SEXUAL REPRODUCTION
Engage
10 MINUTES
To engage students I begin the lesson by explaining that all living things have the following
characteristics in common:
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made of cells
use energy
grow and develop
respond to their surroundings
Then ask students to name one other characteristic that all organisms have in common. (All
organisms reproduce, for example.) Following this brainstorm, focus the rest of the
discussion on reproduction, reminding students that one of the most important things an
organism can do is reproduce. Ask:
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What is the result of reproduction?
Why do organisms bother to reproduce? Why don't they just live forever?
What would eventually happen to a species if every member suddenly lost its ability to
reproduce?
Since the focus of this lesson is asexual reproduction I show the following two videos.
The first video, Cell division of E. coli with continuous media flow, shows the asexual
reproduction of E. coli. The second video is a clip of the movie Multiplicity, which shows
how the main character of the movie, Michael Keaton, has been cloned.
The objective of showing both of these videos is to communicate the idea that asexual
reproduction leads to genetically identical offspring, which can have both positive and
negative results. (MS-LS3-2 - Develop and use a model to describe why asexual
reproduction results in offspring with identical genetic information and sexual reproduction
results in offspring with genetic variation/ CCC - Cause and Effect - Cause and effect
relationships may be used to predict phenomena in natural systems.)
To guide students in seeing this relationship between both videos I have students answer
the following questions:
1. Describe what is occurring in the first video.
2. Does this type of reproduction occur quickly? What can be advantage of this type of
reproduction?
3. In this type of reproduction the off spring are genetically identical. Do you think this is a
benefit or a detriment to the organism? Please explain.
4. What do you notice about the characters in the second video?
5. What is the relationship between the first video and second?
6. What would be some positive or negative outcomes if humans reproduced this way, in
other words if were all genetically identical?
Explore
20 MINUTES
Students in this section explore the The Mating Game PBS Learning media web activity in
pairs. The objective of this activity is for students to see the elaborate and at times costly
reproductive strategies of various species. (MS-LS3-2 Develop and use a model to
describe why asexual reproduction results in offspring with identical genetic information and
sexual reproduction results in offspring with genetic variation/SP2 Developing and Using
Models)
Part 1
It is recommended that students play two rounds of the game and then choose four of the
species highlighted in the activity's Dating and Mating Gallery. Ask students to take notes
on the information provided about each species, focusing on the reproductive similarities
and differences among them. Have pairs of students present their findings to the class while
you record the various reproductive strategies on the board.
Part 2
Ask the class to rank the reproductive strategies on the board in order of relative difficulty, or
"expense," to the animal. For example, the tube sponge's strategy of casting out clouds of
sperm or egg cells into the open water is relatively less expensive than the bowerbird's
efforts to attract a mate by building an elaborate bower. Ask students:
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What are some of the things that animals can't do when they're focusing so much time
and energy on finding or attracting a mate?
What proportion of each parent's genetic material would the offspring of any of these
species have?
Part 3
Ask students to consider why some species might have evolved reproductive strategies that
require a lot of energy and that allow individual organisms to pass only half of their genes on
to their offspring. Ask students what benefits they think sexual selection might have.
Explain
10 MINUTES
In this section of lesson I show students the following video that introduces students to
sexual reproduction. Concepts covered in the video are reproductive cells,
internal/external fertilization, and genetic diversity of offspring.
Students complete the Sexual Reproduction handout after watching video.
Sexual Reproduction
Elaborate
10 MINUTES
In this section of lesson students elaborate on what they have learned by reading two background
essays.
1. Background Essay Floral Arrangements
2. Background Essay Red Queen Hypothesis
Both of these essays elaborate on the information they learned during the engage section of the lesson.
To help students interact with texts I have students complete Writing in the Margins.
Writing in the margins engages readers in the reading task and allows them to document their thinking
while reading. Both writing in the margins and drawing in the margins engages students in actively
thinking about the texts they read. The power of this strategy is not the actual act of writing and drawing
in the margins; instead, it is the thinking processes that students must undergo in order to produce such
ideas.
1. The Writing in the Margin strategy that I have students use for Background Essay Floral
Arrangements is the Summarize strategy. The text discusses various pollination strategies therefore
summarizing is a good way to organize information.
Summarize
Briefly summarize paragraphs or sections of a text. Summarizing is a good way to keep track of
essential information while condensing lengthier passages.
Summaries will...
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state what the paragraph is about
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describe what the author is doing
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account for key terms and/or ideas.
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2. The Writing in the Margin strategy that I have students use for Background Essay Red Queen
Hypothesis is the Clarify strategy. The text discusses the complex idea of the benefit of sexual
reproduction therefore pausing to clarify ideas will increase your understanding of the ideas in the text.
Clarify
Clarify complex ideas presented in the text. Readers clarify ideas through a process of analysis,
synthesis and evaluation. Pausing to clarify ideas will increase your understanding of the ideas in the
text.
In order to clarify information you might...
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define key terms.
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reread sections of the text.
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analyze or connect ideas in the text.
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paraphrase or summarize ideas.
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Writing in the Margins
Background Essay Floral Arrangements
Evaluate
10 MINUTES
The Exit Slip requires students to develop an evidence-based argument to answer "Why
Sex?" (W.7.1 - Write arguments to support claims with clear reasons and relevant
evidence./SP7 - Engaging in Argument from Evidence)