Continuous And Discontinuous Variation
Overview
Tip a bag of garden pea seeds onto a bench and sort them by shape. You finish with two heaps, round and wrinkled, and nothing at all in the space between them: no seed is halfway. Now put those same seeds on a balance, one at a time. This time hardly any two readings match, and every value between the lightest seed and the heaviest is filled in by something in the bag. One handful of seeds, one species, two completely different shapes of difference.
That contrast is the whole of this lesson. You will learn what puts a characteristic into distinct groups and what spreads it smoothly across a range, why some differences are written into an organism at fertilisation while others are picked up during its life, and how to handle the numbers: building a frequency table, choosing between a bar chart and a histogram, estimating a mean from grouped data, picking a sensible sample and spotting the moment a conclusion runs further than the evidence behind it.
Objectives
- The causes of variation include: genetic variation - different characteristics as a result of mutation or reproduction; environmental variation - different characteristics caused by an organism’s environment (acquired characteristics).
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Continuous And Discontinuous 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.
- Which characteristic shows discontinuous variation? A. Body mass B. Hand span C. Seed shape in garden peas D. Height Answer: C
- Continuous variation in a population is usually caused by A. one gene only, with no environmental effect B. many genes together with environmental effects C. the environment only, with no genetic effect D. a single mutation in one individual Answer: B
- Which of these is an acquired characteristic? A. Sex in humans B. A suntan gained during a summer holiday C. A wrinkled pea seed D. Brown eye colour Answer: B
- In a sample of 200 snails, 90 had yellow shells. What percentage of the sample had yellow shells? A. 9% B. 22.5% C. 45% D. 90% Answer: C
- Which process is the original source of new alleles in a population? A. Sexual reproduction B. Asexual reproduction C. Mutation D. Environmental variation Answer: C
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