Overview
This lecture covers biological classification including the three domains and five kingdoms, introduces cell theory, and explains the importance and diversity of bacteria.
Biological Classification: Phylogeny and Taxonomy
- Organisms are grouped by evolutionary ancestry, a process called phylogeny.
- The three domains are Bacteria, Archaea, and Eukarya, which is the broadest classification.
- Bacteria include everyday and helpful bacteria; Archaea are extremophiles that live in harsh environments; Eukarya includes protists, plants, animals, and fungi.
- The five kingdoms are Monera, Protista, Plantae, Animalia, and Fungi.
- Kingdom Monera includes all prokaryotic, unicellular organisms (bacteria and archaea).
- Protists are mostly unicellular eukaryotes, capable of various nutritional modes.
- Plants are multicellular, photosynthetic eukaryotes; animals are multicellular, ingest food, and are motile; fungi absorb nutrition and are nonmotile.
- Taxonomy further divides organisms: kingdom, phylum, class, order, family, genus, species (e.g. Homo sapiens).
Cell Theory and Cell Types
- A cell is the smallest unit of life and the basic unit of biology.
- Cell theory: all living things are made of cells, cells come from other cells, and all cells contain heritable information (DNA or RNA).
- All cells have DNA genes, ribosomes (protein-making organelles), and are bound by a plasma membrane.
- Prokaryotic cells (bacteria and archaea) lack a membrane-bound nucleus and are very small.
- Eukaryotic cells have a nucleus and are generally larger and more complex.
Bacteria: Diversity, Importance, and Adaptations
- Bacteria are ancient, unicellular prokaryotes found everywhere and capable of surviving extreme conditions (extremophiles).
- Archaea are extremophiles living in extreme heat (thermophiles), salt (halophiles), or using chemicals (chemotrophs) for energy.
- Bacteria have three common shapes: cocci (spherical), bacilli (rod-shaped), and spirochete (spiral).
- Eubacteria are common bacteria involved in everyday life and essential processes.
- Bacteria serve vital roles: protecting against harmful microbes, aiding digestion, decomposing organic matter, and cleaning environmental pollutants (bioremediation).
- Bacteria can be autotrophs (make their own food, e.g., cyanobacteria) or heterotrophs (consume organic matter).
Key Terms & Definitions
- Phylogeny — Grouping of organisms based on evolutionary ancestry.
- Domain — The highest, broadest classification level (Bacteria, Archaea, Eukarya).
- Kingdom — The next level in biological classification, grouping organisms with similar fundamental traits.
- Prokaryote — Single-celled organism without a membrane-bound nucleus (includes bacteria and archaea).
- Eukaryote — Organism whose cells contain a membrane-bound nucleus (protists, plants, animals, fungi).
- Extremophile — Organism that thrives in extreme environments (e.g., extreme heat or salinity).
- Cell theory — The principle stating all living things are made of cells, all cells come from other cells, and all have hereditary material.
- Ribosome — Cellular structure that synthesizes proteins.
- Bioremediation — Use of organisms (like bacteria) to clean up environmental contaminants.
Action Items / Next Steps
- Review the differences between the three domains and five kingdoms.
- Memorize the main features distinguishing prokaryotic and eukaryotic cells.
- Prepare for lab observations of protists.
- Read assigned textbook sections on cell structure and bacterial diversity.