Taught through Elvis, panther chameleon
Approx. 50 minutes · KS4 · Also usable as two 25-minute halves
Before you start
Elvis is a real panther chameleon. He lives at Pets on the Green in Warlingham, Surrey. Everything in this lesson describes an animal you can look at.
There is no timer on this lesson. You can stop at any point and the lesson will be where you left it.
What you'll be able to do by the end
- Explain what an adaptation is, and why "it wants to" is never the answer.
- Sort adaptations into structural, behavioural and functional.
- Explain how an adaptation arises through natural selection, using the right words in the right order.
- Correct the most common exam mistake on this topic.
Part 1 — The thing everyone gets wrong
Ask most people why a chameleon changes colour and they will say camouflage.
They are wrong, and Elvis is the proof.
Elvis does not change colour to hide. A panther chameleon's colour change is mostly about temperature and signalling. He goes darker when he is cold, because darker skin absorbs more heat. He goes bright and bold when he is displaying — to a rival male, or to a female. He goes pale and washed out when he is stressed or unwell.
His keeper reads his colour every morning the way you would read a thermometer and a mood at the same time.
Check yourself
Elvis has gone dark brown-grey and is sitting directly under his basking lamp.
What is the most likely explanation, and what evidence in the description supports it?
Answer
He is cold and is warming up. Darker pigment absorbs more radiation, so darkening increases the rate at which he gains heat. The evidence is his position — directly under the heat source. If this were a display, you would expect bright colour and another chameleon present.
Part 2 — What an adaptation actually is
An adaptation is a feature that makes an organism better suited to its environment, and so more likely to survive and reproduce.
Three types. Elvis has all three.
Structural — the body itself
| Feature | What it does |
|---|---|
| Zygodactyl feet — two toes one way, two the other | Grips branches like a clamp. He is arboreal; the ground is not where he lives. |
| Independently moving eyes | Two fields of view at once — one scanning for predators while the other tracks prey. |
| Projectile tongue, longer than his body | Reaches prey without moving his body and giving away his position. |
| Prehensile tail | A fifth limb. Anchors him while both front feet are busy. |
| Laterally flattened body | Casts a narrow shadow and resembles a leaf from the side. |
Behavioural — what he does
- Moves in a slow rocking motion, matching leaves in wind, rather than walking in a straight line.
- Basks under heat in the morning and retreats to shade at midday — thermoregulation by relocation.
- Displays bright colour at a rival rather than fighting him. A fight risks injury; a display costs nothing but pigment.
Functional — what his body does internally
- Colour change through specialised pigment cells, controlled by his nervous system.
- Water absorbed from droplets on leaves rather than standing water — which is why a chameleon will die of dehydration beside a full water bowl if nobody is misting the enclosure.
Check yourself
Sort each into structural, behavioural or functional:
- Rocking as he walks
- Tongue projection
- Darkening under a heat lamp
- Retreating to shade at midday
Answers
1. Behavioural. 2. Structural (the tongue itself) — though the firing of it is functional. 3. Functional. 4. Behavioural.
If you put 2 in "functional," look at what the question is pointing at. A structure is a thing. A function is a process.
Part 3 — Where adaptations come from
This is the part that carries the marks, and the part most answers get muddled.
An adaptation is not something an animal develops because it needs it. Elvis's ancestors did not grow gripping feet because they wanted to climb.
The sequence is always the same:
- Variation. Within a population of chameleons, foot shape varied. Some grip better than others. This variation comes from mutation and is random — it is not produced on demand.
- Selection pressure. Life in trees. A chameleon that falls is a chameleon that is eaten or injured.
- Differential survival. Those with better grip survive more often and for longer.
- Reproduction. Survivors breed. The alleles for better grip are passed on.
- Change over generations. The proportion of the population with gripping feet rises. Repeat over a very long time.
Write "chameleons developed gripping feet in order to climb" and you have described the wrong mechanism. Write "chameleons with better grip were more likely to survive and reproduce, so passed on those alleles" and you have described the right one. The content is the same. The marks are not.
Check yourself
Rewrite this so it would score:
"Chameleons grew longer tongues so they could catch insects further away."
Model answer
Tongue length varied within the population due to random mutation. Chameleons with longer tongues could catch prey at greater distance without moving and exposing themselves, so were more likely to survive and reproduce. They passed the alleles for longer tongues to their offspring, so over many generations longer tongues became more common in the population.
Note what changed: no intention, a source of variation, a reason survival differs, and inheritance. Four things. Get all four in and the answer is complete.
Part 4 — Exam-style questions
1. Elvis's eyes can move independently of each other. Explain how this adaptation increases his chance of survival. (2 marks)
Mark scheme
1 mark: he can watch two directions at once / scan for predators while tracking prey.
1 mark: linked to survival — earlier detection of a predator, or more successful feeding.
Both marks need the link. "He can see two ways" alone is 1 mark.
2. A student says: "Chameleons change colour to camouflage themselves from predators." Using what you know about panther chameleons, evaluate this statement. (4 marks)
Mark scheme
Credit for: colour change is primarily thermoregulatory and for signalling (1); darker colour absorbs more radiation when cold (1); bright colour used in display to rivals or mates (1); acknowledgement that body shape and slow movement do contribute to concealment, so the statement is not wholly wrong (1).
Top answers say what the statement gets wrong and what it gets partly right. An evaluate question wants a judgement, not a contradiction.
3. Panther chameleons obtain water from droplets on leaves rather than from standing water. Explain how a keeper who does not know this could cause the animal's death, and describe the correct provision. (3 marks)
Mark scheme
1 mark: the chameleon may not recognise still water in a bowl as a water source.
1 mark: it will become dehydrated despite water being present.
1 mark: correct provision — regular misting or a drip system producing moving droplets on foliage.
4. Explain, in terms of natural selection, how a population of chameleons came to have prehensile tails. (4 marks)
Mark scheme
1 mark: variation in tail-gripping ability, caused by mutation.
1 mark: those with better grip more likely to survive in an arboreal habitat.
1 mark: survivors more likely to reproduce and pass on the alleles.
1 mark: over many generations the proportion with prehensile tails increases.
Any answer using "wanted," "needed" or "in order to" as the mechanism cannot access the full marks.
If you want to go further
- Watch the live animal cams and see how many of the adaptations in Part 2 you can spot in a different species.
- Elvis's care guide has the full husbandry picture, including what his heating and misting actually cost to run.
- Related lessons: Natural Selection · Classification · Homeostasis and Thermoregulation.
Notes for the adult
Curriculum: GCSE Biology, adaptation and natural selection. Mapped to specification content on adaptations, competition, and inheritance of advantageous characteristics.
The misconception this lesson targets: teleology — the belief that organisms develop features because they need them. It is the single most common reason students lose marks on this topic. The lesson names it explicitly in Part 3 rather than hoping it corrects itself.
Running it in halves: Parts 1–2 stand alone as a 25-minute session on what adaptations are. Parts 3–4 are the natural selection half and assume Parts 1–2 have been done.
Access: read-aloud, dyslexia-friendly font, enlarged text, high contrast and calm mode are available on every page and can be changed mid-lesson. Answer sections are collapsed by default so the page is not visually crowded; they can be set to open by default if a learner finds hidden content distracting.
No timing, no scoring. The check-yourself sections and exam questions are not marked, logged or reported. A learner can look at an answer immediately without it counting against them.
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