Overview
This lecture introduces biology as the study of living organisms, focuses on the development of cell theory, key contributors, and explains the differences between cell theory and spontaneous generation.
Introduction to Biology
- Biology studies living organisms, including their structure, function, and interactions.
- It covers specialized fields like morphology, physiology, anatomy, behavior, origin, and distribution of life.
Learning Competencies & Targets
- State the cell theory.
- Identify key scientists and their contributions to cell theory.
Development of Cell Theory
- Zacharias Janssen (1590) invented the first compound microscope.
- Anton Van Leeuwenhoek (1653) first observed living microscopic organisms, calling them "animalcules."
- Robert Hooke (1665) coined the term "cell" after observing cork slices.
- Matthias Schleiden (1838) concluded all plants are made of cells; co-developed cell theory.
- Theodor Schwann (1839) concluded all animals are made of cells; co-developed cell theory.
- Rudolf Virchow (1855) stated all cells come from pre-existing cells, adding the third tenet of cell theory.
The Cell and Its Structure
- A cell is the smallest unit capable of independent life, forming all living organisms and tissues.
- Main parts: cell membrane (outer layer), nucleus (contains genetic material), cytoplasm (fluid interior).
Three Postulates of Cell Theory
- The cell is the basic unit of life.
- All organisms consist of one or more cells.
- All cells arise from pre-existing cells.
Expanded Cell Theory
- Cells carry genetic material passed to daughter cells during division.
- All cells share similar chemical composition.
- Energy flow and metabolism occur within cells.
Biogenesis vs. Spontaneous Generation
- Biogenesis: Life comes only from pre-existing life (supported by cell theory).
- Spontaneous generation: Proposed that life can arise from non-living matter (disproved, but once popular, especially with Aristotle).
Key Terms & Definitions
- Biology — study of living organisms and their interactions.
- Cell — smallest living unit; building block of all organisms.
- Cell Theory — principle that all life is composed of cells, and all cells come from other cells.
- Biogenesis — concept that life arises only from existing life.
- Spontaneous Generation — outdated belief that life can originate from non-living matter.
Action Items / Next Steps
- Review the major contributors to cell theory and their discoveries.
- Memorize the three postulates of cell theory.
- Read assigned textbook chapters on cellular structure and early cell theory development.