One to two class periods
- identify the different parts of a flower and understand their functions and
- understand the importance of pollen for plant reproduction and diversity.
- For the class: Dissecting microscope
- Computers with Internet access (optional but very helpful)
- Reference materials: books and encyclopedias
Each student will need the following:
- One flower from a school garden, a market, or donated from a florist. Good examples include daisies, carnations, lilies, pansies, violets, daffodils, tulips, hibiscus, gladioli, or petunias. Be sure to offer an assortment of flowers so that students can compare different species.
- Magnifying glass
- One copy of Classroom Activity Sheet: Flower Investigation (see printable version)
- Take-Home Activity Sheet: Pollen Counts (pages 1 and 2) (see printable version)
- Discuss with students the structure of flowers. Begin by making a list of all the flower parts they know. Then show students a diagram of a flower and discuss the locations of the parts of the plants and their functions. The following parts should be included in this discussion: pistil, stigma, ovary, ovule, stamen, anther, petal, and sepal.
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- Once students are familiar with the different flower parts, have each student select a flower to study. Ask students to observe the flower with their eyes and with a magnifying glass. Make sure each student has a copy of the Classroom Activity Sheet: Flower Investigation on which to record observations. First, have them answer the following questions on their sheets:
- How big is the flower?
- What is the shape of the flower?
- Does the flower have a color?
- Does the flower have an odor?
- What flower parts can you see?
- As a class, brainstorm ways that plants are pollinated. Discuss how the structure of plants contributes to pollination. Ask students to consider whether they think insects, other animals, or the wind are involved in pollination. Then, on the basis of their observations and the class discussion, ask students to develop their own hypothesis about the mechanism of flower pollination. Have them write their hypothesis on their observation sheets.
- Have students dissect the flower they chose. Although each student has his or her own flower, students can dissect their flowers in small groups so that they can share ideas and problem solve together. Each student should dissect his or her flower by carefully removing each part, starting from outside the flower and working inward, counting how many of each part is present on the flower. If a dissecting microscope is available, have students look at each part under the microscope.
- Students should record their data on the Classroom Activity Sheet: Flower Investigation. Students could include a sample of the flower part on their chart by taping or gluing it in place. After students have identified all the flower parts, discuss the similarities they found among all the flowers. How were the female parts of each flower similar? How were the male parts similar? Based on this information, challenge students to conclude how each flower is pollinated.
- If students need more information to determine how their plant is pollinated, suggest that they use reference materials available at school or visit the following Web site:
- After doing the necessary research, have students address their hypotheses. Were they correct, or did the experimentation and research prove otherwise? Have students write a conclusion to the activity on their Classroom Activity Sheet: Flower Investigation.
- Assign the Take-Home Activity Sheet: Pollen Counts for homework. After five days, have students bring in their sheets and compare their findings. What did students learn about pollen in their area?
Have students prepare thin tissue samples to study under a dissecting or compound microscope. Students should be able to identify the ovules in an ovary and the pollen sacs in an anther. Estimate how many seeds the flower could produce by counting the number of ovules in the ovary.
- Compare and contrast the structure and function of the flower parts studied. What is similar in each flower? What varied? What functions do they have in common?
- Explain how each flower studied would be pollinated. Which flowers would be best pollinated by a bee? Which would be best pollinated by the wind? How did the stigma of each flower adapt to trap pollen? Is one method of flower pollination more common among the flowers studied than another? Why?
- The angiosperm (flowering) group is the largest, most successful plant group on Earth. Angiosperm species are also the youngest, evolving 125 million years ago. Debate possible reasons for their success. Provide a number of examples to support your hypothesis.
- Compare the number of each flower part among the flowers studied. Was a pattern evident? Classify each flower as a monocot or a dicot. (Monocots have floral parts in multiples of three, and dicots have floral parts in multiples of four or five.)
- Consider how the flowers you studied ensure that pollen grains reach the stigma, which is a necessary process for fertilization. Compare each flower's method of pollination. How successful is each method?
- Discuss the benefits of animal pollination for both flowers and their animal pollinators. Explain how this codependence influences diversification. What disadvantages can be attributed to the mutual dependence of plants and animals?
