Science, Life Science
Grade 3- 6
Students will dissect flowers to discover where seeds originate.
Some plants produce two kinds of flowers on the same plant. One will have only stamens, the other only pistils. These are incomplete flowers. There are also composite flowers (such as dandelions and marigolds) which consist of many complete flowers clustered into one. The flowers used for this activity should have both stamens and a pistil, known as a complete flower. These include flowers like the lily, gladiola, tulip, and fruit blossoms. Select the largest flowers for this lesson and provide a variety of them.
Ask the students if they know how seeds are produced. Tell them they are about to take a flower apart so they can see where seeds are formed. If the students are too young to dissect flowers alone, do this activity as a demonstration.
Distribute data sheets, flowers, magnifiers, and clear tape to students and let them follow the data sheets as they dissect the flower.
Use the transparency How Flowers Reproduce (page 26) to explain the reproduction process to students. Tell them bees are the best pollinators of flowers. When a bee goes to a flower to get nectar and pollen, some pollen drops off the bee's body onto the sticky stigma on the pistil. Beekeepers often rent hives to farms with apple orchards or other trees needing to be pollinated. Other insects which visit flowers also pollinate them. Pollen can also be transferred to the stigma by wind and by some birds and bats.
Explain that fruits and vegetables are really swollen ovaries of a blossom that grew on the plant. Show students an apple and point out the leftover blossom and stem on opposite ends. Cut the apple open to expose the seeds formed inside the ovary. Let the students examine the seeds.
Save the students' flower parts to be used in the next lesson and in the plant journal.
Take students on a walk to search for fruit-bearing plants that show blossoms and fruit. Try to find examples of the transition from blossom to fruit on a plant. Cut open a blossom to expose the swollen ovary inside, the beginning of the fruit.
Have students examine a dandelion flower and one which has gone to seed. This is a great example of a composite flower. Each seed is formed in its own flower but combined with others.