Community Ecology Act II Assignment Submission
pdf
keyboard_arrow_up
School
Ohio Northern University *
*We aren’t endorsed by this school
Course
121
Subject
Mathematics
Date
Apr 3, 2024
Type
Pages
51
Uploaded by BarristerOctopusMaster1049
Community Ecology Act II Assignment Submission Due Nov 19, 2023 at 11:59pm
Points 30
Questions 33
Available Nov 10, 2023 at 12am - Nov 19, 2023 at 11:59pm
Time Limit None
Instructions
Welcome Welcome to your Community Ecology Act II Assignment! In this assignment, you will apply the knowledge and skills you acquired
in the Intergalactic Wildlife Sanctuary and your lab to 1) determine if a change in the density of umbrella trees or spotted gliders
could have caused the dispersal of boreblasters either as a bottom-up or top-down effect, respectively and 2) predict which
predator in the Allurian forest has started eating grabbins.
NOTE: You can return to this page at any time while completing your assignment.
Additional required resources Some of the questions in this assignment require you to refer to data sets, diagrams, or other information. Download the following
files to complete this assignment:
Data: Historical Densities of Umbrella Trees
(https://canvas.asu.edu/courses/157350/files/68872496?wrap=1) (https://canvas.asu.edu/courses/157350/files/68872496/download?download_frd=1)
Data: Historical Densities of Spotted Gliders
(https://canvas.asu.edu/courses/157350/files/68872514?wrap=1) (https://canvas.asu.edu/courses/157350/files/68872514/download?download_frd=1)
The assignment requires you to understand the organisms in the Allurian Forest community. Please access the following field
guide for use in completing the assignment:
Field Guide of Alluria
(https://fieldguide.dreamscapelearn.online/) How to begin
Click the "Take the Quiz" button to begin. After answering all of the questions, please click "Submit" at the bottom of the page to
submit your answers. Additional information
Attempts:
You have only one attempt,
so be sure you are satisfied with your work before submitting your responses.
Time: There is no time limit
for this assignment.
Partners:
You may work with your peers to complete this assignment; however, you must submit this assignment individually to
receive credit. Even though you are allowed to work with your peers, your answers must be in your own words. (This means
you are NOT permitted to copy and paste answers with other students
.)
How you'll be graded
This quiz was locked Nov 19, 2023 at 11:59pm.
Attempt History
Attempt
Time
Score
LATEST
Attempt 1
4,222 minutes
29.8 out of 30
Score for this quiz: 29.8 out of 30
Submitted Nov 14, 2023 at 2:29pm
This attempt took 4,222 minutes.
This assignment is graded based on correct responses.
Due date
Please see Canvas for the due date. Remember, late assignments will not be accepted, so it is advisable to NOT wait until the
last minute to begin your assignment.
Appendix 1
Could a change in the density of umbrella trees have caused the dispersal of boreblasters as a bottom-up effect?
We reasoned that a recent change in food supply might have triggered the dispersal of boreblasters. These creatures feed
primarily on the woody tissue of umbrella trees; therefore, we need to know whether the density of umbrella trees has either
increased or decreased, causing a bottom-up effect on boreblasters (see Figure 1).
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Figure 1.
Left:
A food chain for the Allurian Forest depicting the flow of energy and matter. Center:
A decrease in the density of umbrella trees should directly cause a decrease in the density of
boreblasters and indirectly cause a decrease in the density of spotted gliders. Right:
An increase in
the density of umbrella trees should directly cause an increase in the density of boreblasters and
indirectly cause an increase in the density of spotted gliders. Both scenarios are referred to as a
bottom-up effect.
Using LiDAR, you constructed a map of the forest and estimated the density of umbrella trees to be 27,000 m
of tree tissue per
km
of land. Now, you must see whether the current density is unusual relative to historical values. Remember, no boreblasters in
the sanctuary had never developed into the purple, long-winged form until now; therefore, the density of umbrella trees must be
extremely unusual to support our hypothesis.
I have provided you with the densities of umbrella trees estimated during previous growing seasons in the sanctuary, all of which
occurred before the boreblasters dispersed. Using the links in Canvas, download these data:
Historical densities of umbrella trees (sample size = 31)
2
2
Question 1
1 / 1 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question, (2) your
answer addressed what you would expect when comparing current umbrella tree densities to mean historical densities. As noted in the Act I Assignment, there were two possible bottom-up effects that could have caused the dispersal of boreblasters.
We separately address each scenario below. See the optimal answers for each bottom-up effect below.
Bottom-up effect 1 - The density of umbrella trees increased over time: If the bottom-up effect was that the density of umbrella trees increased over time, then one should expect to observe that the
current density of umbrella trees is higher than the mean historical density. Bottom-up effect 2 - The density of umbrella trees decreased over time: If the bottom-up effect was that the density of umbrella trees decreased over time, then one should expect to observe that the
current density of umbrella trees is lower than the mean historical density.
APPENDIX 1, STEP 1: ANTICIPATE YOUR ANALYSIS
Assume that a bottom-up effect caused the dispersal of boreblasters; specifically, a change in the abundance of umbrella trees
caused a corresponding change in the abundance of boreblasters. What would you expect to observe when comparing the current
density of umbrella trees to the mean historical density?
Assuming that a bottom-up effect caused the dispersal of boreblasters, we would expect to observe the current density of
umbrella trees is likely to be smaller than the mean historical density.
Question 2
1 / 1 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question, (2) your
answer addressed what you would expect when comparing current umbrella tree densities to mean historical densities. See the optimal answer below:
The most logical finding would be that the current umbrella tree density would be similar to the mean historical density. One might
say "not different or equal to" - which is fine in this case because that implies the magnitude of the difference is very small or non-
existent. An even more nuanced answer would recognize that the current density may still be different - but not extremely different
- from the mean historical densities.
Question 3
0.75 / 0.75 pts
Assume that a bottom-up effect did not
cause the dispersal of boreblasters. What would you expect to observe when comparing
the current density of umbrella trees to the mean historical density?
Assuming that a bottom-up effect did not cause the dispersal of boreblasters, we would expect the current mean density of
umbrella trees to be equal to, or similar to the mean historical density.
There are two possible claims as to whether a bottom-up effect caused the dispersal of boreblasters, 1) yes, a bottom-up effect
caused the dispersal of boreblasters, or 1) no, a bottom-up effect DID NOT cause the dispersal of boreblasters,. Complete the bar plots shown below. One of the bar plots illustrates what you would expect to observe with respect to umbrella
tree abundances if a bottom-up effect caused the dispersal of boreblasters. The other illustrates what you would expect to observe
with respect to umbrella tree abundances if a bottom-up effect did not cause the dispersal of boreblasters. The x- and y-axis have
been labeled for these plots.
