act as a catalyst to turn oxygen into ozone.
(See AS Science in Society textbook page 50.)
10
All of the gases absorb infrared radiation and act as greenhouse gases except for
nitrogen and oxygen.
11
Enhancing the greenhouse effect does not alter the rate at which energy arrives at
the Earth from the Sun but it does decrease the rate at which the Earth radiates
energy back into space. This changes the energy balance of the Earth and warms
up the planet.
12
Examples of positive feedbacks:
 as the oceans and atmosphere get warmer, the level of water vapour in the air
rises; water is a powerful greenhouse gas so this enhances global warming.
 the oceans get warmer as the rise in greenhouse gases enhances global
warming, this means that the oceans take up less carbon dioxide from the
atmosphere leading to a further increase in the level of CO2 in the atmosphere.
 a warmer world leads to ice melting at the poles and from glaciers; this lowers
the albedo of the Earth’s surface meaning that less radiation from the Sun is
reflected and more is absorbed leading to further warming;
 warming of wetlands, especially in high latitudes, increases the rate of release
of methane; methane is a powerful greenhouse gas.
13
Examples of negative feedback in the climate system:
 a rise in temperatures increases the moisture in the air so that more clouds
form, this can mean that more of the Sun’s radiation is reflected back into
space before it reaches the surface of the Earth.
 a higher atmospheric carbon dioxide concentration leads to increased growth
of plants which then take up more carbon dioxide from the atmosphere
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14 a) In the short term: volcanic eruptions; changes to the Sun’s radiation during the
sunspot cycle and also cycles in ocean currents which can have a worldwide effect
- such as the shift of warm water from the west Pacific and the Indian Ocean to
the east Pacific during El Niño events
(www.bbc.co.uk/weather/features/el_nino_events.shtml).
b)
Longer term changes in climate can arise from: tectonic movements in the Earth’s
crust that lead to changes in ocean and air currents; long term cycles in the orbit
of the Earth round the Sun that lead to variations in the energy of the radiation
reaching the planet;
15 a) Examples: sugars, starch, cellulose, proteins.
b)
‘Marine biota’ covers all the living things in the sea including fish, plankton,
seaweed and so on.
c)
Changes in land use: clearing woodland to make way for agriculture; extracting
peat to use in compost.
d)
Fossil fuels include coal (mostly carbon), crude oil (hydrocarbons) and natural gas
(hydrocarbons). When these fuels burn the carbon combines with oxygen from
the air to form carbon dioxide.
e)
Manufacturing process based on rocks that adds carbon dioxide to the
atmosphere: making cement; making lime from limestone; extracting iron from
ion ore mixed with limestone in blast furnaces.
16 a) Total mass of carbon passing into the atmosphere each year = 157.1 Gt
b)
Net change in the mass of carbon in the atmosphere each year = (157.1  153.7)
Gt = 3.4 Gt added to the atmosphere
c)
The addition of 5.5 Gt from fossil fuel burning and industry is a significant addition
because it means an overall increase of the carbon (as carbon dioxide) in the
atmosphere. Without this addition the figures suggest that there would a net
removal of carbon from the atmosphere
d)
Most of the added carbon dioxide stays in the atmosphere but some is taken up
by plants growth and by dissolving in the oceans.
17
In reality there are a number of interacting cycles rather than just one. Thinking in
terms of cycles is a reminder that the total amount of the element carbon on
Earth is a constant. The element combines in different ways with other elements
but the quantity does not change. When a fuel burns, the carbon in it does not
disappear but ends up in the air. Modelling all the changes to carbon in the
environment and estimate the amounts in each reservoir and the flows between
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reservoirs makes it possible to assess the significance of human activities that
interfere with the natural cycle.
18 a) Arriving at global budgets for all the components of the carbon cycle is very
difficult. The data comes from a variety of scientific disciplines and is measured
with a great variety of different instruments in different parts of the world.
b)
Different plants in different environments, for example, carry out photosynthesis
and respiration at different rates – and at rates which vary with the time of day.
Coming to an overall figure for the carbon taken up by plant photosynthesis or
given out by respiration of all organisms over the whole land surface and in the
oceans is very challenging.
c)
Measurements of carbon dioxide in the atmosphere are very accurate and it is
relatively easy to estimate the volume of the atmosphere to allow for the changes
of temperature and pressure with altitude. So the amount of carbon in the
atmosphere can be estimated very accurately.
Commercial figures from the coal, oil and gas industries show how much fuel is
being burnt. Similarly the scale of cement manufacturing and other industrial
processes is recorded. This data makes it possible to come up with reasonably
reliable figures for the emissions of carbon dioxide into the atmosphere as a result
of human activities.
19
It is a site far removed from sources of pollution. The surface of the volcano
around the site is bare rock and so there is no vegetation near the sample point.
20 a) In general, global carbon dioxide concentration in the atmosphere is high when
the mean global temperature is relatively high, and low when the mean global
temperature is low. The greenhouse effect is stronger when there is more carbon
dioxide in the atmosphere and weaker when there is less. The most recent glacial
period was about 20 000 years ago There were glacial periods with a 100 000 year
cycle about 150 000, 250 000 and 350 000 years ago.
b)
The concentration of carbon dioxide in the air remained more or less constant for
the 2000 years up to 1750.
c)
The industrial revolution with the introduction of steam engines led to a great
increase in the burning of coal and other fossil fuels.
21
Over relatively short timescales, the components of the carbon cycle likely to
affect the carbon dioxide concentration in the atmosphere are vegetation of land,
organisms in soils, and the surface of the oceans.
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22 a) If plankton in the upper parts of the oceans take up less carbon dioxide when the
water is warmer the concentration of carbon dioxide in the atmosphere tends to
rise. This is positive feedback.
b)
Plants growing faster tends to remove carbon dioxide from the atmosphere rises.
This is an example of negative feedback.
c)
Organisms including microorganisms respire more; this tends to add carbon
dioxide to the atmosphere so this is positive feedback.
d)
Forests are a major carbon sink so if forests die back and grow less there is more
carbon dioxide in the atmosphere. This is positive feedback.
23 a) Methane is found in coal mines and in oil wells. Natural gas consists mainly of
methane. All processes that involve extracting these resources inevitably release
methane into the atmosphere, even though as much as possible is now captured
for use as a fuel.
b)
Microorganisms in the soils of cultivated fields give off carbon dioxide, especially
in rice paddies. Cows are a major source of methane.
c)
When bacteria break down organic wastes they produce methane. If this methane
is collected and burnt as a fuel, its carbon enters the atmosphere as carbon
dioxide.
24
Methane gas absorbs infra red radiation more strongly than carbon dioxide.
25 a) CFCs absorb infra-red radiation strongly; they are also very stable compounds
which stay in the atmosphere for a very long time.
b)
Methane is oxidised in the air. The half-life for methane after release in the air is
about 7 years. Carbon dioxide stays in the air much longer with a half life of about
70 years.
26
The USA.
27 a) Burning fuels to heat buildings releases carbon dioxide into the air.
b)
Organic wastes rot and give off methane as they do so;.
c)
Rice paddies and cows release methane into the atmosphere. The manufacture of
fertilisers uses natural gas, or other hydrocarbons, to make ammonia and in the
process produces a large quantity of carbon dioxide. Much energy is also burned
in cultivating, harvesting and transporting crops.
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d)
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Clearing grassland and forests destroys carbon sinks. Bacteria in disturbed soils
release more carbon dioxide into the air than they do from soils that are not
disturbed.
28 a) There is considerable natural variation in English weather from year. The
atmosphere is a complex system and changes from year to year in the movement
of air masses moving across England mean that mean temperatures and rainfall
fluctuate.
b)
There seems to be no overall trend in the mean precipitation (rain, snow, hail) but
since 1990 the trend line for temperature has moved up and out of the range seen
in the previous 300 years.
29 a) Mean global temperature seem to remain steady in the period 1945 – 1975 also
1890 to 1020.
b)
There was marked global warming from 1920 to 1945 but even more so from 1975
to the present.
30
In the late twentieth century picture the depth of ice over the rocks appears to be
less and the glacier ends higher up the mountain. This suggests that there has
been less snowfall and/or that ice has been melting as a result of climate change.
31
The shells of molluscs consist mainly of calcium carbonate. Sea molluscs include
clams, oysters and many others. When they die, the shells sink to the bottom of
the ocean forming sediments.
32 a) The volume of ice is higher during periods of glaciation (ice ages). The dips in the
graph in figure 4.16 can be matched with the dips in the plot of carbon dioxide in
the atmosphere in figure 4.10.
b)
In both plots there are major dips in the curve, corresponding to periods of
glaciation, at roughly the same times at 100 000 year intervals.
c)
Earth scientists infer information about past climates from a variety of
measurements made on natural archives. The interpretation of the data is based
on theory. Showing that applying different theories to a variety of archives makes
it possible to provide independent estimates of variables such as temperature and
precipitation. If the findings are consistent, this helps to confirm that the theories
are correct.
33
Oxygen-16 atoms are lighter than oxygen-18 atoms. This means that the first
water vapor formed during evaporation of liquid water is slighter richer in water
with oxygen-16 atoms. The water left behind is slightly richer in water with
oxygen-18. Similarly, if the moist air moves to a cooler region, the water vapor
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condenses back into liquid. The liquid formed is slightly richer in oxygen-18 while
the remaining vapor is slighter richer in oxygen 16.
