NY Botanical Gardens 11th Grade:

NY Botanical Gardens: High School

Understanding Flower Reproduction: A Dissection Lab for the Science Classroom

Grade Level: 11th

Learning Standard: Science Standard 4 & 5

Time Requirements: Approximately 1-hour preparation time and 2 hours class time

Topics Covered by this Lesson: Students explore the reproductive function of flowers.

Pre-Visit:

Purpose: To learn the reproductive function of flowers by participating in a flower dissection lab.

Objective: Students will:

§ Observe the inside and outsides parts of a flower and hypothesize how the many parts might aid in its reproduction.

§ Dissect a flower, working from the outermost whorl to the inner most whorl; illustrate and label each part of the flower and understand the reproductive function of each part.

§ Create and label a cross-section diagram of the flower dissected in class, including an explanation of how each part of the flower labeled affects flower reproduction.

Materials required: Paper, lab books or student journals, pens/pencils, tulips or similarly structured flowers (one per pair of students), scalpels (one per pair), magnifying glasses (one per pair), colored pencils.

Student Learning Prerequisites: Explain to students that they will now be dissecting flowers to better understand the functions of their parts. Because the class will be dissecting their flowers together, it is crucial that students remain attentive and follow the steps together. Additionally, students should diagram (using colored pencils) and label the different parts of the flower in their lab books or journals. Begin the dissection by telling students that they will be dissecting in whorls, or layers from the outermost whorl inward.

§ Students examine their flowers and locate the outermost whorl. Students should identify the sepals, the green leaf-like structures at the base of the flower. All of the sepals compromise the calyx. Students should carefully remove and count the sepals. Then, ask what they think the role of this whorl is in flower reproduction (It protects the flower when it is budding). Students next draw and label this whorl in their lab books. (Using the terms calyx and sepal).

§ Ask students to hypothesize on the function of the next whorl, known as the corolla, which is comprised of the flower’s petals and often nectar-producing glands (this layer attracts pollinators). Students then carefully remove and count the petals, and draw and label this whorl in their lab books (using the terms corolla and petal).

§ Ask students to identify the next whorl, called androecium, comprised of the stamens. Ask students to remove the stamens and count them. Then, explain that the stamen is comprised of the filament (the stem like part) and the anther, which is covered with pollen. Give each pair a magnifying glass to better see the pollen grains on the anther. Ask students to identify the function of the stamen (to provide the pollen for reproduction) and to draw and label this whorl, called they gynoecium.

§ Ask students to identify the next whorl, called the gynoecium, comprised of several carpels fused to form the pistol. Explain that each carpel contains at least one placenta, each attached to an immature seed or ovule. Give each pair of students a scalpel and discuss how to safely use the instrument. Then tell the students to make a hole in the bottom of the flower near the stem to find the u-shaped ovary. Students should return their scalpels after the ovary given what they find inside, using their magnifying glasses for a better look (to produce the ovules or immature seeds). Then, tell students to find the stigma, the top part of the pistil. Ask students to touch the stigma and note how it feels. Next, point out that the long piece connecting the ovary and the stigma is called the style, and ask students to hypothesize its function in reproduction (a protective tube linking the pollen-collecting stigma and the ovary). Students draw and label this final whorl in their lab books (using the terms gynoecium, carpal, pistil, ovule, ovary style and stigma).

Vocabulary: Whorls, sepals, gene, pollen, stamens, carpal, style, stigma, gynoecium, calyx, corolla, androecium

Visit: Student will have notebooks and pencils. They will have decided in the previous class who they want to move around the garden with. They will draw, write, and take pictures of the beautiful plans while touring the New York Botanical Gardens. They will tour the rainforest and desert area.

Post Visit:

Assessment: Students will discuss questions we answered and ones we are still not sure about. They will be evaluated based on their presentation after the trip to the garden.

Extensions and suggested homework assignments: Each student creates a cross-section diagram of the flower dissected in class, using their lab notes, diagram and garden notes. Each part of the flower discussed in the dissection should be clearly labeled and correctly colored, accompanied by an explanation for the flower part’s purpose and flower reproduction.

Possible questions that may be brought up:

What is pollination and how does it occur?

What roles do animals and insects play in pollination?

How are the parts of an flower similar to the reproductive structures in animals?

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