Mutualism and Co-evolution
A study of Flowering Plants and their Pollinators
with a focus on

Form and Function

Lesson 11 À ? A

Lesson 12 J

Days 15 & 16

Lesson Intention: In this dissection lab, students will use eye loupes or magnification lenses to look closely at flowers. As the flower is dissected, the functions and role of each part of the flower will be learned . Intermittent showings of the laser disk "Plants" will be shown to reinforce what is being seen in the dissection.

BY THE END OF THIS LESSON STUDENTS WILL BE ABLE TO:

• Recognize and name the parts of a flower
• Explain the function of each part of a flower
• List the steps that occur for sexual reproduction of a plant to take place
• Recognize and name the male reproductive parts, and female reproductive parts of a flower

Materials per student: 1 copy of "Basic Flower Structure," eye loupe, pencil, notebook, colored pencils, tweezers

Teacher Preparation:

Acquire a variety of flowers from a florist or several florists. A larger florist should be able to donate some older flowers. Make sure you give the florists some advance warning so they can set enough aside.

Make copies of "Basic Flower Structure" worksheet and reading.

Make available eye loupes and colored pencils.

Have laser disk of National Geographics’ "Plants" set up to view as dissection proceeds. Also, make an overhead of the "Basic Flower Structure" pictures. A dissecting microscope is a great tool to have too.

Bellwork on board or overhead.

Bellwork: Look at the four test tubes from yesterday’s second test of photosynthesis and reproduction in the dark. What colors are each tube? Is this what you predicted? Why are they each the color they are? Explain clearly.(This could also be a short quiz to test for understanding.)

Step by Step Flower Dissection:

6. Start today’s class by finishing up with yesterday’s demonstration. Allow for 5 -10 minutes of discussion.
7. Begin the flower dissection by handing a flower to a student. Ask him/her to make observations and to describe it. Hand it to another student. Continue to have students describe it until no other observations can be made. While students are describing the flower, have a student be writing the observations on the board or overhead.
8. What might likely occur is that students will what to describe a particular feature of the flower but won’t have the term for it. Don’t give them the term yet. Have them just describe it. (Latter they will make the connection with the terms they are given.)
9. This is a good point to introduce the idea of flower anatomy- that each flower part has a name so scientists can talk about flowers using the same language. It also helps botanists to categorize and identify flowers because of the color and shape of particular parts. Tell students that they will be taking apart a flower today so they can understand how and why a flower functions as it does.
10. Facilitate materials being distributed.
11. Once all students have a flower, ask them, "Why do flowers have petals?" They’ll probably know that they are for attracting pollinators. It’s the flower’s way of dressing up. Explain that all the petals together is called the corolla- a word related to the word corona meaning garland or crown.

[There are 2 ways to proceed at this point- Students and teacher can go through the reading, bit by bit, dissecting the flowers and discussing as you go, coloring in and labeling the "Basic Flower Structure" drawings- OR, students can observe their own flower, describing it and drawing it in their journals, labeling the parts as they are identified. It really depends on how competent the students feel in their drawing abilities. Of course, you could give them the choice...]

12. The teacher should begin with the petals then have the students remove and count the petals of their flowers, taking note of this in their journals. Now the sepals, peduncle, receptacle, stamens and pistils should be visible. One by one draw the students’ attention to each of these areas. Have them use their eye loupes to look closely and to draw diagrams of each part. Ask what they think each part is for. (They will be able to see that the sepals once were the covering for the bud, and notice that the peduncle supports the base of the flower.)
13. Use the laser disk or overhead to help point out any of these parts. A dissecting microscope could also be used. Describe the function of each of the parts.
14. Give the students time to use color pencils to make distinctions in their drawings. Give them opportunities to ask questions and clarify understanding.
15. Have the students remove one entire pistil(they may have to dig down to get the ovary) and look at it closely. Look at the stigma, style and ovary. They can even open the ovary and look inside. They should draw, label and write the function of each part. Do the same with the stamens- anther and filament.
16. Show on the laser disk how the bee goes to the flower, gets pollen from the anther on his body, flies to the next flower and disperses or delivers pollen to that stigma. Explain that the stigma is sticky. Why?

This lesson may take 2 days. Have the students from each team put their naked flowers in the same beaker of water to continue observations the next day. If they didn’t work with the "Basic Flower Structure" worksheet during class, this can be assigned as homework.

 

***** cut this out *****

Flower POW Eighth Grade Science Student Page

This POW is not an experiment. It is a lesson in drying flowers, and practicing your flower anatomy. Just follow the directions given.