To complete these plots, draw the bar plot for what you predict the current umbrella tree abundance would look like in both
scenarios. The bar plot for the historical umbrella tree densities has already been provided. Select "Choose a File" and upload
your bar plots. Upload your figures as a PDF or JPG
.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
umbrella trees bar plots.pdf (https://canvas.asu.edu/files/76764071/download)
Your lab TA used the following criteria to grade this question: (1) you made two plots that have a bar drawn into the “Current”
category for each plot representing your predictions for what you would expect to observe if a bottom-up effect was causing the
dispersal of boreblasters (or not). There were several ways to draw the plot illustrating what you would expect to observe if a bottom-up effect caused the dispersal
of boreblasters. Since we think boreblasters disperse because of a significant change in their environment that significantly alters
the abundance of boreblasters, if a bottom-up effect caused their dispersal, that would imply that the abundance of umbrella trees
changed substantially as compared to historic values. BUT - the umbrella tree density could theoretically change in either direction
(go up or go down) and still cause boreblasters to disperse. Regardless of whether you thought the abundance of umbrella trees
would increase or decrease, don’t worry if your plots don’t exactly match ours - what matters is that your graphs illustrate the
same principles as we did. We separately address each scenario below. Bottom-up effect 1 - The density of umbrella trees increased over time: If the umbrella tree density went up significantly, then boreblasters would become increasingly abundant because more food
sources are available - this would potentially cause a dispersal even because of overcrowding. The figure below illustrates what
one would expect to observe with respect to current vs historical umbrella tree abundances in this scenario. Bottom-up effect 2 - The density of umbrella trees decreased over time: Alternatively, if the umbrella tree density went down significantly, then boreblasters would have fewer food resources available -
increasing competition for food resources and potentially decreasing boreblaster abundance - potentially resulting in a dispersal
event. The figure below illustrates what one would expect to observe with respect to current vs historical umbrella tree
abundances in this scenario.
Finally, let’s look at what one could reasonably expect if a bottom-up effect DID NOT cause the dispersal of boreblasters. Recall
that we think boreblasters disperse because of a significant change in their environment that significantly alters the abundance of
boreblasters. In this case, if the bottom-up effect did not affect the abundance of boreblasters, it would be reasonable to predict
that the current density of umbrella trees likely was not very different from historical observations.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
As always, don’t worry if your plots don’t exactly match ours - what matters is that your graphs illustrate the same principles as we
do here.
Question 4
0.8 / 1 pts
APPENDIX 1, STEP 2: ESTIMATE THE MEAN AND STANDARD DEVIATION OF
TREE DENSITY
Using the historical densities of umbrella trees, you must determine the expected historical density and the uncertainty around this
expected density. In other words, you need to answer the question, “What density of umbrella trees should one have expected to
observe in the Allurian forest before the boreblasters dispersed?”
Start by plotting a frequency distribution of historical tree densities and decide whether this distribution meets the assumptions of a
normal probability distribution. If you are satisfied that a normal probability distribution would reasonably model the data, estimate
the mean and standard deviation of tree density.
Directions
: For question 4, download the Excel file, “Data: Historical Densities of Umbrella Trees,” containing historical densities
of umbrella trees (N = 31) to answer the questions that follow. Use Excel for calculations, modeling, and graphing. Round all
calculated values to the nearest whole number. For example, if you calculate the value as 3.8218, round to 4.
Create a plot of a frequency distribution (also known as a histogram) of the historical densities of umbrella trees. This plot should
follow the formatting guidelines listed below. Your plot should be formatted as a PDF or JPG. Select "Choose a File" and upload
your frequency distribution.
General
Chart type: Histogram
umbrella trees.png (https://canvas.asu.edu/files/76765319/download)
Your lab TA used the following criteria to grade this question: (1) you uploaded a plot that followed the guidelines listed above. Here’s what your graph should generally look like. Don’t worry if it’s not exactly the same (maybe you used a different shade of
grey for example), but the key is that your plot follows the formatting instructions for this graph.
Question 5
0.5 / 0.5 pts
Quick layout: Layout 1
Chart title: “Frequency distribution of historical densities (m
/km
) of umbrella trees”; Font size 18
Y-axes title: “Frequency”; Font size = 18
Y-axis numbers: Font size = 14
X-axis title: “Density (m
/km
)”; Font size 18
X-axis numbers: Font size = 14
2
2
2
2
Based on the frequency distribution you created above, does a normal probability distribution reasonably model the historical
density of umbrella trees?
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
explicitly answered the question “does a normal probability distribution reasonably model the historical density of umbrella trees?”
There were two possible ways to answer this question, depending on how you interpreted the frequency distribution in question 4.
That might be frustrating - but don’t worry, this question was graded for completion only! You could have answered yes or no (or
even maybe) and been correct! The reason why we said yes“Yes” or “No” yes, no, or even maybe are correct is because your answer may depend on how
comfortable you are with the frequency distribution you constructed in question 4 matching a normal probability distribution. Don’t worry, this happens in science all the time! That’s because no sample will ever be perfectly modeled by a normal probability
distribution - hence why sometimes you may end up with some disagreement as to whether the data is reasonably modeled by a
normal probability distribution. Sometimes it’s hard to argue that the data is reasonably modeled by a normal probability
distribution - other times less so. See the next question for more information as to why the answer to this question could be yes or
no.
Question 6
1 / 1 pts
Your Answer:
Based on the frequency distribution that I created, I think that a normal probability distribution would not reasonably model the
historical density of umbrella trees. Explain your answer to question 5. Be sure to discuss the assumptions of a normal probability distribution and why, based on the
frequency distribution, these assumptions seem appropriate (or not) for modeling the historical density of umbrella trees.
I claimed that a normal probability distribution would not model the historical density of umbrella trees for the following reasons.
The histogram that I created does not have a symmetrical shape, but more skewed to the left. In addition, there is one peak that
is not located in the middle of the graph, but more leaning towards the right of the graph, strengthening the point of the historical
density of umbrella trees cannot be modeled by this normal probability distribution.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your lab TA used the following criteria to grade this question:(1) you made a reasonable attempt to answer this question and (2)
explicitly discussed the assumptions of a normal probability distribution and why, based on the frequency distribution, the
assumptions of a normal probability distribution seem appropriate (or not) for modeling the historical densities of umbrella trees.
Checkout an example of an optimal answer (below). Remember, either yes or no were correct for question 5. One could say yes to question 5 because the frequency distribution in question 4 has a single central peak with roughly
symmetrical parts on either side of the peak (or mode).
But, one could also say no because there are more observations on the right side of the frequency distribution’s peak (or mode)
than on the left side, leading to an asymmetric frequency distribution. Again, it’s not abnormal for two people to interpret a frequency distribution like the one in question 4 differently. As with the
previous question - you received full credit for this question as long as you completed it.
Question 7
0.5 / 0.5 pts
Correct!
26,994
26,994 (with margin: 10)
The following criteria was used to grade this question:Y (1) you answered 26994 (m
/km
) with an error margin of 10.
The answer to this question was 26994 (m
/km
). You could have gotten this answer in one of two ways - either manually
calculating the mean or alternatively using Excel. If you manually calculated the mean, then you should have used the following
Directions: Using a normal probability distribution, estimate the mean and standard deviation of the historical density of umbrella
trees for questions 7-8. Round all calculated values to the nearest whole number. For example, if you calculate the value as
3.8218, round to 4.
Mean =
2
2
2
2
formula: If you used Excel, you should have used the function =AVERAGE(INSERT RANGE OF DATA ENCOMPASSING HISTORICAL
DENSITIES OF UMBRELLA TREES)
Question 8
0.5 / 0.5 pts
Correct!
1,008
1,008 (with margin: 10)
The following criteria was used to grade this question: (1) you answered 26994 (m
/km
) with an error margin of 10.
The answer to this question was 1008 (m
/km
). You could have gotten this answer in one of two ways - either manually
calculating the standard deviation or alternatively using Excel. If you manually calculated the standard deviation, then you should
have used the following formula: If you used Excel, you should have used the function =STDEV(INSERT RANGE OF DATA ENCOMPASSING HISTORICAL
DENSITIES OF UMBRELLA TREES)
Standard deviation =
2
2
2
2
Question 9
0.75 / 0.75 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
answered either “greater than,” “less than,” or “greater than OR less than.” You did not receive credit if you answered “equal to”. In the feedback to question 10, we explain why the answer could be “greater than”, “less than”, or “greater than OR less than.”
