Reproduction
Overview
Pull a strawberry plant out of a bed in late summer and you will find it trailing a thin horizontal stem across the soil, with a small rooted plant at the far end. That little plant had no other parent. Every base in its DNA came from the plant you are holding. A few metres away, a bee is carrying pollen between two flowers, and the seed that results from that visit will carry instructions from two different individuals. Both events are reproduction, and the difference between them shapes almost everything that follows in genetics.
This lesson takes the two forms apart. You will see what a gamete is and what actually happens when two of them fuse, why that fusion produces offspring that resemble their parents without copying either of them, and why reproduction from a single parent gives offspring so alike that biologists call them clones. Then you will weigh the two against each other the way this board does: not asking which is better, but asking which one wins in a particular field, on a particular farm, in a particular changing climate. It is a short piece of specification with a long reach, and the Extension Tier biology paper spends fifteen marks on it in a single question.
Objectives
- There are two forms of reproduction: sexual reproduction - the joining (fusion) of male and female gametes. The mixture of the genetic information from two parents leads to variety in the offspring; asexual reproduction - no fusion of gametes and only one individual is needed as the parent. There is no mixing of genetic information and so no genetic variation in the offspring. These genetically identical individuals are known as clones.
Mind map
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Lesson Note
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Lesson Evaluation
Congratulations on completing the lesson on Reproduction. 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 statement about asexual reproduction is correct? A. Two parents are needed B. Male and female gametes fuse C. The offspring are genetically identical to the parent D. The offspring show a wide range of genetic variation Answer: C
- A human body cell contains 46 chromosomes. How many chromosomes are in a human sperm cell? A. 11 B. 23 C. 46 D. 92 Answer: B
- What is a clone? A. A cell formed when two gametes fuse B. Genetically identical individuals produced from one parent C. A sex cell with a single set of chromosomes D. An offspring produced from two parents of different varieties Answer: B
- Which of these plants was produced by sexual reproduction? A. A potato plant grown from a tuber B. A strawberry plant at the end of a runner C. A plant grown from a seed D. A daffodil grown from a bulb Answer: C
- A body cell of a plant contains 24 chromosomes. How many chromosomes are in the nucleus of one of its pollen grains? A. 6 B. 12 C. 24 D. 48 Answer: B
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