Overview
This lecture introduces the definition of cells, the hierarchy of biological organization (cells, tissues, organs), and key contributors to cell theory.
Definition and Hierarchy of Biological Organization
- Cells are the smallest unit of living things.
- Tissue is a group of cells with the same structure and function.
- Organs are collections of tissues that work together for a common function.
- The respiratory system includes organs (like the beak), tissues, and cells.
Discovery of Cells
- In 1665, Robert Hooke observed cork and discovered cells using a simple microscope.
- The term “cell” comes from the Latin word meaning “empty room,” describing the small spaces he observed.
Cell Theory and Contributors
- Early cell theory stated all living bodies are collections of cells.
- Schleiden and Schwann described cells as the smallest structural unit of living things.
- Max Schultze stated cells are also the functional unit of life.
- Rudolf Virchow introduced the idea that all cells come from pre-existing cells (omnis cellula e cellula).
- Robert Brown discovered the nucleus (cell nucleus).
- Ernst Haeckel stated that the cell is a unit of heredity.
Key Terms & Definitions
- Cell — The smallest unit of living things.
- Tissue — Collection of cells with similar structure and function.
- Organ — Collection of tissues performing a specific function.
- Nucleus — The control center of the cell containing genetic material.
- Cell Theory — Scientific theory describing properties of cells: all living things are made of cells, cells are the basic unit of life, and new cells come from existing cells.
Action Items / Next Steps
- Prepare for the next lesson on the differences between prokaryotic and eukaryotic cells.