NATIONAL QUALIFICATIONS CURRICULUM SUPPORT
Biology
Unit 2
Tutorials
[ADVANCED HIGHER]
The Scottish Qualifications Authority regularly reviews the arrangements for National Qualifications. Users of
all NQ support materials, whether published by Education Scotland or others, are reminded that it is their
responsibility to check that the support materials correspond to the requirements of the current arrangements.
© Crown copyright 2015. You may re-use this information (excluding logos) free of charge in any format or medium, under
the terms of the Open Government Licence. To view this licence, visit http://www.nationalarchives.gov.uk/doc/opengovernment-licence/ or e-mail: psi@nationalarchives.gsi.gov.uk.
Where we have identified any third party copyright information you will need to obtain permission from the copyright
holders concerned.
Any enquiries regarding this document/publication should be sent to us at enquiries@educationscotland.gov.uk.
This document is also available from our website at www.educationscotland.gov.uk.
CfE AH Biology – Unit 2 Evolution: Selection Tutorial
The idea behind this tutorial is to look at co-evolution and the co-evolution ‘arms race’ that exists
between pairs of species.
The AH curriculum content area being targeted in this tutorial is primarily:
Unit 2 (a) Evolution (iii) Co-Evolution and the Red Queen
Co-evolution is frequently seen in pairs of species that interact frequently or closely. Examples
include herbivores and plants, pollinators and plants, predators and their prey and parasites
and their hosts. In co-evolution, a change in the traits of one species acts as a selection pressure
on the other species.
The co-evolutionary ‘arms race’ between a parasite and host is known as the Red Queen as both
organisms must ‘keep running in order to stay still’. Hosts better able to resist and tolerate
parasitism have greater fitness. Parasites better able to feed, reproduce and find new hosts have
greater fitness.
However, elements of selection and sexual selection are also touched upon and it is important that
students are able to draw on all areas of their knowledge to be able to discuss the subject area fully.
Background
Because every improvement in one species will lead to a selective advantage for that species,
variation will normally continuously lead to increases in fitness in one species or another. However,
since in general different species are co-evolving, improvement in one species implies that it will get a
competitive advantage over the other species, and thus be able to capture a larger share of the
resources available to all. This means that fitness increase in one evolutionary system will tend to lead
to fitness decrease in another system. The only way that a species involved in a competition for
resources can maintain its fitness relative to other competing species is by improving its specific
fitness. (From Heylighen, 2000)
There are many good reference sources for this topic, and it is never easy to select just one but it has
been decided to focus on Matt Ridley’s 1995 book ‘The Red Queen; Sex and the Evolution of Human
Nature’.
While the whole book is definitely worth reading and an enthralling read for anyone interested in
Biology, it is proposed for the purposes of this tutorial to focus on Chapter I. Human Nature as it
touches on many of the evolutionary threads that are then tackled in more detail later on in the book.
Suggested reading

Francis Heylighen (2000): "The Red Queen Principle", in: F. Heylighen, C. Joslyn and V.
Turchin (editors): Principia Cybernetica Web (Principia Cybernetica, Brussels), URL:
http://pespmc1.vub.ac.be/REDQUEEN.html.

Ridley Matt (1995) The Red Queen: Sex and the Evolution of Human Nature, Penguin Books.
Guidance for teachers
Homework for the tutorial:
It is important that all students read the first chapter of Matt Ridley ‘The Red Queen: Sex and the
Evolution of Human Nature’.
If they have not completed this preparatory work, it will be immediately apparent as the tutorial
progresses.
A series of discussion points has been given for the chapter and there are various options to their use
depending on the size of class, length of tutorial time available etc.
The key to a discussion based tutorial being successful is preparation and an expectation of
contribution. Students must be made aware that they must be willing to put forward well researched
and reasoned answers during the discussion. It is worthwhile making time during the lesson before the
tutorial reinforcing this expectation. The aim of this tutorial is to incorporate three of the four
capacities of Curriculum for Excellence, namely:



Successful learners
Confident individuals
Effective contributors
Possible use of discussion points:




Give each student one/two specific questions that they must be prepared to be able to answer
fully and promote discussion on their question with the rest of the class during the tutorial
Give out all discussion questions to all students and have a general overall discussion with the
whole class
Give out no questions prior to the tutorial and give questions out at the beginning of the
lesson and allocate a period of time (15mins) for students to ensure they are experts on their
question/questions
Give out no questions prior to the tutorial and ask students to come prepared with at least one
discussion point relating to the text themselves.
Tutorial based on – Ridley Matt (1995) The Red Queen: Sex and the Evolution of Human Nature
(Chapter 1).
Discussion Points
1. The antithesis of the Red Queen hypothesis is the ‘Court Jester Hypothesis’ which was put
forward by Professor Anthony Barnosky (University of California – Berkeley) in 1999. The
Court Jester Hypothesis proposes the idea that abiotic forces such as climate change, tectonic
events and other physical factors are the major driving force behind evolutionary change,
rather than biotic competition between species as proposed by the ‘Red Queen Hypothesis’.
2. ‘Of Nature and Nurture’ - In the 1970’s, Richard Dawkins proposed the notion that, because
bodies do not replicate themselves but are grown, whereas genes replicate themselves, it
follows that that the body is an evolutionary vehicle for the gene rather than vice versa.
3. The gene-centred view of evolution infers that no detail of animal courtship mattered unless it
could be explained in terms of the selective competition of genes. For some time it was
thought that humans were exempt from this and emancipated from evolution but this
emancipation itself must have evolved because it suited the replication of genes. Discuss.
4. ‘The Individual in Society’ – why is so important from an evolutionary standpoint that no two
individuals are identical (clearly with the genetic exception of identical twins).
5. It is proposed in Matt Ridley’s book that human intellect itself is a product of sexual rather
than natural selection. Discuss this with specific examples.
6. Why do human beings have two sexes?
7. The concept that all progress is relative, ‘The Red Queen Hypothesis’ means that the faster
you run, the more the world moves with you and the less you make progress. Using specific
examples, discuss this hypothesis.