Question 10
1 / 1 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question. See an
example of what an optimal answer would look like (below). Directions: Use the normal probability distribution for the historical density of umbrella trees to answer questions 9-10. If a change in the density of umbrella trees caused the boreblasters to disperse, would you expect the current umbrella tree
density to be greater than, less than, or equal to the mean historical density?
I would expect the current umbrella tree density to be less than the mean historical density if a change in their density caused the
boreblasters to disperse. Explain your answer to question 9. Specifically, why did you select the answer choice you did? As you write your answer, think
back to your original answers to questions 1-3 at the beginning of this assignment.
I claimed that the current density of umbrella trees would be lower than the mean historical density because of the following
reasons. First, the current density of umbrella trees would be similar to those of historical density under the circumstances of the
umbrella tree does not have a bottom-up effect. But in the case where the umbrella trees caused the boreblasters to disperse, we
would see their current density to decrease since they might be consumed by the large population size of boreblasters. Since the
food resources decrease and are not enough for those boreblasters to survive, they would likely to evolve and disperse to other
areas to find alternate food sources.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Logic: Remember that the key here is thinking about the following questions: (1) Generally speaking, why do we think
boreblasters disperse? What do we know about why species disperse on Earth that could help us answer this question? (2) “If a
change in the density of umbrella trees caused boreblasters to disperse, what kind of change would need to occur?:
Example of an optimal answer: We know that boreblasters disperse when their environment changes enough to cause the
abundance of boreblasters to significantly increase or decrease. If a change in the density of umbrella trees caused boreblasters
to disperse - what kind of change in umbrella tree density would cause the boreblasters to disperse? Well, there are two ways you
could answer this question: You could have said that the umbrella tree density would increase over time - thus the current
umbrella tree density would be greater than the mean historical densities. Alternatively, you could have said that the umbrella tree
density would decrease over time - thus the current umbrella tree density would be less than the mean historical densities. Either
change would likely cause the abundance of boreblasters to significantly change - causing them to disperse. Hence why the
answer to question 9 could have been “greater than”, “less than”, or “greater than OR less than”.
The reason why “equals to” was an incorrect in question 9 is because if the current density of umbrella trees equals the mean
historical density, then this would imply there has been no change in umbrella tree densities over time - thus supporting the
conclusion that the umbrella trees were NOT likely the cause of the boreblasters dispersing. Question 9 was asking what you
would expect to observe IF a change in umbrella trees CAUSED the boreblasters to disperse. Thus, “equals to” as an answer
choice does not answer question 9.
APPENDIX 1, STEP 3: DETERMINE WHETHER OBSERVED DENSITY DIFFERS
GREATLY FROM THE EXPECTED DENSITY
Once you have a mean and standard deviation of historical tree density, you must determine whether the current tree density is
extremely low or high, relative to the historical tree density. Either conclusion would support the hypothesis of a bottom-up effect of
umbrella trees on boreblasters.
Let’s consider how you would accomplish this task. First, compare the current tree density to the mean of the historical tree
density. If the current density is less (or greater) than the mean, we can conclude that the current density is less (or greater) than
expected. However, we still don’t know if the current density is extremely unexpected.
To determine just how extreme the current tree density might be, you need to use the normdist function of Microsoft Excel. This
function requires three pieces of data for a variable: 1) an observed value, 2) the mean, and 3) the standard deviation. The values
are entered into Excel as follows:
=norm.dist(observered_value, mean, standard_deviation, TRUE)
The function returns the probability of observing a value less than (<) the observed value.
For example, entering the following function in Excel
=norm.dist(255, 270, 16, TRUE),
would return 0.1743 (or 17.43%), which equals the probability of observing a value less than 255 when the mean equals 270 and
the standard deviation equals 16.
In the normdist function, enter the current tree density as the observed value but enter the mean and standard deviation of the
historical tree density. The function should return the probability of observing a density less than the current density. If this
probability is less than 5%, we should conclude that the current density is extremely low compared to historical densities.
If you want to know the probability of observing a density greater than (>) the current density, recall that the following relationship:
P
(
y
> x
) = 1 - P
(
y
< x
)
where P
(
y
> x
) equals the probability of observing a value y that is greater than the value x, and P
(
y
< x
) equals the probability of
observing a value y that is less than the value x.
Subtracting the value returned by the normdist function of Excel from 1.0 will yield the probability of observing a density greater
than the current density. If this probability is less than 5%, we should conclude that the current density is extremely high compared
to historical densities.
Directions: Use the normal probability distribution for the historical density of umbrella trees to answer questions 11-12.
Question 11
0.5 / 0.5 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
either answered “less than”, “greater than”, or “less than OR greater than”. You did not receive credit for this question if you said
“equal to”. Remember that the key here is thinking about the following questions: (1) Generally speaking, why do we think boreblasters
disperse? What do we know about why species disperse on Earth that could help us answer this question? (2) “If a change in the
density of umbrella trees caused boreblasters to disperse, what kind of change would need to occur?”
Recall in questions 9 and 10, we already answered these questions - we know that boreblasters will disperse if their abundance
becomes unusually high or low. We also know that IF the umbrella tree density changed enough (compared to historical densities)
to cause the boreblasters to disperse, then the density of umbrella trees should either be increasing OR decreasing over time.
That’s why the answer to question 9 could have been “greater than”, “less than”, or “greater than OR less than”.
The reason why “equal to” is not correct goes back to our understanding of normal probability distribution. A probability is the area
under a portion of the normal probability distribution. One cannot calculate a probability for a single value. One can only calculate
a probability for a range of values. Thus why the answer “equals to” was incorrect for this question.
Question 12
0.5 / 0.5 pts
If you were provided the current density of umbrella trees, which probability should you estimate to determine if that umbrella tree
density is unusual enough to cause the boreblasters to disperse, the probability of observing a historical density of umbrella trees
that is equal to, less than, or greater than the current density?
The probability of observing a historical density of umbrella trees is less than the current density. Calculate the probability of observing a historical density that is more extreme than the current density of 27,000 m
km
(either
less than or greater than the current density, depending on your answer to question 11). Express your answer as a percentage
(%). Round all calculated values to the nearest whole number. For example, if you calculate the value as 213.8218, round to 214.
2
-2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Correct!
50
50 (with margin: 10)
The following criteria was used to grade this question: (1) you answered 50% with an error margin of 10.
Regardless of whether you were calculating the probability of observing a historical density of umbrella trees that is less than or
greater than the current density of umbrella trees, the answer to this question was 50%. The first step to this question is deciding whether you should calculate the probability of observing a historical umbrella tree
density that is less than or greater than
the current density of umbrella trees. Based on the answers and feedback to questions 9 through 11, it’s clear that we can either calculate (1) the probability of
observing a historical umbrella tree density that is less than
the current density of umbrella trees OR (2) the probability of
observing a historical umbrella tree density that is greater than
the current density of umbrella trees. See the feedback in
questions 9 through 11 for more details as to why this is the case. Depending on whether your answers to questions 9-11, you would use one of two formulas in Excel to answer this question. If you thought you should calculate the probability of observing a historical density of umbrella trees that is less than
the current
density of umbrella trees, you should have used the following function in Excel: = norm.dist(observered_value, mean, standard_deviation, TRUE)
If you thought you should calculate the probability of observing a historical density of umbrella trees that is greater than
the
current density of umbrella trees, you should have used the following function in Excel: = 1 - norm.dist(observered_value, mean, standard_deviation, TRUE)
Appendix 2
Could a change in the density of spotted gliders have caused the dispersal of boreblasters as a top-down effect?
