BIOL1020H – FOUNDATIONS OF BIODIVERSITY WEBWriting Assignment – Selection in Natural Populations (10%)
Introduction
How important is natural selection in the wild? Is it pervasive or does it act episodically or
only on certain traits? Answering these questions requires the ability to infer whether selection is
operating in nature. This assignment examines the patterns of selection using an important
measure of fitness: survival. Survival data was collected from a wild, unmanipulated population. If
the trait being measured is linked to survival and if the trait that is measured is heritable it will
evolve.
Survival, especially pre-reproductive survival, is a key component of fitness. If organisms
don’t live long enough to reproduce their fitness is nil. For this reason, survival is one of the most
commonly used measures of fitness. We will study patterns of survival in gall flies. These flies
induce plants to form galls. They do this by tricking the plant; they produce chemicals identical to
the growth hormones made by the plant (Mapes and Davies 2001). Normally these hormones
function to regulate plant development. However, by secreting these plant hormones, the flies
subvert this process and a mass of plant tissue is formed around the young fly larva, protecting and
nourishing the larva.
Study system
Gall flies of the genus Eurosta lay eggs at the tip of goldenrod shoots in mid-late summer
(Figure 1). A few days later, the larva hatches, bores into the plant stem and initiates the formation
of a gall. Galls reach their full size by late summer. In the fall, the plant stem dies but remains
standing. Within the galls, the larva continues to mature and overwinters in the larval state.
Figure 1: A female Eurosta; adult flies are 7 to 9 mm in length (A). Galls are visible around three weeks after
females lay their eggs (B). After eggs hatch, larval flies excrete a plant hormone that induces gall formation
by the plant. The galls have a hard, corky exterior but the interior is composed of specialized nutritive
tissues, which serve as the source of food for the developing fly. The galls continue to protect and nourish
the larva after the plant stem has senesced in late summer and early fall (C). At this stage, the fly larva
excavates a tunnel that it will use to leave the gall in the spring. The larval fly then enters diapause for the
winter. Photo credit: Dr. Warren Abrahamson
Several animals attack goldenrod galls to feed on the developing fly larvae, including insects
(the parasitoid wasps Eurytoma gigantea and E. obtusiventris, and the beetle Mordellistena
unicolor; Figure 2) and birds [namely downy woodpeckers (Picoides pubescens) and black-capped
chickadees (Poecile atricapillus). The two parasitoid wasps attack the larvae during the summer
months while birds attack the larvae over the winter. It is straight forward to determine which of
these animals have eaten the flies within their galls. If wasps or beetles attacked the fly larva, you
will find wasp or beetle larva(e) in the gall instead of a fly larva. If a bird has eaten the fly larva, you
will see a hole in the gall that was made by the bird (Figure 3).
Sources of gall fly mortality
Parasitoid wasps – Parasitoids are insects that lay their eggs on or in a host, but whose effect is to
kill the host (unlike a true parasite). The wasp Eurytoma gigantea is a parasitoid – the female inserts
eggs into the central chamber of goldenrod galls using her ovipositor. Her offspring eats the fly
larva and then switches to a vegetarian diet, eating gall tissue for the rest of the growing season.
Flies in smaller galls may be more susceptible to attack by this parasitoid wasp because wasps can
only attack fly larvae that are within reach of the wasp’s ovipositor. As a result, larger galls should
be protected from parasitoid attack. Therefore, when wasps are present we can predict that gall
size should be subject to directional selection, with flies that induce larger galls having higher
fitness than flies that induce smaller galls.
Beetles – The stems and galls of the goldenrods are attacked by a number of herbivorous insects.
One common herbivore found in the galls is Mordellistena unicolor, a beetle species that lays its
eggs on the surface of galls in early summer. Even though the beetle larvae do not eat the fly, when
many beetle larvae burrow into the gall they cause the death of the fly. Because the ability of
beetles to burrow into the gall is not limited by the size of the gall, beetles are an unlikely source of
selection on gall size.
