Almost all your cells have the same DNA, but they specialise: each develops a shape and contents that suit its job, like a red blood cell packed with haemoglobin or a nerve cell with a long axon.
A nerve cell in your leg can be a metre long. A red blood cell is a tiny squashed disc with no nucleus. Same DNA, same body. Why so different?
Last unit: what all cells share. This one: why they differ.
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: same DNA?
ExploreTry it on the board and compare what happens with your prediction.
Explore: four specialised cells
Try it yourselfYour edits are saved in this browser.
Find every part of the red blood cell and the nerve cell.
Use the board. This ticks when you get there.
Find every part of the muscle cell and the root hair cell.
Use the board. This ticks when you get there.
ExplainUse the particle model to explain what you saw.
Explain: shape suits job
In your book: choose one specialised cell and explain two of its features and how each helps.
Match each feature to how it helps.
Red blood cell: no nucleus
Nerve cell: long axon
Muscle cell: many mitochondria
Root hair cell: long extension
Elaborate TypicalUse the same idea in a new context.
Elaborate: design a cell
Elaborate WiderUse the same idea in a new context.
Elaborate: energy-hungry cells
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
Nearly all your cells have the same DNA; each specialised cell uses different instructions.
A specialised cell's shape and parts suit its job: red blood cells (no nucleus, haemoglobin), nerve cells (long axon), muscle cells (many mitochondria), root hair cells (long extension, no chloroplasts).
For teachers
Students explain that cells with the same DNA specialise, and describe how structural features of specialised cells serve their functions (AC9S8U02, node 1, a hinge node). About 25 minutes.
I can describe two features of a specialised cell and explain how each helps.
I can explain that cells with the same DNA can specialise for different jobs.
I can link a cell's contents (such as mitochondria) to its job.
Before class
A concept tutorial for introducing or revising the idea; it does not replace prepared slides of blood, nerve and muscle tissue. Set the width with ?width=minimum, typical (default) or wider.
The hinge is the structure-function link. Students who list features without the "so that" cannot reason about tissues and organs.
Board notes: diagrams are simplified and not to scale (a nerve cell's axon can be a metre long).
Running the lesson
Engage: the 'different DNA' choice is the misconception to resolve.
Explore: after each cell, ask for one feature and its 'so that'.
Explain: the match covers four cells; the root hair question returns to the DNA idea.
The hard part (on purpose)
Linking each feature to its job ('so that…'). When a student lists features, ask 'so that what?'
When students get stuck
A student says red blood cells lost their nucleus by accident. Ask: What gets more room without it? Fix: Haemoglobin, so it carries more oxygen. It's a feature, not damage.
A student lists features without functions. Ask: So that what? Fix: Each feature: '…, so that the cell can …'.
Stretch and support
Stretch: Stem cells can become many types of cell. Why might that be useful in medicine?
Support: A frame: 'The ___ cell has ___ so that it can ___.'
Where it leads
Next: tissues (node 2), then organs built from tissues (node 3).
In class: prepared slides of blood smear, muscle and nerve tissue; a cheek-cell versus onion-cell comparison.
What each step is for
Engage: same DNA?: Students who think different cells have different DNA will choose that; specialisation by using different instructions is the idea the node needs.
Explore: four specialised cells: Clicking each feature and reading its purpose links structure to function cell by cell.
Explain: shape suits job: Explaining features as adaptations, not labels, is the hinge for tissues and organs.
Elaborate: design a cell: Predicting the features a job needs reverses the reasoning: function to structure.
Elaborate: energy-hungry cells: Comparing organelle numbers across cells extends specialisation from shape to contents.
Now you can
Describe two features of a specialised cell and explain how each helps.
Explain that cells with the same DNA can specialise for different jobs.
Link a cell's contents (such as mitochondria) to its job.