---
title: "Variation in Species"
description: "Explain variation within and between species, distinguishing between continuous variation (e.g. height) and discontinuous variation (e.g. blood group), and between genetic and environmental causes"
canonical: https://lightmysky.com/learn/science/variation-in-species-mt_k1HXbEwG8f
source: https://lightmysky.com/learn/science/variation-in-species-mt_k1HXbEwG8f.md
retrieved: 2026-10-19
---

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# Variation in Species

Explain variation within and between species, distinguishing between continuous variation (e.g. height) and discontinuous variation (e.g. blood group), and between genetic and environmental causes

Subject: Science · Area: Ecosystems & Habitats · Ages 12 to 13
Page: https://lightmysky.com/learn/science/variation-in-species-mt_k1HXbEwG8f

## Ready when they can

- Gives examples of continuous and discontinuous variation in humans
- Distinguishes between genetic causes of variation (inherited differences) and environmental causes (diet, sunlight, etc.)
- Explains why sexual reproduction produces greater variation than asexual reproduction
- Draws or interprets a frequency graph showing continuous variation

## Lesson: Why No Two People Are Exactly the Same

Look around a classroom. No two people are exactly the same height, hair colour, or eye colour, even though everyone belongs to the same species: human. These differences between individuals are called variation. Variation comes in two types. Continuous variation is a whole range of values with no clear gaps, like height. Discontinuous variation falls into a few separate groups with nothing in between, like blood group.

*(drawing: Most students cluster in the middle heights, with fewer very short or very tall. This hump shape is typical of continuous variation.)*

**Example.** Priya's class tested their blood groups. Everyone fit cleanly into one group: A, B, AB, or O. Nobody was half A and half B. That's discontinuous variation: separate categories, no in-between.

Some variation comes from the genes you inherit from your parents. Blood group and eye colour are almost entirely genetic. Other variation comes from your environment: a suntan, a scar, or bigger muscles from exercise. Many traits, like height, come from both. Your genes set a range, and things like diet and health push you up or down within it.

**Tip.** Sexual reproduction mixes genes from two parents, so offspring get a new combination every time. Asexual reproduction just copies one parent's genes, so the offspring is nearly identical to it. That's why species that reproduce sexually show more variation.

**Recap.** Variation can be continuous or discontinuous, and it comes from genes, environment, or both.

## Practice

8 questions on this page, each with its working shown.

## Needs first

- [Chromosomes, Genes & DNA](https://lightmysky.com/learn/science/chromosomes-genes-and-dna-mt_6aJUzBYGNs)
- [Grouping Living Things](https://lightmysky.com/learn/science/grouping-living-things-mt_AylKwhbDWM)
- [Traits: inherited and environmental](https://lightmysky.com/learn/science/traits-inherited-and-environmental-mt_Tls5qJ4p0L)

## Opens up

- [How Natural Selection Works](https://lightmysky.com/learn/science/how-natural-selection-works-mt_FuVEZ1Ac9s)