The History of The Cell Theory
Lesson 2 of 4
Objective: SWBAT will explain the components of the cell theory and the historical persons and events that led to its development.
In this section of the lesson I ask students to review the previous lesson, Cells-The Basic Building Blocks of Living Things, by comparing and contrasting living and non-living things through the use of a Venn Diagram.
Using the information we learned yesterday please compare and contrast living and non-living things. Fill in the Venn Diagram below.
The purpose of this section is to assess students' prior knowledge of cells and engage them in considering the importance of cells in their lives.
Introduction to 3 parts of Cell Theory
In this part of lesson I show students a series of images and video clips that explain one of the three part of the cell theory. I use an inquiry approach where through their observations and evidence gathered they will formulate their own cell theory.
To address - 1) Cells are the smallest unit of structure and function of living things, I show students the clip below and have them answer the following focus questions:
- Why do they compare the building of city to that of a human body? In a human body what is analogous to the bricks in a city)
- According to the video what are the smallest part of living things?
- Write down some examples of human cells.
- Fill in the following sequence : cells > _________ > organs > __________ > organism.
- Without bricks it would be very difficult to build and repair a city. What do you believe would be the outcome if living things had no cells.
To address 2) Cells come from preexisting cells, I have students sketch what they see on the following clip.
Based on your observations where do new cells come from?
To address 3) All organisms are made of one or more cells, I show students the following picture.
- Based on the picture above what are the two type of organisms that exist?
- Are plants and animals multicellular or unicellular? What does it mean to be multicellular?
- Could you infer from the figure that bacteria are living? Why do you think this?
The purpose of this section is for students to explore what the scientists, who helped develop the cell theory, experienced during their cell investigations.
Power of the Microscope
Students will take turns in observing unlabeled prepared slides of both living and non-living things. Students make observations in microscope sketches, circling living or non-living.
1A. oral smear
2A. onion mitosis
2B. fish mitosis
2C. worm mitosis
3A. hand sanitizer
3B. paper cutout of letter A
Students are paired up and if necessary groups of 3 are made. Slides will be numbered with each number indicating what is being observed - 1.animal/plant cells2.dividing cells 3. non-living material I set up the room by having 10 stations each station containing the three type of slides mentioned above.
Probing eliciting questions:
The purpose of these questions is to elicit student responses and most critically, expand on what was learned during the engage part of lesson 1) All new cells come from preexisting cells 2) All organisms are made of one or more cells.
Questions that I ask student during the activity are:
1) Are the specimens on the slide living or non-living? How do you know?
2) What makes something non-living?
3) Is there anything in common between slides that you classify as living? What is it?
4) Why are there so many objects on the slides labeled with a number 2? What do you think these slides show?
5) Do you notice any similarities between the numbered slides?
6) Which slides contain non-living material? How do you know?
7) Based on this investigation, what are living things made of?
8) What can you conclude when comparing non-living material to living material?
9) What did you observe today that tells you not all cells are exactly alike? Do they have anything in common?
10) Where do cells come from? What group of slides show this process?
Purpose of this section of lesson is focus students attention the development of the cell theory particularly gain an appreciation of the vast amount of work it takes to develop a theory.
History of Cell Theory and Microscope
To follow up the explore activity I present cell theory, which has guiding questions for class discussion and describes cell theory including a brief history of its development.
I play a video (follows below), which introduces students to cell theory and the scientists whose work was vital to its development. After watching the video, students complete The History of the Cell Theory as a check for understanding. This is important because this activity will serves as background knowledge for the activity.
The purpose of this section is to extend students' knowledge of cell theory.
Cell Theory Timeline
In this part of lesson I have students work in cooperative groups to create a timeline of the important scientific discoveries that led to the development of the cell theory.
Students can use notes taken during video to help them create a timeline. Groups are also given access to laptops to research dates and discoveries. Each group receives an envelope with pre-cut Cell Theory Cards that they must organize into a chronologically correct timeline.
For those groups that finish early the students can complete microscope history which covers microscope history in more detail.
The purpose of this section is to assess student comprehension of the learning objective.
1) Using evidence from today's lesson, please explain what the cell theory states.
2) What observations did you make during the microscope activity that provides evidence for what the cell theory states.
3) Name at least three scientists and explain their contribution to the development of the cell theory.