34
They can check the results from ice cores by comparing the results over the last
10 000 years or so with the values obtained from studying documentary records,
pollen grains or tree rings.
35
The sensitive techniques of chemical analysis were not available to measure the
concentrations of trace gases until about 50 years ago.
36
Two assumptions: that the gas trapped in a bubble has the same composition as
the atmosphere at the time; that the composition of the trapped air does not
change with time
37
Forest fires, volcanoes, transport and industrial pollution add particulates and
aerosols to the atmosphere which can be swept out of the air by falling snow. In
time some of these pollutants can release or produce carbon dioxide.
38
Some characteristics of snow vary strongly with the seasons. This means that it is
possible to detect the annual layers in an ice core. The layers can be counted like
tree rings to find the age of the layers of ice.
39
A ‘proxy’ is a person that is authorised to act for someone else (for example when
casting a vote). In climate research, a ‘proxy variable’ is something that can be
measured and from which values of a variable of interest can be obtained. Tree
ring widths and analysis of ice core layers gives data that is a proxy for past
temperatures.
40
The nickname ‘hockey stick is used to describe the curve in figure 4.19.
a)
The curve has roughly the same shape as an ice hockey stick.
b)
The most striking feature of the curve is the warming in the latter part of the 20th
century, particularly the latter part of that century and continuing to present day.
The evidence shows that the warming is unparalleled in the past millennium and
therefore very unlikely to be natural.
c)
The more recent values are based on direct instrumental measurements and so
subject to less uncertainty than values obtained by interpreting proxy data.
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d)
International research programmes to collect and collate the data only got
underway on a large scale in response to concerns about human impacts on the
environment. Also several of the techniques for interpreting proxy data depend on
sophisticated instrumental methods of analysis that were not available until the
second half of the twentieth century.
41
The concentrations of the elements in the ice have to be measured accurately. Out
bodies contain solutions of sodium, chloride and other chemicals and so
contamination from the body of the analyst would affect the results. Hence the
need for protective clothing – to protect the samples, not the scientist.
42
When the climate is arid there is less vegetation to protect the ground surface
from the eroding action of the wind. More of the surface of the planet is dry and
dusty so there is more dust to be caught up and blown round the world by the
winds.
43
When the climate is windy there are more waves and sea spray. The water of the
seas are salty so the winds carry salts from the stormy seas to fall with
precipitation in the Arctic.
44
This cooling event is very sudden on geological timescales. The finding shows that
the climate can cool dramatically in a relatively short time.
45
This represents an increase by a factor of about 150 in the number of cells for
which the computer has to handle data and calculate values based on the laws of
physics.
46
See the answers to questions 12 and 13. There remains considerably uncertainty
about the effects of rising moisture levels in the atmosphere in a warmer world.
Water is a greenhouse gas and so a more humid atmosphere tends to reinforce
the greenhouse effect. However increased cloud cover can lead to negative
feedback because of the reflection of sunlight back into space from top of cloud
layers.
47
That it is necessary to take into account anthropogenic effects to explain the
observed rise in global mean surface temperature. In other words, the rise is very
unlikely to have occurred as a result of just natural changes.
48
Testing the models over the last 150 years can be a severe test because there is
data covering a wider range of climate variables – so the tests are more detailed.
Also the measurement uncertainty associated with the data is much less and so
the model values have to lie within a narrower range to be consistent with the
observations.
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49
All estimates about the environmental, social and economic consequences of
global are related to the expected temperature rise over a given period of time as
a result of the increase in greenhouse gases in the atmosphere. Projected
temperature rises in the coming decades are based on the value of climate
sensitivity.
50
If climate sensitivity were solely due to the changes in the level of carbon dioxide
in the atmosphere, it would be relatively easy to estimate. However the value for
sensitivity is strongly affected by all the feedback mechanisms. It cannot be
assumed that the feedbacks that affected the climate system in the past are the
same as the feedbacks that will operate in future in an industrialised world very
much affected by human activities.
51
The graph suggests that the climate sensitivity of the northern hemisphere is 3 C.
52
Climate models are based on all the available data and the theories which
underpin our understanding of the Earth’s climate. The projections from the
models are the best available information we have about the likely consequences
of current trends. We have no better guide when deciding on the policy about our
use of energy resources.
53
The model suggests that warming will be greatest at higher latitudes, especially in
the Arctic.
54
The model shows large increases in rainfall in the monsoon regions of South
America, Africa and Asia.
55
Critical review of published data and theories is the main means by which scientist
test new ideas and information and to reach a consensus about scientific ideas.
Publication is also important because the issue of climate change is of great
importance to energy policy and practice, so politicians and others need to know
what the world of science has to say about the future of the Earth’s climate.
56
The job of the IPCC is to carry out a critical review of the work of others. The IPCC
publishes synthesis reports which are assessments of the current state of scientific
knowledge about climate change. Review of scientific findings by scientific experts
is fundamental to the process. This is peer review.
57
The aim of the IPCC is to inform governments of the consequences for our climate
of the implications of the way that societies use energy and other resources, now
and in the future. Governments have to consider a range of options for policy and
they need to know the implications of the policies they adopt.
58 a) Business as usual: 750 ppm
b)
Best-case scenario: 530 ppm
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Worst-case scenario: 960 ppm
59 a) The only scenario to avoid a doubling by 2100 is B1. A1T only just exceeds the
doubling value by 2100.
b)
Both scenarios are based on the use of renewables in place of fossil fuels Scenario
B1 involves a reduction in the use of materials and the introduction of cleaner and
more sustainable technologies.
60 a) Scenario A1F1 assumes intensive use of fossil fuels which give off carbon dioxide
as they burn. This is the scenario with the highest emissions of carbon dioxide.
b)
Different models vary in the way that they take into account the various feedback
mechanisms that affect the climate system.
c)
All the projections show a rise in the concentration of carbon dioxide in the
atmosphere up to the year 2100. They all show a rise in mean global
temperatures.
61
While the promise of a warmer climate in England might be attractive it is
important to bear in mind that:
 there might be marked changes in rainfall so hotter summers might also be
wetter,
 there might be more extreme weather events including destructive storms and
floods,
 people in England cannot ignore the climate in other parts of the world given
the extent to which they rely on imported food from other countries.
62
Examples of extreme weather events likely to become more common and more
intense as the mean global temperature rises include: heavy rainfall leading to
flooding; increased wind speeds in storms, also droughts that can lead to severe
water shortages.
63 a) Expansion of water in warmer oceans is expected to make the greatest
contribution to sea-level rise.
b)
The project rise in mean sea level by 2100 is 0.59 metres.
c)
The areas of land most vulnerable to sea-level rise are highly populated. They are
also fertile areas where food is grown. Salt water would contaminate soils and
sources of water in these low-lying areas and so damage supplies of food and
drinking water.
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64
Increased flows bring water for irrigation, drinking and industrial purposes. Greatly
increased flow lead to damaging flooding.
65
Threats to global food security include population growth, resistance of pests to
chemicals used to protect crops, the rising cost of fertilizers made using natural
gas or oil, warfare and other forms of political instability.
66
Increased use of fertilizers leads to greater emissions of carbon dioxide during
their manufacture from air and fossil fuels. Adding nitrates to soils leads to
increased emissions of nitrogen compounds that are greenhouse gases. Increasing
the are of cultivated land disturbs soils when they are ploughed and this releases
greenhouse gases. Cutting down forests and woodlands to grow crops destroy
carbon sinks and increases emissions.
67
Forest die-back has a positive feedback effect on warming because the death of
trees not only removes an important carbon sink – trees absorb carbon dioxide for
use in photosynthesis – but also the dead trees release more carbon dioxide back
into the atmosphere when they decay.
68
Reduced food security will lead to further malnutrition; problems of access to safe
drinking water and adequate sanitation cause greater prevalence of water-borne
diseases such as cholera.
69
One example would be the spread of mosquitoes that carry malaria to countries in
northern Europe including the UK. This would have implications for the National
Health Service and also for lifestyles.
70 a) Attempts to mitigate the effects of sea-level rise by building sea defences and
defences against flooding would be very expensive. New investment in the water
industries capacity to store water might be needed to even out the extremes of
rainfall. Farmers might have to change their practices to grow different crops and
to keep different animals. This would have implications not only for farming
practices but also for the food industries based on the products of farming.
b)
In some cases the responses would be unavoidable to secure water and food
supplies. In other cases it might be judged better to ‘let nature take its course’ and
not try to defend areas of land against incursion from the sea.
71
Some countries are richer and have more natural resources so they can afford to
invest in responses to mitigate climate change. The geography of some countries
means that the impacts are less severe.
72
The Kyoto protocol offers three ways for industrialised countries to offset some of
their emissions. Explain why these examples of the three ways can be effective:
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a) helping to pay for reforestation or investment in energy schemes such as solar
power.
b) investing in schemes to replace or improve inefficient, fossil-fuel-powered,
energy generation.
c) buying emissions ‘allowances’ from nations that are in a position to exceed
their targets under the Kyoto Protocol.
73
The coal and oil industries have made huge investments in their mines, wells and
processing facilities. Some oil companies have been shown to support
organisations that argue against the need to respond to climate change. Large
numbers of people that enjoy the benefits of motoring and air travel are likely to
resist attempts to restrict their movements to cut down on the use of fuel.