We reasoned that a change in predation risk might have triggered the dispersal of boreblasters. Spotted gliders hunt along the
trunks of umbrella trees, eating larval boreblasters. Therefore, we need to know whether the density of spotted gliders has either
increased or decreased, causing a top-down effect on boreblasters (see Figure 2).
Figure 2.
Left:
A food chain for the Allurian Forest depicting the flow of energy and matter. Center:
A
decrease in the density of spotted gliders should directly cause an increase in the density of
boreblasters and indirectly cause a decrease in the density of umbrella trees. Right:
An increase in the
density of spotted gliders should directly cause a decrease in the density of boreblasters and indirectly
cause an increase in the density of umbrella trees. Both scenarios are referred to as a top-down effect.
Using the method of mark and recapture, you can estimate the current density of spotted gliders and compare this density to the
density expected from past censuses.
I have provided you with the densities of spotted gliders estimated during previous growing seasons in the sanctuary. Using the
links in Canvas, download these data:
Historical densities of spotted gliders (sample size = 31)
Question 13
1 / 1 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question, (2) your
answer addressed what you would expect when comparing current spotted glider densities to mean historical densities. As noted in Act I’s Assignment, there were two possible top-down effects that could have caused the dispersal of boreblasters. We
separately address each scenario below. See the optimal answers for each top-down effect below.
Top-down effect 1 - The density of spotted gliders increased over time: If the top-down effect was that the density of spotted gliders increased over time, then one should expect to observe that the
current density of spotted gliders is higher than the mean historical density. Top-down effect 2 - The density of spotted gliders decreased over time: If the top-down effect was that the density of spotted gliders decreased over time, then one should expect to observe that the
current density of spotted gliders is lower than the mean historical density.
Question 14
1 / 1 pts
APPENDIX 2, STEP 1: ANTICIPATE YOUR ANALYSIS
Assume that a top-down effect caused the dispersal of boreblasters; specifically, a change in the abundance of spotted gliders
caused a corresponding change in the abundance of boreblasters. What would you expect to observe when comparing the current
density of spotted gliders to the mean historical density?
Assuming that a top-down effect caused the dispersal of boreblasters, I would expect to see the current density of spotted gliders
to be larger than the mean historical density of the creature.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question, (2) your
answer addressed what you would expect when comparing current spotted glider densities to mean historical densities. See the optimal answer below:
The most logical finding would be that the current spotted glider density would be similar to the mean historical density. One might
say "not different or equal to" - which is fine in this case because that implies the magnitude of the difference is very small or non-
existent. An even more nuanced answer would recognize that the current density may still be different - but not extremely different
- from the mean historical densities.
Question 15
1 / 1 pts
Assume that a top-down effect did not
cause the dispersal of boreblasters. What would you expect to observe when comparing
the current density of spotted gliders to the mean historical density?
Assuming that a top-down effect did not cause the dispersal of boreblasters, I would expect to observe the current density of
spotted gliders to be equal to, or similar to the mean historical density of the creature. There are two possible claims as to whether a top-down effect caused the dispersal of boreblasters, 1) yes, a top-down effect
caused the dispersal of boreblasters, or 1) no, a top-down effect DID NOT cause the dispersal of boreblasters.
Complete the bar plots shown below. One of the bar plots illustrates what you would expect to observe with respect to spotted
glider abundances if a top-down effect caused the dispersal of boreblasters. The other illustrates what you would expect to
observe with respect to spotted glider abundances if a top-down effect did not cause the dispersal of boreblasters. The x- and y-
axes have been labeled for these plots.
To complete these plots, draw the bar plot for what you predict the current spotted glider abundance would look like in both
scenarios. The bar plot for the historical spotted glider densities has already been provided. Select "Choose a File" and upload
your bar plots. Upload your figures as a PDF or JPG.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
spotted gliders bar plots.pdf (https://canvas.asu.edu/files/76764530/download)
Your lab TA used the following criteria to grade this assignment: (1) you made two plots that have a bar drawn into the “Current”
category for each plot representing your predictions for what you would expect to observe if a top-down effect was causing the
dispersal of boreblasters (or not). There were several ways to draw the plot illustrating what you would expect to observe if a top-down effect caused the dispersal
of boreblasters. Since we think boreblasters disperse because of a significant change in their environment that significantly alters
the abundance of boreblasters, if a top-down effect caused their dispersal, that would imply that the abundance of spotted gliders
changed substantially as compared to historic values. BUT - the spotted glider density could theoretically change in either
direction (go up or go down) and still cause boreblasters to disperse. Regardless of whether you thought the abundance of
spotted gliders would increase or decrease, don’t worry if your plots don’t exactly match ours - what matters is that your graphs
illustrate the same principles as we did. We separately address each scenario below. Top-down effect 1 - The density of spotted gliders increased over time: If the spotted density went up significantly, then boreblasters would become less abundant due to increased predation on
boreblasters by spotted gliders or because of reduced food availability (spotted gliders eat umbrella trees). This could potentially
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
cause boreblasters to disperse if boreblaster abundance drops substantially. The figure below illustrates what one would expect to
observe with respect to current vs historical spotted glider abundances in this scenario. Top-down effect 2 - The density of spotted gliders decreased over time: Alternatively, if the spotted density went down significantly, then boreblasters would become more abundant due to reduced
predation on boreblasters by spotted gliders or because of increased food availability (spotted gliders eat umbrella trees). This
could potentially cause boreblasters to disperse if boreblaster abundance increases substantially. The figure below illustrates what
one would expect to observe with respect to current vs historical spotted glider abundances in this scenario.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Finally, let’s look at what one could reasonably expect if a top-down effect DID NOT cause the dispersal of boreblasters. Recall
that we think boreblasters disperse because of a significant change in their environment that significantly alters the abundance of
boreblasters. In this case, if the top-down effect did not affect the abundance of boreblasters, it would be reasonable to predict
that the current density of spotted gliders likely was not very different from historical observations. As always, don’t worry if your plots don’t exactly match ours - what matters is that your graphs illustrate the same principles as we
do here.
APPENDIX 2, STEP 2: ESTIMATE THE CURRENT DENSITY OF SPOTTED
GLIDERS
Throughout the galaxy, the method of mark and recapture has been used to estimate the size of a population. This method relies
on a simple assumption: if we mark some proportion of creatures in a population today (time 1), we should recapture that same
proportion of marked creatures in a future census (time 2). This assumption leads to the following relationship:
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 16
0.5 / 0.5 pts
Correct!
649.3
We can re-arrange this equation as follows:
Fortunately, research drones routinely “mark” spotted gliders in the sanctuary with a GPS tag. Thus, for this analysis, a GPS-
tagged glider is equivalent to a marked glider. My monitoring system shows a mean density of 270 GPS-tagged gliders per km
(or 270 km
). Also, you and fellow explorers
counted the number of tagged gliders and untagged gliders in a sample of the population. Collectively, you observed 59 untagged
gliders and 42 tagged gliders.
Therefore, you should be able to calculate the population size from the following information:
1. the number of tagged gliders in the population (# Marked at time 1) 2. the number of tagged gliders in your sample of the population (# Marked at time 2) 3. the sum of tagged gliders and untagged gliders in your sample of the population (Total captured at time 2)
Directions:
For question 16, use the information and the formula above to calculate the population size for an area of 1 km
. This
population size for a given area represents the current density of spotted gliders.
2
-2
2
Use the method of mark and recapture to estimate the density of spotted gliders in an area of 1 km
. Round your answer to the
nearest tenth of a decimal place. For example, if you calculate the value as 3.8218, round to 3.8.
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
649.3 (with margin: 1)
The following criteria was used to grade this question: (1) you answered 649.3 (gliders per km
) with an error margin of 1.
