---
title: "How different are individuals?"
subtitle: "Year 10 Biology · Evolution · Lesson 4"
---

# How different are individuals?

**Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}}

> **Key question:** Look closely at a patch of grass beetles, a school of fish or a class of Year 10s. No two are quite the same. That spread is the raw material of evolution.


:::teacher-note

**In one sentence:** Students measure variation in a population, distinguish continuous from discontinuous and inherited from environmental variation, and explain why inherited variation matters for evolution (AC9S10U02, node 1, a hinge node).

**Students should be able to say:** I can describe the variation in a measured population. I can classify variation as continuous or discontinuous, inherited or environmental. I can explain why only inherited variation is passed on.

**Width:** the unmarked parts are the floor every student does (Engage, Explore, Explain, Evaluate). Typical and Wider sections add contexts, not difficulty. Students work in the online tutorial alongside this sheet.

:::


## Engage


:::keep-together

**You measure the colour of 20 beetles of one species from the same field. What do you predict?**

☐ Completely random: no pattern

☐ A spread of colours, with most near the middle and a few very pale or very dark

☐ They're all the same colour: same species

☐ Two colours only

My prediction, and why:

{{lines-3}}

:::


:::teacher-note

**What happens:** A spread, with most near the middle and fewer at the extremes. A characteristic controlled by many genes usually varies continuously like this.

:::


## Explore

Try it on the board in the tutorial. Was your prediction right? What was different?

{{lines-2}}

## Explain: kinds of variation


:::keep-together

### Continuous or not

**Continuous (any value in a range) or discontinuous (a few distinct groups)?**

Groups: Continuous, Discontinuous

- Height: {{field-15}}
- Blood group (A, B, AB, O): {{field-15}}
- The beetles' colour: {{field-15}}
- Pea flower colour (purple or white): {{field-15}}
- Hand span: {{field-15}}

:::


:::teacher-note

**Answer:** Height → Continuous; Blood group (A, B, AB, O) → Discontinuous; The beetles' colour → Continuous; Pea flower colour (purple or white) → Discontinuous; Hand span → Continuous

:::


:::keep-together

### Where it comes from

**Mainly inherited, mainly environmental, or both?**

Groups: Inherited, Environmental, Both

- Blood group: {{field-15}}
- A scar: {{field-15}}
- Height: {{field-15}}
- Natural eye colour: {{field-15}}
- Speaking French: {{field-15}}

:::


:::teacher-note

**Answer:** Blood group → Inherited; A scar → Environmental; Height → Both; Natural eye colour → Inherited; Speaking French → Environmental

:::


:::keep-together

### What gets passed on

**Why does only inherited variation matter for evolution?**

☐ Environmental variation isn't real

☐ Environmental variation only happens in humans

☐ Only inherited characteristics are passed to offspring through genes

☐ Inherited variation is bigger

:::


:::teacher-note

**Answer:** Only inherited characteristics are passed to offspring through genes

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:::typical

## Elaborate: where variation comes from


:::keep-together

**Which of these makes new inherited variation in a population?**

☐ The environment changing an animal's genes to suit it

☐ Animals trying hard to change

☐ Eating different food

☐ Mutations, plus new combinations of alleles from meiosis and fertilisation

:::


:::teacher-note

**Answer:** Mutations, plus new combinations of alleles from meiosis and fertilisation

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:::


:::wider

## Elaborate: sampling


:::keep-together

**Someone measures only the 5 easiest-to-spot beetles and says the population is mostly dark. What's wrong?**

☐ Beetles can't be measured

☐ They should have measured only pale beetles

☐ Nothing: 5 is enough

☐ The sample is small and biased: the easiest beetles to spot aren't typical

:::


:::teacher-note

**Answer:** The sample is small and biased: the easiest beetles to spot aren't typical

:::

:::


## Evaluate: look back

Write one sentence: "At first I thought… Now I think… because…"

**Revision summary**

- Individuals in a population **vary**; measuring a characteristic gives a **spread**.
- **Continuous** variation takes any value (height); **discontinuous** falls into groups (blood group).
- Variation can be **inherited**, **environmental** or both; only inherited variation is passed on, so only it matters for evolution.
- New inherited variation comes from **mutations** and from **meiosis and fertilisation**.

## Exit ticket

:::keep-together

**Give an example of inherited variation and one of environmental variation in humans.**

{{lines-3}}

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:::teacher-note

**Answer:** For example: blood group (inherited); a scar or a language spoken (environmental).

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