1. Cell Theory
SC.912.L Describe the scientific theory of cells (cell theory) and relate the history of its discovery to the process of science

2. Cell Theory
Objective: Describe the three parts of the cell theory and how the investigations and experiments that produced the evidence that led to our current version of the cell theory.
EQ: How does the development of the cell theory demonstrate the powerful nature of science?

3. Wacky History of the Cell Theory?

4. Developing the Cell Theory
Zacharias Janssen (late 1500’s)
Believed to have invented the compound microscope
The compound microscope
contains two or more lenses

5. Developing the Cell Theory
2. Robert Hooke (1665)
Examined thin slices of cork using a compound microscope – saw what looked like small rooms
First to identify cells

6. Developing the Cell Theory
3. Antwon van Leeuwenhoek (1674)
Examined living cells from bacteria on teeth
Improved the microscope
Single lens rather than
a compound microscope

7. Developing the Cell Theory
4. Matthias Schleiden (1838)
Studied plant tissue – proposed plants were made of cells
Shared his work with
Theodor Schwann

8. Developing the Cell Theory
5. Theodor Schwann (1839)
Studied animal tissue – proposed animals were made of cells, just like plants
Published the first statement of cell theory
Believe in spontaneous generation

9. Developing the Cell Theory
6. Rudolf Virchow (1855)
Proposed that all cells come from other living cells (studied cell division)
Disagreed with Schwann that cells can spontaneously form (“free-cell formation”)

10. Think- Pair- Share What instrument lead to discovery of Cell theory?
How long did it take to establish the cell theory?
Why were more definitive conclusions able to be made as time progressed?

11. Cell Theory: 3 Major Principles
We know recognize the following 3 principles:
All living things are made of cells
All cells come from preexisting cells
The cell is the most basic unit of life
Continuous investigation to develop cell theory

12. Theory Vs Law
Theory- highly supported by evidence, not proven to be true
Law- proven to be true
Why is the cell theory a theory and not a law?

13. The theory of spontaneous generation included the idea that simple organisms like worms and flies were created from abiotic (non-living) things like mud. In the 1600’s Francesco Redi performed an experiment. Maggots developed from the eggs laid by flies in the first flask in the diagram below. No maggots were developed in the remaining two flasks. What proof did the results of this experiment prove or disprove?
Disprove spontaneous generation- flys do not come from nonliving things, they lay eggs and grow

14. What did people believe before Cells were discovered?
Theory of Spontaneous Generation = that living things can come from non-living things
Ex – maggots from meat; or mice from hay

15. QKA Which of the following is one of the principles of cell theory?
Most organisms are made of cells.
The cell is the second most basic unit of life, behind atoms.
Cells are spontaneously generated.
None of the above. e.

16. QKA
How does the history of the formation of the cell theory model the process of science?
Once a conclusion was made about cells it was forever considered valid.
Several scientists conducted research, shared experimental results, and formulated conclusions that advanced scientific knowledge about cells over time.
Scientists worked independently, refusing to compare data in an effort to be the first to make a new discovery about cells.
Scientists all worked to prove each other’s conclusions invalid. b.

17. What is a Cell?
A cell is the smallest unit of life that containing cytoplasm enclosed by a cell membrane

18. Types of Cells Prokaryotic Cell Eukaryotic Cell
do NOT have a nucleus or organelles; DNA is suspended in the cell
Ex. microscopic single-celled organisms
have a nucleus (contains DNA) and other membrane-bound organelles
Ex. single and multi-cellular organisms

19. Cell Theory Timeline
Create a foldable timeline for Cell Theory. On the front write the three principles of the cell theory. Add the scientist’s name and year at the top of each square. In the center, add summary of each scientist’s contribution to Cell Theory AND identify the principle of the cell theory to which each scientist contributed.
C – level 2 voice
H- ask three before me
A- complete the foldable timeline with the scientist’s name, contribution and principle of the cell theory.
M- remain seated. Moving around will result in a strike!
P- complete your timeline and glue into the LEFT side of your notebook.
Success!
Fold the paper that you cut and glued in half, and then in thirds (should have 6 pages total)
Tape the title page to the front and write the three principles of the cell theory underneath.
Tape The pictures of each scientist to the upper left hand corner of each consecutive “page.” Be sure to keep them in order!
Tape the book into your left-side page
Add Scienttists name and year at the top, a summary of each scientist’s contribution to Cell Theory AND identify which principle each contributed to in the middle

20. Exit Ticket Give the 3 main components of cell theory
What was Hooke’s contribution to cell theory?
What was Virchow’s major contribution to cell theory?
How does the development of the cell theory demonstrate the powerful nature of science?