fly lab

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FRUIT FLY BEHAVIOR LAB
Background
Drosophila melanogaster, the common fruit fly, is an organism that has been studied in the
scientific community for more than a century. Thomas Hunt Morgan began using it for genetic studies
in 1907. The common fruit fly lives throughout the world and feeds on fruit and the fungi growing on
rotting fruit. It is a small fly, and one could question why scientists have spent so much time and effort
on this tiny insect. It is about the size of President Roosevelt’s nose on a dime, but despite its small
size, the fly is packed with many interesting physical and behavioral characteristics. Its genome has
been sequenced, its physical characteristics have been charted and mutated, its meiotic processes and
development have been investigated, and its behavior has been the source of many experiments.
Because of its scientific usefulness, Drosophila is a model research organism. Its name is based on
observations about the fly; the fly follows circadian rhythms that include sleeping during the dark and
emerging as an adult from a pupa in the early morning. This latter behavior gave rise to the name
Drosophila, which means lover of dew.” The explanation for the species name melanogaster should
be clear after observing the fly’s physical features. It has a black “stomach,” or abdomen. No doubt
the dew-loving, black-bellied fly will continue to make contributions to the scientific community and
to student projects.
Objectives
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To investigate the relationship between a model organism, Drosophila, and its response to
different environmental conditions
To design a controlled experiment to explore environmental factors that either attract or repel
Drosophila in the laboratory setting
To analyze data collected in an experiment in order to identify possible patterns and
relationships between environmental factors and a living organism
To work collaboratively with others in the design and analysis of a controlled experiment
Prelab Questions
Write this down in your lab notebook
1. What is taxis and what is kinesis?
2. What is geotaxis?
3. What is chemotaxis?
4. What is phototaxis?
Introduction to fruit fly behavior
1. Count the exact number of flies in your choice chamber
2. Invert the flask and count the number of flies at each end of the flask after 5 minutes.
3. Lay the choice chamber flat for 1 minute and repeat 2 more times
4. Create a table for the data. Calculate mean, standard deviation, and SEM. Graph results with +/- 1
SEM
Statistical Analysis
In order to determine whether or not data collected in an experiment in meaningful, a statistical
test is often used. In this case you will be using a chi square test (χ2) to determine if there is any
statistically significant difference in the location of the flies. The null hypothesis states that there is no
significant difference. In other words, there is an equal probability that the flies will be at any location.
The alternative hypothesis does.
 identify the null hypothesis and write it down in your lab book
Set up the following table:
Number of flies after 5 minutes
post inversion
Top
bottom
Observed (o)
Expected (e)
Calculate χ2 in your notebook showing the calculation
Determine the degrees of freedom and the critical value from the table using p = .05
Compare your χ2 value to the critical value from the table.
Do you accept or reject the null hypothesis and what does that mean?
Questions
1. Is the fly behavior taxis or kinesis? Explain
2. What is the environmental stimulus?
STUDENT DESIGNED EXPERIMENT
You will be using a choice chamber to determine the attraction of fruit flies to different substances.
Several items than can be used will be available for examination. Identify four items you wish to test
Examine the choice chamber and think about how you might set up your experiment.
You and your lab group should now design your experiment. Remember, your experiment must be
CONTROLLED.
Use the whiteboard to start designing your experiment. When we have gone over this, transfer the
procedure to your lab notebook and begin your experiment. Collect your data.
After you have identified which substances the fruit flies prefer design an experiment to compare the
preferences of the fruit flies to 2 the tested substances.
Perform your chi square tests
You will write a lab report for your student designed experiment which will include:
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Abstract: a brief summary of your experiment and results obtained
Introduction: include background pertaining to what you are testing. The introduction
should have your hypothesis/hypotheses
Materials and procedure
Data including tables, graphs, and statistical tests
Conclusion summarizing your data, interpretation of results, any sources of error. Think
about the following questions when formulating your conclusion.
o Which substances do fruit flies prefer the most?
o Which substances do fruit flies prefer the least?
o Do preferred substances have any characteristic in common?
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