Goldenrod+Gall+Lab+TA+Manual

Goldenrod galls (TA manual)

The purpose of this lab is to introduce students to parasite/host and interspecies interactions. Students develop a hypothesis about galls and or gall forming insects, their parasitoids and or predators. They determine what variables they need to measure/record and then share their list with the class. Each group will then collect data for each variable that each group needs. The class thus compiles an extensive data set that will help every group test their hypotheses. At the end of the lab period, each group presents their data to the class. This lab has become the basis for our discussion of statistics.

Objectives: - Apply the scientific method to evaluate the interactions of various aspects of gall phenotypes (e.g. height on stem & gall diameter) - Develop testable hypotheses and predictions - Learn additional presentation skills - Collect data that can be used in different statistical tests.

Equipment: -2 knives - forceps - 1 field magnifier - 1 meter stick - documentation - gall ID guides

The type and number of galls varies. Usually we can give 4 round galls/group, and/or 1 elliptical gall/group, and/or 1 rosette gall/group.

For the activity, pass out the galls to each group. Let each group look at their galls without any dissection etc. and have them brainstorm and formulate one question that they are interested in investigating. They need to develop a hypothesis and corresponding predictions based on their question. These are to be listed on their data sheet, along with a graph of their predicted outcome. Next, they need to list the dependant variables that need to be measured and recorded in order to answer their question. All variables should be listed on the board. Each group will then use their 5 galls to collect data for each and every variable for the whole class.

Before anyone starts to collect data, the TA should go through each variable with the whole class to make sure everyone knows what needs to be recorded. The reason we do this is because many times students are not clear about what they need when they list their variable.

Once everyone is sure about what they need to measure, let each group start collecting data. It’s very important that students measure all of the outside variables before cutting up the galls! Otherwise we will not get accurate measurements for the outside variables. Remind students that the knives are sharp and that they need to be careful when cutting open the galls. In the lab meeting we will determine the best way to open the galls, but I think it is to cut them lengthwise, following the stem as your guide. The steps I use are 1. Place blade gently on gall 2. Apply pressure with palm of hand fingers splayed. Do this until you’ve gone ~ ¼ through the gall. 3. Twist knife gently while holding the gall.

Have your students use the Gall ID guides to ID the parasites and or evidence of parasitoids. This part of the lab is very cool. The students really have fun looking at and figuring out what kind larvae they are looking at.

Compile a huge class data set on the board/screen so each group can list their data for each variable.

Each group then needs to use the class data set to test their hypothesis. Their results and conclusions should be written on their data sheets. They then need to prepare an overhead with their question, hypothesis, prediction, prediction graph, and their actual results graph and their conclusions.

This lab has become a two part lab. The first session is about data collection. The second session is about descriptive statistics and hypothesis testing statistics. By the end of these two labs, students will have been introduced to t-tests, chi-square, and correlation/regression.

Grading 10 pts each week Lab 1: 3 pts. Hypothesis 3 pts. Prediction 2 pts. Data 2 pts. Graph 1 pt. Quality of work

Lab 2: 2 pts. Descriptive statistics 1 pt. Hypotheses, null & alternative 1 pt. Correct inferential statistic used (t-test, Chi-square, regression) 2 pts. correctly reported df, p-value, R squared value, t-value 1 pt. Statistic conclusion 3 pts. Biological conclusion, Graph, Referencing graph in biological conclusion

See gall keys and other info in the file cabinet.