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Flowers: Form and Function Based upon a lesson by Roxane Johnson Modified by Kirstin Bittel and Rachel Hughes http://biology.arizona.edu/sciconn/lessons2/Roxane/flow.htm Time : 1 class period Preparation Time : Collecting flowers, loupes, fruits and seeds. Photocopying student sheets. Materials : Flowers for each students (Flower shops often will be very generous with flowers that have seen better days- make sure they are simple flowers not composite flowers) Eye loupe Fruits and seeds Abstract In this dissection lab, students will use eye loupes or magnification lenses to look closely at flowers. As the flower is dissected, students determine the function of each part by observing the form. Intermittent use of plant videos can be shown to reinforce what is being seen in the dissection. Objectives Students will be able to: 1. Recognize and name the parts of a flower 2. Explain the function of each part of a flower 3. List the steps that occur for sexual reproduction of a plant to take place 4. Recognize and name the male reproductive parts, and female reproductive parts of a flower National Science Education Standard: Content Area C – The Interdependence of Organisms Organisms both cooperate and compete in ecosystems. The interrelationships and interdependencies of these organisms may generate ecosystems that are stable for hundreds or thousands of years. Teacher Background http://www.emc.maricopa.edu/faculty/farabee/BIOBK/BioBookflowers.html http://www.biologie.uni-hamburg.de/b-online/e02/02f.htm Related and Resource Websites http://www.saburchill.com/chapters/chap0042.html http://www.learn.co.uk/default.asp?WCI=Unit&WCU=2330 Activity 1. On each group’s desk have a beaker containing a mixture of flowers, a seed and an item easily identifiable as a fruit. The presence of the flowers is often a good catch for students. Ask them to describe either in words or pictures the relationship between flowers, fruits and seeds. Notebook Preassessment 2. 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 write the observations on the board or overhead. What is likely to occur is that students will want 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. (Later they will make the connection with the terms they are given.) 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. 4. Students observe their own flower, describing it and drawing it in their notebooks, labeling the parts as they are identified. 5. Pass out a flower to each student. 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 are called the corolla- a word related to the word corona meaning garland or crown. 6. 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.) 7. Give the students time to use color pencils to make distinctions in their drawings. Give them opportunities to ask questions and clarify understanding. 8. 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. 9. Having identified the anthers, stamen and stigma ask students how they think pollen gets from the anthers to the stigma. Introduce the idea that it is more beneficial for plants to cross pollinate, that plants are designed to have pollen move from one plant to another. Looking at the flowers in front of them can students identify how pollen might move from one plant to another? Have students suggest methods of pollination. Provide the definition that pollination is the movement of ripe pollen to a ripe stamen. 10. Provide students with the attached chart. Students should be able to suggest wind, water, insect and bird as vectors for pollination. Have them observe the flowers again and identify what factors are necessary for which type of pollination. Once the class has correctly identified a structure as appropriate for a type of pollination they should note that in the chart also. Direct students to the website: http://www.learn.co.uk/default.asp?WCI=Unit&WCU=2330 This website has some simple diagrams that will support students’ comprehension of pollination. Students should draw flowers on their charts that represent each form of pollination. Assessment: Have students identify the parts of an unknown flower. They should make suggestions as to how the male and female structure organization plays a role in pollination. Pollination The process by which …………………………………………………………………………………. Type of Pollination Structures associated Example of flower Does the plant have with this type of specific ways of pollination attracting pollination?
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