74
Global warming is a consequence of increased levels greenhouse gases trapping
radiation emitted from the Earth and passing out into space.
Ozone depletion is the result of chemicals, such as CFCs, that speed up the break
down of ozone in the upper atmosphere in sunlight. The thinning of the ozone
layers allows more of the Sun’s UV radiation to reach the surface of the Earth
where it can harm living things.
75
The answer here depends on your experience and awareness of media reports of
climate change. This is report by an experienced journalist in the field with his
reflections about the views of the media to climate change:
http://www.panos.org.uk/?lid=28406. See also this report:
http://www.cjr.org/the_observatory/public_opinion_and_climate_par.php.
76
This New Scientist web site is a guide to the perplexed and gives questions and
answers: http://www.newscientist.com/article/dn11462.
Review questions
77 a) An example is the law that predicts how the mean wavelength of radiation
emitted from an object varies with its temperature. The hotter the object the
shorter the mean wavelength so peak radiation from the Sun is in the visible and
UV regions of the spectrum while radiation emitted from the surface of the Earth
is in the infra-red region.
b)
This is illustrated by the complex models which scientist use to account for past
data on temperature and rainfall at the surface of the Earth.
c)
Scientists, in general, are confident about the theory of the greenhouse effect
because they can account for it in terms of well established physical and chemical
explanations.
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The theory if global warming is quantitative and can be modelled in detail. The
theory can account for past variations in climate. The models can be used to
predict future patterns in the climate which can be tested experimentally.
78 a) Instrumental records are only available for a relatively short time in the Earth’s
history. Major changes to climate have occurred over millions of years and
scientists need to be able to test their models over long time scales.
b)
See the answer to question 13.
c)
See the answer to question 12.
d)
A major source of uncertainty is that it is impossible to predict the scale of
technological innovation and policy change all over the world. In other words it is
not possible to anticipate which, if any, of the IPCC scenarios will apply (see page
124).
e)
Climate sensitivity measures the average change of mean surface temperature of
the Earth as a whole. Estimates of climate sensitivity can be made by looking at
data from the past, but the atmosphere has changed markedly since the start of
the industrial revolution and so climate models based on current data provide the
best way of coming up with a value for climate sensitivity.
79 a) A great diversity of data has to be collected from a variety of sources using many
different kinds of measuring instrument. Each set of proxy data has to be
interpreted according to different sets of scientific explanations. Different
specialists are needed in the different fields.
b)
In the UK Research Councils fund a variety of climate change research. This is an
area which scientists, politicians and informed members of the public think is
important. Research is also funded by interest groups such as oil companies who
want to know how they should respond technically and politically to the threat of
climate change. The news reports at this web site reflect the variety of people and
organisations concerned about climate change research:
http://www.tyndall.ac.uk/.
c)
Some of the factors to consider: the reputation of the scientists who carried out
the research; the source of the funding for the research; the extent and scale of
the research, whether or not the research has been published in a peer reviewed
journal; the response of other scientists to the research and whether the findings
have been checked or replicated in some way.
80 a) The impacts of climate change are predicted to happen over a much longer
timescale that the time that politicians are in power. Scientists attach measures of
uncertainty to their predictions are not able to say that events will definitely turn
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out in a particular way. Serious attempts to deal with the threat of climate change
will need significant changes in lifestyle and will be expensive. This is difficult for
elected politicians to deal with.
b)
The precautionary approach applies when the science is still uncertain but there is
a realistic risk of harm to people’s health or the environment. A precautionary
approach to policy making takes into account the science (in so far as it is known),
the scale of the risk, the costs of policy interventions as well as public opinion. The
approach is controversial: some see it as common sense (‘better safe than sorry’);
others regard it as a serious threat to potentially valuable technological
innovations.
81 a) Data has to be collected from all over the world in order to monitor climate
change. The are many aspects to developing the theory of climate change so lots
of scientists, with different kinds of expertise, have to be involved. The impacts of
climate changes and the policies needed to mitigate them vary from regions to
regions and so people with local knowledge and expertise have to be involved.
b)
Climate change is the result of greenhouse gas emissions. This is a global problem
as gases given out by one country go into the atmosphere and effect the whole
world. A concerted international response is essential if levels of greenhouse gases
are to be reduced.
82
You could start by visiting council web site and searching with terms such as
‘climate change’ and ‘sustainability’. This would allow you to assess what the
council is already doing, if anything. Having assessed the situation you could send
e-mails to local councillors expressing your views and asking for a response. You
could also contact your local MP and contact the local media. You might also get in
touch with local branches of voluntary groups or pressure groups such a your local
wild-life trust.
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A2 Science in Society
Answers to the questions
Chapter 5 Energy futures
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included
which go beyond the direct requirements of the question.
1
USA: 98 000 kWh per person per year
UK: 49 000 kWh per person per year
DR Congo: 3600 kWh per person per year
2
Per capita energy consumption in the USA is about 27 times greater than in the
Democratic Republic of the Congo.
3
Unlike the DR Congo, most people in the USA are heavily reliant on motor
vehicles, they live in homes that are heated in winter and air conditioned in
summer. Almost all people can rely on a mains electricity supply and they use a
wide range of electrical equipment.
4
In all countries there are disparities of wealth. Extremes of wealth mean that even
in rich countries there are poor people who cannot afford to use much energy
while in poor countries there are very rich people who enjoy a lifestyle that is
heavily dependent on energy supplies.
Countries with a very small number of extremely rich people but a very large
number of poor people may have a high average level of income, even though the
most people in the country have a low ‘standard of living’.
5
Standard of living is an indicator of the goods and services that people can afford
to pay for with their income including food, homes, household goods, energy
supplies, health care and transport.
People can enjoy a good quality of life without necessarily having a large income if
they live somewhere where the law prevails so that they feel safe, if they can earn
enough to meet their basic needs, if they can enjoy a social life with family and
friends, and if they live in a pleasant and healthy environment.
6 a) Technologies that needs a relatively large amount of fuel or electricity include
devices for heating homes and water, air conditioning and transport including
motor vehicles and aeroplanes.
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Technologies that do not require the user to pay for a lot of energy include
personal electronic devices (MP3 players and mobile phones), energy efficient
lighting and many kinds of sporting activities where human muscle power provides
the energy such as cycling, swimming and working-out in a gym.
However a considerable amount of energy made be needed to make or service
the associated technological devices. The servers and other parts of the
infrastructure that support the internet around the world, for example, use as
much energy as air travel.
7
Most farming activities such as ploughing and harvesting are now carried out by
machine. The manufacture of fertilisers uses natural gas and uses 3-5% of world
natural gas supply. Food processing and storage need energy. Refrigerators to
keep food fresh need energy. Much food is imported into the UK by ship and air
and then is transported to depots and then on to supermarkets. The scale of road
transport for food means that HGVs carrying food account for about 25 per cent of
the distance travelled by freight vehicles on our roads.
8
There are many possible examples: all processes that burn fossil fuels give out
carbon dioxide which is a greenhouse gas; some also give out oxides or nitrogen or
sulfur which give rise to acid rain and can affect people’s health. The increase in
the use of biodiesel has led to the clearance of tropical forests to grow more crops
and at the same time increased food prices as crops are used to make fuel instead
of food. Motoring leads to road accidents which injure and kill people.
9 a) Features that are little changed: most of the primary energy is from fossil fuel; the
contribution from coal is about the same as is the contribution from renewable
fuels that burn.
b)
Two significant changes: the use of natural gas has increased while oil has declined
relatively; there has been a growth in energy from nuclear power; renewables
such as solar and wind contribute relatively little but have increased significantly.
10
In the period from 1973 to 2005 what was the increase in world TPES:
a)
Increase: 5307 Mtoe
b)
Percentage increase from the 1971 figure: 87%.
11
Percentage of world TPES from fossil fuels:
a)
in 1973 – 86.6%
b)
in 2005 – 81.0%
12
The energy intensity of a country falls if there is a general improvement in:
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 the energy efficiency of appliances and buildings, for example through the use
of different building materials and methods to improve insulation,
 the fuel economy of motor vehicles, or a reduction in the number of journeys
and the distances travelled,
 a change in the economy from heavy manufacturing industries that use a lot of
energy to commercial activities in the financial and service sectors which
require less energy.
13
There is a correlation between the total primary energy used per capita and GDP
per capita. However countries with roughly the same GDP can have widely
different values for energy used per capita because of differences in the energy
efficiencies of the economies.
14
The overall energy intensity of a country depends on both the energy efficiency of
the lifestyle of the people and the energy efficiency of all its commercial and
manufacturing activities. Japan has increased its energy efficiency by a shift from
heavy to light industries, and by having a national policy for energy efficiency and
conservation in all sectors.
15 a) The carbon combines with oxygen to form carbon dioxide. They hydrogen
combines with oxygen to form water.
b)
If fuels burn in a limited supply of air the carbon forms the highly toxic gas carbon
monoxide. At high temperatures, during burning, nitrogen from the air can
combine with oxygen to give oxides of nitrogen which in turn give rise to acid rain.
Carbon dioxide is a greenhouse gas and adds to global warming.
16
The main product of burning coal is carbon dioxide. Fuels containing a higher
proportion of hydrogen from more water and less carbon dioxide when they burn
to give the same amount of energy.
