Time for Student Lesson One

This lesson will take three-45 minute periods. 
Period 1. An overview of Drosophila. Students should have read lesson one and the chapters in “The Monk in the Garden”.
Period 2-3: Completion of lesson one.

Part 1: A first look
Encourage students to generate questions beyond the ones offered as they look at the flies.  Remind them to write these in their journal. At the end of the first day, they could be amassed on the chalkboard or butcher paper for further discussion or, as an extension, assigned to student groups to research and answer later. 

Part 2: A closer look
Students should be able to see eggs and larvae under the stereomicroscope.

Part 3: Life cycle of the fruit fly
This is general information and students should be able to refer to the life cycle when needed.  It might be useful to require students to copy this into their journal for easy reference. This life cycle is temperature dependent, and a nice extension would be to see how cool or warm temperatures affect the life cycle.

Part 4:  Parts of the fly: external anatomy
Refer to An Introduction to Drosophila melanogaster on techniques to anesthetize flies. Students need to focus on major features such as:
Head:  

Thorax:

Abdomen:

Be sure students are not looking at virgin or immature flies as these characteristics are quite different.

Part 5: How to tell males from females
There are several ways to differentiate between the sexes since fruit flies exhibit sexual dimorphism.

1.  The shape of the posterior end of the abdomen is very significant.  Males are rounded whereas females are more pointed.
2.   The male posterior is solid black, not banded, as is the female. 
3.  Females tend to be larger especially their abdomens.
4.  On the front legs of the males is a darkened area called the sex comb. This is absent in females
5.  The genitalia showed marked differences.

Check that students have correctly sexed their flies.  It is important that all group members know how to do this in case one is absent when making crosses. 

Pictures comparing male and female flies

Part 6: Culturing flies
Refer to An Introduction to Drosophila melanogaster on techniques to anesthetize flies.

Student groups should keep their flies vials together.  Remind them to write the date and fly type on the vials. (You could ask them what is needed on the vial and have the class come up with ideas instead of telling them).  At the end of this lesson, students should have two vials of wild-type flies.  You may want them to make cultures of mutants at this time, also, or wait until lesson two.

Part 7. Assessment
Journals can be collected and graded in a variety of ways:

1.  Drawing the external anatomy

Each student needs to have their own drawing to refer to and permanently placed in their Drosophila journal.

Are all parts of the fly’s anatomy present?

Is it drawn to scale?

Are the colorations accurate?

Is it neatly drawn? 

2.  Differences between male and females

Are the descriptions accurate?

Are several differences included?

Is the drawing of the abdomens (ventral and dorsal):

3. Sexing flies

How many times did it take for the student to get it right?  A verbal assessment is recommended at this point; however reinforce the idea that it is of vital importance to be able to distinguish the difference between the two when making crosses.

4. Journal

Is the entry complete?  Is there a synopsis of what they did each day?

5. Additional assessment to check student understanding on: