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Screen capture from video "The Wacky History of Cell Theory”

Screen capture from the TED Ed video, “The Wacky History of Cell Theory.”

STEM in Context

The Wacky History of Cell Theory

Let's Talk Science

Summary

It took several scientists building on each other’s discoveries to come up with Cell Theory - one of the cornerstones of biology.
The wacky history of cell theory (2012) by Lauren Royal-Woods (TED Ed) (6:11 min.).

When you hear the word “scientist,” what do you think of? A person in a white coat working in a laboratory? It’s true that many scientists do important work this way. But scientific theories don’t usually come from a single person working in a lab. They often come from several different scientists building on each other’s discoveries.

Case in point: Cell Theory. This theory is one of the foundations of biology. Cell theory has three parts:

  1. All organisms (living things) are made up of one or more cells.

  2. The cell is the basic unit of structure and organization in organisms.

  3. All cells come from preexisting cells.

It took a few steps and a few scientists to come up with this theory.

Part One: The Microscope

Reproduction of an optical device believed to have been invented by Zacharais Janssen
Reproduction of an optical device believed to have been invented by Zacharais Janssen (Source: US Government [public domain] via Wikimedia Commons).

The story of cell theory started in the Netherlands in the 1600s. There, a spectacle-maker named Zacharais Janssen is said to have invented a compound microscope. A compound microscope uses two lenses. One lens is close to the object being viewed. This is called the objective lens. The other lens is close to the viewer. This is called the eyepiece. Microscopes became extremely popular among scientists.

 

Did you know?

Many people believe Zacharais Janssen invented the first microscope and telescope. But this has never really been proven. There were many other scientists working on similar inventions at the time.

Part Two: The Discovery of Bacteria

Another Dutch scientist, Antoine van Leeuwenhoek, decided to make his own microscope. He began looking at all kinds of matter with his invention. He even looked at the scrapings off his own teeth. That’s how he discovered bacteria!

Did you know?

Van Leeuwenhoek thought bacteria looked like little animals. So he called them animacules. 

Two drawings by van Leeuwenhoek of what he called animacules
Two drawings by van Leeuwenhoek of what he called animacules (Source: Internet Archive Book Images [No restrictions] via Wikimedia Commons).

 

Part Three: The Discovery of Cells

Van Leeuwenhoek wrote letters to a scientist friend in England named Robert Hooke. Hooke also studied objects with a microscope. He studied a piece of cork and noticed it was divided up into little chambers. These reminded him of monastery cells. So, he named his discovery cells.

Drawings of cork done by Robert Hooke
Drawings of cork done by Robert Hooke (Source: Wellcome Images via Wikimedia Commons).

Parts Four & Five: More discoveries about cells

Next came the work of two German scientists. Matthias Schleidan was a botanist. He used microscopes to study plants. Eventually, he realized that all the plants he looked at were made of cells. 

Meanwhile, Theodor Schwann studied slides of animal cells. He concluded that all animals were also made of cells!

Onion cells, a type of plant cell, on the left and frog cells, a type of animal cell, on the right
Onion cells, a type of plant cell, on the left and frog cells, a type of animal cell, on the right (Sources: kaibara87 [CC BY 2.0] via Wikimedia Commons and weisschr via iStockphoto).

Part Six: Preexisting Cells

Eventually, Schneidan and Schwann joined forces and started to develop the cell theory. But they disagreed on the third point: that all cells come from preexisting cells. It took a third scientist, Rudolf Virchow, to prove that cells did indeed come from other cells. But the research he used to prove this actually came from a German Jewish scientist named Robert Remak!

What can we learn from the history of cell theory?

So, what does this story tell us? Two things. First, scientific theories often involve building off of other people’s discoveries. Second, you never know where a scientific theory might come from. It could be sitting in the guck on your teeth!

STARTING POINTS

Connecting and Relating

  • Have you ever wondered what the smallest living thing was? Explain.
  • What are some of the smallest things you have seen using just your eyes?
  • What are some things you have looked at with either a microscope or a magnifying glass?
Connecting and Relating

  • Have you ever wondered what the smallest living thing was? Explain.
  • What are some of the smallest things you have seen using just your eyes?
  • What are some things you have looked at with either a microscope or a magnifying glass?
Relating Science and Technology to Society and the Environment
  • The journey into the microscopic world is similar to our current explorations of outer space. Describe how our explorations of these two worlds are similar and how they are different.
Relating Science and Technology to Society and the Environment
  • The journey into the microscopic world is similar to our current explorations of outer space. Describe how our explorations of these two worlds are similar and how they are different.
Exploring Concepts

  • What are the three parts of the cell theory? Which part tends to be the hardest to support with evidence?
  • What technology was fundamental in the formulation of the cell theory? Explain.
  • What is the difference between a “fact” and a “theory”? Why do you think “Cell Theory” is still called a theory?
Exploring Concepts

  • What are the three parts of the cell theory? Which part tends to be the hardest to support with evidence?
  • What technology was fundamental in the formulation of the cell theory? Explain.
  • What is the difference between a “fact” and a “theory”? Why do you think “Cell Theory” is still called a theory?
Nature of Science/Nature of Technology
  • What is the purpose of a theory? Explain how the cell theory achieves this goal.
  • Many scientists discover things by chance. Explain how chance played a role in the development of the cell theory.
  • It is often the case that many scientific discoveries are met with disbelief and opposition among scientists. Do you think this is more or less true today than in the past? Explain.
  • How is the invention of the microscope an example of how technology improves our understanding of scientific concepts? Explain.
Nature of Science/Nature of Technology
  • What is the purpose of a theory? Explain how the cell theory achieves this goal.
  • Many scientists discover things by chance. Explain how chance played a role in the development of the cell theory.
  • It is often the case that many scientific discoveries are met with disbelief and opposition among scientists. Do you think this is more or less true today than in the past? Explain.
  • How is the invention of the microscope an example of how technology improves our understanding of scientific concepts? Explain.
Media Literacy

  • If social media was around when cell theory was first proposed, do you think it would have helped the advancement of this theory or hindered it? Explain.
  • Many television ads highlight the newest technology. Do you think the invention of the microscope made people as excited then, as new iPhones or iPads make us today? Explain.
Media Literacy

  • If social media was around when cell theory was first proposed, do you think it would have helped the advancement of this theory or hindered it? Explain.
  • Many television ads highlight the newest technology. Do you think the invention of the microscope made people as excited then, as new iPhones or iPads make us today? Explain.
Teaching Suggestions
  • This video can be used to support teaching and learning of biology, technology and the history of science related to Cell Theory. Concepts introduced include cell theory, compound microscopes and cells. 
  • While viewing the video, teachers could have students use a Video Review learning strategy to summarize key points from the video. Download ready-to-use reproducibles using the Video Review Learning Strategy for this article in [Google doc] and [PDF] formats.
  • To help students consolidate learning and practice questioning skills, teachers could have students complete a My Questions Round Robin learning strategy. Download ready-to-use reproducibles using the My Questions Round Robin Learning Strategy for this article in [Google doc] and [PDF] formats.
  • Students could use the internet to create a timeline to illustrate the development of the cell theory by researching when and who made significant contributions.
  • To conclude and assess students’ understanding of this topic, teachers could provide students with an Exit Slip.  Download ready-to-use reproducibles using the Exit Slip Learning Strategy for this article in [Google doc] and [PDF] formats.
Teaching Suggestions
  • This video can be used to support teaching and learning of biology, technology and the history of science related to Cell Theory. Concepts introduced include cell theory, compound microscopes and cells. 
  • While viewing the video, teachers could have students use a Video Review learning strategy to summarize key points from the video. Download ready-to-use reproducibles using the Video Review Learning Strategy for this article in [Google doc] and [PDF] formats.
  • To help students consolidate learning and practice questioning skills, teachers could have students complete a My Questions Round Robin learning strategy. Download ready-to-use reproducibles using the My Questions Round Robin Learning Strategy for this article in [Google doc] and [PDF] formats.
  • Students could use the internet to create a timeline to illustrate the development of the cell theory by researching when and who made significant contributions.
  • To conclude and assess students’ understanding of this topic, teachers could provide students with an Exit Slip.  Download ready-to-use reproducibles using the Exit Slip Learning Strategy for this article in [Google doc] and [PDF] formats.

Learn more

The Evolution of The Cell Theory 

Interactive timeline by Preceden of the evolution of The Cell Theory from 1595 to present.

Cell Theory: A Core Principle of Biology (2019)

Article from ThoughtCo by Regina Bailey discussing the original Cell Theory and how it compares to the more modernly accepted Cell Theory; includes interesting infographics and images of cells. Note that this resource was also used as a reference.

References

Harris, W. (2008, January 14). How the scientific method works. How Stuff Works.

Robinson, R. (n.d.). History of biology: Cell theory and cell structure. Biology Reference.