17
Greater energy efficiency means that the same electricity energy can be supplied
while burning less fuel. Burning less fuel means that less carbon dioxide is formed.
18
Wood chippings, and other forms of biomass, are formed by plants as they grow.
The same amount of carbon dioxide is given out as biomass burns as was taken in
by photosynthesis during plant growth. However biomass cannot be completely
carbon neutral because of the fossil fuel burnt to supply the energy for harvesting,
processing and transporting the biomass.
19
The existence of oil wells off the coast of the UK suggests that CCS might be
feasible in this country. In March 2005, a POST report for MPs
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(www.parliament.uk/documents/upload/POSTpn238.pdf) came to these
conclusions:
 Carbon capture and storage (CCS) in geological structures is technically feasible,
although further development is needed to optimise it.
 CCS potentially offers carbon emissions reduction at costs similar to offshore
wind and nuclear power.
 CCS offers a low-carbon way to use fossil fuels toensure security of electricity
supply.
 Enhanced oil recovery in the North Sea could reduce the cost of CCS and could
also act as a showcase for UK technology and raise public awareness of CCS.
 Under present economic conditions CCS is not financially viable. Creating
incentives for CCS forms part of the wider debate on economic strategies to
reduce CO2 emissions.
 CCS could play a key role in reducing future emissions from the developing
world.
20
CCS requires energy to separate carbon dioxide from flue gases, compress the gas
and inject it underground or under the sea. This means that more energy is
needed to generate electricity from a power station using CCS. This makes
generating electricity from a coal-fired power station more expensive.
21
This is a matter of opinion. The decision has to balance the importance of ensuring
secure electricity supplies from a diverse range of fuels against the damage to the
environment of increased emissions of carbon dioxide.
22
The differences in the processes can be seen from figure 5.10. In the nuclear
powered station it is the nuclear reactor that generates the heat which turns
water into steam to drive the turbine. However, the heating is indirect with the
reactor heating a gas or liquid which in turn heats up water in the boiler via a heat
exchanger. In the coal-fired power station it is the burning of the coal that
generates the heat – the rest is the same.
23
Fossil fuels provided the energy for mining uranium ore, extracting uranium and
then enriching the ore. More energy from fossil fuels is used during the
construction of a nuclear power plant. Yet more energy from fossil fuels is
required to handle, transport and store nuclear wastes.
24
People tend to overestimate the risk from rare events and underestimate risks
that are familiar. They fear dangers that inspire dread that are new or not fully
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understood. They also fear dangers that they cannot control and are likely to
affect future generations. There seems to be a deep rooted fear of things such as
radiation and poison that, in some way, get into the body and cause long term
health effects. In the case of radiation the harmful effects include cancers which
may develop many years after exposure. Cancer is a disease that kills many people
and which many people fear. Another association that can add to dread is the link
with nuclear weapons.
25
Examples of risks that are tolerated: risk of a traffic accident, risk of injury from a
sporting activity, risks from medical treatments.
Examples of risks that are accepted: risk of an accident at home (such as falling
downstairs or using knives), risks of using electrical appliances and many other
aspects of normal everyday life.
26
Figure 5.19 shows that the physical bulk of radioactive waste is largely made up of
low-level waste but that almost all the radioactivity is associated with high-level
waste.
27 a) Routine leaks: leaks into the air are likely to mainly affect people living nearby;
leaks into the sea can spread quite widely and if fish are contaminated affect
those who eat a diet with fish.
b)
Stored nuclear waste: in the short term this is only likely to affect people working
in the industry unless there are leaks from storage tanks which release radioactive
materials into the environment.
c)
Nuclear accidents: the Chernobyl accident showed that the most serious effects
are experienced by people living in the region. A circular exclusion zone with a
radius of 30 Km was established after the accident and this meant that 120 000
people from 90 communities had to move permanently from their homes.
However the cloud of radiation travelled a long distance and affected people over
a huge area as illustrated by figure 5.20.
28
Most high-level nuclear waste is currently stored in tanks above ground. This is a
temporary stage while solutions to long-term methods are developed. The nuclear
industry only began in the middle of the twentieth century and so there is only
about 60 years experience of dealing with waste that will have to be disposed of in
ways that isolate it from the environment for thousands of years.
29
A POST report for MPs published in 2004
(www.parliament.uk/documents/upload/POSTpn222.pdf) covers these four
aspects of the risk assessment:
 Intelligence: assessing the nature of the threat.
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 Vulnerability: assessing the physical robustness of nuclear facilities.
 Security: assessing the resilience of security regimes.
 Consequences: evaluating the impact of an attack.
30
In the UK nuclear power grew out of the military use of nuclear energy and so in
the early years the industry was secretive. There were accidents, such as the
Windscale fire, but these were ‘hushed up’. This led to a lack of trust in the
industry. Other accidents such as Chernobyl in the Ukraine and Three Mile Island
in the US have shown that the consequences of a disaster can be very serious,
widespread and long-lasting. People are worried that there is still no agreed
solution to the problem of dealing with radioactive waste.
31 a) Nuclear power stations generally run all the time providing the base load for the
national electricity grid. They can contribute to security of electricity supplies so
everyone in the country can benefit.
b)
Risks tend to be more narrowly distributed than the benefits. People who work in
nuclear power stations may be exposed to higher levels of radiation. People living
in the area where the new power station is built will have to put up with the
increased traffic during the period of construction and the setting up or more
pylons near their homes.
c)
The main compensation could be the new opportunities for employment in an
area which is likely to be fairly remote from centres of population. The nuclear
industry could well sponsor local charities and contribute to the development of
local facilities for recreation, sport and healthcare.
32
The association means that the development of nuclear power remains a highly
political issue. Hans Blix, in a speech to the World Energy Council in 2001
(http://www.world-nuclear.org/sym/2001/blix.htm) put the case for nuclear
power from the perspective of the nuclear industry:
“Nuclear energy is not alone in being susceptible to both peaceful and military
uses. Airplanes can be used for transportation - and to drop bombs. Explosives can
be used to blast ores in mines - but also to destroy cities. Indeed, a simple knife
can be used for good and for bad. It depends upon us how we use nuclear energy.
As we know that nuclear weapons could destroy human civilization, it is certainly a
rational task to work for both the non-proliferation and the elimination of these
weapons.”
However there are many who are opposed to the further developments of nuclear
power and among the arguments used are those which cite the potential military
use of the radioactive materials used to generate nuclear power. See, for example,
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this statement from the Time for Change web site (http://timeforchange.org/prosand-cons-of-nuclear-power-and-sustainability.
“During the operation of nuclear power plants, radioactive waste is produced,
which in turn can be used for the production of nuclear weapons. In addition, the
same know-how used to design nuclear power plants can to a certain extent be
used to build nuclear weapons (nuclear proliferation).”
33
Unprocessed spent nuclear fuel will decay to below the activity of the original
uranium ore in under ten thousand years. Radioisotopes decay exponentially. This
means that decay is fastest in the early stages so for most of the time that fuel is
stored the waste is at a significantly lower level of activity than at the start.
34
Intermediate level waste is made up of some waste from reprocessing wastes and
some reactor components from decommissioning (www.worldnuclear.org/info/inf60.html). This waste is sufficiently radioactive to need
shielding and there is considerably more of it, by volume, than high level waste
(figure 5.19).
35
The reprocessing facilities at Sellafield were expensive to build and are costly to
operate. It helps if some of the costs are recovered by reprocessing nuclear fuel
for other countries as a commercial business.
The waste fuel has to be transported to Sellafield and then returned to the
country of origin after processing. There are risks associated with transhipment
and transport of radioactive materials. There might be an accident that released
some of the material – though great care is taken to avoid this. However there is
also the danger of hazardous material falling into the wrong hands – notably of
terrorists interesting in making a ‘dirty bomb’.
36
Dumping in a deep ocean – the idea is to bury the waste in deep deposits of clay
well away from boundaries between tectonic plates. The arguments in favour are
that clays are very impermeable and the cold water at the bottom of the oceans
does not mix with water above it. However there is the danger that the canisters
enclosing the waste would, in time break open and that there would then be
unpredictable interactions between salt water and waters. Ocean currents could,
in time, spread the waste with damaging consequences.
Burying under Arctic ice – one of the problems of dealing with high level waste is
the energy released that means that the waste heats up its surroundings. The
waste would melt the ice, affect the stability of the ice sheets and make it likely, in
time, that waste would escape into the environment. This solution is not
permanent or secure over the timescales involved.
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Firing into space – this could be a permanent and secure solution but it doubtful
that the capacity could exist to fire all the material to be disposed of into space.
The risk of a catastrophic failure during the launch of the rocket taking the
material into space means that it cannot be regarded as safe.
Keeping on the surface in containers – many scientists think that this is the only
wise solution at present given the uncertainties associated with other methods –
this method but depends on continuous maintenance and monitoring. It is not
permanent and not secure if there is a breakdown in law and order or a military
attack. the advantage is that the waste can be observed allowing problems to be
detected and managed. After a century of storage the radioactivity will have
declined to an extent which allows the waste to be contained more easily.
Burying in an underground repository – this has been the preferred solution for
the nuclear industry. If it were possible to find a geologically stable rock formation
that could contain the waste for ever without fear of material escaping as a result
of earth movements, percolation of water or earthquakes, this could be regarded
as permanent and secure. There is powerful opposition from local communities
whenever underground storage is proposed in a particular location.
