Bio113_chp22

• 13.7 BYA: Universe began with the Big Bang
• 4.6 BYA: Our solar system began
• 4.55 BYA: The earth formed
• 4 BYA: Earth Cooled (enough for the outer layers to solidify and Oceans to form)
• 4 - 3.5 BYA: Life emerged

• Earth formed 4.55 BYA
• For the first 1/2 billion years after earth formation it was too hot to allow water to accumulate on its surface.
• By 4 BYA the Earth had cooled down enough for the outer layers of the planet o solidify and for oceans to begin to form.

Little or no Oxygen in the atmosphere

• Atmosphere full of H-rich Gases
• SH2, NH3, and CH4 etc.

Also carbon dioxide, carbon monoxide, & gaseous nitrogen

Subject to Meteor bombardments because early solar system full of debris

Lots of Volcanic activity & intense Electrical storms

No Ozone = lots of UV radiation exposure

• 1. Origin of organic molecules were produced prior to the existence of cells
• 2. Organic polymers may have formed on the surface of clay
• 3. Cell-like structures may have originated when polymers were enclosed by a boundary.
• 4. Cellular characteristics may have evolved via chemical selecion, beginnning with an RNA world

occurs when a chemical within a mixture has special properties or advantages that cause it to increase in number compared to other chemicals in the mixture

preserved remains of past life on earth

Many rocks with fossils are sedimentary

Sediments pile up and become rock

Organisms buried quickly, hard parts replaced by minerals

Older rock is deeper, older organisms are deeper in rock bed

Fossils dated using elemental isotopes in rock

Half-life – length of time required for exactly one-half of original isotope to decay

Measure amount of a given isotope as well as the amount of the decay product

Usually nearby igeneous rock dated

• DNA is less likely to suffer mutations
• Relieve RNA of the info storage role so that it can do other functions
• Proteins have greater catalytic potential, are more efficiency, provide structure & transport