8. The Red Queen is not present at all evolutionary events, give an example of this.
9. ‘Of Conflict and Cooperation’ -Ridley proposes that the Red Queen never appears without the
presence of another evolutionary contributor; co-operation and conflict. What does he mean
by this?
10. ‘To Choose’ - There are many references to ‘sexual selection’ throughout the text. What is
meant by this and why is it important in an evolutionary context?
CfE AH Biology – Unit 2 Evolution: Costs and benefits of reproduction tutorial
The idea behind this tutorial is for a class to work collaboratively with each other and with
their teacher to produce a web based revision tool for costs and benefits of reproduction. It is
anticipated that this would work best after the section has been taught; as the theory behind
this active tutorial is that it would act as reinforcement rather than a learning activity
introducing new concepts.
The aim of this tutorial is to incorporate three of the four capacities of Curriculum for
Excellence, namely:



Successful learners
Confident individuals
Effective contributors
The AH curriculum content area being targeted in this tutorial is primarily:
(b) Variation and sexual reproduction (i) Costs and benefits of reproduction
Note to teachers: we plan to update the content below soon. Online collaboration and
editing can now be done easily within the Glow365 environment. Users within Glow also
have access to unlimited storage space on their OneDrive.
Google Docs is a free, web-based office suite and data storage service. It allows users to
create and edit documents online while collaborating in real-time with other users. It is
extremely useful in the classroom as it facilitates active participation with the whole class
contributing cooperatively.
Setting up a Google Docs presentation is very straightforward but it does require some
preparation beforehand in order to maximise time spent on the presentation during the
tutorial.
Preparatory work for tutorial (teacher)
To set up a Google Docs presentation, it is necessary for the teacher to have a Gmail email
account and be the owner of the presentation. I do not suggest that you use a personal email
account but instead set a special account that can be kept specifically for school use.
It takes less than a minute to set up a Gmail account.



Once you have confirmed your Gmail account, go to Google Docs homepage and
enter in your Gmail address and password.
At the top left hand side, there is a Create button, select this and then choose
Presentation from the drop down menu.
You will then see a page that looks like the one shown below:





As this is a collaborative exercise, you need to select Collaboration.
The screen will now look like the one shown below and you are ready to
prepare the introductory couple of slides. These will act as the basis for the
work.
How the work from this section of the AH course is divided up will obviously depend
upon the number in the AH Biology class and the time allocated to complete the task.
For the purposes of this guide, I have structured it for a class of 7 but each school will
vary and the work can be restructured to suit each individual class number.
This tutorial has been planned for a 1 hour lesson but obviously it can be tailored to
meet individual time constraints.
Student preparation for the tutorial
This will take about 15 minutes and it could be incorporated into part of a teaching lesson and
prep for the tutorial given as homework.
Access to computers would be required, ideally on an individual basis or one between two.
To be participants in the Google Docs presentation, it is necessary that students have a Gmail
email account. Once again, I do not suggest that they use a personal email account but
instead, get everyone in the class to set a special account that can be kept specifically for
school use. It takes less than a minute to set up a Gmail account.
I would advise that all students are allocated their particular topic area the lesson before the
tutorial to give them time to go over their notes and be well prepared to create their part of the
presentation.
Tutorial
Setting up the actual presentation for students to access it is very easy. The teacher (the
owner) has to select the blue Share button and add each student to the presentation. At that
point everyone in the class can see exactly what each member of the class can see. The
structure of the lesson has been given on the Google docs information slide. Students will
have a set period of time in which to create their portion of the class presentation. As the
work is done in real time, every student can see exactly what is being added by each other as
they add to the presentation. The work is also auto saved on an ongoing basis by Google docs.
At the end of the time, by using the Arrange facility, slides can be moved into their correct
order.
There will then be a time allocated to allow students to edit each other’s work. I would
suggest that two or more students work together and crit each of the pages they were involved
in and amend if it seems appropriate.
Teaching role throughout the tutorial is to facilitate and ensure that all Biological elements
being added onto the presentation are correct.
By the end of the lesson, the class should have developed a presentation of revision of the key
concepts of that section of the course and it is available to them all times.
CfE AH Biology: Unit 2 Organisms and Evolution
Tutorial: Sex and parasitism
This tutorial is designed to support the following areas of the arrangements document.
Unit 2: Organisms and Evolution
1 Field techniques for biologists
(c) Identification and taxonomy
2 Organisms
(a) Evolution
(b) Variation and sexual reproduction
(c) Sex and behaviour
(d) Parasitism
The tutorial is based around the Abstract of a research article published in the journal PLoS
ONE. The article has been selected as it has excellent breadth and depth of coverage of many
linked concepts and it is one that should be fairly accessible to a group of AH students with
help from their teacher or lecturer.
The aim of the tutorial is twofold: for students to demonstrate that they can read and make
sense of the Abstract, and also that they can communicate this understanding and link it to the
biological knowledge relevant to their course.
It would be desirable to give students access to the paper in advance of the tutorial. It is likely
that the task could lend itself to an alternative approach using Google docs or a similar
platform.
The article is freely available on the PLOS website at the following address
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0039506
The citation for the article is:
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and
Hybridisation in Monogenean Parasites. PLoS ONE 7(7): e39506.
doi:10.1371/journal.pone.0039506
A written extension activity is also included uses the related abstract found at the following
address http://beheco.oxfordjournals.org/content/3/4/346.short
The citation for this article is:
Houde, AE & Torio, AJ (1992) Effect of parasitic infection on male color pattern and female
choice in guppies Behavioral Ecology 3 (4): 346-351. doi: 10.1093/beheco/3.4.346
Sex and parasitism tutorial: student information
Access the following research article:
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and
Hybridisation in Monogenean Parasites. PLoS ONE 7(7): e39506.
doi:10.1371/journal.pone.0039506
Task 1: Knowledge
Your first task is to read the Abstract of this article carefully and attempt to understand what
it is saying. In order to do this there are various terms that you will probably need to look up
to increase your background knowledge. As you read through the Abstract you will find lots
of references to concepts and ideas contained within your Advanced Higher course. You
should also look through some other parts of the research article in order to get a better
understanding of what the Abstract is trying to say. In particular you should scan the
Introduction, Source of Animals and Infection Procedures, Figure 2, Figure 3, Figure 4 and
Discussion.
