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
What a learner can do afterwards
- 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
The lesson
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.
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.
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.
Variation can be continuous or discontinuous, and it comes from genes, environment, or both.
Watch it
Where it sits
This opens up
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.