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Looking Inside an Onion

Looking Inside an Onion. Microworlds Lesson 11. Think & Wonder. Blood Cells. When Robert Hooke looked at a sliver of cork under his microscope, he saw rows of “little empty boxes” that reminded him of rows of prison or monastery cells.

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Looking Inside an Onion

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  1. Looking Inside an Onion Microworlds Lesson 11

  2. Think & Wonder Blood Cells • When Robert Hooke looked at a sliver of cork under his microscope, he saw rows of “little empty boxes” that reminded him of rows of prison or monastery cells. • He was the first to describe these structures, and in naming them coined a new use for the word “cell”. *

  3. Think & Wonder • Other scientists have called them “the building blocks of all living things. • In this lesson you will move from the outside of an onion in, until you reach the smallest living unit, the cell. *

  4. CELLULAR STRUCTURES • Cell wall • supports and gives shape to the cell. • Cell membrane • Holds the living parts of the cell • Nucleus • The control center for the cell *

  5. FOR EACH TEAM small onion slices 1 water dropper bottle 1 pair of scissors 1 pair of forceps toothpicks Paper towels or newspaper FOR EACH STUDENT LRB 1 microscope 1 hand lens 2 slides Activity Sheet 6 Materials FOR THE CLASS 1 container of rinse water

  6. Process • Observe the outside of the onion. • Describe the exterior and record this in your LRB. • Sketch your prediction of the interior in the appropriate location on Activity Sheet 6. • Now, sketch what you see when the onion is sliced lengthwise. * Remember: Predictions are never incorrect. Do not change your prediction, they are a record of your thinking, not observations!

  7. Process • What do you think the onion will look like if you cut it through the roundest part? • Sketch and record this in your LRB and Activity Sheet 6. • Now, sketch what you see when the onion is cut through the roundest part. • Sketch your prediction of the onion under the microscope. *

  8. Process • Separate the layers of the onions. Using your fingernails or the forceps, peel off a piece of the thin skin found between the layers. • Lay the ½ inch long piece of onion skin flat on your slide. (Be careful not to fold or wrinkle it!) • Use a toothpick to smooth it out. • Squeeze a drop or two of water on top of the onion skin, then lower a cloverslip or slide on top. *

  9. Onion Cells

  10. CLEAN-UP • Please clean the slides thoroughly. • Cut and glue your activity sheet into your LRB.

  11. Final Activity • Cells were named by Robert Hooke because their shape reminded him of small, boxlike, prison or monastery cells. Other scientists have called cells “the building blocks of all living things.” • Reflect on why cells are compared to building blocks. • Record this in your LRB. *

  12. Update your Table of Contents

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