Beacon Lesson Plan Library

Autumn Leaves: Where does the color come from?

Jacqueline Roberts
Bay District Schools

Description

In Autumn most people enjoy colorful leaves, brought about by external stimuli. In this lesson students explore leaf pigmentation through chromatography.

Objectives

The student knows that organisms respond to internal and external stimuli.

The student knows that investigations are conducted to explore new phenomena, to check on previous results, to test how well a theory predicts, and to compare different theories.

Materials

- Plant leaf
- Coin or blunt object used to scrape
- 600 ml beaker
- Ruler
- Filter paper
- Liquid solvent - ethyl alcohol
- Pencil or Popsicle stick
- Masking tape


SUGGESTED RESOURCE MATERIALS:
- Johnson, George B., [Biology: Visualizing Life]. Holt, Rhinehart and Winston, Inc., Orlando, Florida, 1994 and 1998.
- Kaskel, Albert., Hummer, Paul J. and Daniel, Lucille. [Biology: An Everyday Experience]. Charles E. Merrill Publishing Co., Columbus, Ohio, 1988.
- Strauss, Eric. and Lisowski., [Biology: The Web of Life]. Scott Foresman-Addison Wesley Publishing Co., Atlanta, Georgia, 1998.
- [Encyclopedia Britannica]. (hardcopy and/or online)

Preparations

TEACHER PREPARATION:
Teacher and students
- Understand why leaves are green.
- Understand how trees lose their green color in autumn.
- Understand photosynthesis
- Understand plant structure and function
- Takesinventory of materials and supplies
- Know plant pigment separates into four colors:
a. chlorophyll a - blue green
b. chlorophyll b - olive green
c. xanthophyll - pale yellow
d. carotene - reddish/orange/yellow
- Organize cooperative learning group:
a. Leader - responsible for coordinating group activities.
b. Secretary - reads the lab out loud to group and maintains data sheet.
c. Materials Manager - gathers equipment/supplies
Note: Leader and Materials Manager share responsibility of lab set-up

Procedures

WHOLE GROUP INSTRUCTION:
A. CONTENT

1. Review definition of photosynthesis.

2. Discuss how the change of season (external stimuli) affects color of leaves (internal condition).

3. Demonstrate experiment

B. LAB

1. Safety Procedures

a. Safety goggle and laboratory aprons should be worn throughout the investigation.
b. Ethyl alcohol can be harmful if mishandled and misused. Read label carefully. Follow directions.

2. Teacher reviews clean-up procedures. (Clean-up is everyone's responsibility.)

3. Set -up cooperative learning groups.

LABORATORY ACTIVITY:
1. Student (secretary) prepares data sheet. (See attachment)

2. All students prepare a hypothesis

3. Student cuts filter strip 13x2 cm.

4. Student places leaf on filter paper 1 cm. from the end.

5. Student rubs across the leaf with coin or blunt object leaving a dark green line.

6. Student pours liquid solvent into beaker to a depth of 1 cm.

7. Student attaches top portion of filter paper (area without line) to pencil or popsicle stick with tape.

8. Student places bottom portion of filter (area with green line) in the solvent. Do not allow solvent level to come above rubbing line.

9. Students observe solvent moving up paper. As soon as solvent is 2 cm from the top remove paper and allow it to dry.

10. Student records observations made by the group.

11. Student writes a conclusion.

Assessments

ASSESSMENT:
1. Laboratory Rubric - see attachment
2. Written Assignment - students write an essay describing -Changes in Leaves-. The essay should encompass the following information:
a) What makes a leaf green?
b) What other pigments do leaves contain?
c) Why don't we see these pigments?
d) Why does the green color disappear in the autumn?
e) What external stimulus causes the leaf to change from green to other colors?

Attached Files

1. Data Worksheet 2. Laboratory Rubric 3. Written Essay     File Extension: pdf

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