37 a) Her main reasons: the dangers of climate change as a result of global warming are
so severe that alternatives to fossil fuels must be found; security of supply mean
that it is increasingly important not to be dependent on any one energy resource
and especially not on imported gas and oil; renewables can make a contribution
but not on a large enough scale with including nuclear power in the mix.
b)
This is a matter of opinion. Your answer should include arguments which give
evidence and show how the evidence supports your point of view.
38 a) Hydroelectric power was the renewable source that supplied most electricity in
1990?
b)
There are a limited number of suitable sites for setting up hydroelectricity
schemes. All the large sites have been used. Now that other renewables have
been developed on a larger scale, the relative importance of hydroelectric power
has declined.
39
The tides rise and fall twice a day. Peak output from a tidal barrage corresponds to
the times when the rate of water flowing through the turbines is at its highest as
the tide comes in, and then goes out again. At high tide and at low tide, when the
tides are turning, there is no flow through the turbines. (See the simple animation
at: www.technologystudent.com/energy1/tidal3.htm.)
40 a) The barrage would generate at least 5% of the UK electricity needs. The barrage
would provide a permanent link between England and Wales. Building the barrage
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would create employment and there would be continuing growth in employment
associated with the barrage, the transport crossing and the lagoon created
upstream. Once built the barrage would continue to operate for a very long time
without creating emissions of carbon dioxide.
b)
The environmental impact of a Severn barrage would be huge. As a result
campaigning organisations such as WWF, the RSPB and Friends of the Earth
campaign against the scheme. See for example:
 www.wwf.org.uk/search_results.cfm?uNewsID=163
 www.rspb.org.uk/news/details.asp?id=tcm:9-181048
 www.foe.co.uk/cymru/cymraeg/severn_barrage_report.html
41
The UK has a long coastline relative to its land area. Much of the west coast is
exposed to big waves from the Atlantic ocean.
42 a) Nearly 800 large 5 MW wind turbines could, in theory, produce as much power as
Drax.
b)
The wind does not blow all the time and the wind strength varies. A modern wind
turbine produces electricity 70-85% of the time, but it generates different outputs
depending on the wind speed. Over the course of a year, it will typically generate
about 30% of the theoretical maximum output.
c)
Just over 80 000 homes.
43
The UK will need to back-up power stations for the many days when it is not windy
enough. In the short term this back-up power will come from fossil fuelled power
stations – mainly gas fired. The British Wind Energy Association argues that all
forms of power generation require back up and no energy technology can be
relied upon 100%. The UK's transmission system already operates with enough
back-up to manage the instantaneous loss of a large power station.
44
Wind turbines are large and wind farms cover large areas so some people object
to wind power because of its effect on the landscape. Wind turbines can be noisy,
they may kill birds and bats. Also lines of pylons have to be built to connect wind
farms in remote, windy places to the national grid.
45 a) Scenario A2 leads to the largest emissions of carbon dioxide which is expected for
a scenario that is coal-intensive because of the high proportion of carbon in coal.
b)
The C cases are ecologically driven to lower carbon dioxide emissions and limit
climate change. C1 depends on the development of renewables and the phasing
out of nuclear power so seems the most sustainable. This incorporates challenging
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environmental and energy taxes to simultaneously protect the environment and
transfer wealth from North to South to enhance economic equity.
46
The net emissions are lower than gross emissions because they take into account
carbon dioxide taken up by photosynthesis and by carbon dioxide dissolving in the
oceans.
47
Scenarios A3, C1 and C2.
48
Scenarios A3 is one of the high growth scenarios which nevertheless greatly
reduces carbon dioxide emissions. It represents a major shift in the direction of
policy and development from current trends and so it would be a major challenge
to work to this scenario.
49
The answer here depends on your attitudes and temperament. Some people are
much more politically active and inclined to campaign than others. Developments
which often provoke many citizens to start campaigning are those which affect the
local environment near to where they live; for example a proposal to create a
wind farm, a nuclear waste repository or a waste incinerator to generate
electricity.
50
You can read the WWF report from which this quotation comes at:
http://www.panda.org/news_facts/newsroom/index.cfm?uNewsID=134321
WWF is concerned that more coal fired power stations will be built and allowed to
start operating before it has been established that carbon capture and storage can
be made to work. So an untested technology is being used to justify building
power plants that will greatly increase carbon dioxide emissions.
51
The RSPB is in favour of the development of renewable energy including wind
farms despite the evidence that suggests that wind farms can harm birds in three
possible ways – disturbance, habitat loss or damage, and collision of birds with
turbine blades. Poorly sited wind farms have caused some major bird casualties
when planners have failed to consider adequately the likely impact of putting
hundreds, or even thousands, of turbines in areas that are important for birds of
prey. As a result many hundreds of birds have died. The RSPB can use its expertise
to ensure that wind farms are created away from major migration routes and
important feeding, breeding and roosting areas of those bird species known or
suspected to be at risk. RSPB can help to monitor the environmental impact of
wind to help planners to adapt new schemes as more is learnt about the impacts
of wind farms on birds.
52
If so, the implication is that energy policy will have to include new nuclear power
and/or more fossil fuel power stations if the UK is to have secure electricity
supplies and the lights are to stay on all day and every day. The aim of reducing
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carbon dioxide emissions means that nuclear power will have to part of the mix
unless there is substantially more investment in developing renewables and
methods of energy efficiency.
53
Take the example of wind power. Hundreds of wind turbines are needed to
replace a power station. Large quantities of concrete, steel and other materials
are needed to makes and install the turbines and yet more material is needed to
connect the turbines to the national grid. This means that the capital cost is high,
but once built there are no fuel costs for a wind farm, only maintenance costs.
Much less material is needed per MW of power to built a conventional power
station and connect it to the grid, but throughout its life there is the cost of buying
the fuel.
54
The UK helped to pioneer the use of nuclear power after the second World War. In
the optimistic period of the 1950s – 1960s scientists and politicians believed that
nuclear power would prove so successful that electricity would become very
cheap. This led to the development of the existing nuclear power stations. Nuclear
accidents and the association of nuclear power with warfare led to a marked
change in public attitude brought nuclear developments for civilian uses in the UK
to a halt – apart from work on reprocessing at Sellafield.
The discovery of oil and gas in the North Sea at the end of the 1960s and the
beginning on the 1970s meant that the UK has not been dependent on imports of
these fossil fuels until recently as production has started to decline. This meant
that the public became used to secure and relatively cheap energy supplies for
over 30 years. This has reduced the attractiveness of more expensive renewable
forms of energy in the UK.
55
A ‘feed in’ law provides an incentive that can stimulate investment and innovation
by encouraging businesses and individuals to develop renewable sources of
energy. Energy companies are obliged to buy electricity generated locally from
renewables at a price that helps to compensates for the extra costs. The German
experience suggests that this approach can be very effective at increasing the
proportion of electricity generated with renewables.
56
The UK is adjusting to the decline in North Sea gas and oil and the need to start
importing these fuels.
57
The UK is heavily dependent of natural gas for heating and generating electricity.
The country becomes very vulnerable to price rises and political instability if it has
to reply on imports from countries that are not allies. It is also important to store
reservoirs of liquefied gas to deal with emergencies. New underground storage
facilities are being developed. In 2007 the UK could only store about 4% of its
annual consumption, compared with 24% in France and 19% in Germany.
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58 a) The main technology proposed is carbon capture and storage but this has not yet
been proved to work on a large scale. It could be 10 years or more before the
technology can be introduced for UK power stations.
b)
The UK needs to generate electricity from a range energy resources to ensure
security of supply. Coal can be mined in the UK on a large scale and in many
countries of the world. Coal fired power stations are a tried and tested means of
generating electricity. The urgent challenge is to find a way to burn coal in power
stations while not adding significantly to carbon dioxide emissions to the
atmosphere.
59
Global warming and climate change are world-wide problems which can be
damaging to every country in the world. The problems cannot be solved by
countries working alone. This means that it is in the interest of the UK to
collaborate with the rest of the World to bring about changes in energy supplies
that reduce emissions of greenhouse gases.
60
Biofuels from crops, forestry and farm waste or algae can be used in place of
conventional petrol or diesel. Hydrogen can be produced for use as a fuel by using
electricity from renewable sources to split water into hydrogen and oxygen. The
most efficient way to use hydrogen is in fuel cells. A third possibility is to use
electric vehicles running on batteries that are charged up with electricity from
renewables. (See section 5.9)
61
As the country can no longer rely on gas and oil from the North Sea, energy prices
will have to be higher. This encourages people to save energy.
Increasing use of renewables should lead to a reduction in greenhouse gas
emissions.
Investing in renewables can help to ensure security of electricity supplies by
adding to the variety of power sources while cutting dependence on imported
fuels.
62
The standards for motor vehicles and domestic appliances are set internationally.
The UK is part of the EU and subject to European standards. The market for cars is
international because of the cost of developing new vehicles so the UK cannot
impose standards unilaterally.
63
People had little incentive to cut their use of electricity so long as electricity was
relatively cheap. In these circumstances manufacturers have made it much easier
to leave TV sets and other appliances on stand-by rather than to turn them off.
Remote controls are designed to switch devices to standby. They can be designed
to switch appliances off.
