Dissection of a flower

By Laura Hospitál on May 01, 2015

This activity gives students an opportunity to experience tactually and visually (for low vision students) the basic structure of a flower.  I have chosen a large flower with clearly differentiated male a female parts for clarity. 

I recommend covering plant reproduction in angiosperms including pollination and the formation of seeds on the day prior to this lab. Use the text and an appropriate model to introduce the students to the plant structures .  Enasco.com has a nice flower model. 

See review. http://www.perkinselearning.org/accessible-science/giant-dicot-flower-model.  As this model is quite expensive (about $550), I have also reviewed a simpler student model made by the same company.  It costs $225.  

 http://www.perkinselearning.org/accessible-science/student-edition-giant-dicot-flower-model

Caution:  Find out about any allergies that students have prior to this activity.

Resource used: http://www.desertmuseum.org/center/edu/docs/k-5_DesertGardeners_flowerDissection.pdf

Related Vocabulary:

  • angiosperm - flowering plant
  • pollination - the transfer of pollen from the male reproductive strutures to the female reproductive structures in plants
  • pollen tube - a tubular structure that grows from a pollen grain, enters the embryo sac, and allows the male reproductive cells to move to the ovule
  • pistil - the female reproductive part of a flower that products seeds and consists of an ovary, style and stigma
  • ovary- in plants, the lower part of the pistil that produces eggs in ovules
  • ovule - a structure in the ovary of seed plants that contains an embryo sac and that develops into a seed after fertilization
  • stamen - the male reproductve structure of a flower that produces pollen and consists of an anther at the tip of a filament
  • anther - in flowering plants, the tip of the stamen, which contains the pollen sacs where grains form
  • filament- the long slender structure in a flowering plant which supports the anther- part of the stamen
  • sepals - in  a flower, one of the outermost rings of modified leaves that protect the flower bud
  • petals - one of the ring or rings of the usually brightly colored, leaf-shaped parts of a flower utilized by the flower to attract pollinators

Preparation:

  1. Purchase a large white lily for each group of 2 students.  White provides better contrast for most students.  I recommend calling ahead to the flower shop as some shops remove some or all of the reproductive parts.  Ask them to hold flowers for you and NOT to remove the reproductive parts.
  2. Place one flower on a tray at each lab station with a dull plastic knife.

Materials

  • One lily for every 2 students
  • One plastic knife for every 2 students. 
  • One cafeteria tray (or other tub or bin) for every group
  • Raised line graphic, model and/or large print picture from the text of a flower
  • gloves if desired (Latex -free if necessary)

Procedure

I  Review 

1. Have students look at the raised line or picture of the flower while you discuss pollination and seed formation.

  • Ask - What is pollination remembering yesterday's discussion?  Students should answer that pollen from the male part of a plant travels to the female  part of the plant (or another plant).
  • Ask - What does pollen contain?  Students should answer that pollen contains the male sex cells or sperm.   
  • Ask - Who carries the pollen in angiosperms?  (Remind the students what angiosperms are if necessary.)Students should mention insects (butterflies, bees, etc) and may also mention birds
  • Ask - Looking at this picture, do you remember which part is the male and which the female part?   Discuss the pistil and the numerous stamen in the picture with the students.  The pistil is the female part of the flower and the stamen are the male parts.  Discuss the fact that pollen from the stamen pollinates the pistil. 
  • Ask - What happens when pollen reaches the pistil? Students should answer that pollen travels down the pistil in a pollen tube and after it pollinates the ovules, seeds are formed. 

(This description is probably too advanced for younger elementary students and may be simplified if necessary.)

II. Dissection

  1. Direct the students attention to the petals.  Explain that the sepals of some flowers are green and easiy differentiated  from the petals but that this is not the case for lilies.  Tell students that the sepals are the outermost layer of tissue the protec the flower bud before it is open
  2. Have students remove a petal each and observe it.  Does it have color?  Does it smell?  What other observations can they make.  Why does it benefit the plant for the petals to be colorful and to smell good? (It attracts pollinators.)   
  3. Have students find the stamen.  They may be able to do this independently otherwise guide them if necessary. Have students feel the pollen at the top of the anther and make observations about it?  What does pollen contain? (The male sex cells.)  
  4. Students will know identify the female part of the flower (pistil).  Again, guide students only if necessary and allow them to take time to look for it independently.  Have students feel the top of the pistil.  Ask if it is sticky. Why do they think the top of the pistil would need to be sticky.  The pollen will stick to the top of the pistil and travel down the pollen tube to unit with the ovules.   Follow down from the top with your finger until you reach the rounded base (ovary). Students will break open the ovary with the plastic knife.  What would they expect in this part of the flower.  developing seeds

III.  Discussion

  • After all of the students have completed the dissection, discuss the function of a flower and it's structure.  
  • A guiding theme in life science is the connnection between structure and function.  Note this as the students discuss the flowers.  
  • Have one student describe each structure - petal, stamen, anther, pistil, etc and discuss the function and the structure of each.
  • Alternate closure:  If time allows, have students write a paragraph describing what they learned about flowers while dissecting.  
  • Depending on literacy levels, guide students as appropriate.

 

Variations

  • Type of flower utilized:  If lilies are not available, the best flower types to dissect are tulips, daffodils, alstroemarias, and gladiolus.
  • For younger students, the terms "pistil" and "stamen" can be omitted and simply described as "girl parts" and "boy parts".

NGSS Standards:

1st Grade: Structure, Function and Information Processing

LS1.A: Structure and Function     
All organisms have external parts. Different animals use their body parts in different ways to see, hear, grasp objects, protect themselves, move from place to place, and seek, find, and take in food, water and air. Plants also have different parts (roots, stems, leaves, flowers, fruits) that help them survive and grow. (1-LS1-1)

LS1.B: Growth and Development of Organisms
Adult plants and animals can have young. In many kinds of animals, parents and the offspring themselves engage in behaviors that help the offspring to survive. (1-LS1-2)

Grade 3 - Inheritance and Variation of traits: Life Cycles and Traits

LS1.B: Growth and Development of Organisms
Reproduction is essential to the continued existence of every kind of organism. Plants and animals have unique and diverse life cycles. (3-LS1-1)

Grade 4 - Structure, Function, and Information Processing

LS1.A: Structure and Function
Plants and animals have both internal and external structures that serve various functions in growth, survival, behavior, and reproduction. (4-LS1-1)

MIddle School - Structure, Function, and Information Processing

LS1.A: Structure and Function
In multicellular organisms, the body is a system of multiple interacting subsystems. These subsystems are groups of cells that work together to form tissues and organs that are specialized for particular body functions. (MS-LS1-3)

Middle School - Growth, Development, and Reproduction of Organisms

LS1.B: Growth and Development of Organisms

  • Organisms reproduce, either sexually or asexually, and transfer their genetic information to their offspring. (secondary to MS-LS3-2)
  • Plants reproduce in a variety of ways, sometimes depending on animal behavior and specialized features for reproduction. (MS-LS1-4)

High School - Structure and Function

LS1.A: Structure and Function
Systems of specialized cells within organisms help them perform the essential functions of life. (HS-LS1-1)

dissecting a flower collage


 

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