Overview
This lecture covers the development of cell theory, its three main principles, and the colorful history behind its key contributors.
The Cell Theory: Three Main Principles
- All organisms are composed of one or more cells.
- The cell is the basic unit of structure and organization in organisms.
- All cells come from preexisting cells.
Early Microscopy and Discoveries
- Zacharias Janssen is credited with inventing the first compound microscope in the early 1600s, though this claim is disputed.
- The microscope became a popular scientific instrument among naturalists and scientists.
- Anton van Leeuwenhoek built his own simple microscope and discovered bacteria from dental scrapings, calling them "animalcules."
- Leeuwenhoek corresponded with other scientists through letters to share his findings.
Robert Hooke and the Origin of "Cells"
- Robert Hooke observed cork under a microscope and coined the term "cell" to describe small chambers he saw.
- Hooke worked in various scientific fields and had a rivalry with Isaac Newton, which impacted his legacy.
- Much of Hooke's research was lost or misplaced due to his conflicts with Newton.
Expansion of Cell Theory in the 1800s
- Matthias Schleiden concluded that all plants are composed of cells through extensive microscopic studies.
- Theodor Schwann determined all animals are made of cells and had a type of nerve cell named after him.
- Schleiden and Schwann communicated and collaborated on developing cell theory.
- Disagreement existed about cell origin: Schleiden believed in spontaneous cell formation, while Schwann and later Virchow supported cells arising from preexisting cells.
Virchow, Remak, and Finalizing Cell Theory
- Rudolph Virchow provided evidence that all cells come from preexisting cells.
- Virchow's research was based on work by Robert Remak, whose findings were not properly credited.
Key Terms & Definitions
- Microscope — an instrument that magnifies small objects for detailed viewing.
- Cell Theory — the biological theory stating all living things are made of cells, which are the basic unit and come from preexisting cells.
- Animalcules — the term Leeuwenhoek used for microscopic organisms, now known as bacteria.
- Spontaneous Generation — the disproven idea that cells can form from non-living matter.
- Schwann cell — a type of nerve cell identified by Theodor Schwann.
Action Items / Next Steps
- Review the three parts of cell theory for understanding.
- Study the contributions of Janssen, Leeuwenhoek, Hooke, Schleiden, Schwann, Virchow, and Remak to cell theory.
- Prepare for questions on the development and historical controversies of cell theory.