Origin of Life and First Cells

Universe 14 byo
Solar system 4.5-5 byo

Earth - 4.5 byo

- atmosphere of early earth (Image) thought to contain:

         carbon monoxide

         carbon dioxide


         water vapor

         BUT NO FREE OXYGEN and no ozone layer

- atmosphere of present day
         78% nitrogen N2
         21% oxygen O2
         0.036% carbon dioxide CO2
          traces of rarer gases

Origin of life - life began 3.5-4.0 bya (clock analogy) Fig 19.3

Eukaryotes evolved about 2.1 bya and multicellular eukaryotes evolved by 1.2 bya

Origin of life by chemical evolution - abiotic synthesis  - formation of monomers > polymers > origin of self-replication molecules > microspheres (Image) > primitive cells

- terrestrial synthesis

   - Miller-Urey (Image)
    - shallow seas - Primordial soup

    - bubble model (Fig 19.2)
hydrothermal vents             Hydrothermal vents in action

    - lightning Fig 19.1

- extraterrestrial - comets, asteroids, meteors (Panspermia)

Define prokaryotic, eukaryotic, heterotrophic and autotrophic

The evolution of
prokaryotes Early and modern prokaryotes (Image)

- earliest fossils are 3.5 billion years old = stromatolites - Fossil (Image) & Modern
- evolved 3.6 bya - 4.0 bya
- 2.0-3.5 bya
(photosynthetic) oxygen revolution

Organisms divided into 3 domains. Image characteristics of 3 domains.

Domain Bacteria


Domain Archaea

Archaea vs. Bacteria

Cell walls lack peptidoglycan which Bacteria cell walls have

Not inhibited by antibiotics

Archaea has more in common with Eukarya than with Bacteria

Archaea Diversity



Thermoacidophiles Fig 19.8

Structural Characteristics- Lack membrane-bound organelles and nuclear membrane. Table 19.1a and 19.1b

Size Image

Three shapes of prokaryotes (Image)

Gram-positive vs. Gram-negative (Image) Fig 19.4

Structure of flagella (Image)          Pili (Image) Fig 19.6

Special membranes (Image)

Bacterial conjugation and plasmids Fig 19.5

Diversity of prokaryotes (Image)

Types of metabolism (Image) Autotrophs and heterotrophs



Prokaryotes and the environment

Bacteria as Human Pathogens - a parasitic relationship Table 19.2

Examples: cholera, (water), leprosy, tetanus, anthrax, Lyme disease, bacterial pneumonia, whooping cough, syphilis, gonorrhea, bubonic plague, (life cycle)

Can be used as agents of bioterrorism

More than half of our antibiotics come from soil bacteria. Antibiotics do not work on viruses, but evolved as a method for some bacteria to be able to kill other bacteria - an extreme form of competition.

The Viruses

Viruses and Disease Table 19.3

Prions and mad cow disease Movie


Get more information on diseases at the CDC.