Photosynthesis Supplement: Biological Reactions
• Make a broader connection to the simple chemical reactions experienced in the lesson and forge an introduction to the concept of living things as biochemical machines.
• Plants produce chemical reaction products just like the products observed in the lesson.
• Plants can produce oxygen when they have adequate resources such as light.
note: This extention is composed of two modules that can be integrated or used independently by the teacher.
Module 1. Plants produce a gas when light is provided
Each Student
1 Air bubble record sheet
Each Group (4 students)
4 Flask or test tube filled with declorinated water
4 Elodea cutting (found at most tropical fish stores)
2 lamps
The Entire Class
1 Sheet of butcher paper
Preparation
Fill test tubes or beakers with declorinated water (declorination drops can be found at most pet stores). Prepare Elodea cuttings for each group by cutting a branch of Elodea with a blade. Lightly crush the end of the branch and place the branch in the test tube or flask upside down. Label a sheet of butcher,"How we could make more air bubbles."
Lesson Parts
A. Leading/prior knowledge
B. Making air bubbles with photosynthesis
C. Reviewing the results
D. Understanding the results
E. Introduction to photosynthesis
F. Reflection and connections
Lesson Outline
A. Leading/prior knowledge
???
B. Making air bubbles with photosynthesis
Have students place the two lamps next to just two of the Elodea. The light should be 3-5cm from the container. Next, have the students wait one minute and then have the students count the number of bubbles developing and rising from the plants. Each student might be assigned one plant to make recordered observations. They should count bubbles for 5 minutes. Each student should record all the findings on their own record sheet at the end of this period. Have students follow up by drawing one Elodea under the light and one that was not provided added light.
C. Reviewing the results
Have the students calculate the average number of bubbles for each treatement (light/no extra light). On their record sheets have the students make a bar graph of the average number of bubbles .
D. Understanding the results
Review the results with the students and then brainstorm. Try to elicit their explaination for the findings. Why did the plants in the light have more bubbles? Did all plants in the light have the same number of bubbles? Why not? How does the generation of gas by the plant relate to the excersise with the calcium cloride and baking soda?
E. Introduction to photosynthesis
Read the story of photosynthesis to the students.
F. Reflection and connections
Ask students if they think that photosynthesis could explain the bubbles in the Elodea. Ask the students how they could get the Elodea to produce even more bubbles. Make a list of these ideas. They will be partially correct if they suggest more light. Rap up the lesson by indicating that they did indeed observe the products of a very special reaction. A reaction that occurs in plants and one that is very important to each student. This is because, photosysnthesis produces an important component of air (because your students are acquainted with mixtures in solution you may be able to easily expand this concept to gases), namely oxygen. Each student breaths in oxygen with every breath as many of the students will be able to identify prior to this lesson. Be sure to discuss with the students how plants on land also produce gas, even though you can't see it.
Module 2. Photosynthesis for entire ecosystems can be measured and how is light related
Materials
Each Student
1 Photosysnthesis data sheet
Each Group (4 students)
One computer with the data pages bookmarked
The Entire Class
1 Overhead of example results (link)
Lesson Parts
A. Leading/prior knowledge
B. Making air bubbles with photosynthesis
C. Reviewing the results
D. Understanding the results
E. Introduction to photosynthesis
F. Reflection and connections
Lesson Outline
A. Introduce the lesson
Recap module 1 with the students and review the list of ways the students could get the plants to make more air bubbles. Remind students that this special reaction that occurs in plants seems to need light in order for oxygen to be produced. Today the students will investigate if more light can lead to more air.
B. Introduce the remote data
Use the "photosynthesis slide show" to acquaint the students with the remote sites and the data that can be obtained from the sites.
C. Observing the data
Tell the students that they will now be in charge of finding out if light intensity imacts photosynthesis. If possible send groups of students to utilize the student web pages for this lesson. The web pages allow students to select different days, time of day, and the various sites. Average oxygen production for the site will be provided as well as average light intensities. Students will need to graph at least 10 points on the light vs. photosysnthesis data sheets.
D. Reporting the findings
Each student should write one paragraph describing their findings. While students are writing it might be benificial to have an aid or student produce overheads of each group's results for the following part of this lesson.
E. Comparing Results
Show students the example results on the overhead. Make lists of the similarities and differences with the pattern in the example data and the students' data. Focus on the similarites while reminding students that the data may come from differnt sites. Also, guide the students to realize that photosynthesis is a common phenomenon in vegetated ecosystems. With the list of differences ask students to generate hypotheses (logical expecations) to explain why each pattern was not exactly the same. Tell the students that they may not be able to collect their own data to test their hypotheses, but they will be able to ask a scientist if the question has already been answered (send a confimation communication to confirm that there is staff ready and able to promptly answer any student/teacher inquiries). Next, ask a PISCES scientist if they know if you might be correct (email link here). Teachers can also check the archive of past patterns, hypotheses, and evaluations by a PISCES scientist.
The responses are likely to be returned at a later class time. Schedule 20 minutes to review and discuss the responses to the students' hypotheses.
F. Reflecting
Make a class list of all the things the students have learned about reactions that occur in plants.
Downloads
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Data and Resources
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Links