Students should be able to label a diagram showing the parts of a flower, observe and describe their flowers using appropriate language, develop their own hypothesis based on their observations, create a detailed data chart, and verify their hypotheses based on class discussions and research. Use the following three-point rubric to evaluate students' work during this lesson:
- Three points: labeled an accurate diagram of a flower, observed their flower, wrote detailed descriptions, completed all parts of the recording sheet, developed an hypothesis, performed the necessary research to verify the hypothesis, and wrote a complete conclusion to the investigation
- Two points: identified, diagrammed, and labeled at least eight parts of a flower; observed their flower; wrote an adequate description; completed most of the recording sheet; developed an hypothesis; performed enough research to at least partially explain the hypothesis; and wrote an adequate conclusion to the investigation
- One point: identified, diagrammed, and labeled at least five parts of a flower; observed their flower; wrote short descriptions; completed approximately one-half of the recording sheet; developed an hypothesis; performed some research about the hypothesis; and wrote a short paragraph or an outline summarizing the investigation
Dissect a Fruit
After studying a number of different flowers, have students study fruits. What part of the fruit was the ovary? What part of the fruit were the ovules? Compare the fruit structure of apples, berries, and olives (or other one-seeded fruits).
Design a Flower
Have students work in groups to design models of flowers that are pollinated various ways. One flower could mimic an insect to attract other insects for pollination. Another flower could rely on humans for pollination. Still another flower could be pollinated by the wind. Display the designs in the classroom with small captions describing the flower's unique characteristics.
Sex in your Garden
Angela Overy. Fulcrum Publishing, 1997.
With a touch of humor and more than 250 color photographs, the author of this appealing and entertaining book describes the reproductive processes of garden plants. She pays special attention to the ways plants attract pollinators, paralleling their activities with those of flirtatious humans, and relates how a variety of common pollinators accomplish their tasks.
The Forgotten Pollinators
Stephen L. Buchmann & Gary Paul Nabhan. Island Press, 1996.
The authors, one, a leading authority on plant pollination, and the other, an award-winning writer, provide an in-depth exploration of the relationships between plants and the animals and insects they depend upon for reproduction. Descriptions and detailed illustrations of their observations around the world make their discussions of ecology and botany come to life.
Access this resource at:
The Great Plant Escape
This site covers everything educators would want to teach their students about plants. Students are able to read information about plants and take a quiz at the end of the activity.
The Pollination Scene
This site illustrates the process of pollination by bees. It explains the difference between good pollination and bad pollination.
Partners in Pollination
This site is provided by the Smithsonian Center for Education and Museum Studies. It is composed of many reproducible pages for use in the classroom
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Credit: Mary C. Cahill, middle school science coordinator, Potomac School, McLean, Virginia.
Definition: A class of vascular plants having seeds enclosed in an ovary.
Context: Angiosperms are in class of seed plants that produce flowers that become fruits.
Definition: The part of the stamen that develops and contains the pollen.
Context: The stamen on a flower consists of a four-chambered sac called the anther in which pollen is produced.
Definition: A subclass of angiosperms with an embryo that contains two cotyledons, branching leaf veins, and flower parts in multiples of four or five.
Context: A subclass of angiosperms with an embryo that contains two cotyledons, branching leaf veins, and flower parts in multiples of four or five.
Definition: A subclass of seed plants with an embryo that contains one cotyledon, parallel leaf veins, and flower parts in multiples of three.
Context: Monocots are angiosperms, such as tulips and daffodils, that have flower parts in multiples of three.
Definition: Sweet liquid secreted by flowers that bees use to make honey.
Context: A sweet-smelling substance, called nectar, is produced in some flowers to attract insects, which help pollinate the flower.
Definition: The outgrowth of the ovary of a plant that encloses an embryo sac; the part of the plant that is pollinated and grows into seeds.
Context: After being pollinated, many of the small ovules in the flower's ovary will become seeds, which, when planted, can grow into new flowering plants.
Definition: One of the modified leaves of a flower that protects its reproductive organs.
Context: The petals of a flower enclose and protect the flower's reproductive organs.
Definition: The seed-bearing organ of a plant that consists of the ovary and its appendages.
Context: The seed-bearing organ of a plant that consists of the ovary and its appendages.
Definition: Fine powder dust that contains the sperm from a male plant.
Context: Male flower parts, called stamens, produce pollen in sacs in the anther. The anther bursts open and releases many pollen grains, which contain a sperm nucleus for fertilization.
Definition: Transfer of pollen from the anther of a stamen to the ovule of a flower.
Context: For flower reproduction to occur, pollen from the male anther is transferred to the stigma, found in the pistil. Wind, water, and insects can help pollination occur.
Definition: The part of a flower's pistil where the pollen grains are germinated.
Context: The pollen grains enter the pistil and are germinated in the flower's stigma.