Lesson 2 Cell Theory
Development of the Cell Theory
The cell was not recognized as important to life until the 1830s.
A2.2 The green sections are the cell nuclei
During the 1830s, more scientists started to recognize that the theory of spontaneous generation was wrong and instead started working on studying the cell. Through the experiments of four main scientists, a theory emerged about cells and what their
function was. It became clear that cells were very important to life and were, in fact, what all life was made from.
Robert Brown was the first scientist to see the nucleus and determine that it must have some importance to cell structure and function. However, Brown did not know what the function of the nucleus was.
Robert Brown was the first scientist to see the nucleus and determine that it must have some importance to cell structure and function. However, Brown did not know what the function of the nucleus was.
Two scientists named M. J. Schleiden and Theodor Schwann took Brown’s observation and built on it. They discovered that the nucleus was found in both plant and animal cells. Since it was found in both types of cells, they felt it must be the structure
that controlled the rest of the cell. It was an amazing breakthrough in the scientific community. Not only did plants and animals both contain cells, but these cells contained similar structures and so must perform similar functions.
A2.3 Animal and plant cell structure
A scientist by the name of Rudolf Virchow supported Schleiden and Schwann’s theory but felt they got one part wrong. Schleiden and Schwann suggested cells formed from non-living materials or by budding from the surfaces of other cells. Virchow
felt cells could not come from non-living materials, as this would be spontaneous generation. He made microscopic observations of cells dividing to make more cells and concluded cells must come from other cells. This led to the final point
of the cell theory.
The cell theory:
- All living things are made up of one or more cells and the materials produced by these cells.
- All life functions take place in cells, making them the smallest unit of life.
- All cells are produced from pre-existing cells through the process of cell division.
A2.4 Cells undergoing cell division
Did You Know?
A2.5 Repetition is important in science.
Many scientists were amazed by Schleiden and Schwann’s discovery, so they decided to test it for themselves. Experiment after experiment showed the same results and provided supporting evidence for the theory.
Learn More
Read This
Please read pages 251 and 252 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on the scientists and what they
discovered about cells. It is also important you know the cell theory. Remember, if you have any questions or you do not understand something, ask your teacher!
Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice
questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.
- Write the three points of the cell theory in your own words. This means you cannot copy the points down; you must use words that make sense to you.
Your answer should be a variation of the following: Cells make up the building blocks that all living things are made of. Everything you need in order to be alive is done in a cell. Only cells can produce other cells.
- In point form, outline the development of the cell theory.
Brown discovered the nucleus and suggested it held an important job within the cell. Schleiden saw the nucleus in plant cells and suggested it was responsible for the development of the cell. Schleiden discussed this with Schwann, and Schwann made similar observations in animal cells. This lead to the first two points of the cell theory. Virchow observed that cells divided to make new cells, which led to the final point in the cell theory.