--- title: "Variation in Species" description: "Explain variation within and between species, distinguishing continuous variation (e.g. height) from discontinuous variation (e.g. ABO blood group), and genetic causes from 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: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Variation in Species Explain variation within and between species, distinguishing continuous variation (e.g. height) from discontinuous variation (e.g. ABO blood group), and genetic causes from 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 usually produces more genetic variation among offspring than asexual reproduction - Interprets a frequency graph showing continuous variation ## Lesson: Variation Within and Between Species Variation means differences in traits. Members of one species, such as humans, can differ in height or hair texture. Species also differ from one another, such as cats with fur and birds with feathers. Continuous variation includes intermediate measurements across a range, like height, mass or arm length. Discontinuous variation has separate categories, like ABO blood group. *(drawing: Invented heights of 21 students, in cm. Each number above a bar counts the students in that range.)* **Example.** In the ABO system, each person has blood group A, B, AB or O. AB is a separate category, not a halfway measurement between A and B. The example chart counts people in each group. Frequency means how many observations fall in a group or range. Compare the numbers above the bars to find the largest frequency. Height ranges must not overlap: 145 to <155 cm means at least 145 cm but less than 155 cm. Genes inherited from parents influence ABO blood group, eye colour and natural hair texture. Diet, sunlight, health and exercise are environmental factors. Extra sunlight can cause a tan, although genes affect skin colour and tanning too. Height depends on both genes and environment. Plants with the same genes can grow differently in different soils. Family resemblance can support an inherited explanation, but does not prove the cause. Sexual reproduction joins genetic material from egg and sperm cells, usually from two parents. Some plants can self-fertilise. Offspring from sexual reproduction usually have more genetic variation than asexual offspring from one parent because they inherit different combinations of genes. Cuttings usually copy a plant's genes. Mutations are changes in DNA and can create genetic differences in either group. Growing conditions can affect both groups. **Recap.** Variation can be continuous or discontinuous, and it comes from genes, environment, or both. *Lesson, questions and flashcards written for this dataset. OpenStax records were studied for scientific background.* ## 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) ## Optional connections - [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)