Variation
Overview
No two individuals of a species are exactly alike, and that variety is the raw material of evolution. Some differences fall into neat, separate categories; others form a smooth range. Understanding which is which, and where new variation comes from, is the bridge between genetics and natural selection.
In this lesson you will define variation, distinguish continuous from discontinuous variation with examples, link each to its causes, investigate both types, and explain mutation as the source of new alleles, including what raises the mutation rate and (for Extended) the other sources of genetic variation in populations.
Objectives
- Describe variation as differences between individuals of the same species
- State that continuous variation results in a range of phenotypes between two extremes; examples include body length and body mass
- State that discontinuous variation results in a limited number of phenotypes with no intermediates; examples include ABO blood groups, seed shape in peas and seed colour in peas
- State that discontinuous variation is usually caused by genes only and continuous variation is caused by both genes and the environment
- Investigate and describe examples of continuous and discontinuous variation
- Describe mutation as genetic change
- State that mutation is the way in which new alleles are formed
- State that ionising radiation and some chemicals increase the rate of mutation
- [Supplement] Describe gene mutation as a random change in the base sequence of DNA
- [Supplement] State that mutation, meiosis, random mating and random fertilisation are sources of genetic variation in populations
Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Variation. Now that youve explored the key concepts and ideas, its time to put your knowledge to the test. This section offers a variety of practice questions designed to reinforce your understanding and help you gauge your grasp of the material.
You will encounter a mix of question types, including multiple-choice questions, short answer questions, and essay questions. Each question is thoughtfully crafted to assess different aspects of your knowledge and critical thinking skills.
Use this evaluation section as an opportunity to reinforce your understanding of the topic and to identify any areas where you may need additional study. Don't be discouraged by any challenges you encounter; instead, view them as opportunities for growth and improvement.
- Variation is best defined as: A. differences between individuals of different species B. differences between individuals of the same species C. the inheritance of alleles D. a change in the environment Answer: B
- Which is an example of continuous variation? A. ABO blood group B. tongue rolling C. human height D. seed shape in peas Answer: C
- Discontinuous variation is usually caused by: A. the environment only B. genes only C. genes and the environment D. diet only Answer: B
- Mutation is best described as: A. the shuffling of existing alleles B. genetic change that forms new alleles C. a type of meiosis D. an environmental effect Answer: B
- Which factor increases the rate of mutation? A. a balanced diet B. ionising radiation C. regular exercise D. drinking water Answer: B
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Available on the Green Bridge App
Download the Green Bridge CBT app on your phone or computer to access full lesson notes, practice questions, and more.
Recommended Books
Practice Mock Questions
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