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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.

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Presentation on theme: "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."— Presentation transcript:

1 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

2 CH 20 VIRUSES AND PROKARYOTES 20.2 Prokaryotes

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

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

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

6  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.

7 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.

8 Three Archae Varieties 1. Thermoacidophiles  Live in hot and acid environments such as hot springs and coal debris, still keep internal pH around 7.

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

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

11 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.

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

13 Energy Capture  Page 486.

14 Energy Release  Page 487.

15 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.

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

17 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.

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

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

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

21 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.

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


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