Useful words:
Ubiquitous = existing everywhere
Specious = having many species (when used to describe a genus)
Use a web search to introduce yourself briefly to the following:
Gyrodactylus, a genus of parasitic Platyhelminthes (egg www.gyrodb.net)
Poecilia reticulata, a teleost fish, often used as a model organism
Hybridisation and hybrid vigor
Microsatellite marker
Task 2: Comprehension and application
Your second task is to try to identify and explain the key ideas in each of the sentences of the
Abstract. You may have to re-read particular parts of the research article or search elsewhere
for information that you are unsure of. Use the Sex and parasitism tutorial: key ideas
document to help you structure your notes
Task 3: Evaluation
A tutorial discussion is a great opportunity to evaluate your understanding and help others
who may be having difficulties. You will need to refer to your notes during the tutorial and
should modify them if your understanding changes as a result of discussion.
Sex and parasitism tutorial: key ideas
The eight sentences below form the Abstract of the following article:
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and
Hybridisation in Monogenean Parasites. PLoS ONE 7(7): e39506.
doi:10.1371/journal.pone.0039506
Sentence 1: Theory predicts that sexual reproduction promotes disease invasion by increasing
the evolutionary potential of the parasite, whereas asexual reproduction tends to enhance
establishment success and population growth rate.
Key ideas:
Explanation:
Sentence 2: Gyrodactylid monogeneans are ubiquitous ectoparasites of teleost fish, and the
evolutionary success of the specious Gyrodactylus genus is thought to be partly due to their
use of various modes of reproduction.
Key ideas:
Explanation:
Sentence 3: Gyrodactylus turnbulli is a natural parasite of the guppy (Poecilia reticulata), a
small, tropical fish used as a model for behavioural, ecological and evolutionary studies.
Key ideas:
Explanation:
Sentence 4: Using experimental infections and a recently developed microsatellite marker,
we conclusively show that monogenean parasites reproduce sexually.
Key ideas:
Explanation:
Sentence 5: Conservatively, we estimate that sexual recombination occurs and that between
3.7–10.9% of the parasites in our experimental crosses are hybrid genotypes with ancestors
from different laboratory strains of G. turnbulli.
Key ideas:
Explanation:
Sentence 6: We also provide evidence of hybrid vigour and/or inter-strain competition, which
appeared to lead to a higher maximum parasite load in mixed infections.
Key ideas:
Explanation:
Sentence 7: Finally, we demonstrate inbreeding avoidance for the first time in platyhelminths
which may influence the distribution of parasites within a host and their subsequent exposure
to the host's localized immune response.
Key ideas:
Explanation:
Sentence 8: Combined reproductive modes and inbreeding avoidance may explain the
extreme evolutionary diversification success of parasites such as Gyrodactylus, where hostparasite coevolution is punctuated by relatively frequent host switching.
Key ideas:
Explanation:
Task 4 Extension activity: Effect of parasitic infection on mate choice
Access the abstract of the following research article:
Houde, AE & Torio, AJ (1992) Effect of parasitic infection on male color pattern and female
choice in guppies Behavioral Ecology 3 (4): 346-351. doi: 10.1093/beheco/3.4.346
The abstract can be found at the following web address:
http://beheco.oxfordjournals.org/content/3/4/346.short
Read this abstract and use some of the skills developed earlier in this activity to write some
comments on the findings outlined in this abstract in terms of the following aspects of your
course:
Sexual investment and optimal reproduction
Courtship, female choice and honest signals of fitness
Notes to tutor
It is suggested that the article is printed and distributed or students are given the link. The
preparation and development of knowledge in Task 1 would be well suited to a homework
task and ideally students should complete this individually.
Task 2 would be well suited to pair work as close discussion will boost comprehension and
allow the knowledge to be applied in the identification of key ideas and their explanation. It
may be effective to ask particular students or pairs to focus on particular sentences to analyse.
Task 3 would be best carried out as a verbal discussion with students given the opportunity to
communicate and develop their ideas as they evaluate their understanding. Students should be
encouraged to continue to add to their notes during the tutorial.
An extension is provided as Task 4 and this involves an additional abstract that extends the
tutorial into the areas of mate choice and sexual selection but uses the same study organisms.
It is anticipated that students who have completed Tasks 1–3 would have the skills and
knowledge to be able to read this second abstract with confidence and be able to discuss its
findings. This is presented as a written task, but you may wish to carry this out verbally.
Possible key ideas and brief explanations
Sentence 1
Costs and benefits of reproduction: greater genetic variation in sexual reproduction; asexual
reproduction builds numbers up quickly.
Rate of evolution: increased by sexual reproduction.
Co-evolution and the Red Queen: sexual reproduction increasing evolutionary potential of
parasite will result in host evolution.
Sentence 2
Ectoparasites: external.
Taxonomy: monogeneans are a group of parasitic flatworms; teleosts are bony fish; this
information allows us to put knowledge into context and relate it to other organisms in same
categories or similar.
Ubiquitous and specious: these monoeneans are very successful parasites; they breed on their
host (definitive host) and largely spread by direct contact so require no intermediate host.
Reproductive strategies/sexual investment/paradox of males/parthenogenesis/meiosis: a
single monogenean parasite can seed a population as it is already pregnant at birth
(hyperviviparous); first offspring is a clone derived by mitosis; second offspring can be
produced by parthenogenesis; up to five further offspring produced via parthenogensis or
sexual reproduction.
Sentence 3
Binomial classification: Latin names are given here so that genus and species of both study
organisms is clear.
Justification: it is stated that this is a naturally occurring parasitic relationship, so presumably
the findings are applicable outside the laboratory.
Model organism: the guppy is a frequent study subject and its behaviour, ecology and
evolution are already well understood – this new evidence can more easily be placed in
context; the findings from model organisms can be extrapolated to other related but less well
studied species, egg other teleost – monogenean interactions.