The answer to this question was 649.3 (gliders per km
). You should use the following equation to estimate the density of spotted
gliders:
Remember that the AI’s monitoring system indicated there was a mean density of 270 GPS-tagged gliders per km
(or 270 km
).
Also, recall that you observed 59 untagged gliders and 42 tagged gliders during your previous mission at the Intergalactic Wildlife
Sanctuary. Here how you should have used that information to estimate the density:
(1) the number of tagged gliders in the population (# Marked at time 1) = 270 gliders
(2) the number of tagged gliders in your sample of the population (# Marked at time 2) = 42 gliders
(3) the sum of tagged gliders and untagged gliders in your sample of the population (Total captured at time 2) = 59 untagged
gliders + 42 tagged gliders = 101 total gliders
2
2
2
-2
APPENDIX 2, STEP 3: ESTIMATE THE MEAN AND STANDARD DEVIATION OF
GLIDER DENSITY
Using the historical densities of spotted gliders, you must determine the expected density and the uncertainty about this expected
density. In other words, you need to answer the question, “What density of spotted gliders should one expect to observe in the
Allurian forest?”
Start by plotting a frequency distribution
of historical glider densities and decide whether this distribution meets the assumptions
of a normal probability distribution. If you are satisfied that a normal probability distribution would reasonably model the data, use
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 17
1 / 1 pts
spotted gliders density.png (https://canvas.asu.edu/files/76766215/download)
Your lab TA used the following criteria to grade this question: (1) you uploaded a plot that followed the guidelines listed above. Here’s what your graph should generally look like. Don’t worry if it’s not exactly the same (maybe you used a different shade of
grey for example), but the key is that your plot follows the formatting instructions for this graph. the functions in Excel called average
and stdev
to estimate the mean and standard deviation of the historical glider density,
respectively. Directions
: For question 17, download the Excel file, “Data: Historical Densities of Spotted Gliders,” containing historical densities
of spotted gliders (N = 100) to answer the questions that follow. Use Excel for calculations, modeling, and graphing. Round all
calculated values to the nearest tenth of a decimal place. For example, if you calculate the value as 3.8218, round to 3.8.
Create a plot of a frequency distribution (also known as a histogram) of the historical densities of spotted gliders. This plot should
follow the formatting guidelines listed below. Your plot should be formatted as a PDF or JPG. Select "Choose a File" and upload
your frequency distribution.
General
Chart type: Histogram
Quick layout: Layout 1
Chart title: “Frequency distribution of historical densities (individuals/km
) of spotted gliders”; Font size 18
Y-axes title: “Frequency”; Font size = 18
Y-axis numbers: Font size = 14
X-axis title: “Density (individuals/km
)”; Font size 18
X-axis numbers: Font size = 14
2
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 18
0.75 / 0.75 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
explicitly answered the question “does a normal probability distribution reasonably model the historical density of spotted gliders?”
Although the best answer in this case was yes, we understand that given the explanation to similar questions in the past you may
be thinking that the answer to this question could be yes or no. In this case, there is less uncertainty regarding whether this data is
reasonably modeled by a normal probability distribution. Although no sample will ever be perfectly modeled by a normal probability
distribution, as we discuss below in the next question, this frequency distribution appears to be reasonably modeled by a normal
probability distribution. If you said no...don’t worry, this question was graded for completion only! See the next question for more information as to why the
best answer to this question was yes.
Based on the frequency distribution you created above, does a normal probability distribution reasonably model the historical
density of spotted gliders?
Based on the frequency distribution I created, a normal probability distribution would reasonably model the historical density of
spotted gliders
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 19
1.25 / 1.25 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question. See an
example of what an optimal answer would look like (below). In this case, the best answer to the previous question is yes because the frequency distribution has a single central peak with
roughly symmetrical parts on either side of the peak (or mode). We don’t see the same level of skewness in the data as we have in previous frequency distributions. As with the previous question
- you received full credit for this question as long as you completed it.
Question 20
0.5 / 0.5 pts
Correct!
399.2
399.2 (with margin: 1)
The following criteria was used to grade this question: (1) you answered 399.2 (individuals/km
) with an error margin of 1.
Explain your answer to question 18. Be sure to discuss the assumptions of a normal probability distribution and why, based on the
frequency distribution, these assumptions seem appropriate (or not) for modeling the historical density of spotted gliders.
I claimed that a normal probability distribution would reasonably model the historical density of spotted gliders because of the
following reasons. The distribution is symmetrical at both tails, and there is a peak roughly located in the middle of the distribution.
Directions: Using a normal probability distribution, estimate the mean and standard deviation of the historical density of spotted
gliders for questions 20-21. Round all calculated values to the nearest tenth of a decimal place. For example, if you calculate the
value as 3.8218, round to 3.8.
Mean =
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
The answer to this question was 399.2 (individuals/km
). You could have gotten this answer in one of two ways - either manually
calculating the mean or alternatively using Excel. If you manually calculated the mean, then you should have used the following
formula: If you used Excel, you should have used the function =AVERAGE(INSERT RANGE OF DATA ENCOMPASSING HISTORICAL
DENSITIES OF SPOTTED GLIDERS)
Question 21
0.5 / 0.5 pts
Correct!
51.5
51.5 (with margin: 1)
The following criteria was used to grade this question: (1) you answered 51.5 (individuals/km
) with an error margin of 1.
The answer to this question was 51.5 (individuals/km
). You could have gotten this answer in one of two ways - either manually
calculating the standard deviation or alternatively using Excel. If you manually calculated the standard deviation, then you should
have used the following formula: 2
Standard deviation =
2
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
If you used Excel, you should have used the function =STDEV(INSERT RANGE OF DATA ENCOMPASSING HISTORICAL
DENSITIES OF SPOTTED GLIDERS)
APPENDIX 2, STEP 4: DETERMINE WHETHER OBSERVED DENSITY DIFFERS
GREATLY FROM THE EXPECTED DENSITY
Once you have a mean and standard deviation of historical glider density, you must determine whether the current glider density is
extremely low or high, relative to the historical glider density. Either conclusion would support the hypothesis of a top-down effect
of spotted gliders on boreblasters.
First, compare the current glider density to the mean of the historical glider density. If the current density is less (or greater) than
the mean, we can conclude that the current density is less (or greater) than expected. However, we still don’t know if the current
density is extremely unexpected
.
To determine just how extreme the current glider density might be, you need to use the normdist function of Microsoft Excel. This
function requires three pieces of data for a variable: 1) an observed value, 2) the mean, and 3) the standard deviation. The
function returns the probability of obtaining a value that is less than the observed value.
In the
normdist
function, enter the current glider density as the observed value but enter the mean and standard deviation of the
historical glider density. The function returns the probability of observing a density less than
the current density. If this probability is
less than 5%, we should conclude that the current density is extremely low
compared to historical densities.
If you want to know the probability of observing a density greater than
(>) the current density, recall that the following relationship:
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 22
0.75 / 0.75 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
you answered either “greater than”, “less than”, or “greater than OR less than”. You did not receive credit if you answered “equal
to”. In the feedback to question 23, we explain why the answer could be “greater than”, “less than”, or “greater than OR less than.”
Question 23
1 / 1 pts
Your Answer:
P
(
y
> x
) = 1 - P
(
y
< x
)
where P
(
y
> x
) equals the probability of observing a value y
that is greater than the value x
, and P
(
y
< x
) equals the probability of
observing a value y
that is less than the value x
.
Therefore, subtracting the value returned by the normdist function of Excel from 1.0 will yield the probability of observing a density
greater than the current density. If this probability is less than 5%, we should conclude that the current density is extremely high
compared to historical densities.
