1 Review In what ways do prokaryotes differ from one another Evaluate Use pg 486. Which category of prokaryote is the most flexible in the energy sources it can use- explain 2 Review List three ecological roles played by prokaryotes Explain Why are nitrogen fixing bacteria so important

Ch 20 Viruses and Prokaryotes

Classifying Prokaryotes Unicellular organisms that lack a nucleus Has DNA, but it is not found in a membrane- bound nuclear envelope.

Prokaryotes are classified as Bacteria or Archaea Two of the three domains of life.

Bacteria Larger of the two groups Do not agree exactly how many phyla Live almost everywhere.

Surrounded by a cell wall that protects the cell from injury and determines its shape Contains peptidoglycan Some have flagella Pili Serve mainly to anchor the bacterium to a surface or to other bacteria.

Archaea Look very similar to bacteria But Walls of archaea lack peptidoglycan Membranes contain different lipids DNA sequences of key archaea genes are more like those of eukaryotes than those of bacteria Live in extremely harsh environments.

Three Archae Varieties Thermoacidophiles Live in hot and acid environments such as hot springs and coal debris, still keep internal pH around 7.

Three Archae Varieties 2. Halophiles Live in high salt concentrations Ocean borders, great salt lake, dead sea.

Three Archae Varieties 3. Methanogens Produce methane Anaerobic Live in thick mud and the digestive tracts of animals.

Size, Shape, and Movement Bacilli Rod-shaped prokaryotes. Cocci Spherical prokaryotes. Spirilla Spiral and corkscrew-shaped prokaryotes Also be distinguished by whether they move and how they move 1-5 micrometers.

Nutrition and Metabolism Store energy as sugars Energy is released during cellular respiration, fermentation, or both.

Energy Capture Page 486.

Energy Release Page 487.

Growth and Reproduction Binary fission Replicates its DNA and divides in half, producing two identical cells Asexual Does not involve the exchange or recombination of genetic information With optimal conditions can replicate every 20 minutes Endospore Thick internal wall that encloses the DNA and a portion of the cytoplasm during unfavorable conditions.

Mutation Mutations are one of the main ways prokaryotes evolve Mutations are inherited by daughter cells produced by binary fission.

Conjugation Exchange of genetic information in prokaryotes Hollow bridge forms between two bacterial cells Genetic material, usually a plasmid, moves from one cell to the other.

The Importance of Prokaryotes Essential in maintaining every aspect of the ecological balance of the living world.

Decomposers Decompose complex organic molecules into simpler molecules Supply raw materials Treat industrial sewage Purify water Produce fertilizer.

Producers Among the most important producers Many food chains dependant on them.

Nitrogen Fixers Nitrogen in atmosphere is not useable by the majority of species Nitrogen-fixing bacteria and archaea provide 90 percent of the nitrogen used by other organisms Legumes Symbiotic relationship between plants and nitrogen fixing bacteria that live in nodules in the plant’s roots.

Human Uses of Prokaryotes Yogurt, sauerkraut, and buttermilk Digest petroleum and remove human-made waste from water Synthesize drugs and chemicals.