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Ch 16: Prokaryotes and Viruses

Concept 16.1 Prokaryotic Life Began on a Young Earth

I. The Oldest Fossils

  1. Stromatolites- are thin layers of rockthat contain ancient fossils
  2. Prokaryotes are simple organisms that lack true nuclei and many of the organelles found in eukaryotes

II. How Did Life Begin?

  1. The early Earth was able to produce organic molecules that are essential to life and this was duplicated by Stanley Miller
  2. Miller’s experiment was able to produce simple molecules but experiments show that even more complex molecules could be created by duplicating the early Earth
  3. RNA is thought to be the molecule that started to store genetic information and direct protein synthesis
  4. Experiments have shown that polypeptides can come together and form microscopic, fluid-filled spheres
  5. All of the experiments support a hypothetical four-stage sequence for how life could have developed

III. Where Did Life Begin?

  1. It used to be thought that life began in shallow water
  2. Deep Sea vents are populated with prokaryotes that resemble some of the earliest cells

Concept 16.2 Diverse prokaryotes populate the biosphere

I. Diversity of Prokaryotes

  1. Most bacteria do not cause disease and many can be helpful to humans or other organisms
  2. Prokaryotes help cycle nutrients between organisms, the soil and the atmosphere
  3. The are two Types of Prokaryotes

1. Archaea- which means “ancient” live in some of the most extreme environments on Earth

2. Bacteria- differ from archaea in their nucleic acids, enzymes and cell wall

II. Structure and Function of Bacteria

  1. Cell Shape

1. Cocci- Spheres

2. Bacilli- Rods

3. Spirochetes- Spirals

B. Cell Wall Structure- Gram positive or Gram negative

C. Motility- About half are motile

III. Reproduction

  1. Rapid Reproduction-Some bacteria can divide every 20 minutes
  2. Genetic Transformation

1. Transformation- Bacteria take up DNA from the environment and incorporate it

2. Conjugation- Two bacterial cells join together and transfer genetic material

  1. Endospore Formation- Some bacteria form spores when environmental conditions become severe
  1. Modes of Nutrition

1. Photo- gets energy from photosynthesis

2. Chemo- gets energy from chemical sources

3. Autotrophs- obtain carbon atoms from CO2

4. Heterotrophs- obtain carbon from existing organic molecules

IV. Cyanobacteria and the “Oxygen Revolution”

  1. Earth’s early atmosphere very little or no free oxygen
  2. Cyanobacteria release oxygen as a byproduct of photosynthesis
  3. Nearly all eukaryotes are aerobic and owe their evolution to cyanobacteria

Concept 16.3 Prokaryotes perform essential functions in the biosphere

I. Chemical Recycling

  1. Many prokaryotes perform an essential function by breaking down organic waste products and dead organisms in the environment
  2. Carbon is returned into the atmosphere as carbon dioxide, nitrogen is taken from the atmosphere and “fixed” in nitrogen compounds in soil and water

II. Human uses of Prokaryotes

  1. Humans use bacteria to remove pollutants from water, air and soil in a process called bioremediation
  2. Pseudomonas bacteria has been shown to be able to help clean up oil spills
  3. Bacteria are also used to clean up arsenic, copper, zinc, lead and mercury. They can also be used to make vitamins and antibiotics
  4. Genetic engineering is finding more and more uses for bacteria

Concept 16.4 Some prokaryotes cause disease

I. How Bacteria Cause Illness

  1. Bacteria and other microorganisms that cause disease are called pathogens
  2. Most pathogenic bacteria cause disease by producing one of two types of bacterial poisons. One type is secreted by the bacterium and the other is a component of the bacteria’s cell wall

II. Defense Against Bacterial Diseases

  1. The major reason for the decline in bacterial diseases is better hygiene and public health measures
  2. The human body has built in defenses against disease
  3. The other way to defend against bacterial diseases is through the use of antibiotics

Concept 16.5 Viruses Infect Cells by Inserting Genes

I. Virus Structure and Reproduction

  1. A virus is composed of a short piece of DNA or RNA surrounded by a protein coat
  2. There are two ways that viruses reproduce

1. Lytic Cycle- the virus attaches itself to the host and injects its DNA

2. Lysogenic Cycle- the virus injects its DNA into the host and it is incorporated into the host cell’s DNA

II. Viruses and Disease

  1. A virus that causes disease must use the host cell to reproduce
  2. Antibiotics do not work on viral illness so the body’s immune system must destroy the virus

III. HIV: A Retrovirus

  1. AIDS is the disease which is caused by the HIV virus
  2. HIV is a retrovirus which means their genetic information is carried in RNA
  3. The RNA is transcribed into DNA with the help of the enzyme reverse transcriptase

IV. Defense Against Viral Disease

  1. Vaccines are deactivated varieties or small pieces of pathogen that stimulate the immune system to respond to a particular pathogen
  2. The first vaccine was for smallpox; it was invented in the 1700’s by Edward Jenner
  3. Some viruses mutate rapidly and are not recognized by the body, such as the flu and HIV