Directions: Use the normal probability distribution for the historical density of spotted gliders to answer questions 22-24. If a change in the density of spotted gliders caused the boreblasters to disperse, would you expect the current density of spotted
gliders to be greater than, less than, or equal to the mean historical density?
I would expect the current density of spotted gliders to be greater than the mean historical density of the creatures. Explain your answer to question 22. Specifically, why did you select the answer choice you did? As you write your answer, think
back to your original answers to questions 13-15 earlier in this assignment.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question. See an
example of what an optimal answer would look like (below). Logic:
Remember that the key here is thinking about the following questions: (1) “Generally speaking, why do we think
boreblasters disperse? What do we know about why species disperse on Earth that could help us answer this question?” (2) “If a
change in the density of spotted gliders caused boreblasters to disperse, what kind of change would need to occur?:
Example of an optimal answer:
We know that boreblasters disperse when their environment changes enough to cause the
abundance of boreblasters to significantly increase or decrease. If a change in the density of spotted gliders caused boreblasters
to disperse - what kind of change in spotted glider density would cause the boreblasters to disperse? Well, there are two ways you
could answer this question: You could have said that the spotted glider density would increase over time - thus the current spotted
glider density would be greater than the mean historical densities. Alternatively, you could have said that the spotted glider density
would decrease over time - thus the current spotted glider density would be less than the mean historical densities. Either change
would likely cause the abundance of boreblasters to significantly change - causing them to disperse. Hence why the answer to
question 22 could have been “greater than,” “less than,” or “greater than OR less than.”
The reason why “equals to” was an incorrect in question 22 is because if the current density of spotted gliders equals the mean
historical density, then this would imply there has been no change in spotted glider densities over time - thus supporting the
conclusion that the spotted gliders were NOT likely the cause of the boreblasters dispersing. Question 22 was asking what you
would expect to observe IF a change in spotted gliders CAUSED the boreblasters to disperse. Thus, “equals to” as an answer
choice does not answer question 22.
Question 24
1 / 1 pts
I claimed that the current density will be greater than the mean historical density because of the following reasons. As I predicted
in the bar plots, the current density of the spotted gliders will be similar to the historical density of them if they did not cause any
top-down effect. However, in the case that spotted gliders caused the boreblasters to disperse, their density would likely increase
more than the previous density. The boreblasters are spotted glider's prey, so their population would likely to decrease since they
are facing intense predation from the spotted gliders. Hence, the boreblasters need to evolve and disperse to maintain their
survival, reproduction, and face less predation from spotted gliders.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
you either answered “less than,” “greater than,” or “less than OR greater than.” You did not receive credit for this question if you
said “equal to.”
Remember that the key here is thinking about the following questions: (1) “Generally speaking, why do we think boreblasters
disperse? What do we know about why species disperse on Earth that could help us answer this question?” (2) “If a change in the
density of spotted gliders caused boreblasters to disperse, what kind of change would need to occur?”
Recall in questions 22 and 23, we already answered these questions - we know that boreblasters will disperse if their abundance
becomes unusually high or low. We also know that IF the spotted glider density changed enough (compared to historical densities)
to cause the boreblasters to disperse, then the density of spotted gliders should either be increasing OR decreasing over time.
That’s why the answer to question 23 could have been “greater than,” “less than,” or “greater than OR less than.”
The reason why “equal to” is not correct goes back to our understanding of normal probability distribution. A probability is the area
under a portion of the normal probability distribution. One cannot calculate a probability for a single value. One can only calculate
a probability for a range of values. Thus why the answer “equals to” was incorrect for this question.
Question 25
0.5 / 0.5 pts
Correct!
If you were provided the current density of spotted gliders, which probability should you estimate to determine if that spotted glider
density is unusual enough to cause the boreblasters to disperse: the probability of observing a historical density of spotted gliders
that is equal to, less than, or greater than the current density? The probability of observing a historical density of spotted gliders is greater than the current density.
Calculate the probability of observing a historical density of spotted gliders that is more extreme than the current density (either
less than or greater than the current density, depending on your answer to question 24). Express your answer as a percentage
(%). Round all calculated values to the nearest tenth of a decimal place. For example, if you calculate the value as 3.8218, round
to 3.8.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
0
0 (with margin: 1)
100 (with margin: 1)
The following criteria was used to grade this question: (1) you answered either 0% or 100% with an error margin of 1.
The reason why the correct answer is either 0% or 100% depends on whether you thought the density of spotted gliders was
increasing or decreasing over time and thus was likely to be greater than or less than the mean historical density of spotted
gliders, respectively. If you thought that the density of spotted gliders was increasing
over time and that the current spotted glider density was greater
than
the historical density of spotted gliders, then you should have calculated the probability of observing a historical density of
spotted gliders that is greater than
the current density of spotted gliders. As such, you should use the following equation to
calculate this probability (see below). Your answer should have been 0% in this case. = 1 - norm.dist(observered_value, mean, standard_deviation, TRUE)
If you thought that the density of spotted gliders was decreasing
over time and that the current spotted glider density was less
than
the historical density of spotted gliders, then you should have calculated the probability of observing a historical density of
spotted gliders that is less than
the current density of spotted gliders. As such, you should use the following equation to calculate
this probability (see below). Your answer should have been 100% in this case. = norm.dist(observered_value, mean, standard_deviation, TRUE)
Directions: Recall that we’re trying to help the AI determine whether a top-down or bottom-up effect caused the boreblasters to
disperse. To answer this question, we needed to determine if the current umbrella tree or spotted glider abundances were
extremely unusual as compared to historical observations. In both instances, an extremely unusual value is one where the
probability of observing a more extreme value (either less than or greater than) in the historical observations must be less than
5%. Use your calculations (above) and these criteria to answer questions 26-27.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 26
1 / 1 pts
Correct!
top-down effect caused by an increase in spotted gliders
That’s correct. In question 27, we explain why this claim is the best supported claim. In essence, it’s because the probability of
observing a historical spotted glider density greater than the current spotted glider density is much less than 5%, in fact it’s close
to 0%! What does that mean? That means that one has a near 0% chance of observing a historical spotted glider density that is
greater than the current density. This suggests that the current spotted glider density is unusually high. top-down effect caused by a decrease in spotted gliders
bottom-up effect caused by an increase in umbrella trees
bottom-up effect caused by a decrease in umbrella trees
This question was graded based on the following criteria: (1) you selected “top-down effect caused by an increase in spotted
gliders.”
Question 27
2 / 2 pts
Your Answer:
Based on the data that you analyzed for umbrella trees and spotted gliders, select the claim that is best supported by the
evidence. Boreblasters likely dispersed because of a...
Summarize the evidence that supports your claim in question 26, including how you determined whether the dispersal of
boreblasters was caused by a top-down or bottom-up effect based on probabilities. Be sure to compare current vs historical
densities for umbrella tree densities and spotted glider densities. Use quantitative evidence when possible. Remember that an
extremely unusual value is one whose probability of occurring in a historical population is less than 5%. I claimed that a top-down effect caused by an increase in spotted gliders because of the following reasons. The density of spotted
gliders in an area of 1 km
is 649.3 while the historical mean density was 399.2, so the current number could be an outlier to the
data. In addition,the probability of observing a historical density of spotted gliders that is more extreme than the current density is
0% and this value is less than 5%. Therefore, we can conclude that the population of spotted gliders is significantly increasing
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
you accurately compared historical and current densities of umbrella trees and spotted glider densities, including commenting on
the probability of observing the current densities in historical populations. If you also cited means and standard deviations, that’s perfectly fine as long as your answers address probabilities as well. See the answer below for an example of an optimal response. Logic:
Although this explanation seems lengthy, we unpack the logic and calculations that led us to selecting the claim
“Boreblasters likely dispersed because of a top-down effect caused by an increase in spotted gliders.” The key to determining
what caused the boreblasters to disperse is determining if the current umbrella tree or spotted glider densities are extremely
unusual - meaning the probability of these current densities occurring in a historical population is less than 5%.
