Cell theory: all living things, including plants, fungi and bacteria, are made of cells. Some organisms are a single cell; others are made of many.
A gum tree, a mushroom, the bacteria in yoghurt and you. One thing they share that a rock, a cloud and a robot don't.
In Year 3 you sorted living from non-living. This lesson gives the deeper reason.
Engage: Commit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Explore: Try it on the board and compare what happens with your prediction.
Explain: Use the particle model to explain what you saw.
Elaborate: Use the same idea in a new context.
Evaluate: Look back at your first ideas and what changed.
WidthMore contexts, same idea.
Make your prediction first. Help opens once you've locked it in.
EngageCommit to a prediction before you test anything. A wrong guess is fine: it shows you what to look for.
Engage: does a tree have cells?
ExploreTry it on the board and compare what happens with your prediction.
Explore: one cell or many?
Each of these is a whole living thing: one cell.
These are two cells out of the many that make up an animal and a plant.
Try it yourselfYour edits are saved in this browser.
Find the cell membrane and cytoplasm in the bacterium and the yeast.
Use the board. This ticks when you get there.
Find the cell membrane and cytoplasm in the animal cell and the plant cell.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: cell theory
In your book: state cell theory, then explain why a mushroom and a bacterium are both living things.
Single-celled or multicellular?
Bacteria in yoghurt
Yeast
A gum tree
A mushroomA mushroom is made of many fungal cells.
An amoeba
You
Elaborate TypicalUse the same idea in a new context.
Elaborate: is it alive?
Made of cells (living, or once living) or not?
A slice of breadOnce living: wheat cells (and dead yeast).
A wooden tableWood is dead plant cells, walls and all.
A pebble
A cotton T-shirtCotton fibres are single plant cells.
Plastic
Elaborate WiderUse the same idea in a new context.
Elaborate: the smallest living thing
EvaluateLook back at your first ideas and what changed.
Evaluate: look back
Write one sentence: "At first I thought… Now I think… because…"
Revision summary
Cell theory: all living things are made of one or more cells; the cell is the smallest unit of life; cells come from other cells.
That includes plants, fungi and bacteria, not only animals.
Single-celled organisms (bacteria, yeast) are one cell doing everything; multicellular organisms are many cells working together.
For teachers
Students state cell theory, explicitly including plants, fungi and single-celled organisms, and distinguish single-celled from multicellular organisms (AC9S8U01, node 2, a hinge node). About 20 minutes.
I can explain that plants, fungi and bacteria are made of cells too.
I can give examples of single-celled and multicellular organisms.
Before class
A concept tutorial for introducing or revising the idea; it does not replace microscope work (onion skin, cheek cells, yoghurt bacteria). Set the width with ?width=minimum, typical (default) or wider.
The hinge misconception is that only animals have cells. The Explore step shows a bacterium and yeast before any animal cell.
Board notes: diagrams are simplified models, not to scale; students click parts to name them, and a tick marks each found.
Running the lesson
Engage: count how many chose 'only animals' or 'animals and plants'.
Explore: ask what every diagram had (membrane, cytoplasm).
Explain: the first question is the checkpoint; the sort includes the mushroom on purpose.
The hard part (on purpose)
Accepting that trees, fungi and bacteria are made of cells too. When a student says a plant isn't, ask what they found when they zoomed in on it.
When students get stuck
A student says a tree isn't made of cells. Ask: What did you find in the plant cell on the board? Fix: A membrane, cytoplasm and more: a leaf is made of millions of cells like it.
A student says bacteria aren't alive. Ask: Do bacteria feed, grow and reproduce? Fix: Yes: each one is a whole living cell.
Stretch and support
Stretch: Why can't a single cell grow as big as a cat? Think about getting food in through the membrane.
Support: Give a three-column card (bacterium, plant cell, animal cell) to tick the parts found in each.
Where it leads
Next: the parts every cell shares (node 3), then plant cells' extra parts (node 4).
In class: onion epidermis with iodine and cheek cells with methylene blue under a microscope.
What each step is for
Engage: does a tree have cells?: Students who think only animals have cells will say no; the board shows plants, fungi and bacteria as cells too.
Explore: one cell or many?: Finding the same basic parts in a bacterium, a yeast cell, a plant cell and an animal cell makes 'all living things are cells' concrete.
Explain: cell theory: Stating cell theory and sorting organisms explicitly includes the plants and microbes students don't expect.
Elaborate: is it alive?: Using cells as the test for living sharpens the Year 3 distinction.
Elaborate: the smallest living thing: Asking what the minimum for life is uses cell theory to reason about a boundary case.
Now you can
State cell theory.
Explain that plants, fungi and bacteria are made of cells too.
Give examples of single-celled and multicellular organisms.