Adaptive Radiation: A process in evolution where organisms diversify rapidly into a wide variety of forms to adapt to different environments.

Adaptive radiation is the opposite of mass extinction.

Mass extinction: extraordinary, sudden, and temporary changes in the environment causes species to die on a huge scale

Background extinctions: normal environmental change, emerging disease, predation, or competition reduces populations to zero. This normally happens and is different from a mass extinction.

If the actual rate of extinction is much greater than the background extinction rate, then it may be a mass extinction event.

Chapter 26: Prokaryotes

Mind Map: Comparing Bacteria and Archaea

Central Idea

Bacteria vs. Archaea

Main Branches

1. Cell Structure

• Bacteria

  • Peptidoglycan cell wall

• Archaea

  • No peptidoglycan

  • Has unique phospholipids in their cell wall

2. Genetic Material

• Bacteria

  • Simple transcription and translation processes

• Archaea

  • More complex transcription and translation processes

3. Metabolism

• Bacteria

  • Commonly heterotrophic or autotrophic

• Archaea

  • Often extremophiles (thermophiles, halophiles)

4. Habitat

• Bacteria

  • Found in a variety of environments (soil, water, human body)

  • Some pathogenic

• Archaea

  • Often found in extreme environments (hot springs, salt lakes)

  • Generally non-pathogenic

5. Evolutionary Relationships

• Bacteria

  • Diverged early in the tree of life

  • More diverse in terms of species

• Archaea

  • Closer to eukaryotes in evolutionary terms

  • Less diverse than bacteria

Conclusion

Bacteria and Archaea share similarities in being unicellular and having circular DNA, but differ significantly in cell structure, metabolism, habitat, and evolutionary relationships.

Prokaryotes are pretty much found everywhere on Earth and greatly outnumber eukaryotes.

Virulence: the ability of an organism to cause disease. Virulence is heritable and varies from individual to individual

Endospore: tough thick-walled dormant structures formed by prokaryotes during times of environmental stress to protect themselves

Prokaryotes have multiple processes of gene transfer:

1. Transformation — a cell dies and another cell sucks up the DNA left behind

2. Transduction — a virus transfers DNA from one cell to another

3. Conjugation — a tube transfers DNA from one cell to another

Prokaryotes exhibit diverse morphology:

• Size varies greatly

• Shape varies greatly

• Methods of motility varies (the way that the prokaryote moves)

Gram positive bacteria — bacteria that has a thicker peptidoglycan cell wall. Turns purple/blue during gram staining.

Gram negative bacteria — bacteria that has a thinner peptidoglycan cell wall and an outer membrane. Turns pink/red during gram staining.

The extra outer membrane of gram negative bacteria makes it significantly harder to treat with antibiotics.