Let’s start with the umbrella trees. Regardless of whether you were calculating the probability of observing a historical density of
umbrella trees that was less than or greater than the current density of umbrella trees, the probability was 50%. What does that
mean? That means one has a 50% chance of observing a historical umbrella tree density that is either greater than or less than
the current umbrella tree density. It’s basically a flip of a coin! Essentially, the current umbrella tree density is considered NOT
unusual at all.
Now let’s focus on the spotted gliders. You could calculate the probability of observing a historical spotted glider density that was
either less than or greater than the current density - you will still reach the same conclusion. Let’s see how! If you calculated the
“less than” probability - then you should end up with a probability of 100%. What does that mean? That means that one has a
100% chance of observing a historical spotted glider density that is less than the current density. This means that one is almost
certain to observe a historical spotted glider density that is less than the current density. What does that mean for our question? Well - this finding suggests that the current spotted glider density is unusual - but NOT
unusually low...it suggests that the spotted glider density is unusually HIGH. You could check this by subtracting the “less than”
probability from 100% (or 1, if you calculated a proportion). That will tell you the probability of observing a historical spotted glider
density greater than the current density. 100% - 100% is 0% - which means that the probability of observing a historical spotted
currently. Because of this increment, they are more likely to hunt boreblasters more frequent, causing the population of the
boreblasters to decrease and they need to evolve and disperse to stay away from being extinct. Therefore, it could be reasonable
to claim that there is a top-down effect caused by an increase in spotted gliders.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
glider density greater than the current density is 0%...well below our 5% threshold. This means that the current spotted glider is
extremely unusual - unusually HIGH. As you’ll see in the next paragraph - you'll reach the same conclusion if you simply
calculated the probability of observing a historical spotted glider density that was greater than the current density. If you chose to calculate the probability of observing a historical spotted glider density that was greater than the current density,
you would get 0%. Just as we thought in the previous paragraph. What does that mean? That means that one has a near 0%
chance of observing a historical spotted glider density that is greater than the current density. This suggests that the current
spotted glider density is unusually HIGH. See - regardless of whether you calculated the “less than” or “greater than” probability
for spotted gliders - you ultimately end up with the same conclusion. The current spotted glider population is extremely high
compared to historical observations. Let’s put all of this into an optimal answer:
Minimum optimal answer: The reason why the claim, the “boreblasters likely dispersed because of a top-down effect caused by
an increase in spotted gliders,” is supported because the current spotted glider density is unusually high as compared to the
historical densities. In fact, it’s so high that one has a near 0% chance of observing a historical spotted glider density greater than
the current density. The spotted glider population exploded in size! We can also eliminate any bottom-up effects because the
current umbrella tree densities were not unusual at all as compared to historical densities. One has a near 50% chance of
observing a historical umbrella tree density that was either less than OR greater than the current density - suggesting that the
current umbrella tree density is NOT unusual at all. If your answer also compared the mean and standard deviation of the historical densities to current densities of umbrella trees and
spotted gliders, that’s great! But, the key to this question was incorporating the probabilities into your answer.
Appendix 3
Could a change in the diet of a predator explain all of the events observed in the Allurian forest? And if so, which predator do you
think has started eating grabbins? If we are going to discover the source of disruption in the Allurian Forest, we need to develop a model that accounts for all of your
observations.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Let’s begin by summarizing the conclusions you have drawn so far.
Were the boreblasters infected or poisoned? Conclusion
:
Did the boreblasters disperse because their density increased or decreased?
Conclusion
:
Did the density of umbrella trees increase or decrease?
Conclusion
:
Did the density of spotted gliders increase or decrease?
Conclusion
:
Each of these conclusions becomes an observation that must be explained by our model. But what should our model look like?
Since we observed changes in the densities of several species, we need to consider a model that accounts for this process.
Recall that density is defined as the abundance in a given area (e.g., the number of organisms per km
). Therefore, density
changes as a population grows or shrinks. This change in abundance, called population growth, depends on the birth rate and the
death rate of organisms in the population. A population grows when the birth rate exceeds the death rate (and shrinks when the
death rate exceeds the birth rate).
The birth rate and death rate of a species depend on interactions with other species. Predators eat prey, contributing to the death
rate of prey populations. Prey nourish predators, contributing to the birth rate of the predator population. In this way, the
interactions between predators and prey affect the population growth (and hence the density) of the predatory species and the
prey species. Therefore, we need a model that captures these predator-prey interactions. This type of model has many names
throughout the universe, but your biologists on Earth call it a food web.
We’re going to need a food web for the Allurian Forest to solve this mystery of the sick frogcats, and everything else we have
observed.
2
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
APPENDIX 3, STEP 1: CONSTRUCT A FOOD WEB FOR ALLURIAN FOREST
As shown in Figure 3, a food web illustrates the flow of energy and matter among species in a community. Use the Field Guide to
Alluria
to study the diet of each species. Then use this information to construct a food web.
As your intergalactic mentor, let me suggest a tip to make the job easier. Start by making a matrix that lists the prey of each
species (see below). Once your matrix is complete, create vertical food chains that extend from a species of autotroph to a top
species of predator. Finally, connect these food chains horizontally by species that consume more than one species of prey. This
systematic approach should help you model all of the interactions among species in the food web.
Figure 3.
In this food web, arrows illustrate the flow of energy and matter from
one species to another. Therefore, energy and matter flow directly from species
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 28
1 / 1 pts
A to species B and species C, and indirectly from species A to species D and
species E. Species A is an autotroph that acquires its energy from sunlight.
Directions: For question 28, construct a matrix showing the connections between predators and prey in the Allurian Forest
community.
In the matrix shown below, potential predators are listed in rows and potential prey are listed in columns. Using this fillable PDF
(https://canvas.asu.edu/courses/157350/files/68872506?wrap=1) (
.docx also provided
(https://canvas.asu.edu/courses/157350/files/68872537?wrap=1) ), for each potential predator, place an “X” in the columns that
reflect known species of prey (based on the Field Guide). Leave a cell blank if no evidence of predation exists in the Field Guide
to Alluria. Select “Choose a File” and upload your matrix as a PDF. Potential prey
boreblaster daggerjaw flamster frogcat grabbins legs lyrac ridgehead sonar
spotted
gliders
torch
umbrella
tree
Potential
predators
boreblaster
daggerjaw
flamster
frogcat
grabbins
legs
lyrac
ridgehead
sonar
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
matrix.pdf (https://canvas.asu.edu/files/76764648/download)
Your lab TA used the following criteria to grade this question: (1) you checked all the correct boxes in the matrix. See the matrix
below to see which boxes should have been checked.
The matrix below shows that umbrella trees, torches, and lyracs are not predators because they are not consuming any other
organisms in the community. This would make them autotrophic organisms - much like plants on Earth. Frogcats and flamsters only eat lyracs, making them herbivores. Legs only eat torches, also making them herbivores. Finally,
boreblasters and ridgeheads only eat umbrella trees, making them herbivores as well. Sonar prey on frogcats and flamsters, making them a predator. Spotted gliders are also a predator - even though they eat
umbrella trees - they also eat boreblasters. Thus spotted gliders are omnivorous - they are both herbivorous and carnivorous.
