Asexual Reproduction

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Objective

SWBAT to explain the characteristics and results of asexual reproduction.

Big Idea

Students explore how asexual reproduction results in offspring with identical genetic information.

NGSS

1 minutes

This is lesson 1 of a 3-part lesson on reproduction. 

Lesson 1 - Asexual Reproduction

Lesson 2 - Sexual Reproduction

Lesson 3 - Investigating Reproductive Strategies

 

The first two lessons provide the background knowledge needed for lesson 3. The lessons address the following:

NGSS standard:

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. 

Cross Cutting Concept:

Cause and Effect

Cause and effect relationships may be used to predict phenomena in natural systems. 

Science and Engineering Practices:

Developing and Using Models

Develop and use a model to describe phenomena.

Engage

10 minutes

To engage students I begin the lesson by explaining that all living things have the following characteristics in common:

  • 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:

  • 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

15 minutes

In this section of lesson we explore asexual reproduction by looking at some organisms that reproduce asexually.

1.  Show students the video below and discuss the following: 

  • What type of reproduction -- asexual or sexual -- do most single-celled organisms use?
  • What must a single-celled organism do before it can reproduce?
  • When a single-celled organism reproduces, what is the result?
  • In what ways, if any, does a single-celled organism differ from its parent?

2.  Show students the video below (up to minute 1:40) and discuss the following:

  • What type of reproduction -- asexual or sexual -- do the whiptail lizards in the video use?
  • How many parents do whiptail lizards have?
  • How do young whiptail lizards differ from their parents, if at all?
  • How much of their parent's genetic material do whiptail lizards have?

Explain

15 minutes

Now, I show students the following video that introduces students to the different types of asexual reproduction (i.e. budding) and contrasts it to sexual reproduction in terms of genetic composition of offspring. 

Students complete the Asexual Reproduction handout after watching this video.

Elaborate

15 minutes

In this section of lesson students elaborate on what they have learned by reading two background essays.

1.  Background Essay Single Celled Organisms

2.  Background Essay Asexual Reproducers

Both of these essays elaborate on the information they learned during the explore 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 I have students use for Background Essay Single Celled Organisms is visualize since it is helpful for students to draw the various ways for asexual reproduction for comprehension.

Visualize

Visualize what the author is saying and draw an illustration in the margin. Visualizing what authors say will help you clarify complex concepts and ideas.

When visualizing ask:

  • What does this look like?
  • How can I draw this concept/ idea?
  • What visual and/ or symbol best represents this idea? 

2. The Writing in the Margin strategy I have students use for Background Essay Asexual Reproducers is question since this article most likely will bring up a lot of student questions, in particular to parthenogenesis.

Question

Question both the ideas in the text and your own understanding of the text. Asking good questions while reading will help you become a more critical reader.

While reading you might ask...

  • What is the author saying here?
  • What is the author doing?
  • What do I understand so far?
  • What is the purpose of this section?
  • What do I agree/disagree with? 

Evaluate

5 minutes

In this section of lesson students complete an Exit Slip that assesses their knowledge on asexual reproducers, different asexual reproduction mechanisms, and consequences of asexual reproduction.(W.7.1Write arguments to support claims with clear reasons and relevant evidence/SP7 - Engaging in Argument From Evidence.)