Sentence 4
Experimental infections: this is not an observational study but an experimental one where a
variable (infection) has been manipulated by a researcher.
Microsatellite marker: this allows DNA fingerprinting of the parasite to be able to distinguish
the different clones and identify any offspring of different parental types.
Conclusive: the authors are confident that there is no doubt that they have shown that the
monogeneans are reproducing using sex in their study.
Sentence 5
Conservatively 3.7–10.9%: they are being skeptical and presenting data.
Sexual recombination/hybrid genotypes: these offspring have parents of two distinct
genotypes.
Different laboratory strains: these are inbred (homozygous) strains that have been isolated for
1, 8 and 12 years; the latter represents about 2000 generations of inbreeding.
Sentence 6
Hybrid vigour: the enhanced phenotype and competitive advantage commonly reported in
hybrids.
And/or: the data do not allow the researchers to distinguish between these ideas without
further experimentation.
Inter-strain competition: two strains of the parasite are competing for the same resource.
Higher maximum parasite load in mixed infections: hosts find it more difficult to combat
mixed infections because sexual reproduction between different strains of parasite increases
the variation present within the parasite burden.
Sentence 7
Inbreeding avoidance: an unwillingness to breed with those that share a very close genotype.
Platyhelminthes: the order that includes non-parasitic flatworms as well as tapeworms, flukes
and the monogeneans.
Which may: the statement is a new hypothesis that arises from this study and could be tested
in future.
Distribution of parasites within a host and their subsequent exposure to the host’s localised
immune response: the host will learn to combat parasites with particular antigens, so it is in
the parasite’s best interest to avoid inbreeding so that offspring are diverse enough to evade
the immune response.
Sentence 8
Combined reproductive models: another reference to the mixture of asexual and sexual
reproductive strategies shown by monogeneans.
Extreme evolutionary diversification success: an adaptive radiation of many existing taxa
arising from one ancestral form.
Host–parasite coevolution: the Red Queen, where evolutionary change in a parasite drives
evolutionary change in its host.
Punctuated: sudden evolutionary event, rather than gradual change.
Host switching: a new species of host becomes commonly affected by a parasite.
CfE AH Biology: Unit 2 Organisms and Evolution
Tutorial: Sex and parasitism
This tutorial is designed to support the following areas of the arrangements document.
Unit 2 Organisms and Evolution
1 Field techniques for biologists
(c) Identification and taxonomy
2 Organisms
(a) Evolution
(b) Variation and sexual reproduction
(c) Sex and behaviour
(d) Parasitism
The tutorial is based around the Abstract of a research article published in the journal PLoS
ONE. The article has been selected as it has excellent breadth and depth of coverage of many
linked concepts and it is one that should be fairly accessible to a group of AH students with
help from their teacher or lecturer.
The aim of the tutorial is twofold: for students to demonstrate that they can read and make
sense of the Abstract, and also that they can communicate this understanding and link it to the
biological knowledge relevant to their course.
It would be desirable to give students access to the paper in advance of the tutorial. It is likely
that the task could lend itself to an alternative approach using Google docs or a similar
platform.
The article is freely available on the PLOS website at the following address
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0039506
The citation for the article is
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and
Hybridisation in Monogenean Parasites. PLoS ONE 7(7): e39506.
doi:10.1371/journal.pone.0039506
A written extension activity is also included uses the related abstract found at the following
address: http://beheco.oxfordjournals.org/content/3/4/346.short
The citation for this article is:
Houde, AE & Torio, AJ (1992) Effect of parasitic infection on male color pattern and female
choice in guppies Behavioral Ecology 3 (4): 346-351. doi: 10.1093/beheco/3.4.346
Sex and parasitism tutorial: student information
Access the following research article:
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and
Hybridisation in Monogenean Parasites. PLoS ONE 7(7): e39506.
doi:10.1371/journal.pone.0039506
Task 1: Knowledge
Your first task is to read the Abstract of this article carefully and attempt to understand what
it is saying. In order to do this there are various terms that you will probably need to look up
to increase your background knowledge. As you read through the Abstract you will find lots
of references to concepts and ideas contained within your Advanced Higher course. You
should also look through some other parts of the research article in order to get a better
understanding of what the Abstract is trying to say. In particular you should scan the
Introduction, Source of Animals and Infection Procedures, Figure 2, Figure 3, Figure 4 and
Discussion.
Useful words:
Ubiquitous = existing everywhere
Specious = having many species (when used to describe a genus)
Use a web search to introduce yourself briefly to the following:
Gyrodactylus, a genus of parasitic Platyhelminthes (egg www.gyrodb.net)
Poecilia reticulata, a teleost fish, often used as a model organism
Hybridisation and hybrid vigor
Microsatellite marker
Task 2: Comprehension and application
Your second task is to try to identify and explain the key ideas in each of the sentences of the
Abstract. You may have to re-read particular parts of the research article or search elsewhere
for information that you are unsure of. Use the Sex and parasitism tutorial: key ideas
document to help you structure your notes
Task 3: Evaluation
A tutorial discussion is a great opportunity to evaluate your understanding and help others
who may be having difficulties. You will need to refer to your notes during the tutorial and
should modify them if your understanding changes as a result of discussion.
Sex and parasitism tutorial: key ideas
The eight sentences below form the Abstract of the following article:
Schelkle B, Faria PJ, Johnson MB, van Oosterhout C, Cable J (2012) Mixed Infections and Hybridisation in Monogenean
Parasites. PLoS ONE 7(7): e39506. doi:10.1371/journal.pone.0039506
Sentence 1: Theory predicts that sexual reproduction promotes disease invasion by increasing the
evolutionary potential of the parasite, whereas asexual reproduction tends to enhance establishment
success and population growth rate.
Key ideas:
Explanation:
Sentence 2: Gyrodactylid monogeneans are ubiquitous ectoparasites of teleost fish, and the
evolutionary success of the specious Gyrodactylus genus is thought to be partly due to their use of
various modes of reproduction.
