Origin of Life; Prokaryotes

I. Introduction

-revisit the "Tree of Life"

-major events in the history of life

II. Evidence for the Origin of Life

A. First forms were prokaryotic

-stromatolites

B. How did life come about?

1. A.I. Oparin and J.B. S. Haldane: 1920

a. non-oxidizing atmosphere

b. liquid water present

c. small inorganic precursors present

d. energy sources available

"The Organic Soup"

2.. Stanley Miller and Harold Urey: 1953

test apparatus

a. gas phase

b. electrical energy

c. 0-100 C temperature

d. sterile

3. Criticisms of Miller/Urey

C. New Ideas

1. Submerged volcanoes and deep sea vents

2. Extraterrestrial Infall

carbonaceous chondrite meteorite comets

3. The RNA World

-formation of RNA

-Thomas Cech

-ribozymes

-natural selection at the molecular level

D. The First Cells

1. Protobionts

-liposome

-example

2. Eubionts

Synthetic Life

III. Prokaryotes

A. Introduction

• prokaryotes found everywhere
• the most species?
• Archaea or bacteria: which group is more closely related to eukaryotes?

B. Metabolic Diversity

Self-feeders (autotrophs)

Chemoautotrophs-derives energy from chemicals (deep sea vents: H₂S)

Photoautotrophs-photosynthetic, derives energy from sunlight (CO₂ from atmosphere)

Eaters (heterotrophs)

Photoheterotrophs-light energy, plus organic compounds (not CO₂ for carbon)

Chemoheterotrophs-most common, uses organic substrates for carbon and energy

Example:  Chemoheterotrophs

oil spill clean-up

La Brea tar pit bacteria