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19.1 Bacteria
Prokaryotes
• Unicellular organism lacking a nucleus.
Bacillus
• Rod-shaped prokaryote.
Coccus
• Spherical prokaryote.
Spirillum
• Spiral or corkscrew-shaped prokaryote.
Chemoheterotroph
• Organism that must take in organic molecules for both energy and carbon.
Photoheterotroph
• Organism that is photosynthetic but needs organic compounds as a carbon source.
Photoautotroph
• Organism that uses energy from sunlight to convert carbon dioxide and water to carbon compounds.
Chemoautotroph
• Organism that makes organic carbon molecules from carbon dioxide using energy from chemical reactions.
Obligate Aerobe
• Organism that requires a constant supply of oxygen in order to live.
Obligate Anaerobe
• Organism that cannot live in the presence of oxygen.
Facultative Anaerobe
• Organism that can survive with or without oxygen.
Binary Fission
• Type of asexual reproduction in which an organism replicates its DNA and divides in half, producing two identical daughter cells.
Conjugation
• Form of sexual reproduction in which paramecia and some prokaryotes exchange genetic information.
Endospore
• Type of spore formed when a bacterium produces a thick internal wall that encloses its DNA and a portion of its cytoplasm.
Nitrogen Fixation
• Process of converting nitrogen gas into ammonia.
Key Concept
• Bacteria are vital to maintaining the living world. Some are producers that capture energy by photosynthesis. Other are decomposers that break down the nutrients in dead matter and the atmosphere.