Key ideas:
Explanation:
Sentence 3: Gyrodactylus turnbulli is a natural parasite of the guppy (Poecilia reticulata), a small,
tropical fish used as a model for behavioural, ecological and evolutionary studies.
Key ideas:
Explanation:
Sentence 4: Using experimental infections and a recently developed microsatellite marker, we
conclusively show that monogenean parasites reproduce sexually.
Key ideas:
Explanation:
Sentence 5: Conservatively, we estimate that sexual recombination occurs and that between 3.7–10.9%
of the parasites in our experimental crosses are hybrid genotypes with ancestors from different
laboratory strains of G. turnbulli.
Key ideas:
Explanation:
Sentence 6: We also provide evidence of hybrid vigour and/or inter-strain competition, which
appeared to lead to a higher maximum parasite load in mixed infections.
Key ideas:
Explanation:
Sentence 7: Finally, we demonstrate inbreeding avoidance for the first time in platyhelminths which
may influence the distribution of parasites within a host and their subsequent exposure to the host's
localized immune response.
Key ideas:
Explanation:
Sentence 8: Combined reproductive modes and inbreeding avoidance may explain the extreme
evolutionary diversification success of parasites such as Gyrodactylus, where host-parasite coevolution
is punctuated by relatively frequent host switching.
Key ideas:
Explanation:
Task 4 Extension activity: effect of parasitic infection on mate choice
Access the abstract of the following research article:
Houde, AE & Torio, AJ (1992) Effect of parasitic infection on male color pattern and female
choice in guppies Behavioral Ecology 3 (4): 346-351. doi: 10.1093/beheco/3.4.346
The abstract can be found at the following web address:
http://beheco.oxfordjournals.org/content/3/4/346.short
Read this abstract and use some of the skills developed earlier in this activity to write some
comments on the findings outlined in this abstract in terms of the following aspects of your
course:
Sexual investment and optimal reproduction
Courtship, female choice and honest signals of fitness
Notes to tutor
It is suggested that the article is printed and distributed or students are given the link. The
preparation and development of knowledge in Task 1 would be well suited to a homework
task and ideally students should complete this individually.
Task 2 would be well suited to pair work as close discussion will boost comprehension and
allow the knowledge to be applied in the identification of key ideas and their explanation. It
may be effective to ask particular students or pairs to focus on particular sentences to analyse.
Task 3 would be best carried out as a verbal discussion with students given the opportunity to
communicate and develop their ideas as they evaluate their understanding. Students should be
encouraged to continue to add to their notes during the tutorial.
An extension is provided as Task 4 and this involves an additional abstract that extends the
tutorial into the areas of mate choice and sexual selection but uses the same study organisms.
It is anticipated that students who have completed Tasks 1–3 would have the skills and
knowledge to be able to read this second abstract with confidence and be able to discuss its
findings. This is presented as a written task, but you may wish to carry this out verbally.
Possible key ideas and brief explanations
Sentence 1
Costs and benefits of reproduction: greater genetic variation in sexual reproduction; asexual
reproduction builds numbers up quickly.
Rate of evolution: increased by sexual reproduction.
Co-evolution and the Red Queen: sexual reproduction increasing evolutionary potential of
parasite will result in host evolution.
Sentence 2
Ectoparasites: external.
Taxonomy: monogeneans are a group of parasitic flatworms; teleosts are bony fish; this
information allows us to put knowledge into context and relate it to other organisms in same
categories or similar.
Ubiquitous and specious: these monoeneans are very successful parasites; they breed on their
host (definitive host) and largely spread by direct contact so require no intermediate host.
Reproductive strategies/sexual investment/paradox of males/parthenogenesis/meiosis: a
single monogenean parasite can seed a population as it is already pregnant at birth
(hyperviviparous); first offspring is a clone derived by mitosis; second offspring can be
produced by parthenogenesis; up to five further offspring produced via parthenogensis or
sexual reproduction.
Sentence 3
Binomial classification: Latin names are given here so that genus and species of both study
organisms is clear.
Justification: it is stated that this is a naturally occurring parasitic relationship, so presumably
the findings are applicable outside the laboratory.
Model organism: the guppy is a frequent study subject and its behaviour, ecology and
evolution are already well understood – this new evidence can more easily be placed in
context; the findings from model organisms can be extrapolated to other related but less well
studied species, egg other teleost–monogenean interactions.
Sentence 4
Experimental infections: this is not an observational study but an experimental one where a
variable (infection) has been manipulated by a researcher.
Microsatellite marker: this allows DNA fingerprinting of the parasite to be able to distinguish
the different clones and identify any offspring of different parental types.
Conclusive: the authors are confident that there is no doubt that they have shown that the
monogeneans are reproducing using sex in their study.
Sentence 5
Conservatively 3.7–10.9%: they are being skeptical and presenting data.
Sexual recombination/hybrid genotypes: these offspring have parents of two distinct
genotypes.
Different laboratory strains: these are inbred (homozygous) strains that have been isolated for
1, 8 and 12 years; the latter represents about 2000 generations of inbreeding.
Sentence 6
Hybrid vigour: the enhanced phenotype and competitive advantage commonly reported in
hybrids.
And/or: the data do not allow the researchers to distinguish between these ideas without
further experimentation.
Inter-strain competition: two strains of the parasite are competing for the same resource.
Higher maximum parasite load in mixed infections: hosts find it more difficult to combat
mixed infections because sexual reproduction between different strains of parasite increases
the variation present within the parasite burden.
Sentence 7
Inbreeding avoidance: an unwillingness to breed with those that share a very close genotype.
Platyhelminthes: the order that includes non-parasitic flatworms as well as tapeworms, flukes
and the monogeneans.
Which may: the statement is a new hypothesis that arises from this study and could be tested
in future.
Distribution of parasites within a host and their subsequent exposure to the host’s localised
immune response: the host will learn to combat parasites with particular antigens, so it is in
the parasite’s best interest to avoid inbreeding so that offspring are diverse enough to evade
the immune response.
Sentence 8
Combined reproductive models: another reference to the mixture of asexual and sexual
reproductive strategies shown by monogeneans.