Figure 2: Several insects attack gall fly larvae, including the parasitoid wasps Eurytoma gigantea (A) and
Eurytoma obtusiventris (B) and the stem-boring gall inquiline (an inquiline is an animal that lives in another
animal’s home) Mordellistena convicta (C). The wasps use their long ovipositors to pierce the gall and lay an
egg in the gall chamber. Because the ovipositor has a fixed length, the success of the wasp’s attack depends
on the thickness of the gall wall; if it is thicker than the length of the ovipositor the fly will escape predation
by the wasp’s offspring. However, the beetle is a stem borer; the larvae attack the flies from within the stem
and the success of attack is independent of the size of the gall. Photo credit: Dr. Warren Abrahamson.
Figure 3: Damage to fly galls caused by woodpeckers (left) and chickadees (right). Photo credit: Dr. Warren
Abrahamson
Avian predators – Downy woodpeckers (Picoides pubescens) and black-capped chickadees (Parus
atricapillus) also prey on the gall fly larvae. These birds peck through the tissue of the gall and
extract the soft-bodied fly larva. These birds are visual predators and thus larvae living in galls more
easily seen by birds may suffer higher rates of mortality. If gall size affects the likelihood that a bird
will see and attack the gall, then predation by birds will cause directional selection on the size of
galls. Chickadees make large irregular holes; bits of gall are torn away to form the hole.
Woodpeckers make small, tidy, conical holes in the galls (Figure 3).
Plant interactions – Plants have mechanisms to resist herbivory that cause the death of the
herbivore. This may be an explanation of the phenomenon of Early Larval Death for Eurosta flies – a
common source of mortality for flies on goldenrods, which often leads to smaller gall sizes because
of the early death of the fly larva.
Procedure -Sampling galls
Goldenrod plants having galls were collected from open fields in southern Ontario during in the fall
of 2018. Using calipers, the diameter of each gall at its widest point was measured to the nearest
0.1 mm. Using a knife, the gall was opened to look inside the gall to determine whether the fly
survived attack. If a cream-colored, fat fly larva was present in the gall, that fly had survived all the
mortality agents discussed above. If the gall contained anything other than a fly larva, the fly did not
survive. The specific cause of larva mortality was determined using an online key.
(http://www.facstaff.bucknell.edu/abrahmsn/solidago/gallkeyintro.html).
The gall diameter and the fate of the fly were recorded. A two sample t-test was performed to
determine if the was a significant difference in the size of the galls containing larvae that survived
vs. those containing larvae that had died. See posted webcasts for additional information.
References
Mapes, C.C. and Davies, P.J. 2001. Indole-3-acetic acid and ball gall development on Solidago
altissima. New Phytologist. 151: 195-202.
Writing Assignment – 10% of your final grade – DUE Monday, April 4, 2022 by 5:00 PM
Students should follow the format outlined in the Guidelines for Writing Lab Reports
provided on the course Blackboard site, using the suggestions below to help you decide on the
content to include in your report. A rubric is posted on Blackboard to help. The marks assigned to
each section are indicated below.
Title (2 marks)
You will need to come up with your own title for the report
Abstract (½ page; 2 marks)
The abstract is a quick summary of your study. It should include your primary objective (1
sentence), how you addressed the objective (1-2 sentences), your main findings (1 to 2 sentences)
and your broad conclusion (e.g., “I conclude that the results were consistent with the hypothesis
that…”). Essentially, it has one main point or two from each section in your paper. The abstract is
usually written once the rest of the paper is written.
Introduction (1 page; 6 marks)
Provide some background information on the topic of natural selection. Introduce the key
aspects of the biology of the system with special reference to the causes of mortality of gall flies
and the expected direction of selection on the size of the gall for each source of mortality. State the
hypothesis examined and a brief statement about how you tested it.
