Prokaryotes - Earth's First Inhabitants

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Objective

SWBAT identify characteristics of prokaryotes through a close study of bacteria.

Big Idea

Challenge students misconception of the most important prokaryote of all - BACTERIA !!!

Engage

5 minutes

To engage students about the topic we are about to cover I show this video.  The reason  I chose this video - its spectacular animated graphics that draws in students and shows them "both sides" of the bacteria story.  

The objective of this lesson is for students to gain a better appreciation of bacteria (a prokaryote), and in particular it's importance to our everyday lives (i.e. the food we eat).  Students, as well as many adults, see bacteria through a negative lens which portrays them as disease causing agents that must be vanquished immediately.  

This is evidenced by the plethora of anti-bacterial products at our local stores.  As a life science teacher it is my objective for my students to appreciate all forms of life, even unicellular forms, and their contributions to our lives.  

The directions that I give students are to write down ten observations as they watch the video.  I have students focus particularly on the text that is overlaid throughout the video.  After the video has ended we have a whole group discussion on some of the observations students made.

Some possible teacher guiding questions:

1)  According to the video how many sides are there to bacteria?  

2)  What have been some of the benefits of having bacteria both in the past and in the present?

3)  Why do you think people are scared of bacteria?

4)  Are bacteria alive? 

Teacher Note:  Depending on maturity of class you might want to stop video at areas you want to emphasize especially if it's a class that becomes easily distracted.  In addition asking clarifying questions is a good way of checking for understanding.  Area I would emphasize is the point in the video where bacteria go from being portrayed from being pathogens to beneficial organisms to our survival.

Explore

30 minutes

In this part of the lesson students use their prior knowledge of bacteria to read a text dealing with bacteria.  The purpose of this is section is for students to generate ideas and explore questions and possibilities regarding the significance of bacteria in our lives.  This activity requires students to read the text and determine the central idea or conclusion of text by providing an accurate summary of the text (RI-7.2).  In addition student are required to engage in a collaborative discussion with their group members on the texts they have been assigned to read, building on others' ideas and expressing their own clearly (SL-7.1).

Directions

1.  Students are grouped in teams of 4, for collaborative group work.

2.  Each group receives a set of Four Articles About Bacteria dealing with the following topics:

  • History of Life on Earth
  • Health & Disease
  • Food
  • Bacteria Trivia

 

3.  Depending on the maturity of the class, you might allow students to choose which article they want to read and report on to the group, or you may choose it for them.  In my class I assign students group numbers (#1-4) which allows me to say "All #1's will read the text on health and disease .." 

4.  Students are given 5 minutes to read their individual article and write down 5 facts from their article using individual summaries handout.  Students then use those facts to write a summary of their article. ( 5 min)

5.  After the 5 minutes have passed each student has 1 minute to share with their group members what their text was about.  Other students are instructed to put pencils down and focus on the reader. (4 min)

6.  After each group member has presented their text, the group is then instructed to write a summary of all 4 articles, including a descriptive and informative title that encompasses the spirit of all four articles using Group Presentation handout.  Students are given poster paper and markers to create their team poster. Students are given 10 minutes to create their poster. (10 min)

7.  Groups present their poster to the rest of of the class. (10 min)

Explain

10 minutes

The purpose of this part of the lesson is to clarify any misconceptions of bacteria and answer any questions that might have come up during the explore activity.  In particular this is where students are introduced to the concept of prokaryote, as unicellular living things (MS-LS1).  In particular the understanding that prokaryotes do not have a nucleus and membrane bound organelles is vital for comparing and contrasting them with the more complex eukaryotic cells.

Directions:

1.  Before I play the animation I handout a KWL chart which I use to assess students prior knowledge and any misconceptions.  I also use this to assess questions that students might have regarding bacteria.

2.  I use an an animation from BrainPop which does a great job in discussing complex topics such as bacteria and prokaryotes, making them accessible to all learners. BrainPop requires a paid subscription. Other similar choices are found at Cells Alive, Smart Site (University of California), and Interactive Concepts in Biochemistry.

3.  To check for understanding of animation I have students complete a True/False handout.

4.  Students complete The L part of the KWL chart.

Elaborate

5 minutes

The purpose of this part of the lesson is for students to focus on prokaryotes and to establish the relationship between prokaryote and bacteria.  It's imperative for students to understand that prokaryotes and bacteria are not two separate things but that bacteria is an example of a prokaryote.  In the next series of lessons in this unit we will begin to study the more complex eukaryotes which are descendants of the more simple prokaryotes.

Directions

1.  Students complete a Prokaryote Coloring page which requires students to read and find evidence (RI - 7.1) to answer included questions.  

Evaluate

5 minutes

The purpose of this lesson is for students to tie in everything they have learned into one logical claim, supported by evidence from a variety of sources. (W-7.1).

Directions

1.  Students complete Exit Slip and turn it in at end of class or complete it for homework.

Note:  The objective of this exit slip is to begin having students practice developing an argument through the use of claims and evidence.  This skill will be emphasized throughout the semester since it's a focus skill at our school.