Extreme evolutionary diversification success: an adaptive radiation of many existing taxa
arising from one ancestral form.
Host–parasite coevolution: the Red Queen, where evolutionary change in a parasite drives
evolutionary change in its host.
Punctuated: sudden evolutionary event rather than gradual change.
Host switching: a new species of host becomes commonly affected by a parasite.
CfE AH Biology: Unit 2 Organisms and Evolution
Tutorial on Helminth Genomics: The implications for human health
This tutorial is designed to support the following areas of the arrangements document.
Unit 2: Organisms and Evolution
1 Field techniques for biologists
(c) Identification and taxonomy
2 Organisms
(a) Evolution
(i) Drift and selection
(iiii) Co-evolution and the Red Queen
(d) Parasitism
(i) The parasitic niche
(iii) Immune response to parasites
(vi) Challenges in treatment and control
The tutorial is based around a review article published in the journal PLoS Neglected Tropical
Diseases. The article has been selected as it has excellent breadth and depth of coverage of
several linked concepts and it is one that should be fairly accessible to a group of AH students
with help from their teacher or lecturer.
The tutorial may work best if students are guided in their reading of the paper. It would be
appropriate to point out that the tutorial discussion will focus on the questions provided so
students can focus their reading. If desired, students could be divided into groups with
responsibilities for reading and understanding different parts of the paper. These groups
would then participate at appropriate points during the tutorial discussion.
The article is freely available on the PLOS website at the following address
http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0000538
The citation for the article is:
Brindley PJ, Mitreva M, Ghedin E, Lustigman S (2009) Helminth Genomics: The
Implications for Human Health. PLoS Negl Trop Dis 3(10): e538.
doi:10.1371/journal.pntd.0000538
Helminth Genomics Tutorial
Access the following article in advance of the tutorial:
Brindley PJ, Mitreva M, Ghedin E, Lustigman S (2009) Helminth Genomics: The
Implications for Human Health. PLoS Negl Trop Dis 3(10): e538.
doi:10.1371/journal.pntd.0000538
During the tutorial there will be discussion of the following areas. Please make sure that you
have read the relevant sections and thought about those areas for discussion. You may find it
helpful to make notes in advance of the tutorial.
Useful words:
Metazoa = animal
Orthologue = genes with common origin in related species
Tutorial questions
Journal title:
1.
The journal is PLoS Neglected Tropical Diseases. Which types of diseases might be
neglected tropical diseases?
Review article:
2.
Above the heading of the article is the word ‘Review’. What does this mean in this
context?
Article title:
3.
What are ‘Helminth Genomics’?
Abstract:
4.
After reading the abstract, suggest two benefits of studying helminth genomics.
Helminth Infections – The Great Neglected Tropical Diseases:
5.
Why is ‘helminth’ not a true taxonomic group?
6.
Give some reasons why diseases of parasites have been ‘neglected’?
Genomics Approaches to Investigating Helminths:
7.
Which common model organism is mentioned in paragraph 2 of this section? Suggest
why it is easier to study this model organism than some of the other species mentioned
in the paragraph.
8.
Using information from paragraph 3 on the evolution of Schistosomes, identify genes
that have been lost through evolution and gene families that have diversified. In both
cases, which types of mutation may have been involved?
Evolution of Parasitism in Helminths:
9.
Draw a flow chart type model of the stages in the evolution of parasitism in nematodes.
Host–Parasite Relationships:
10.
Outline mechanisms of host immune system suppression by parasites as described in
paragraph 2.
11.
In paragraph 3 the interaction between parasitism and the immune system is linked to
allergies and autoimmune diseases in humans. Suggest how an absence of immune
suppression may account for this link.
The “Dependent” Helminth:
12.
Using the loss of a synthesis pathway as an example, explain why some parasites are
obligate.
Challenges for the Future:
13.
Identify the two main technological advances that will take place in the field of
helminth genomics.
14.
Contrast the type of treatments currently available for helminth infection with the type
of treatments that may become available as a result of helminth genomics.
Helminth Genomics Tutorial: Notes to tutor
It is suggested that the article is printed and distributed or students are given the link. For
homework the students must read the article. Ideally they should read the entire article,
making annotations for discussion later. It may be effective to ask particular students to focus
on particular areas of the article to answer questions in class. You may also wish to pre-issue
a list of the topics that will be discussed during the tutorial.
Brindley PJ, Mitreva M, Ghedin E, Lustigman S (2009) Helminth Genomics: The
Implications for Human Health. PLoS Negl Trop Dis 3(10): e538.
doi:10.1371/journal.pntd.0000538
Tutorial questions
Journal title:
1.
The journal is PLoS Neglected Tropical Diseases. Which types of diseases might be
neglected tropical diseases?
Suggestions may include diseases associated with poverty, those that are difficult to
study, those that have little funding associated with them, those that are rare, or those
easily dealt with by current treatments.
Review article:
2.
Above the heading of the article is the word ‘Review’. What does this mean in this
context?
From arrangements: A review summarises current knowledge and relevant findings in
a particular field.
Article title:
3.
What are ‘Helminth Genomics’?
Helminths are worm-like parasites such as the parasitic flatworms and roundworms.
Genomics is the study of genomes.
Abstract:
4.
After reading the abstract, suggest two benefits of studying helminth genomics.
Benefits outlined in the summary are the increased understanding of helminth biology
and the associated likelihood of identifying vaccine candidates and drug targets.
Students may quote that 2 billion people are infected with helmith parasites.
Helminth Infections – The Great Neglected Tropical Diseases:
5.
Why is ‘helminth’ not a true taxonomic group?
In taxonomy, all members of a true group should be more closely related to each other
than to members of any other group. Instead the Nematodes and Platyhelminthes are
both more closely related to other animal phyla than to each other. They are grouped
under the name helminthes for convenience only.
6.
Give some reasons why diseases of parasites have been ‘neglected’?
