Introduction to Mitosis & Cell Division: Microscope Lab

An online microscope lab for middle school and high school science on StudyScope. Students work through 3 real prepared microscope slides in order: Onion Root Tip Mitosis (Longitudinal Section), Ascaris Female (Cross Section), and Cotton Leaf (Cross Section).

Students hunt for the stages of mitosis in an onion root tip, see how an animal cell divides differently in roundworm eggs, then look at a mature leaf to see why most cells are not dividing at all. You drive the slides; students follow on their own screens and can pan and zoom. Each hunt is followed by a step that reveals labeled examples, so students check their own work. Have students sketch in a notebook as they go. About 35–40 minutes.

Grade level
Middle school and high school
Time
40 minutes
Subject
Cell Biology
Slides
3
NGSS
MS-LS1-1, HS-LS1-4

NGSS alignment

Lab steps

  1. Plant cells dividing: onion root tip

    Slide: Onion Root Tip Mitosis (Longitudinal Section)

    • This is the tip of a growing onion root, cut lengthwise. The rounded end is the root cap, which protects the root as it pushes through soil. Just behind it, the cells are small, packed tight, and stained dark. Where along the root do you think new cells are being made? Why?
    • Zoom in on these small, boxy cells. Most have a smooth, round nucleus. These cells are in interphase, not dividing right now. Hunt for cells that look different: • chromosomes lined up across the middle (metaphase) • two groups of chromosomes pulling toward opposite ends (anaphase) Sketch one of each.
    • Check your hunt. The boxes mark one cell in each stage: interphase → prophase → metaphase → anaphase → telophase Do your sketches match? Find a second example of any stage you missed.
    • Pick one patch and count 20 cells. How many are dividing (in any stage except interphase)? If only a few are dividing at any moment, what does that tell you about how much of its life a cell spends dividing?

  2. Animal cells dividing: roundworm eggs

    Slide: Ascaris Female (Cross Section)

    • Now an animal: a cross section of a female roundworm (Ascaris). The two big oval tubes in the middle are full of tiny eggs. Each egg is a single cell that will divide again and again to build a new worm. Why is this a good place to look for mitosis?
    • Zoom in on the eggs. Each one has a thick shell around it. Inside, look for dark chromosomes. In some eggs they are lined up; in others they are pulling apart. Find one egg in metaphase.
    • Check the boxes. Now look closely at "Late cleavage." Instead of building a new wall between the two cells, this cell is pinching in at the middle. How is this different from the way the onion cells divided?

  3. Cells that stopped dividing: cotton leaf

    Slide: Cotton Leaf (Cross Section)

    • This is a slice through a mature cotton leaf. Find the row of tall, tightly packed cells. These palisade cells do most of the leaf's photosynthesis. Look for nuclei inside them. Can you find a single cell that is dividing?
    • Compare this leaf with the onion root tip. Why would a root tip be full of dividing cells while a grown leaf has almost none? Name one place in your own body where cells divide often, and explain why they need to.

Slides used in this lab

Teach it live

Present the lab live and every student screen follows your slide, zoom, and current step, with students joining by room code on Chromebooks, iPads, or any browser, no student accounts. Add the lesson to your library to edit the steps, reorder slides, and add your own teacher notes.

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