Methods (1 page; 4 marks)
Include enough detail on what you measured and how you measured it that someone else
could duplicate what you did. Although you are not conducting the statistical analysis yourself be
sure to mention the name of the analysis and how the analysis enables you to test your hypothesis.
Results (up to 1 page plus a figure; 8 marks)
Include all figures of the data provided by your instructor. Explain clearly what each figure
illustrates. Include a clear statement about the result of the statistical test and whether you could
reject the null hypothesis (i.e., the statistical hypothesis). Report the results of the t-test (the
statistical test used in this lab) using text along the lines of: ‘There was no significant difference in
the size of the galls containing larvae that survived vs. those containing larvae that had died (t =
1.78, P = 0.30)’. The value of t (“1.78” in this example) is the value of the test statistic; the larger the
value the more likely there is to be a significant difference between the groups being compared (in
this case galls in which the fly larva survived vs. galls where the larva did not). The t and P-values are
located in the Two Sample t-test output. Note, in this example, there was no significant difference
in gall sizes for larvae that died vs. survived. You might find something else! A significant difference
in gall sizes between the two categories of fly larvae (alive vs. dead) would be indicated by a P-value
of less than 0.05. Refer to the results of this test in the same part of your Results section in which
you report the mean gall sizes for each group of flies (dead vs. alive). The test performed is
specifically a test of whether the mean gall sizes for the two groups of flies are different.
Your Instructor will provide you a plot showing the mean (average) sizes of galls for fly
larvae that have survived compared to those that have not. The plot enables a visual comparison of
the data for galls in which fly larvae have survived vs. those in which the larvae have died. The plot
consists of two dots indicating the means, each with “whiskers” that indicate the magnitude of the
standard deviation (sd). The sd is a measure of how spread out the numbers associated with each
mean are. These numbers, the mean and sd, are directly related to the values used to calculate the
t-value for the statistical test described above. When you describe the plot in your Results section,
describe the degree of overlap (or lack thereof) in the sd of the gall size between flies that were
alive vs. dead. If there is a significant difference in the mean size of the galls for flies that were dead
vs. alive you should also see that the standard deviations for each category of fly are offset from
one another, with one mean and sd located substantially higher than the other, corresponding with
larger galls for one category of fly compared to the other. You can also refer to the specific sources
of mortality in general in this section (recall, we did not consider the specific cause in our statistical
test). For example, you can state which forms were most/least common and then refer the reader
to the raw data in the Appendix.
Discussion (up to 4 pages; 8 marks)
This is the critical thinking part of your report. Have you supported or rejected your
hypothesis? If there is no significant difference in gall size for flies that survived vs. those that did
not, the result is still potentially interesting and should provoke further questions.
The variation you have documented may be due to environmental or genetic factors. Think
of at least one other hypothesis that could account for your Results. How would you test this
additional hypothesis? From what you have observed and read, to what extent do you think the
distribution of gall sizes in your study population is the outcome of natural selection in previous
generations? You can consult the raw data that includes the specific sources of mortality to help
you interpret your findings.
Conclusion (3 marks)
The conclusion provides an overall summary of the study and answers the questions posed
in the introduction. The conclusion should be based on your results, and how they relate to the
broader scope of the study topic.
References (minimum 3 references to the primary literature; i.e. journal articles; 2 marks)
You will find your textbook and other sources helpful for background information when
writing your report, but you should also try to find new references that support your ideas /
conclusions or with which you compare and contrast your results. Try to find studies that have used
a similar approach or that have used the same (or related) species to investigate a similar topic.
DEPARTMENT OF BIOLOGY
TRENT UNIVERSITY
BIOL1020H WEB – FOUNDATIONS OF BIODIVERSITY
2022 Winter
WRITING ASSIGNMENT 1 (5% of final grade)
This course examines the roots of biodiversity from descriptions of the variety of organisms in nature, to
their roles in the environment, and finally to the process of evolution that gave rise to those organisms.
