Why No Two People Are Exactly the Same

Science · Ecosystems & Habitats · ages 12-13

Name ______________________ Date ____________

Which of these is an example of discontinuous variation?
- Weight
- Blood group
- Arm length
Which of these is an example of continuous variation in humans?
- Height
- Blood group
- Sex (male or female)
Environmental causes of variation include things like diet and sunlight.
Circle one: True False
Look at the graph of student heights. Which range has the most students?
- 140-150cm
- 160-170cm
- 180-190cm
Twins Alex and Sam have the same genes. Alex plays outside every day and has a deep tan. Sam stays inside and is pale. What causes this difference?
- Genetic variation
- Environmental variation
- Discontinuous variation
Maya has curly hair like her mother and grandmother. What kind of cause explains this?
- Genetic, inherited through genes
- Environmental, caused by diet
- Discontinuous, caused by blood group
A gardener grows new plants two ways: from seeds (sexual reproduction) and from cuttings of one parent plant (asexual reproduction). Which group will show more variation?
- The plants grown from cuttings
- Both will show exactly the same variation
- The plants grown from seeds
A farmer says: 'My cloned plants are genetically identical, so growing them in richer soil next year will make no difference to how they turn out.' What's wrong with this claim?
- Nothing, clones can't show any variation at all
- Even genetically identical plants can vary due to environmental differences like soil quality
- Clones only show discontinuous variation, never continuous

Answer key

For grown-ups. Fold this page away before handing over the rest.

Blood group · Blood group fits into a few distinct categories (A, B, AB, O), with nothing in between. Weight and arm length can take any value across a range.
Height · Height can take any value across a range, so it's continuous. Blood group and sex fall into separate categories, so they're discontinuous.
True · Diet, sunlight, and exercise are all part of your environment, and they can change traits like weight, skin tone, and muscle size.
160-170cm · The tallest bar, 160-170cm, has 14 students, more than any other range.
Environmental variation · Alex and Sam share the same genes, so the tan comes from their environment, time spent in the sun, not from inherited differences.
Genetic, inherited through genes · Hair type passed down through a family is inherited through genes, so it's a genetic cause of variation.
The plants grown from seeds · Seeds come from mixing genes from two parent plants, creating new combinations. Cuttings are copies of one parent, so they're nearly identical.
Even genetically identical plants can vary due to environmental differences like soil quality · Genetically identical plants can still look different if they grow in different environments, like richer or poorer soil. Genes aren't the only cause of variation.