Grabbins exclusively eat spotted gliders, making them a predator as well - albeit one that is higher on the food chain. Finally,
daggerjaws eat ridgeheads, legs, and sonars - making daggerjaws the top predator, also known as the apex predator, in this
community. spotted
gliders
torch
umbrella
tree
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 29
1 / 1 pts
food web.pdf (https://canvas.asu.edu/files/76764856/download)
Construct a food web illustrating the flow of energy between each of the species in the matrix that you constructed above. Use
boxes to represent each species in the community. Use arrows to indicate the direction that energy flows, from species of prey to
species of predators. Select “Choose a file,” and upload an image of your food web as a PDF or JPG.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your lab TA used the following criteria to grade this question: (1) you uploaded a correct food web. The food web below shows
how energy flows between each population of organisms in this community. Remember - boxes represent populations of species
in this community, arrows indicate the flow of energy in this community. Using the matrix we built in the previous question, let’s start with the species likely to be at the bottom of the food web - the
species that does not appear to prey on any other species in the community. In this case, umbrella trees, torches, and lyracs
should be the species at the bottom of the food web because they are not predating on other species in this community. Frogcats and flamsters only eat lyracs. As such, there needs to be two separate arrows, each pointing from the lyracs to the
frogcats and flamsters. Legs only eat torches, also making them herbivores - hence why there is an arrow pointing from torches to
legs. Finally, boreblasters and ridgeheads only eat umbrella trees - which is why there are two separate arrows, each pointing
from the umbrella trees to the boreblasters and ridgeheads. Sonar prey on frogcats and flamsters - so there should be separate arrows connecting frogcats and flamsters to sonar. This
illustrates that energy is flowing from frogcats and flamsters to sonar. Similarly, since spotted gliders eat boreblasters and umbrella
trees, there should be separate arrows connecting boreblasters and umbrella trees to spotted gliders. That last two predators - grabbins and daggerjaws - are high up on the food web. Grabbins exclusively eat spotted gliders - so
there should be an arrow pointing from spotted gliders to grabbins. Finally, daggerjaws are the top predator in this community -
they eat ridgeheads, legs, and sonars. So we draw separate arrows pointing from ridgeheads, legs, and sonars to daggerjaws.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
APPENDIX 3, STEP 2: IDENTIFY THE MOST LIKELY PREDATOR OF GRABBINS
Even with my enormous computational power, one observation still perplexes me. How did a grabbins---a predator at the top of
the food chain in the Allurian Forest---become prey? The most likely hypothesis is that one of the predators in the food web has
shifted or even expanded its diet to include grabbins. But which species is the predator?
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 30
0.5 / 0.5 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you listed at least one species that could be the most likely
predator of grabbins. The two species most likely to be predators of grabbins are sonars and daggerjaws.
Question 31
2 / 2 pts
Once you have a food web for the Allurian Forest, you must identify the most likely predator of the grabbins. At first glance, one
might argue that any predator could eat grabbins. But use these criteria to narrow your list:
The species must be a carnivore that has evolved to capture and digest prey.
The species must have the size and power needed to subdue a grabbins. Once you have a list of species that meet these criteria, use the following strategy to evaluate each species on the list. First,
modify the food web by drawing an arrow pointing from grabbins to the hypothetical predator of grabbins. Then, trace the indirect
effects of adding this predator-prey interaction to the food web.
The indirect effects should account for all of the observations we have made, including the sick frogcats, the dispersing
boreblasters, and the change in densities of umbrella trees, boreblasters, and spotted gliders. If you can identify a predator that
could have caused all of these disruptions to the food web, we will have a hypothesis worth testing.
Directions: Use the food web that you constructed above and the Field Guide of Alluria to answer questions 30-33.
What is the most likely predator of grabbins?
The predator of grabbins is most likely be the daggerjaw.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question and (2)
your explanation minimally references the following criteria (a) The species must be a carnivore that has evolved to capture and
digest prey and (b) The species must have the size and power needed to subdue a grabbins. The two species most likely to be predators of grabbins are sonars and daggerjaws. Here are some reasons why each species
could be preying on grabbins. Daggerjaws are carnivorous and they are extremely large - especially compared to grabbins.
Sonars are also carnivores and could potentially prey on grabbins despite being approximately the same size - this is because
sonars appear to be ambush predators - taking their prey by surprise - potentially giving them the advantage if they were to prey
on grabbins. However, daggerjaws are much more likely to prey on grabbins than sonars given their size and strength.
Question 32
0.75 / 0.75 pts
Explain why you selected this creature as the most likely predator of grabbins? Your answer should minimally reference the two
key criteria the AI provided to narrow your list.
I claimed that the daggerjaw would likely be the predator of grabbins for the following reasons. First of all, they are carnivore
species that has evolved to capture and digest prey. They have the pair of mandible-like limbs that are used to disable and kill
prey. Even though grabbins have disruptive camouflage adaptation that allows them to blend in umbrella trees, daggerjaws are
also well-camouflaged, and they can use tympanums (organs for sensing vibrations) to find their prey. The average mass and
size of a daggerjaw are much larger than those of a grabbins. An average size of a daggerjaw is 220-250cm with an average
mass of 1200-1600kg while those of a grabbins are 152-183cm and 59-72kg, respectively. Also, an adult daggerjaw has one of
the strongest bites in the forest (as much as 28,000 kPa of pressure). Therefore, a daggerjaw has both the size and power
needed to subdue a grabbins.
Now, modify the food web that you previously constructed. Draw an arrow pointing from the grabbins to the species that you
believe has started preying on grabbins. This arrow should differ in color from the other arrows.
Once you have done that, indicate the direct and indirect effects of this new predator-prey relationship by adding a “+” or “-”
symbol next to the box representing each species. Place a “+” next to a species whose abundance should increase because of
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
new, annotated food web.pdf (https://canvas.asu.edu/files/76769048/download)
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question, (2) you
drew an arrow showing the flow of energy from grabbins to the new predator of grabbins, and (3) you put a “+”, “-”, or “0” next to
each species to indicate how you think the abundance of those species will be impact by this new predator-prey relationship. The two species most likely to be predators of grabbins are sonars and daggerjaws. Below are two separate, updated food webs
illustrating how the abundance of other species in the food web might be impacted by these new predator-prey relationships. the new predator of grabbins. Place a “-” next to a species whose abundance should decrease because of the new predator of
grabbins. If you think a species’ abundance will remain the same, place a “0” next to that box. It’s recommended that you make
the “+”, “-”, and “0” symbols different colors so they stand out in the food web. Upload an image of this new, annotated food web
as a PDF or JPG.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
Question 33
2 / 2 pts
Your Answer:
Your lab TA used the following criteria to grade this question: (1) you made a reasonable attempt to answer this question. The most direct form of evidence would be actually observing the creature prey on grabbins. Since those kinds of observations
can be difficult to obtain, a good substitute would be observing the presence of grabbins tissue in the gut or fecal contents of the
What evidence would you need to collect to support your hypothesis that the creature you indicated in question 30 is preying on
grabbins? Answer as specifically and thoroughly as you can. To support our hypothesis that the daggerjaw is preying on grabbins, we should collect the death rate of grabbins in the area, the
population size of grabbins, the population size of spotted gliders (birth rate and death rate of spotted gliders), and the population
size of boreblasters (birth rate and death rate). We would likely to see that the death rate of grabbins increase, and the birth rate
of the spotted gliders to increase.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help
predator. If one lacks any of that information, they could attempt to match bite or claw marks on carcasses of grabbins to the
predator. This is not an exhaustive list of potential forms of evidence though! Quiz Score: 29.8 out of 30
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help