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Many people are unaware of the amount of electric power used by different
devices. Some people definitely respond to the challenge of cutting their power us
if they can see how electricity is being used in their homes. In a similar way, the
real-time display of fuel consumption in some modern cars is helping petrol to
drive in a way that cuts fuel consumption.
65 a) Much greater energy efficiency is possible in homes, businesses and in transport.
Increase efficiency could do much to tackle the problems of addressing global
warming, energy security, and the depletion of fossil fuel reserves. Changing the
energy market to reward efficiency and reduce electricity consumption would be a
good thing.
b)
In the UK, energy suppliers are obliged by the government to encourage people to
use energy more efficiently by helping with the supply and costs of installation of
energy saving measures and providing advice on energy efficiency. However it is
hard to see how they could charge their customers more if they lose less energy,
so the reward for selling less energy more efficiently would have to be some sort
of government backed scheme. Decoupling of the profits of power companies
from the generation of electricity has been implemented by a number of states of
the USA. The generating companies get paid for their plant and equipment and
increase their profits by winning incentive payments from the states for reducing
electric demand.
66
Low carbon technologies: it is more expensive to produce biofuels than to make
fuels from crude oil; petrol cars can use a blend of petrol and bioethanol without
modification if the percentage of biofuel is low but using a higher proportion of
bioethanol means that engines have to be adapted; the petrol stations exist to
supply petrol but not separate biofuels or hydrogen. Moving to electric vehicles
requires people to buy new cars and then charging points have to be installed.
Electric vehicles are only low-carbon if the electricity is generated with renewables
and this is more expensive.
Welfare cost of changes: people depend on their cars and public transport to go to
work, shop, engage in leisure activities and so on; significantly reducing the
demand for travel would have a major impact on people’s lives.
67
Regulation: the EU has regulations to cut air pollution from vehicle exhausts by
setting limits to the emissions of oxides of nitrogen, carbon monoxide,
hydrocarbons and particulates; the EU is planning to set limits to carbon dioxide
emissions from vehicles as well.
Voluntary agreements: the EU has established voluntary agreements with the
motor industry to reduce carbon dioxide emissions but generally these
agreements have not worked.
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Taxation: it has been UK government policy since the early 1990s to progressively
increase the tax on petrol. The increasing level of taxation on fuel is designed to
discourage car use. The government is also raising the annual road tax on larger
cars that use more fuel to encourage people to buy more economical vehicles.
68
Biofuels cannot be produced on a large enough scale to replace petrol and diesel
from crude oil. In the short and medium term biofuels can help to reduce
emissions from transport while the radical innovations are developed to make it
possible to move from fossil fuels to low carbon technologies.
Second generation biofuels based on biomass and algae could play a part in the
longer term because they do not compete with food crops. They could not be the
whole answer to the problem but could be a partial solution.
69
Algae produce oil and can generate fifteen times more oil per hectare than other
plants used for biofuels, such as corn. Algae can grow in salt water, freshwater or
even contaminated water, at sea or in ponds, and on land not suitable for food
production.
See for example:
http://news.bbc.co.uk/1/hi/scotland/tayside_and_central/7495635.stm
70
An example of a social development would be a move from private to public
transport thus reducing the overall quantity of fuel burnt for transport. Political
and economic developments are those which make biofuels economic through
regulation or subsidy while they are more expensive than fossil fuels. Developing
sustainable production will depend on continued R & D to make second
generation biofuels a reality.
71
There are no natural sources of hydrogen. The gas is so reactive that it is always
found combined with other elements in water, hydrocarbons and other
compounds. Energy is needed to separate hydrogen from these compounds so
that it can be used as a fuel.
72
In principle a fuel cell uses all the energy from oxidising the fuel in the home
because it can be a source of both electricity and energy for heating in the home
itself. Conventional gas boilers release energy into the atmosphere with the hot
flue gases. Fossil fuel power stations similarly only convert a proportion of the
energy from burning into electrical energy.
73 a) and b) The burning of the Hindenburgh airship during the accident in 1937 has
given hydrogen a bad reputation. The safety issues depend on how the hydrogen
is stored whether as gas under high pressure, as a very cold liquid, or absorbed
into a solid medium such as a metal. Research into the hazards associated with
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these methods of storing hydrogen suggest that the risks are no more severe than
those associated with hydrocarbon fuels.
c)
Gas and petrol are both highly flammable. From time to time there are very
destructive gas explosions. However, as a society, we have learnt how to live with
these fuels so that accidents are relatively uncommon. It should be possible to
develop technologies for using hydrogen as a fuel safely. One problem with
hydrogen is that its molecules are so small and light that the gas is able to diffuse
and escape faster than natural gas. this can be a danger and an advantage. It does
mean that if the gas escapes it disperses much faster than other fuels.
74
Fuel cells can run on fuels produced from renewable resources. All the energy
from the fuel can be used for heating or as electricity. The waste products from
the fuel cell can be non-polluting.
75
Solar cells are still relatively inefficient and expensive. Much more R & D is needed
to develop solar cells that could meet a substantial proportion of the World’s
energy needs. The cells need to be more efficient and also be based on materials
that can be manufactured relatively cheaply on a large-scale without causing
pollution.
76
One application would be to cover the windows of glass office blocks with sheets
of transparent solar cells to generate some of the electricity needed by the people
in the building.
Fabrics could incorporate fibres made from the plastic to power LEDs. Lower
power devices such as radios or music players could be coated with the plastic to
help maintain the charge in the batteries.
77
Technologies already exist to reduce energy use. It is, for example, well known
how to design buildings so that they need less energy for heating in winter or
cooling in summer. So long as fuels have been relatively cheap, it has been
politically easier to use energy resources wastefully rather than invest in energy
conservation.
We need both changes in design and lifestyle so that we use less energy and also
investment in the development of new energy resources to make the shift from
fossil fuels to renewable resources.
Review questions
78
All these points are illustrated by the nuclear industry.
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a)
Extracting and concentrating radioactive uranium and using it to generate
electricity in power stations has created new risks at each stage of the process
from the initial mining through to the processing and disposal of waste particularly
because of the long term hazards of high level wastes.
b)
Nuclear engineers have always been confident that they could manage nuclear
power stations safely. In practice accidents, though rare, have nevertheless been
more frequent and more damaging than was initially expected. The effects of
exposure to radiation are long term, so long as the radiation dose is not fatal, and
so scientists are still learning from the histories of those exposed to radiation after
nuclear explosions (such as Hiroshima) and accidents (such as Chernobyl).
c)
The consequences of a nuclear accident are potentially so severe and widespread
(as shown by the Chernobyl accident) that extreme precautions have to be taken
to prevent them from happening. Many more people die each year from coal
mining than from the use of nuclear fuels, but this seems less drastic because
mining accidents are limited to those involved and do not have such long term
consequences. Over 6000 people die each year in the coal mines of China. Many
more suffer from lung disease because of exposure to coal dust.
d)
Adding extra layers of protection and shielding around a nuclear reactor help to
reduce the risk of radioactive materials escaping or of terrorist attack; however
they can greatly increase the cost of the reactor.
e)
This weighing up or risks and benefits has been taking place for years in the UK as
the nuclear industry searches for a permanent solution to the problem of dealing
with high-level nuclear waste. The preferred solution by the industry is an
underground repository but this is resisted by those who live close to sites where
a repository might be built.
79 a) The Health and Safety Executive (http://www.hse.gov.uk/nuclear/index.htm) is an
example of a regulatory body with responsibility for workers who may be exposed
to radiation and for inspecting the nuclear industry. It regulates the nuclear
industry through its nuclear directorate.
b)
The nuclear industry is still relatively young. The long term health effects of
exposure to radiation are still the subject of research. Regulators have to revise
their rulings from time to time in the light of new research findings. There is
considerably uncertainty about the feasibility of underground storage of high-level
nuclear waste because it has to be contained for such a very long time.
c)
This is illustrated by the cost-benefit analysis carried out by the Stern Review
(p 129) in its assessment of the economic case for intervening early to cut
greenhouse gases by investing in new energy technologies. At the moment the
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cheapest way to generate electricity is to use fossil fuels but the long term costs of
doing so could be very serious.
d)
Energy policy in the UK is now heavily influenced by international agreements to
cut greenhouse gas emissions. This means that there has to be a shift from fossil
fuels to renewable resources such as wind power and other ways of generating
electricity such as nuclear power.
e)
Some notable instances are the opposition of the public and pressure groups to
building new nuclear power stations, creating a Severn Barrage and to setting up
large wind farms in areas of natural beauty.
f)
Industries with a major interest in areas of policy can fund the work of scientists
designed to find new evidence, or reinterpret existing evidence, to oppose policies
that they wish to resist. This is something with some oil companies have done in
relation to climate change.