Underlying our understanding of all of what biologists call ‘organismal biology’, is knowledge of the
taxonomy (the science dealing with the description, identification, naming, and classification of organisms),
and systematics (the study of the diversification of living forms, both past and present, and the
relationships between living things through time) of our particular group of interest (e.g., fish, birds,
insects, plants, fungi, etc.). Thus, to understand nature from the perspective of the whole organism, we first
need to be able to classify that organism. Classification comes from both early roots of simply identifying
organisms based on their phenotype (i.e., its observable characteristics or traits) (e.g., Linnaeus in the mid1700’s) to more recent advances in molecular biology, that allow us to identify organisms sometimes solely
on the basis of their genetic code (or at least a portion of that genetic code, e.g., DNA barcoding).
For this writing assignment you are to choose ONE of the following species listed below.
Assassin Bug
Dense Blazing Star
Bobolink
Pygmy Snaketail
Wild Bergamot
Northern Flicker
West Virginia White
Green Dragon
Horned Grebe
For your Writing Assignment (NOT a formal lab report) you will be using several websites to find a variety of
information on your chosen species. This will give you an idea as to what sorts of resources are freely
available to the public about taxonomy and the status of species globally.
1-1
BIOL1020 – Writing Assignment #1 (5% of final grade)
DUE: Monday, February 28, 2022 by 5:00 PM
You are to complete the 5 questions below. Please use the ‘Writing Assignment # 1 Winter 2022’
file posted to Blackboard to fill in your answers, re-save the document once you have answered
the questions, and submit an electronic copy in the drop box on Blackboard – found in the
‘Writing Assignment #1’ Folder
Where appropriate, your answers should be in full sentences.
TOTAL MARKS = 23
1. The full biological classification of an organism consists of its domain, kingdom, phylum, class, order,
family, genus, and species. When reporting these, domain to family are written in regular font (i.e., not
bolded, underlined, or italicized), but there are particular, very specific conventions for reporting the
genus and species of an organism. Together these make up the scientific name of an organism. For
example, we belong to the species ‘Homo sapiens’, written in this particular style (both words in italics,
capital for ‘Homo’ but NOT for ‘sapiens’), and this is the style that you should use to write the scientific
name of your chosen organism (and all scientific names that you ever write during your career as a
Biologist!). Note also that the scientific name of an organism requires BOTH the genus name and the
species name. The genus ‘Homo’ can stand on its own, but you wouldn’t just say ‘sapiens’ to indicate the
human species – ‘Homo sapiens’ is correct. In literature that emphasizes taxonomy, scientific names are
often also followed by both the name of the ‘taxonomic authority’ and, if it’s an animal, a year (e.g.,
Homo sapiens, Linnaeus, 1758). [Note that ‘Linnaeus’ is not in italics]. It is acceptable (and common) for
the taxonomic authority to only be abbreviated (e.g., ‘L.’ for Linnaeus).
a. For your organism, list the kingdom, phylum (ITIS calls this ‘division’ if your organism is a
plant), class, order, family, genus, and species in the proper format. To find this, look up your
species using the Integrated Taxonomic Information System (ITIS) (www.itis.gov). Be sure to
include the taxonomic authority (full or abbreviated) given by ITIS and (if your organism is an
animal) the year. (3 marks)
b. For scientific names of animals, what does the year after the taxonomic authority refer to?