Materials: a flower, a stack of books, newspaper, white paper, glue

Procedures:

17. On Monday! Find 2 living flowers(on a living plant!) of the same flower that are in bloom. Cut the flower blooms off with a few inches of stem.
18. Take one flower and cut it in half lengthwise with a sharp knife(This is so you can see all the parts inside.
19. Make a drawing of what your flower looks like. Label the parts listed: peduncle, petals, sepals, receptacle, corolla, stamen, pistil, anther, stigma, ovary
20. Take the two halves, face the openings up and place them on a piece of newspaper. Put the uncut flower next to it. Place another newspaper over the flowers.
21. Place a stack of books over the newspaper. Leave your flowers to dry until Thursday night.
22. Now look at your flowers, they probably have changed color a bit. Very carefully pick up one flower section at a time, put some white glue on the back of it and glue it to plain white paper. Leave some room between flowers.
23. Label the parts of one of the flowers that has been cut in half using the above list.
24. In the lower right hand corner, name the type of flower if you can, put the location where you found it and the time and date.
25. Hand in your drawing stapled to your dried flowers. Make sure your name is visible.

 

 

Growing Pollen Tubes

Lesson 13 À A ? _

Days 17,18 and ?

Lesson Intention: This lesson is designed for students to observe pollen’s many forms, sizes and shapes and then to experiment with growing pollen tubes from a variety of pollen. This will enhance the students’ understanding of sexual reproduction in flowers and the role of the stamen and stigma. Students will also learn about how to make solutions of sugar based on the percentage of sugar to water. They will devise a method of figuring out which percent solution is the best for growing pollen tubes of a particular flower.

BY THE END OF THIS LESSON STUDENTS WILL BE ABLE TO:

• grow pollen tubes using a sucrose solution
• prepare a slide and watch pollen tubes grow under a microscope
• explain where pollen comes from and where pollen tubes form in a flower
• prepare a sugar solution at a given percentage
• design an experiment which determines the best percentage of sugar to grow a particular type of pollen

Materials per student: in class journal, pencil, Pollen Tube Lab &Figuring Percent Solutions student worksheet, rubber apron

Materials per Team: 2 microscopes(24 microscopes needed for the entire lab),100 ml graduated cylinder, triple beam balance, 2 petri dishes, paper towels, 10 cm. square pieces of wax paper for measuring sugar on scale,1 small funnel, 1 plastic spoon a small beaker of sugar, several slides and coverslips, 2 small camel hair brushes, a hot plate.

Teacher Preparation:

Make sure you have a supply of about 8 different types of flowers. Wildflowers or flowers from a garden are the best. Florists tend to get rid of the anthers on their flowers. If you do use flowers from the florist, use pollen from a bud the has just opened. It should still have its pollen.

Set up, as different stations, several microscopes with a different pollen grain under each one. Pick up the powdery pollen from the stamens of a flower with a small camel’s hair brush(rinse the brush between flowers) and deposit a small amount on a slide. Add a drop of water and a coverslip. Adjust the low power of the microscope to look for tiny grains. Switch to high power to get one grain in focus. The grains from each flower should be different in appearance. Label the microscopes as to which type of flower pollen is being viewed.

Copy Pollen Tube Lab &Figuring Percent Solutions student worksheet for each student. Make an overhead of the student worksheet and of the Pollination and Fertilization Diagram.

Bellwork on overhead or board.

.

Bellwork: Answer in a paragraph or a diagram: Where does the pollen come from on the flower? How does the pollen travel to a new flower? What occurs after the pollen lands on the stigma? How does the male sperm cell reach the ovary?

Step by step Lab and Lesson:

1. Begin by reviewing Bellwork. Clarify any misconceptions. Use the Pollination and Fertilization Diagram to help students understand when the growth of the pollen tube occurs, and how it delivers the male sperm cell to the ovary which eventually becomes the fruit that carries the fertile seeds.

2. Tell the class that they will be observing different pollen grains today. They should take such detailed notes and drawings of the grains that if they saw the pollen again, they would be able to recognize it from their notes. Have them set up their notebooks with appropriate date and title. (Don’t start observing yet!)

Show the students that they will also be growing pollen tubes from the different flowers available. Each team will be assigned a different flower. Hand out the Pollen Tube Lab &Figuring Percent Solutions. As you and the students read the procedures, show them how the pollen is collected and the slides are prepared.

Then point out the Figuring Percent Solutions Table and ask: What percent of a dollar is a nickel? What percent of a dollar is a quarter? What is the method for figuring out percentages of something? What is an easy way using decimals? Using the overhead, review how to fill out the table and make a certain percent solution of sugar water.