These diseases are found in the poorest people in the poorest regions of the world, so
there is no financial leverage from the end-user of any treatment. Also parasites are
very difficult to study in the lab due to their reliance on hosts – the standard laboratory
methods using cell lines, in vitro culture and animal models is not available. Thirdly,
the helminthes are eukaryotes and therefore have more complex metabolism compared
to many other pathogens.
Genomics approaches to investigating Helminths:
7.
Which common model organism is mentioned in paragraph 2 of this section? Suggest
why it is easier to study this model organism than some of the other species mentioned
in the paragraph.
The nematode Caenorhabdites elegans is one of the most well-studied model organisms.
C. elegans is not a parasite so can be easily cultured. It is small, transparent and has a
very short lifecycle.
8.
Using information from paragraph 3 on the evolution of Schistosomes, identify genes
that have been lost through evolution and gene families that have diversified. In both
cases, which types of mutation may have been involved?
1000 protein domains lost – including for basic metabolic pathways. Genes for
proteases involved in penetration of host have diversified. Mutations likely to be
deletions for loss and duplications followed by point mutations for diversification.
Evolution of Parasitism in Helminths:
9.
Draw a flow chart type model of the stages in the evolution of parasitism in nematodes.
Fungal feeder (arrow to) Plant parasite (arrow to) Animal parasite
Host–Parasite Relationships:
10.
Outline mechanisms of host immune system suppression by parasites as described in
paragraph 2.
Immune suppression leading to an anti-inflammatory environment (which increases
parasite survival). Parasite products influence cytokines, signalling and enzyme
function.
11.
In paragraph 3 the interaction between parasitism and the immune system is linked to
allergies and autoimmune diseases in humans. Suggest how an absence of immune
suppression may account for this link.
Our immune systems may have evolved to ‘expect’ a certain level of immune
suppression as a result of parasite burden. Without that parasite burden, our immune
systems may be too active and target self in error.
The “Dependent” Helminth:
12.
Using the loss of a synthesis pathway as an example, explain why some parasites are
obligate.
Some parasites are unable to synthesise fatty acids, sterols and purines for example.
They are obliged to rely on the metabolism of their host to synthesise these compounds.
Challenges for the future:
13.
Identify the two main technological advances that will take place in the field of
helminth genomics.
The speed of sequencing of genomes will increase. The software platforms that allow
the sequences to be compared will be improved.
14.
Contrast the type of treatments currently available for helminth infection with the type
of treatments that may become available as a result of helminth genomics.
Currently helminth infections are treated with two or three drugs. Resistance to these
drugs is already noted in helminthes. Helminth genomics aims to targets for drugs
much more specific in their action.
CfE AH Biology: Unit 2 Organisms and Evolution
Tutorial: Prevention of population cycles by parasite removal
This tutorial is designed to support the following areas of the arrangements document.
Unit 2 Organisms and Evolution
1 Field techniques for biologists
(b) Sampling wild organisms
(d) Monitoring populations
2 Organisms
(c) Sex and behaviour
(i) Sexual investment
(ii) Courtship
(d) Parasitism
(i) The parasitic niche
(ii) Transmission and virulence
The tutorial is based around an original findings article published in the journal Science. The
article has been selected as it involves a long-term, large-scale, replicated experimental study
to collect field data as well as describing the use of a computer model to simulate conditions
not tested in the field. The study aims to test the importance of parasites in determining
population cycles and reaches a firm conclusion (which has been questioned by others since).
What is more, the study involves the Red Grouse, a species of importance within the Scottish
economy, the management of which is controversial. The article should be fairly accessible to
a group of AH students with help from their teacher or lecturer.
The article is freely available on the Science website at the following address
http://www.sciencemag.org/content/282/5397/2256.full
A PDF of the article is also available for download at the above
web address.
The citation for the article is:
Hudson, P.J., Dobson, A.P. & Newborn, D. (1998) Prevention of Population Cycles by
Parasite Removal Science 282 (5397), 22562258. [DOI:10.1126/science.282.5397.2256]
Prevention of Population Cycles by Parasite Removal Tutorial
Access the following article in advance of the tutorial:
Hudson, P.J., Dobson, A.P. & Newborn, D. (1998) Prevention of Population Cycles by
Parasite Removal Science 282 (5397), 22562258. [DOI:10.1126/science.282.5397.2256]
During the tutorial there will be discussion of the following areas. Please make sure that you
have read the relevant sections and thought about the areas for discussion. You may find it
helpful to make notes in advance of the tutorial.
Useful words:
Fecundity = ability to produce offspring
Intrinsic = an essential or inherent property
Use a web search to introduce yourself to the following, if necessary:
1. Red Grouse Lagopus lagopus
2. Trichostrongylus tenuis, parasitic strongyle worm (Nematoda)
3. Population cycles in lynx and snowshoe hares
Tutorial questions
Journal title:
1.
The journal Science claims to be the World’s leading journal of original scientific
research, global news, and commentary. How easy would it be for a scientist to publish
an article in Science?
Reports:
2.
Above the heading of the article is the word ‘Reports’. What do you think that this
refers to?
Article title:
3.
Using the example of lynx and snowshoe hares explain what is meant by a ‘Population
Cycle’?
Abstract:
4.
After reading the abstract, identify the independent and the dependent variables.
Paragraphs 1 & 2 (text on p.2256)
5.
What aspects of this study design are intended to increase the reliability of the results
obtained?
Figure 1
6.
Describe the relationships shown in A, B and C.
Paragraph 3 (text on page 2257)
7.
Would a study of this type require any special permissions?
8.
In the study, it was estimated that between 15 and 50% of each population was treated.
Suggest how the population sizes were estimated.
Figure 2
9.
Using the three graphs in Figure 2 (confusingly, also labelled A, B and C), describe the
effect of the parasite control treatment on the population cycles in red grouse.
Paragraphs 4, 5 & 6 (text on page 2258):
10.
This study concludes that ‘parasites’ played a key role in causing population cycles.
What other ecological factors could, in theory, influence population cycles?
Table 1, Figure 3 and References and Notes as well as the study as a whole
11.
This study combines an observational study, with an experimental study to test the
observations, along with computer modeling to make predictions beyond what has been
tested. Can you identify which part is which?