(If your organism is a plant, you are still to answer this question). (1 mark)
2. The International Union for the Conservation of Nature (IUCN) (www.iucn.org) is the most authoritative
source on the conservation status of organisms on earth. Species that have been assessed are listed on
the IUCN Red List of Threatened Species (www.iucnredlist.org). Use the search function to look up your
species. If it is listed, answer a, b, and e. It if is not listed, answer c, d, and e.
a. What is the IUCN Red List Category and Criteria of your species (in full, not the two-letter
abbreviation)? (1 mark)
Provide a brief (1-2 sentences) definition for this category. (1 mark)
b. In what year was it assessed? You may need to click on the link for your species name to
get more information. (1 mark)
OR
c. If a species is not listed on the Red List, it usually means that that species does not have a
particular conservation status. Assume that the conservation status is the least concerning of
the IUCN categories. What is the name of this category? (1 mark)
Provide a brief (1-2 sentences) definition for this category. (1 mark)
1-2
d. The IUCN will refer you to a different source to find information on your species if it is not
listed in the IUCN. What is the name of this different information source? (i.e., to where are
you referred if your species is not on the Red List?). (1 mark)
e. Include a screen capture of your organism’s page either from the IUCN or the website
from ‘d’, as appropriate to your organism. (1 mark)
3. Next, look up your species in the Catalogue of Life (www.catalogueoflife.org; “Monthly edition” Scroll
down to find it). The Catalogue of Life is an online database of the world’s known species. It currently
has information on 84% of ALL the species known to scientists! Click on the link of your species name
once you have searched for it.
a. What is the distribution, or range of your species according to Catalogue of Life?
NOTE: you are to summarize the distribution stated on the website rather than cutting-andpasting from the website. If there is no distribution stated on the Catalogue, then state that
and then look elsewhere for the answer. (1 mark)
b. Is your species native to Canada? (You may have to look elsewhere to find this information. It
can be a website). (1 mark)
Regardless of where you find the answer, be sure to include a proper citation. (1 mark for
citation)
For the next two questions you will need to use the searching tools that you learned during the Library Skills
Program. A scientific paper is a peer-reviewed paper, not a web site (although the paper could well be on a
web site) nor a book.
4. Find one scientific paper that mentions something about the ecology of the species that you have
identified. [The species might not be the sole subject of the paper. The paper may mention this and
several other species but do not worry about that as long as it has something about its ecology or that
of the community (collection of species) that it lives with.]
a. Summarize the findings of the paper in your own words in 150 words or less. (4 marks)
b. Provide the reference of the paper in the style indicated on pages 6-7 of ‘GUIDELINES FOR
WRITING LAB REPORTS’ (Under ‘Writing Assignment #2’ folder on Blackboard) (2 marks)
5. Find one scientific paper that mentions something about any other topic (e.g., conservation,
taxonomy, physiology, genetics, agriculture) about your chosen species.
a. Summarize these findings, also in 150 words or less. (4 marks)
[Note again that the species might be listed as one of many included in the study.]
b. Include the reference of the paper as you did for Question 4. (2 marks)
1-3
Writing Assignment #2 – Selection in Natural Populations
FORMAT:
•
Use 12 point font, 1 inch margins, and double spaced text. Include page
numbers.
•
While your Abstract and References sections are single spaced, your
Introduction, Methods, Results, and Discussion sections must be double
spaced! Figure captions and Table headings can also be single spaced.
•
Do not use a title page (name, student number, and title on first page of text).
