Module 4 Lab 1 PDF

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Mod 4 Lab 1...

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Variables We know that the basic needs for photosynthesis are simple -- light, water, and carbon dioxide. If these inputs are available, shouldn’t the plant thrive and make sugar molecules successfully? Not necessarily. A variety of environmental variables can influence the process of photosynthesis. You will examine this idea in the following experiment. To study the chemical process of photosynthesis we need a tool, a way to know that photosynthesis is occurring. We are going to use the floating leaf disk assay to determine if photosynthesis is occurring and its approximate rate. During this assay you will use a sodium bicarbonate solution as your CO2 source. As photosynthesis is occurring in your leaf disk, they will start to float because of the oxygen being produced. However, remember that these leaf disks will also be using the O2 produced by photosynthesis for cellular respiration.

Materials: Baking Soda Dish Soap Leaves (Spinach is shown, but anything that is green works) Syringe – you can get a syringe for measuring liquid medicine for babies at a local pharmacy, or use a syringe for injecting meat (take off the needle) Hole Punch Clear container (a drinking glass is shown) ¼ teaspoon measuring spoon Measuring cup Light Source Ruler

BIOS 1010 General Biology 1

Procedure: (The Variables PowerPoint has pictures of the procedure and a link to a video demonstrating the procedure.) 1. Prepare the bicarbonate solution by adding about 1/8th of a teaspoon to one cup of water. 2. Add 1 drop of dish soap to this solution. Stir to mix. 3. Cut 10 leaf disks from the leaf provided using the hole punch. 4. Remove the plunger from the syringe barrel, place the leaf disks into the barrel and replace the plunger. 5. Pull a small amount of sodium bicarbonate solution into the syringe. Tap the syringe to suspend the leaf disks in the solution. 6. Holding a finger over the syringe opening, draw back on the plunger to create a vacuum. While holding the vacuum swirl the leaf disks to suspend them into solution. Release the vacuum. Repeat until all the leaf disks sink. If after 3 repetitions, your leaf disks still are not sinking, add more liquid soap to your solution. 7. Pour the disks and solution into a clear container and add bicarbonate solution to a depth of about 3 centimeters. 8. Place the leaf disks under the light source and start the time. At this point measure the distance from the light source and the temperature of your solution; record on your Data and Observation page. 9. At the end of each minute record how many leaf disks are floating on the table provided on the Data and Observation page. Graph this data.

Designing your own experiment Now that you have a control for your experiment, pick a question about photosynthesis that you want to test. This can be changing the color of the container, the distance that the light is from the container (or making it dark), changing the temperature or anything else you find interesting. 1. Write down your experimental. 2. Do your experiment and record your data. 3. Answer the questions on the Data and Observation page.

Variables BIOS 1010 General Biology 2

Data, Observation and Analysis Greser Information about the control Type of plant used: Spinach Distance from the light source: 10 inches Temperature of the solution: 72 degrees F

Minute

Number of leaf disks floating

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

0 0 1 1 1 4 5 5 6 8 8 10 10 10 10 10 10 10 10 10

BIOS 1010 General Biology 3

Name ___Aspen

Experimental Design

Question: Does cutting down the distance of the light source from the water affect the time it takes for the leaves to float? Hypothesis: I think having the light source closer to the water will make the leaves float sooner How am I going to do the experiment? I will proceed with the same steps, but I will move my light source closer to the water, cutting the distance from 10 inches to 5 inches

Information about my experiment Type of plant used: Spinach Distance from the light source: 5 inches Temperature of the solution: 71 degrees F Variable that I changed: I cut the distance from the light source in half

Minut e

1 2 3 4 5 6 7 8 9 10 11

Numb er of leaf disks floatin g 1 2 4 5 7 9 10 10 10 10 10 BIOS 1010 General Biology 4

12 13 14 15 16 17 18 19 20

10 10 10 10 10 10 10 10 10

Paste a picture of your experimental set up here.

Analysis BIOS 1010 General Biology 5

1. How did your variable affect the rate of photosynthesis? The light source being closer to the water did in fact make the leaves float sooner 2. Why do you think that effect occurred? I think the light attracted the leaves and brought them to the surface quicker as it was moved closer 3. Was the result what you expected?

Yes

BIOS 1010 General Biology 6...