The bigger picture
12.
Due to its role within the Scottish economy, the population dynamics of the red grouse
are relatively well understood in comparison to those of many other species. Large
parts of Scotland are managed to maximize income from shooting red grouse. This
management is not without conflict, particularly where illegal raptor control is
involved. Do some further research, develop a viewpoint and back it up with some
evidence before your tutorial.
Prevention of Population Cycles by Parasite Removal: Notes to tutor
It is suggested that the article is printed and distributed or students are given the link. For
homework the students must read the article. Ideally they should read the entire article,
making annotations for discussion later. It may be effective to ask particular students to focus
on particular areas of the article to answer questions in class. You may also wish to pre-issue
the list of the topics that will be discussed during the tutorial.
Hudson, P.J., Dobson, A.P. & Newborn, D. (1998) Prevention of Population Cycles by
Parasite Removal Science 282 (5397), 22562258. [DOI:10.1126/science.282.5397.2256]
Tutorial questions
Journal title:
1.
The journal Science claims to be the World’s leading journal of original scientific
research, global news, and commentary. How easy would it be for a scientist to publish
an article in Science?
Not easy! It is a peer-reviewed journal so the article would be assessed in terms of its
scientific merit. It is a leading journal so it can be choosy about which articles to print
– only about 10% of the articles submitted to Science make publication.
Reports:
2.
Above the heading of the article is the word ‘Reports’. What do you think that this
refers to?
Reports are reports of original findings.
Article title:
3.
Using the example of lynx and snowshoe hares explain what is meant by a ‘Population
Cycle’?
These data are from fur trapper records from the Hudson Bay Company in what is now
Canada. They show peaks in snowshoe hare being followed by peaks in lynx, resulting
in troughs of snowshoe hare resulting followed by troughs of lynx, resulting in peaks of
snowshoe hare and so on. As the article describes, “a density-dependent response
acting with a time-delay between natural enemies and their prey”.
Abstract:
4.
After reading the abstract, identify the independent and the dependent variables.
Independent variable: nematode parasite burden
Dependent variable: red grouse population
Paragraphs 1 & 2 (text on p.2256)
5.
What aspects of this study design are intended to increase the reliability of the results
obtained?
Long-term
Large-scale
Replicated
Figure 1
6.
Describe the relationships shown in A, B and C.
A: Red grouse population (measured in two different ways) shows cyclic troughs in
population.
B: Annual population growth rate of red grouse is negatively correlated with intensity
of parasite infection in red grouse
C: Chick mortality increases with intensity of parasite infection in red grouse.
Paragraph 3 (text on page 2257)
7.
Would a study of this type require any special permissions?
Wild birds are protected by The Wildlife and Countryside Act 1981 as well as the
Nature Conservation (Scotland) Act 2004.However, in the eyes of the law certain
native species birds, like the red grouse, are not ‘wild birds’ but instead ‘game birds’.
Game birds are protected during the close season by the Game Acts; outwith the close
season (for red grouse 12 Aug – 10 Dec) they can be killed or taken (captured). This
study, which involved the interference of breeding birds, would have been licensed by
the appropriate scientific council.
8.
In the study, it was estimated that between 15 and 50% of each population was treated.
Suggest how the population sizes were estimated.
A mark-recapture method would have been used. A known number were marked and
then the proportion of marked birds in the final sample (the shooting bag, perhaps)
would allow estimation of the total population.
Figure 2
9.
Using the three graphs in Figure 2 (confusingly, also labelled A, B and C), describe the
effect of the parasite control treatment on the population cycles in red grouse.
A is the control and shows population declines in both samples at times spaced four
years apart. B is a single antihelminth treatment and this shows a reduction in the
decline in one sample followed by a steep decline four years later. The other sample in
B shows a reduced decline in both years. In C, one sample shows no real decline in
either year whereas the other sample shows a slight reduction in the second year.
Paragraphs 4, 5 & 6 (text on page 2258):
10.
This study concludes that ‘parasites’ played a key role in causing population cycles.
What other ecological factors could, in theory, influence population cycles?
Potentially, the following are considered to have an impact upon red grouse
populations:
Climate – wetter climates are thought to increase survival of free-living parasites
Intraspecific behaviour: territorial aggression is also considered to limit grouse
density
Kin selection: grouse are more tolerant of relatives, so there is less aggression and
higher densities when neighbours are related
Interspecific competition: other species of birds may compete for food with young
grouse chicks
Habitat availability: grouse moorlands are burnt periodically to encourage a
monoculture of heather with a mosaic of different ages for breeding, shelter, feeding
and rearing chicks
Predation: some raptors, such as the hen harrier, are known to prey upon grouse
Table 1, Figure 3 and References and Notes as well as the study as a whole
11.
This study combines an observational study, with an experimental study to test the
observations, along with computer modelling to make predictions beyond what has
been tested. Can you identify which part is which?
The observational study involves the correlation of data in Fig 1. The experimental
study involves the results shown in Fig 2. The experimental study aims to gain
understanding of the causation of the correlation. Data gathered from field studies is
used to define the population parameters shown in Table 1. These then can be modelled
using the equations shown in the References and Notes section. The results of the
computer modelling is shown in Fig 3 and has been used to identify the proportion of
birds in the population that have to be treated in order to smooth out the population
cycle. This figure can then subsequently be assessed in further field trials.
The bigger picture
12.
Due to its role within the Scottish economy, the population dynamics of the red grouse
are relatively well understood in comparison to those of many other species. Large
parts of Scotland are managed to maximize income from shooting red grouse. This
management is not without conflict, particularly where predator control is involved. Do
some research, develop a viewpoint and back it up with some evidence before your
tutorial.
This study is unusual in that the aim is to achieve population stability in order to allow
shooting to occur annually, without years where the red grouse population is too low to
shoot. This may seem unsavoury to some students but reflects the reality of some areas
of biological research. Students will have opinions about the relative importance of
shooting to the Scottish economy and of the necessity of predator control in the Scottish
countryside. The conflict surrounding the hen harrier (Circus cyaneus) makes an
interesting case to look into further for students who are interested.