Unit 4, Chapter 12, Section 2- Meiosis

Biology-The Dynamics of Life, Glencoe, pp. 298-305

Introduction:

The teacher will briefly introduce the day’s topic of meiosis by stating that meiosis is a kind of cell division that produces gametes containing half the number of chromosomes as a parent’s body cell. The students will then be shown a video of the steps of meiosis using the laserdisc player.

Objective and Purpose:

At the end of this lesson, the students will be able to:

· Distinguish between diploid and haploid cells

· Describe homologous chromosomes

· Explain the steps of meiosis

· Discuss how meiosis allows for genetic variation and explains Mendel’s results

The purpose of this lesson is to understand the process of meiosis because it allows for the process of heredity that we discussed in the previous lesson.

Instructional Input:

The teacher will provide the following input:

· Introduce the terms diploid and haploid cells

· Discuss the relationship of homologous chromosomes to diploid cells

· Explain why meiosis, rather than mitosis, is the form of cell division that allow offspring to have the same number of chromosomes as their parents

· Go through the steps of meiosis I & II using the overhead picture to illustrate

· Discuss how meiosis allows for genetic variation and explains Mendel’s results

The laserdisc video will then be shown again so that the students can see the phases as they actually occur and visually reinforce what we have just discussed.

Guided Practice:

The students will be shown an overhead with illustrations of the phases of meiosis in random order. They will then be asked to draw and label the phases in correct order and write a description of what is occurring at each step.

Independent Practice:

The students will read chapter 12, section 2, answer the following questions from p.304, and define the following terms from p.298.

1. How are the cells at the end of meiosis different from the cell at the beginning of meiosis? Use the terms chromosome number, haploid, and diploid in your answer.

2. What is the role of meiosis in maintaining a constant number of chromosomes in a species?

3. Why are there so many varied phenotypes within a species such as humans?

4. How do the events of meiosis explain Mendel’s law of independent assortment?

Terms:

Diploid

Haploid

Homologous chromosome

Meiosis

Sperm

Egg

Zygote

Sexual reproduction

Crossing over

Genetic recombination

Closing:

You are now beginning to understand the process of meiosis and why it is relevant to science. Your homework assignment will also reinforce what we have gone over today, and you will see how this ties to Mendel and heredity.