Assign a flower to each group. Organize a way for students to gather materials. Tell the students that while they’re waiting 20 minutes for the first pollen tubes to grow in the 10% solution, they will be observing the different grains of pollen at the stations. Each student should take no longer than 2-3 minutes at each of the 8 microscopes.

Groups have enough materials to grow pollen grains using two different solutions at a time. They can get 1 set done today, devise their methods of testing then continue the rest of the study on day 2 and possibly 3.

 

Student Page

Pollen Tube Lab

Goals:

Learn how to grow pollen tubes and observe pollen tube growth under a microscope.

Take this knowledge and figure out a method to determine which of any four sugar concentration solutions is the best for growing pollen tubes at the fastest rate.

Come up with your own procedures, sugar solutions, and data table to relay your findings

Materials per student: in class journal, pencil, Pollen Tube Lab &Figuring Percent Solutions student worksheet, rubber apron

Materials per Team: 2 microscopes(24 microscopes needed for the entire lab), eye dropper, 100 ml graduated cylinder, triple beam balance, 2 petri dishes, paper towels, 4 beakers for mixing solutions,10 cm. square pieces of wax paper for measuring sugar on scale, 1 small funnel, 1 plastic spoon a small beaker of sugar, distilled water, several slides and coverslips, 2 small camel hair brushes.

Procedures:

1. Mix the first sugar concentrate solution using the required amounts of water and sugar. Stir well. Label that beaker with the % solution.

6. Place a drop of this solution on a slide.
7. Use the camel hair brush to collect some pollen from a stamen of your assigned flower.
8. Drop the pollen onto the microscope slide with the drop of solution.
9. Add a coverslip and place the slide in a petri dish lined with a moist paper towel. Put the lid on the petri dish
10. Record the time.
11. Place the dish in the assigned "warm spot."
12. Check the growth for the first time at 20 minutes, then at 10 minute intervals after that.

8. While you’re waiting for the first batch, talk to your team about your plan: the percent solutions you will test, the intervals you check the growth, the data table you will collect the data, the method you will use to measure growth.

 

Student page

Figuring Percent Solutions.

To make a certain concentrate of sugar solution you must measure, measure, measure!

1. First measure the amount of sugar you need using the triple beam balance. Remember to subtract the weight of the wax paper square!

2.Add just enough water to make 100 ml of the solution. DON’T JUST ADD 100 ml OF WATER! THAT’S NOT CORRECT! ADD JUST ENOUGH WATER TO MAKE 100 ml OF THE SOLUTION.

3. Stir until the sugar is dissolved. If the water has decreased, after the sugar is dissolved, add just a bit more so the volume of water + sugar = 100ml

4.Label this beaker with the % solution it contains.

5. Dissolving the sugar is very important. Using warm water helps to dissolve the sugar faster. If the sugar isn’t dissolved than it isn’t a solution!

6. You may use a hot plate to warm the water in the beakers and aid you to dissolve the sugar if you are trying to make very concentrated amounts.

How to figure % solutions of sugar and water EASY EASY EASY!!!

% solution	grams of sugar	add enough water to make 100 ml of solution
10%	10 g	add enough water to make 100 ml of solution
20%		add enough water to make 100 ml of solution
25%		add enough water to make 100 ml of solution
30%		add enough water to make 100 ml of solution
40%		add enough water to make 100 ml of solution
50%		add enough water to make 100 ml of solution
75%		add enough water to make 100 ml of solution
80%		add enough water to make 100 ml of solution
90%		add enough water to make 100 ml of solution
60%		add enough water to make 100 ml of solution

Pollination and Fertilization Diagram

Overhead

 

 

Growing Pollen Tubes

Lesson 13 À A ? _

Days 17,18 and ?

Lesson Intention: This lesson is designed for students to observe pollen’s many forms, sizes and shapes and then to experiment with growing pollen tubes from a variety of pollen. This will enhance the students’ understanding of sexual reproduction in flowers and the role of the stamen and stigma. Students will also learn about how to make solutions of sugar based on the percentage of sugar to water. They will devise a method of figuring out which percent solution is the best for growing pollen tubes of a particular flower.

BY THE END OF THIS LESSON STUDENTS WILL BE ABLE TO:

13. grow pollen tubes using a sucrose solution
14. prepare a slide and watch pollen tubes grow under a microscope
15. explain where pollen comes from and where pollen tubes form in a flower
16. design an experiment which determines the best percentage of sugar to grow a particular type of pollen

The University of Arizona
Department of Biochemistry and Molecular Biophysics
General Biology Program for Secondary Teachers
warder@email.arizona.edu