1.4: Lab 1 Procedures (Leaves Version)

PROCEDURE 1: MAKING MEASUREMENTS

Equipment we’ll need:

• 2 graduated cylinders
• Tape and pen
• Dropper bottle of water
• Electronic balance (scale)

1. Obtain two graduated cylinders. Place tape towards the top of each and use a Sharpie or pen to label one A and the other B.
2. Turn on the electronic balance, place graduated cylinder A on the silver disc, and press “Zero” to calibrate the scale to start at 0.
3. While standing, with your point of view over the top of graduated cylinder A, add 5mL of water into the graduated cylinder.
4. Place graduated cylinder A with 5mL of water on the scale and record the mass in Table 1.
5. Place graduated cylinder B on the electronic balance and Zero it out.
6. This time, crouch down so the graduated cylinder on the table is at eye level. Notice how the water in graduated cylinder A curves into a meniscus. Add water to graduated cylinder B until the bottom of the meniscus reaches the 5mL mark. 
7. For example, the image to the right shows 21.7mL of water.
8. If you add too much water, use a long pipette to draw water out.
9. Place graduated cylinder B with 5mL of water on the scale and record the mass in Table 1.
10. Work through the questions in the Answer Sheet to calculate the percent error for each graduated cylinder. 

Clean up/Disposal

1. Pour water into the sink.
2. Remove tape from graduated cylinders and throw the tape in the trash.
3. Place the graduated cylinders back in the containers on the counter. 
4. Place the dropper bottles of water back in the boxes.

PROCEDURE 2: BIOLOGICAL MEASUREMENTS

Equipment we’ll need:

• 3 leaves of each plant species per group
• Electronic balance
• Ruler (with metric measurements)

Now let’s apply what we learned about making measurements to living things. We’re going to measure the length and mass of the leaves of two species of California native plants, black sage (Salvia mellifera) and white sage (Salvia apiana) [depending on availability, we may use related species in class, such as Mexican bush sage (Salvia leucantha)]. Each group will have the chance to make measurements on a few individuals, and then the class will combine all our data to compare the species of plants.

Figure 3. Representative leaves of black sage (Salvia mellifera; left), white sage (Salvia apiana; right), and Mexican bush sage (Salvia leucantha; bottom). Image credit: Shawn McEachin and Polly Parks.

1. Use a ruler to measure the length of each leaf from tip to stem, to the nearest 0.1cm. For example, the leaf in the image below is 4.1cm. Record the data in Table 2 on the Answer Sheet.

2. Use an electronic scale to measure each leaf’s mass, one at a time. Record the data in Table 2 on the Answer Sheet.
   • Make sure that we match each individual’s length with that same individual’s mass.
3. Record the group’s data on the board or in the Lab 1 Class Data Google Sheet (provided by the instructor). After all groups report their data, we will calculate the class averages to complete Table 3 in the Answer Sheet.
4. The instructor will run a t-test, allowing us to determine whether leaf length or leaf mass are different between these two species of plant.
5. Answer the rest of the questions on the Answer Sheet.

Clean up/Disposal

1. Return all measuring devices to their original locations.
2. Return the used leaves to the correct piles.

PROCEDURE 3: ASKING SCIENTIFIC QUESTIONS

From our experience measuring samples today, we might have a few questions about why there are differences between our samples. There are many types of questions we can ask about the world around us. Some of these questions are answerable by performing experiments, while other questions cannot be answered through scientific experiments. Figuring out the difference between these types of questions and how to come up with answerable questions is our next task.

1. Watch the video one time without writing anything down: Fun with termites.
2. Re-watch the video a few more times. In the Answer Sheet, write down all of the things we observe happening.
3. In the Answer Sheet, write down as many questions as we can think of about what we just witnessed.

Generally, scientific questions need to focus on measurable differences as we’ve discussed in this lab so far. One type of question that builds this in is called a comparative question. These types of questions include the dependent variable and a comparison between two groups or situations within the question. For today’s lab, our comparative question was, “Are the leaves on black sage plants longer and/or heavier than the leaves on white sage plants?” Within this question, we included our dependent variable of length and mass. This question also clearly included the comparison we were making.

4. Review the questions from the Answer Sheet. Choose three of the questions and turn them into a comparative question. Bring this for next class!