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LESSON VI:
SEXUAL REPRODUCTION
To Address NYS Standards:
2 (Organisms inherit genetic information in a variety of ways that result in continuity of
structure and function between parents and offspring) and 4 (The continuity of life is
sustained through reproduction and development).
Behavioural Objective:
The students will be able to accurately and sensibly connect the concept of meiosis with
the benefits of recombination and sexual reproduction. Students will also understand the
varied means of sexual reproduction in bacteria, algae, and animals. Human reproduction
will be covered in a later lesson
Explanation of Lesson Plan:
This lesson will acquaint students with the basic notions behind sexual reproduction.
Students will compare and contrast their ideas on asexual reproduction and sexual
reproduction to generate a list of benefits and detriments. Students will discover the
ultimate purpose of the haploid cells produced by meiosis.
Hook: (3 minutes)
“So far we’ve seen that organisms grow by mitosis and at the proper age, begin to
produce gametes by meiosis. Now, our goal is to get those gametes aReal intimate, and
see what happens. What do you know about sexual reproduction?”
Test of Prior Learning: (5 minutes)
1. Sex cells are called what? What is their ploidy?
2. Why can they combine successfully?
3. Why is this combination good?
New Learning: (30 minutes)
1. When we think of sexual reproduction, we usually think of mammalian reproduction.
There are, of course, a bout a bah-jillion different organisms, each with their own way of
sexually reproducing.
2. Spirogyra bacteria are haploid in their adult stage, and therefore, when they combine,
form a diploid zygote. How do you suppose it gets back to a haploid organism?
(meiosis)
3. Bacteria can use sex pili to transfer plasmids from one organism to the other.
4. Often, these organisms are not male or female, but + or – mating types.
5. Paramecia can conjugate to exchange genetic material. They have two nuclei, both of
which play a distinct role.
6. The goal, however, is to get back to whatever you started with, except with plants,
‘cause they’re all screwy.
7. This diagram will be placed on a poster and conspicuously displayed in the classroom
for present and future reference.
8. Humans do the same thing, only they produce motile (contrast with mobile) sperm,
and eggs. The two combine to make a diploid zygote. When they combine, something
interesting happens. The egg has a reaction that uses calcium to prevent another sperm
from fertilizing the egg. Why?
Test of New Learning: (5 minutes)
1. What is the goal of sexual reproduction?
2. What are some benefits of asexual reproduction?
3. What can go wrong with sexual reproduction?