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Tracy F- Flower Dissections

Flower Dissection (YouTube)

Flower Dissections

 

Tracy Foster

Lesson Plan for 7th Grade Life Science

55 Minute Class (M-F)

Angiosperms (Flowering Plants)

 

 

 

 

Principles Investigated:

 In this lesson, students will be able to (SWBAT):

 ● Describe the parts of a flower and explain their functions, including the:

○ Petals

○ Sepals

○ Stamen (including the anther and filament)

○ Pistil (including the stigma, the style, and the ovary)

● Dissect an actual flower and identify its structures (and their functions). Students may also

            reassemble their flowers, labeling their structures and their functions.

● Compare/Contrast the structures of different species of flowers, and make

inferences on the relationships between structure, function, and adaptation to their environment.

 

Explanation:

This lesson (dissection) is designed to give the students practice in identifying the structures of a flower on an actual specimen (as opposed to a picture in a textbook). When students get a chance to observe the real thing, including similar structures in different species of flowers, they develop a better understanding of the commonalities that they share, as well as the variation and diversity that occur in nature. By taking apart the flower with their own hands, the visual, kinesthetic, and tactile elements of learning are strongly emphasized. In terms of Bloom’s taxonomy, this lesson uses real life examples of flowers to apply the concepts they have already learned. By comparing and contrasting two different flowers, students are using analytical reasoning. They are also using synthetic reasoning when they hypothesize how different variations of structures might be best suited for a particular environment or condition.

 

 

 

California Content Standards:

1. All living organisms are composed of cells, from just one to many trillions, whose details usually are visible only t

through a microscope.  As a basis for understanding this concept:

b. Students know the characteristics that distinguish plant cells from

            animal cells, including chloroplasts and cell walls.

d. Students know that mitochondria liberate energy for the work that cells

            do, and that chloroplasts capture sunlight energy for

photosynthesis.

5. The anatomy and physiology of plants and animals illustrates the

complementary nature of structure and function.  As a basis for understanding this

concept:  

a.       Students know plants and animals have levels of organization for

structure and function, including cells, tissues, organs, organ

systems, and the whole organism.

b. Students know organ systems function because of the contributions of

            individual organs, tissues, and cells.  The failure of any part can

            affect the entire system.  

f. Students know the structures and processes by which flowering plants

            generate pollen, ovules, seeds, and fruit.

 

Student Prior Knowledge:

The students should already know that flowers are the reproductive structures in Angiosperms. They should have a basic understanding of the parts of the flower, as well as their role in the reproductive cycle (including pollination and fertilization). This lesson is designed as an application of their knowledge, not as a first introduction. The students should also have a developing awareness of the relationship between form and function, which will be illustrated in the variety of flowers they observe.

 

 

 

Materials:

● A Variety of Flowers (preferably both wild and cultivated)

                        ○ For beginners, select flowers with structures that are easy to identify,

                                    and that correspond closely with the textbook (lilies are a common

                                    choice).

                        ○ For more advanced students, you may select more challenging flowers,

with structures that differ somewhat from those illustrated in the text. This will expose them to the variety of structural designs that are present in nature, and give them a more realistic appreciation of

the natural diversity and adaptations.

● Hand Lenses (Magnifying Lenses) for Investigating Details

● Science Journals (to Record Observations)

● Scissors or Scalpels (Scalpels are not necessary in most cases- Cuticle

                        scissors work well)

            ● Posterboard, for Mounting Re-assembled Specimens

            ● Glue Sticks

            ● Pens & Markers for Labeling

 

Procedure:

            

1.  Begin by reviewing what the students already know about flowers. This may

            include the parts of the flower, as well as their functions. You may also

            discuss the stages of the reproductive cycle, including pollination and

            fertilization. Students should know that there are male flowers, female

            flowers, and “perfect flowers”, which contain both male and female

            structures.

2.  Students may write “connections” in their journals, where they describe some

            of their experiences and associations with flowers. They may share these

            with the class. The teacher should guide the students by relating these

            experiences to concepts such as similarities (common features) between

            different species, as well as the diversity that exists in nature.

3.       The teacher can show examples of flowers that illustrate the variety found in

nature, as well as the idea that not all flowers are pleasant-smelling.  This

is a good time to make inferences as to why these flowers are different,

and what purposes their differences might serve. How are they adapted to

their environment? What might pollinate them? (A classic example is the

corpse flower, which smells like rotten flesh, and is pollinated by….flies).

4.      The students should now be primed to not only dissect the flowers, but

observe and analyze them within the conceptual framework of

“form determines function”.

5.   Distribute the flowers, scissors, hand lenses, and other equipment.  

6.  Begin the dissection.  The instructor can lead the dissection using the

            document projector, or, the students can perform the dissection

            independently. The students should:

● Remove the sepals and petals from the flower.

● Remove the stamens, (filament with anthers).

● Remove the pistil, (stigma, style, and ovary).

7.  Students may also illustrate their flowers in their science journals, and

            compare/contrast two different varieties of flowers. What structures do

            they share in common? How many petals do the flower have? How many

            stamens? Are the anthers large or small? Can you see pollen?

8.       Students will reconstruct their dissected flower using the posterboard and

            glue. They should label all the parts, and describe the function of each.

Questions:

1.Why do you think flowers are different colors? What is the significance of the

petal color?

 

            Answer: Petals with different colors are often pollinated by different species.

            Hummingbirds tend to be attracted to red flowers, while bees often pollinate

            yellow and blue flowers, as they can see well in the portion of the spectrum.

 

2. Many flowers have their male and female structures far away from each other.

            What do you think would be the effect of this structural arrangement?

            What consequences would it have for the plant?

 

Answer: Having the male and female parts away from each other makes it less

likely that the plants will self-pollinate. Generally speaking, plants (and other

species) are healthier when they cross-pollinate, rather than self-pollinate, as this

increases their genetic diversity.

 

3. Other than being pretty, what significance do flowers have in our everyday

lives? How are they important to humans?

 

Answer: The vast majority of plant foods that humans eat come from flowering

plants or Angiosperms. All the major grain crops, such as corn, wheat, rice, and

oats, as well as all the fruits we consume, are produced from flowering plants.

Pollinators, such as honeybees, are also, therefore, very important for agricultural

purposes.

 

Applications to Everyday Life:

Flowering plants are important part of ecosystems around the world. They serve not only as major food sources for humans, but for the majority of other living organisms as well. The fruit, seeds, nectar, leaves, and other parts of flowering plants provide the basis for many organisms’ diet. These animals, in turn, often serve as the food source for predatory species higher up the food chain. Flowering plants, therefore, are the base of the food pyramid around the world. Without them, we could not survive.

 
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Norman Herr,
May 12, 2011, 1:33 PM
ĉ
Norman Herr,
May 12, 2011, 1:33 PM
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