•
Submit document as a PDF
GRADING SCHEME (Total: 35 marks)
Title (2 marks)
Abstract (½ page; 2 marks)
Introduction (1 page; 6 marks)
Methods (1 page; 4 marks)
Results (up to 1 page plus figure(s); 8 marks)
Discussion (up to 4 pages; 8 marks)
Conclusion (3 marks)
References (minimum three citations of primary literature; 2 marks)
BIOL 1020H Foundations of Biodiversity – Rubric Overview for Writing Assignment
Below Expectation
Meets Expectation
Above Expectation
Missing or Little insight to subject of paper
Informative re: subject matter but either too
brief or too long
(1.5 points)
Descriptive, specific, and concise title re: subject matter,
intriguing & not too long (2 points)
Clear, concise, relevant aspects presented
Brief overview of objectives, summary of methods,
principle results, significance of findings (2 points)
/ 4
Very unclear
Experiment cannot be repeated OR written as
‘recipe’ or point form (0 – 1 point)
No text or missing essential components
(e.g., observations, description of graph(s),
statistics, any differences or lack thereof)
Irrelevant details included and/or interprets
results (0 – 1 point)
Some figures missing or poorly done
Irrelevant information is included Substantial
errors in figures/tables
No captions or substantial errors in captions
(0 – 1 point)
Key aspects sufficiently presented but missing
summary of two or more parts, brief, unspecific
Irrelevant details included (1.5 points)
Insufficient background information
No citations or citations are not relevant
Irrelevant details included
Purpose of experiment unclear
Hypothesis & prediction stated reasonably well
(3 -4 points)
Site mentioned & study design described fairly
well
Some mention of data analysis/summary
Missing minor details
Irrelevant details (2 – 3 points)
All components present, fairly clearly written
and organized
Interprets results or simply repeat information
in tables and figures
(2- 3 points)
Table/figures include irrelevant information
Information is presented in an unclear way,
does not enhance understanding of results
Few errors in captions or figures
(2 – 3 points)
/ 8
Too general /basic interpretation of results and
how they apply to study’s question(s)
Results poorly used to support arguments
No to little comparison of results to other
research
Primary literature not used to support
arguments (0 – 3 points)
Adequate interpretation of results and how they
apply to the question(s) being addressed
Sufficient use of results to support arguments
Some comparison of results to other research
Primary literature seldom used to support
arguments (4 – 6 points)
Clear, relevant, and supporting background information
Well researched with relevant references
Adequately introduces all topics to understand study
Clear statement of objective, hypothesis, and prediction
(5 – 6 points)
Clear, complete, and proper description of procedures
and any equipment used
Mentions study area and is in chronological order
No irrelevant /all relevant details included
Data collection & analysis accurately described (4 points)
Clear, complete, and concise summary of key trends
Patterns and findings that are relevant to objectives
No interpretation of results or repeat of tables/figures
Figures/tables referred to appropriately in text of results,
and presented in an organized and logical way (4 points)
Figures/Tables present key results clearly
Are appropriate for predictions
Numbered, and captions are complete & informative
Axes and row/column headings properly labelled
(4 points)
Clearly relates findings to original question, hypothesis,
and/or predictions
Solid interpretation and discussion of results
Good utilization of results to support arguments
Sources of experimental error or limitations discussed
Good comparisons of results to other research
Utilizes carefully selected primary literature to support
arguments & proposes future studies
Discussion points are well thought out and logically
presented (7 – 8 points)
/3
Poor to satisfactory understanding of purpose
Missing some connections to purpose or the
experiment (0 – 1 point)
Summary only
Conclusions are made, but not very clear
(2 points)
Follows clearly from discussion
Clear understanding of purpose and succinctly summarize
findings of the experiment (3 points)
Citations inappropriate/ insufficient Cited rarely
Citations appropriate and/or sufficient
Cited occasionally (1.5 points)
Well-chosen citations, cited often and correctly
Proper formatting (2 points)
Title
/ 2 (0 – 1 point)
Abstract
/ 2
Missing altogether or missing key aspects
Abstract is too brief and contains little to no
relevant information (0 – 1 point)
/ 6
Too general or brief
Little to no background provided
Does not state purpose of the experiment
Hypothesis and prediction stated, but not
clear/poorly stated
(0 – 2 points)
Introduction
Methods
/ 4
Results – Text
/ 4
Results – Figures
and/or Tables
Discussion
Conclusions
References
/ 2 Problems with formatting (0 – 1 point)
Mean Gall Diameter (mm)
t = 2.0
P = 0.038
Dead
Gall Fly Larval Fate
Alive
Frequency (number of gall fly larva)
Alive
Dead
0
10
12
14
16
18
20
22
24
Gall Diameter (mm)
26
28
30
32
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Formatting
Title Page
Citation
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