80 a) Much of the UK electricity grid was built in the 1950-60s, when it seemed efficient
to build large coal-fired plants, mainly close to mines, and transmit electricity to
where it was needed. Consequently, the Grid is heavily reinforced in former coalmining regions. By contrast, there are no high voltage transmission lines in many
areas suitable for renewable electricity generation (like North West Scotland
where wind speeds are high, or Mid-Wales). The net flow of electricity is from
North to South. There are bottlenecks limiting the total power that can be
transmitted. Large nuclear power stations were added to this system. They were
created around the coast away from large centres of population. Greenpeace can
argue that this system locks the country into sources of energy that are polluting
and risky while inhibiting the development of renewables
(http://www.greenpeace.org.uk/nuclear/problems).
b)
Greenpeace favours distributed generation with much more emphasis on
renewables (http://www.greenpeace.org.uk/blog/climate/the-convenientsolution-20070718). Those that favour distributed generation argue that
generating electricity close to where it is used reduces losses; also, using waste
heat delivers efficiency savings. Moving to a distributed system favours renewable
energy
81 a) Two types of solar panel could be installed on the roof: panels to generate
electricity and panels to heat water. At the same time the house could be
insulated to the best of modern standards to reduce the energy needed for
heating (www.newbuilder.co.uk/news/NewsFullStory.asp?ID=2619).
b)
A hillside in West Wales might well have streams running down it that could be
harnessed to generate electricity through a micro-hydro scheme. the exposed
summit of the hillside might be suitable for wind turbines.
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c)
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An arable farm in Norfolk grows crops with produce waste such as straw that can
be used as a fuel in boilers. The straw could be used in a small-scale combinedheat and power system to provide electricity and heating for the farm. Norfolk is
flat so there is also the potential to install wind turbines to generate electricity.
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A2 Science in Society
Answers to the questions
Chapter 6 Sustaining the Variety of Life on Earth
The answers suggested here should not be read as model answers. They are intended to
indicate a possible approach. In some cases, information and comments are included
which go beyond the direct requirements of the question.
1
Fossils only form under special conditions, for example when a dead organism
becomes covered by fine sediments. Most organisms decay and do not fossilize.
2
Identifying species is essential for the study of biology (knowing which species is
being talked about), understanding evolution and for conserving
species/biodiversity.
3
Larger and more conspicuous organisms such as mammals are nearly all named.
But there are unknown numbers of un-named species in groups such as insects
and micro-organisms. Some of these live in remote places or deep in the ocean.
There is also uncertainty over whether some populations comprise one species or
more than one.
4
This provides a sample for scientific study representing different ages, sexes and
varieties.
5
This makes it easier for scientists to place new fossil finds, from anywhere in the
world, in the context of existing knowledge. Comparisons with type specimens and
the range of forms within each species helps to determine whether a new fossil
find represents a new species, or one already named.
6
To explain and promote its activities to taxpayers and other members of the
public.
To educate the public about biological science.
To recruit future biological scientists.
To disseminate new discoveries to the media.
To encourage the public to inform the museum about their own discoveries or
observations.
To market the museum’s publications and other products.
To put on special exhibitions.
7
Answers might include: warm blooded/homeothermic, feed young on milk,
possess hair, breathe air, young nourished by placenta.
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8
Sexual reproduction produces variation in the offspring. Variation is the raw
material of natural selection.
9
98.6%
10
Fig. 6.6 shows that chimpanzees are more closely related to humans than they are
to gorillas, whereas Fig. 6.5 shows the opposite.
11
Classification aims to reflect evolution. The first phylogenies (evolutionary trees)
were based on comparative anatomy and physiology. More recently, molecules
such as proteins and DNA have been compared, and these have led to new
interpretations. There can also be disagreements between scientists about which
phylogeny best fits the evidence, and so phylogenies undergo continual revision.
12
Small samples of rock can be taken from the type specimens and analysed for
their content of radioactive elements. This allows dating of the rocks from which
they came.
13
The half life of the element must be on a similar scale to the age of the rocks being
dated, providing a measurable ratio of the radioactive element and its decay
product.
14 a) Carbon-14 has too short a half life to measure the age of rocks, but is appropriate
for dating dead organisms up to a few thousand years in age.
b)
It must be certain that the decay product has not leaked out of the sample, as this
would give an under-estimate of its age. It also needs to be confirmed that the
bone was deposited in the layer where it was found, and has not moved since.
c)
Nearly all the original carbon-14 will have decayed, so any inaccuracies in
measuring its concentration will cause a large error in the calculation of the
sample’s age.
15 a) Removal of a high outlier would depress the mean b) The best-fit line would be
lower.
16
Check, if possible, that the outlier is not due to an error in measurement by
repeating that measurement. Test whether the outlier is statistically significantly
different from the rest of the data.
17
The best-fit line implies that the rate of extinction has steadily declined over
geological time. This might be because conditions on earth became more stable
and/or because organisms became more adaptable and better able to withstand
environmental stresses.
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18 a) The extinction rate shows many peaks and troughs, possibly cyclical in nature.
b)
There was a burst of new families in the Cambrian (first multi-cellular life) and
another starting in the Jurassic and still continuing (possibly related to stable
environmental conditions).
c)
Only the Permian extinctions are well above background extinctions.
19
More complex ecosystems contain more families and more mobile organisms.
20
Collaboration provided an overview as it pooled evidence from all over the world.
21
The crater could be dated to see if it coincided with the timing of the great dying.
Simulations of the impact could allow scientists to evaluate its likely effect on
living organisms.
Dinosaurs are part of popular culture. This began in the 19th century when
dinosaur fossils were first displayed in places such as the Natural History Museum.
Dinosaurs have also been the subject of fiction, and films such as Jurassic Park.
The popularity of dinosaurs has led to the great fascination about why they
became extinct.
23 a) There are examples of flood basalts which do not correspond with mass
extinctions, such as the Madagascan, or Caribbean Plateau.
22
b)
There is a correlation in the timing of major volcanic activity and mass extinctions.
c)
That volcanic activity caused mass extinctions.
24
The average rate of extinction in times between mass extinctions.
25
Mass extinctions are few and far between, with long periods of background
extinction occurring between. Background extinction rates are quite high.
26
Natural selection favours organisms which are able to adapt (or happen by chance
to be pre-adapted) to changing conditions. Species which fail to adapt become
extinct.
27
Overfishing and pollution lead to the simplification and destabilizing of ecosystems
by reducing biodiversity. Examples include the loss of major fish stocks, whales
and coral reefs. Deforestation indirectly damages marine ecosystems by increasing
run-off into estuaries. Air pollution also harms marine ecosystems via its effect on
climate change.
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28
Taxonomy gives each species a name and a place in a phylogeny. If we are to
conserve biodiversity we need to know the scale of the problem and prioritise
conservation effort. There also needs to be an awareness of genetic diversity
within each species to ensure conservation of representative sub-species and
races and that remaining populations are genetically viable.
29
Uncertainty about extent of biodiversity loss: There is uncertainty because
scientists have not classified all species and many ecosystems are not fully
researched, so their biological health is not known. Political factors cause some
countries and international companies to hide the extent to which they are
damaging ecosystems or allowing species to be poached.
Uncertainty about effects of biodiversity loss: There is incomplete understanding
about the extent to which biodiversity loss will lead to a failure of life-support
systems on the planet – e.g. the provision of water, air, food, raw materials and
amenable climate. There might be a threshold/tipping point beyond which the
planet’s ecosystems crash. Ecosystem modeling is not well developed.
30
Darwin realized that his ideas would cause a strong reaction from those who held
religious beliefs about the uniqueness of humans and how they were created. But
in 1858 he received a letter from Alfred Russel Wallace proposing similar ideas to
his own (developed independently) and was persuaded by the Linnean Society to
publish his ideas jointly, and to write his book published in 1859.
31
Light, mineral ions, water, space, shelter, food, mates, breeding sites etc.
32 a) Roots provide anchorage and stability and take up water. b) Provides roots with
oxygen in mud that is low in oxygen. c) leaf turning avoids damage by excessive UV
light/heat of sun.
33
Graph A.
34
Only a), shark body mass data.
35 a) The heights did not show a normal distribution – they were skewed.
b)
By taking a larger sample, representative of a wide range of (adult) human
populations.
36
There are many niches within the lake.
The lake periodically partially dried up, isolating populations in many separate
lakes. These populations were unable to interbreed when reunited, becoming
different species.
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37
The Nile perch competes for resources with the cichlids. The numbers and variety
of cichlids have greatly declined.
38
Rabbits multiplied to great numbers, destroying vegetation on which native
species (such as kangaroos) depended, leading to damaged and impoverished
ecosystems and eroded soil.
39 a) Wolves and moose both show cyclical changes in population.
The numbers of wolves reach a maximum of only about one fiftieth of the moose
population.
Wolf peaks lag behind moose peaks by about 5 years.
b)
Wolves eat moose. Moose numbers determine wolf numbers. Wolves are slower
breeders so there is a lag in their population response to increased moose
numbers. Predation by wolves may cause a decline in moose numbers (or moose
numbers may be controlled by an outside factor such as cycles in the sun’s
output).
c)
There is long term stability because the populations show negative feedback,
which dampens population fluctuations in both species.
40
High plant diversity is necessary to support orang-utans, which in turn maintain
the diversity by dispersing seeds. This is a chicken and egg question!
41
The sea urchins increase in numbers and destroy the coral.
42
A more genetically diverse population is more likely to contain genes which allow
individuals to survive if conditions change.
43
Ecosystems in unstable climates contain species which are adapted to seasonal or
yearly changes in climate. Species in stable climates lack structures, physiology or
behaviour which allow them to survive climate change.
