Botany Lab: Flower Dissections
Premise: This lab is designed to be used in an introductory biology class during a unit on plant biology. Prior to doing the lab, students should have already done some reading about and discussing of plant anatomy and reproduction. Angiosperms compose the largest group of plants currently found on Earth. Their distinguishing characteristic is that they produce flowers. Most of the plants that students are familiar with are likely to be angiosperms, and the majority of plants that humans use for food also fall within this group. Thus, it is important for students to be familiar with the structure and function of angiosperm flowers. In this lab, students will be dissecting two different kinds of flowers, and answering questions based on their observations. This lab is designed for a 1.5 hour block period. It covers material required under the NC Standard Course of Study, biology sections 4.02 and 4.03 (plant reproduction and adaptations).
Goals:
1. Students will review what they have been learning about angiosperm anatomy through hands-on activities.
2. Students will continue to practice using both dissecting and compound microscopes.
Objectives: Following this lab the student will be able to…
1. identify the major parts of a flower: sepals, petals, style, stigma, ovary, filament, anther and stamen.
2. explain what role each flower part has in angiosperm reproduction.
3. determine whether a flower is complete or incomplete.
4. compare and contrast monocots and dicots.
Lab Materials:
• Fresh lily flowers (enough for every two students to share one)
• Fresh squash flowers (enough for every two students to share one)
• Lily leaves
• Squash leaves
• Razor blades
• Goggles
• Dissecting microscopes
• Compound microscopes
• Microscope slides and cover slips
• Worksheets for students
• Colored pencils
• Potted plants displayed (and labeled) around the classroom for the extra credit assignment
Introduction to Lab:
Statement of Goals: Tell students that during this lab they will be investigating flowers (the reproductive parts of angiosperm plants). Specifically, they will be dissecting lily and squash flowers, and comparing them. Additional objectives will be listed on the worksheet accompanying the lab. For the lab, students will need to draw on the knowledge that they have gained about flower parts, flower types and plant classification over the course of the past couple class periods. If necessary, they can consult their textbooks, additional books in the classroom library and each other for assistance.
Microscope/Sharps Review: Inform students that they will be using both dissecting and compound microscopes during this lab. Students should already be experienced using these microscopes, but before they begin, check for understanding by calling on students and asking questions about the proper use of microscopes. Also, tell students that they will be using razor blades to dissect some of the flower parts. Remind students that they need to wear safety goggles while using the razor blades. Although students have used razor blades earlier in the year, quickly model proper use and storage of sharp objects as a review. After introducing the lab and showing students where to find supplies, hand out worksheets (click here for worksheet) and divide students into groups of two. Ask students to read over the worksheet and then begin the lab. (time: 10 minutes; supplies: worksheets, razor blade/goggles for review)
Doing the Lab: Tell students that they will have one hour to work on the lab. If they finish the activities and questions early, ask them to work on an extra credit assignment listed at the end of the worksheet. As students work on the lab, circle the classroom offering assistance where needed. Also, monitor that microscopes and razor blades are being used properly. (time: 1 hour; supplies: lab materials listed above)
Lab Clean-up: After an hour has passed, ask students to finish what they are doing. Then, have students throw away their dissected plant parts and return microscopes to the proper storage area. (time: 10 minutes)
Review and Closure: Have students return to their desks. Review the main ideas covered in the lab by asking students questions:
• What differences did you notice between the lily and squash flowers?
• What is the difference between a complete and an incomplete flower?
• What is the difference between a monocot and a dicot?
Tell students that for homework they should finish answering any questions on the worksheet that they did not get to during the lab, and to bring their completed worksheets to class the next day. (time: 10 minutes)
Source Consulted:
Biggs, Alton, Chris Kapicka and Linda Lundgren. Biology: The Dynamics of Life. Glencoe. New York, New York. 1995.