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Flower Dissection - (Eric Blinder)

Lesson Plan for 7th Grade Life Science
Monday - Friday  54 minute class period
Chapter  6  - Botany
 

 

Principles Investigated: Students will be able to describe the different structures of flowering plants including the petal, the sepal, the stamen including the anther and filament, and the pistil including the stigma, the style and ovary.  Students will be able to dissect a flower and label it structures and functions.  Students will be able to assemble the dissected flower parts and recreate the original plant.


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


Materials:
  • Flowers - (Choose a flower with large, visible structures that are easy to identify.  Lilies were used in this demonstration.)
  • Tagboard
  • Scissors
  • Scalpel
  • Tape
  • Pen/Marker
  • Pine cone

Procedure:
1.  Illustrate the difference between gymnosperms and angiosperms.  Pass around the pine cone showing that the seeds do not form inside the fruit, but outside of the ovum.  Compare this to angiosperms.

2.  Pose the following line of questions to the class: "What do you know about flowers?  How do flowers behave?  What do flowers                 have in common?

3.   Show photos of flowers that do not fit the classic idea of being "pretty" or "smelling good".  Explain how and why flowers are differentiated.  

4.  Explain that although flowers species are differentiated, they all must somehow contain reproductive structures inside.  Explain the difference between perfect and imperfect flowers and sex switching.  Show a diagram of the reproductive structures of perfect flowers for use of this demonstration. 

5.  Pass out the flowers, tagboard, tape, scissors, and scalpel.  (Note: Scissors and scalpel may not be necessary - Only use what is necessary for the specific lab you are doing.  The species of flower may make a difference in the tools necessary.)

6.  Begin the dissection.  The instructor demonstrates on the overhead/ELMO projector while the students follow at their desk.

7.  Remove the sepals and petals from the flower.

8.  Isolate and remove the stamen, (filament with anthers).  

9.  Isolate and remove the pistil, (stigma, style, and ovary).

10.  Rearrange the flower on the tagboard, labeling the previously identified structures.


Student Prior Knowledge:
The students should already be familiar with plant cells and cell differentiation.  Students would have also been exposed to the diagram of the different structures of plants.  Students are also familiar with the function of the reproductive structures. Students know how the pollen tube is formed and the egg becomes fertilized and forms the seed.


Explanation:  
This dissection is performed in the classroom to illustrate to the students how to identify the structures of flowering plants.  Looking at a diagram in the textbook is not the same as actually holding the flower and taking it apart by hand.  By touching the structures and taking them apart, students are receiving the information in multiple modalities and forming their own opinions about how to describe these structures.  Rearranging the flower and labeling it requires students to think about the organization of the structures as they are found in nature.  This dissection is an engaging method for teaching flower structure and function.

Question and Answer:
1.  What might be a result of a species of flower that has its stamen and pistil located far away from each other on the plant?
      Answer:  It would be more difficult for the pollen to reach the stigma.  It would have to travel a farther distance.  
      Perhaps an insect with a corresponding body shape would pollinate it.

2.  Scientists observe a deformity appearing in a certain species of flowering plants.  The deformity causes the pollen to change   shape and become smooth, not sticky.  What might be a result of this deformity?
    Answer:  The pollen would not easily stick to the stigma and therefore reduce the chance of fertilization.  Also, if the pollen    changes shape, it may not be able to fertilize the egg.  Most likely, this would be a sterile plant.

3. Most fruits that we eat are actually large, swollen ovaries of flowering plants.  Why do you think that fruits develop from these structures?  What purposes might they serve?
    Answer:  The fruits form to protect the seeds.  That is why in most cases, for example an apple, the seeds are found in the center of the edible fruit.  Also, the sweet, nutritious characteristics of the fruit make it desirable for animals to eat.  Animals that eat the fruit then disperse the seeds and increase the area of coverage of the seeds and increase the chance of successful germination for the plant.


Applications to Everyday Life:
Students are surrounded by plants all the time.  By explaining how plants function and allowing students to dissect, analyze, and touch the plant structures, students are becoming increasingly critical of their own environment.  Where students may have previously never thought about how plants reproduce, now they are generating their own questions about how their environment functions.  This is a great example of scientific methodology, and inquiry based learning.  By learning about something that students previously "took for granted", they are forced to ask themselves, "What else don't I know about my environment?".  This critical thought process is very important for students to develop and will only enhance their enjoyment and performance in science as well as all other content areas.
 
References / Links:
 
 

Photos:

Corpse Flower - Foul Smelling - Huntington Botanical


The dissected flower (lily)



The rearranged flower (This is what students' work should resemble)





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Oct 4, 2010, 11:22 AM
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MTTM(FlowerDissection2)[www.keepvid.com].3gp
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Norman Herr,
Oct 4, 2010, 11:27 AM
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