44
Crops on intensive farms are of similar genotype over a large area, and are known
as monocultures. If a pest arrives it will spread to the whole crop, so pesticides are
used against insects and viral and fungal diseases. Particular weeds can find a
perfect niche in crops and need to be controlled with herbicides, since there are
few natural controls. Fertilizers are used because the crop takes nutrients from
the soil, which are not replaced by decomposition or by nitrogen fixing plants.
45
People support conservation charities because:
 They enjoy wildlife and country pursuits.
 They want to preserve and create a better environment for their children.
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 They are aware that many human activities are harmful to wildlife and wish to
make amends.
 Biodiversity is the object of scientific research.
46 a) Meadow 1
b)
Meadow 1
47
Increases.
48
Decreases.
49
Fig.6.30 supports the generalization since tropical and sub-tropical ecosystems
support the most species and tundra/taiga support the fewest. Ecoystems which
do not fit the trend include Mediterranean forests, mangroves and tropical
coniferous forests.
50
The higher the altitude, the less stable are the environmental conditions. Stability
favours biodiversity.
51
Few species are able to adapt to the extreme conditions. Winter daylight is very
short so there is little photosynthesis for much of the year. Nutrients are locked up
in the frozen ground. [However there are many migratory birds and large numbers
of herbivorous mammals, such as reindeer/elk].
52
It takes time for species to become adapted to a niche by natural selection, with
slower breeding species taking the longest time. Niches need to be present for
long enough for species to fill them. In more stable environments, species tend to
be more specialized but their populations are smaller.
53
People living in proximity to threatened species and habitats must benefit from
conservation policies if they are to support them. Conservation policies which do
not take account of the needs of local people will always fail in the long term.
54
The current extinction is caused by humans rather than by natural events such as
meteorite impact or volcanic activity.
55 a) Plants provide food, wood, fibres, paper, herbs, medicines etc. They release
oxygen and absorb carbon dioxide. Forests affect rainfall, climate and water
drainage. Genes from wild relatives can be used to improve crops.
b)
Animals provide food and genetic resources, pollination, biological control,
transport, cultivation, pets, guides for the blind, drug detection etc. Animal
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research develops new drugs and medical techniques, and shows humans’ place in
the natural world.
Animals and plants provide spiritual and aesthetic resources.
56
Genes from wild plants can be introduced to crop species to provide resistance to
disease, pest tolerance, drought resistance and other qualities.
57
Plants evaporate water from their leaves, forming clouds and rain. They slow runoff from hillsides, evening out fluctuations in river levels. Animals filter water of
debris. Micro-organisms break down toxins and organic matter in polluted water.
Reed beds and mangroves filter water.
58
Diverse ecosystems encourage ecotourism, hunting/shooting/fishing, and genetic
resources for crop breeding and medicines. They can provide sustainable sources
of plant food, such as heart of palm, cacao and brazil nuts, as well as honey, meat
and skins from animals.
59
Mining fossil fuels, rocks and minerals. Generating power. All mechanical forms of
transport. Weapons manufacture. Chemical and plastics industries.
60 a) Biodiversity can be reduced accidentally or by people exploiting biodiversity for
their own gain. Regulations act as a deterrent and allow prosecution of
lawbreakers.
b)
There is international trade in endangered animals for pets, body parts such as
ivory and tiger bones, and for medical research. Endangered plants such as orchids
may be taken from the wild for gardens and collectors. International regulations
coordinate efforts to control such trade, enforced by customs and police.
61
There is short-term gain from exploiting biodiversity at long term expense. The
gain can go to a limited number of people or one country whereas the expense is
often shared more widely. This means that there is often little incentive for people
to protect wildlife. Lack of education, poverty and conflict increase the chances
that people will adopt a short-term, unsustainable, strategy.
62 a) Boats on canals, rivers etc b) Floodplains take overspill from rivers. Some are
artificial such as the Ouze Washes in Cambridgeshire. c) water skiing, fishing,
swimming etc.
63
Climate change can decrease rainfall and increase evaporation. Temperature rise
reduces the concentration of dissolved oxygen in water, increases metabolic rate
and can change the behaviour of animals: it can even alter the sex ratio of some
aquatic reptiles. Higher temperatures favour some plants more than others, and
can encourage algal blooms.
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64
If the hydrological conditions (water supply and quality) are right, species can
recover their numbers or recolonise a wetland.
65
Training local people in conservation provides a long-term strategy for conserving
wetlands. Local people use their knowledge and expertise and educate others
about using the wetland resource sustainably.
66
There is insufficient funding and human resources to attempt to conserve all
species and ecosystems. Priorities are decided on the basis of biodiversity present
and the likelihood that investment will be worthwhile.
67 a) Coral cover decreased from 1999 to 2002, then increased up to 2005. Algal cover
was generally greatest when coral cover was least. b) Coral cover returned to its
original level.
68 a) Interquartile range and standard deviation. b) e.g. whether or not they can
interbreed to produce fertile offspring.
69
The intact coral reefs provide protection from wave action and erosion.
70
Ecosystem conservation helps all the species of the ecosystem. Species
conservation does not work unless the habitat is maintained.
71
Effects of new technologies can be unpredictable/unexpected.
72
The cause of the decline, DDT, was removed before peregrines were reintroduced.
Peregrine habitat and food supply were still present.
Reintroduced peregrine chicks were cared for in the wild until they were
independent. Reintroduction was on a wide scale.
73
Reeds removed to grow rice ---> lake silts --> fish die --> people burn reeds to hunt
lemurs --> lake silts more etc
74 a) The reed beds help to keep the water clean: fish need clean water: people eat fish.
75
Points might include:
 The UK is not self-sufficient in raw materials or food.
 The population density of SE England is now similar to Holland’s – Europe’s
most densely populated country.
 Sustainable energy generating technologies such as wind and wave power may
reduce dependence on non-renewable fuels such as gas.
 Economic development could encroach on agricultural land, but reduced meat
consumption and improved (eg genetically modified) crops could compensate.
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 Existing technologies rely on the depletion of finite resources, but could be
replaced by those using renewable resources such as biofuels and bioplastics.
76
Population growth.
77
The costs include loss of climate services, water retention, food and medicine
resources, control of atmospheric composition.
78
Conservation must be continuous and long term: once a species is lost it cannot be
replaced. Hotspots are often in poor countries or remote areas and are unlikely to
be conserved without international funding and cooperation. Hotspots often cross
international boundaries.
Review questions
79 Species are classified to show their evolutionary relationships, based on the theory
of evolution by natural selection (Darwin and Wallace). This is called a natural
classification. Species which are believed to share a recent common ancestor are
placed in the same group (taxon). For example monkeys and apes, including
humans, are placed in the order Primates. DNA evidence is increasingly used to
refine or reassess classification.
Some species look superficially similar through convergent adaptation to a
common environment (eg sharks and dolphins look similar as both are adapted to
rapid swimming, but they are not closely related).
80
Humans share many of the planet’s resources such as the open sea, unprotected
land and the atmosphere. When humans take fish from the sea, logs from a forest
or pollute the atmosphere, they can greatly benefit personally (at least in the
short term) but the damage they do is shared across the whole population. Such
activities erode biodiversity but there is little incentive for individuals to change
their behaviour. The inhabitants of Easter Island felled the last trees resulting in
the extinction of the island’s human population. Cod fishers in Newfoundland and
herring fishers in the North Sea destroyed the fish stocks irreversibly. Poachers
may soon take the last tigers in the wild. These are extreme examples of the
tragedy of the commons. However, there is increasing awareness of the potential
damage resulting from the tragedy of the commons, leading to international
agreements about conservation and sustainable uses of natural resources.
81 a) Scientists do not always know the size of natural populations, and have only
identified a small proportion of the species occupying any habitat. Causes of
decline are not always known (eg the worldwide decline in amphibians), and the
relationships between species in ecosystems is not fully understood. The tolerance
of different ecosystems to disturbance and their ability to recover varies.
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A2 Science in Society – answers to chapter 6 questions
page 1
b)
There are international agreements such as the Rio convention (1992) and CITES
which many countries have signed up to. Development must not harm wildlife or
habitats protected by these agreements and each signatory must have a written
policy showing how they will meet agreed targets.
c)
Public opinion tends to be focused on attractive animals and beautiful places,
giving these added protection. Less obvious but significant habitats can be
ignored, for example mangrove swamps, which protect coastlines and act as
nurseries for fish. Big beautiful animals such as gorillas or elephants tend to get
more funding at the expense of animals such as reptiles and invertebrates.
Tropical rain forests get a lot of attention whereas temperate ancient woodlands
do not. Special interest groups may plead successfully for industrial development
or housing at the expense of threatened habitats and species. For example the
Thurrock grasslands near London are threatened by warehouses even though they
support many rare invertebrate species. New airports/runways are likely to go
ahead because they are popular with the public and support a country’s economy,
even though they are environmentally harmful.
d)
E.g. European fish stocks. Scientists make an annual assessment of fish stocks,
present data and advise on quotas. Politicians in Brussels repeatedly fix quotas
above recommendations, under pressure from fishing interests.
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Endangered species may have unknown benefits for human welfare: they may be
important in ‘ecosystem services’, helping to maintain the atmosphere and water
supply or supporting a food chain. It can be argued that even ‘useless’ species
have as much right to exist as other species. We do not have the right to deprive
future generations of biodiversity for our own short term gain. Loss of biodiversity
is nearly always a sign of unsustainable development.
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