Variation and mutation Cambridge IGCSE Biology (9–1) revision
Not started
Learn it
In plain words
No two people are exactly alike, not even brothers and sisters. Some differences fall into clear groups: your blood group is A, B, AB or O, nothing in between. Others shade gradually from one extreme to the other, like height. Differences come from genes, from surroundings, or both.
Three things to know
- Discontinuous variation has a few distinct categories with nothing in between (blood group). It is caused by genes alone. Continuous variation has a complete range of values (height, mass). It is caused by genes and the environment together.
- A mutation is a change in a gene (a random change in the base sequence of DNA). It is how new alleles appear.
- Mutations happen naturally at random. Ionising radiation and some chemicals make them more likely.
Tips and tricks
- Discontinuous: bar chart, separate bars. Continuous: histogram, a smooth hump with most people in the middle.
- Most mutations have no effect; some are harmful; a few are useful.
It lands in your notebook with its questions as flashcards.
Variation and mutation: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Which is an example of discontinuous variation?
There are only four categories.
What causes continuous variation?
Height depends on your genes and on things like diet.
What is a mutation?
It is a random change in the DNA.
Which increases the rate of mutation?
Radiation can damage DNA.
How do new alleles arise?
Mutation is the only source of new alleles.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 6 marks. Write your answers on paper, then check them.
Variation and mutation
Cambridge IGCSE Biology (9–1) 0970 · 6 marks · papermunch.org
Name ______________________________ Date ______________
State the difference between continuous and discontinuous variation, with an example of each.[2]
Show answerHide answer
Continuous variation shows a range of values between two extremes, such as height. Discontinuous variation has a limited number of distinct categories, such as blood group.
State what is meant by a mutation, and give one thing that increases the rate of mutation.[2]
Show answerHide answer
A genetic change (a random change in the base sequence of DNA). Ionising radiation, or some chemicals.
Two plants grown from cuttings of the same parent are genetically identical, but one is taller. Suggest why.[2]
Show answerHide answer
Their environments differ: one had more light, water, minerals or warmth.
Answers: Variation and mutation
- 1. Continuous variation shows a range of values between two extremes, such as height. Discontinuous variation has a limited number of distinct categories, such as blood group.
- 2. A genetic change (a random change in the base sequence of DNA). Ionising radiation, or some chemicals.
- 3. Their environments differ: one had more light, water, minerals or warmth.