How the cricket lost its song - Part 1
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Featured scientist: Robin Tinghitella from the University of Denver
Background:
Some of the most vibrant and elaborate traits in the animal kingdom are signals used to attract mates. These mating signals include the bright feathers and loud calls of birds or the swimming dances performed by fish. Most of the time the males of the species perform the mating signals, and females use those signals to choose a mate. While mating signals help attract females, they may also attract unwanted attention from other species, like predators.
Robin is a scientist who studies the mating signals of Pacific field crickets. These crickets live on several of the Hawaiian Islands. Male field crickets make a loud, long-distance song to help females find them and then switch to a quiet courtship song once a female comes in close. Males use specialized structures on the wings to produce songs (Figure 1a). One summer, Robin noticed that the crickets on one of the islands, Kauai, were unusually quiet. Only a couple of years before, Kauai had been a very loud place to work; however, that year Robin heard no males singing!
After taking the crickets back to the lab, she noticed that there was something different about the males’ wings on Kauai. Most (95%) of males were missing all of the structures that are used to produce the calling and courtship songs (Figure 1b)—they had completely lost the ability to produce song! She decided to call this new type of male a flatwing male. But why did these males have flat wings?
(a) Male wing with normal calling structures. (b) Male wing with the flatting mutation. (c) Female wing.
A parasitoid fly sitting on top of it’s cricket host.
On Kauai, songs of the male crickets attract female crickets, but they are also overheard by a deadly parasitoid fly (Figure 2). The fly sprays its larvae on the backs of the crickets. The larvae then burrow into the crickets’ body cavity and eat them from the inside out! Robin thought that maybe the flat wings and lack of a song helped the male crickets remain unnoticed by the parasitoid flies. To test this idea, Robin dissected the males to look for fly larvae. She compared infection levels for 67 normal males— collected before the flatwing mutation appeared in the population—to 122 flatwing males that she collected after the flatwing mutation appeared. She expected fewer males to be infected by the parasitoid fly after the appearance of the flatwing mutation in the cricket population.
Scientific Question: Why do most male crickets on Kauai have flat wings? Could parasitoid flies have contributed to the loss of song for male crickets?
Scientific Data:
Find the hypothesis in the Research Background and copy/paste it below. A hypothesis is a proposed explanation for an observation, which can then be tested with experimentation or other types of studies.
Click on the graph tab, and explore the available variables. What data will you graph to explore the first hypothesis? Independent variable:
Dependent variable:Create your graph, and add Collection Data Type to your z-axis. Paste your graph below:
4. Identify any changes, trends, or differences you see in your graph. Write one sentence describing what you see.
Interpret the Data:
5. Make a claim that answers the scientific question.
6. What evidence was used to write your claim? Reference specific parts of the tables or graph.
7. Explain your reasoning and why the evidence supports your claim. Connect the data back to what you learned about the flatwing mutation and the parasitoid flies.
8. Did the data support Robin’s hypothesis? Use evidence to explain why or why not. If you feel the data were inconclusive, explain why.
Your next steps as a scientist:
9. Science is an ongoing process. What new question(s) should be investigated to build on Robin’s research? What future data should be collected to answer your question(s)?
These questions are a digital extension of the original Data Nuggets activity. The data manipulation and graphing tasks within are best completed here on DataClassroom.
10) Typically, scientists make use of statistical analysis to determine that any difference between two values is reflective of natural phenomena regardless of the population being surveyed. Go to the Graph Driven Tests located at the upper right corner of your screen and list which test would be the most appropriate to test if having the flatwing mutation affects the parasitism status of flies. Explain why.
11) Before conducting the graph-driven test, calculate what the expected number of crickets with and without the flatwing mutation you would expect to be parasitized in the scenario that presence or absence of the mutation was unrelated to the infection status of the crickets. Make sure to show all the steps in your calculation.
12) Paste results from the graph driven test below.
13) How would you interpret the P - value obtained with this dataset?
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This dataset and content is provided our by our friends at Data Nuggets.
Visit DataNuggets.org to see the original activity and additional materials