BIOLOGY 2

CHAPTER 24 Notes

The history of living organisms and the history of Earth are linked.

• Pangea breakup and biotic diversity

• Photosynthetic organisms released oxygen and atmospheric ozone buildup on Earth

Scientists use evidence from various sources to reconstruct life's history

• Fossil record, although an incomplete record

• Morphology, comparison of structure of past and present organisms

Life appears between 3.5 and 4.0 billion years ago

Earliest organisms were bacteria

• Bacteria appear 2 billion years before the oldest eukaryotic fossil

• Stromatolites‑ domes of sediment layers constructed by colonies of

bacteria living in salty marshes

Chemical evolution

*Early Earth atmosphere, had little oxygen, hot, ultra violet light prevalent, meteorite

bombardment

*Four common elements needed for organic life fon‑n present: C,H,O,N

*These elements combined to form basic compounds needed to make amino acids:

ammonia, hydrogen gas, water, methane gas

*Protobionts‑ droplets which fon‑ned from their chemical surroundings ( precursors to

living things)

• Coacervates‑irregular droplets made from many different molecules

• Microspheres‑ round droplets make from one type of molecule

A.I. Oparin & J.B.S. Haldane 1920's‑ showed that early Earth's atmosphere favored

spontaneously development or protobionts therefore life.

Stanley Mille & Harold Urey ‑ Tested Oparin/Haldane hypothesis, they actually

produced amino acids in laboratory using the four basic compounds stated earlier.

Additional experiments produced all 20 amino acids, ATP, some sugars, lipids , purine

and pyrimidines and bases or RNA & DNA.

9 researchers say RNA evolved first and was the pattern for DNA to develop from.

Alternate views about the origins of Ii

1. Charles Darwin‑ Decent with modification (Evolution)

2. Panspen‑nia‑ Meteorites and comets brought life from another place

3. Sea floor vs. shallow pools of water. ( due to harsh environments at surface)

4. Julius Rebek 1991 ‑ synthesized simple organic molecule therefore he states that a

simpler hereditary system had to evolve before nucleic acid genes. ( this supports the

theory that RNA was to complicated to be the first hereditary molecule to evolve.

Robert H Whittaker 1969 ‑ 5 kingdom system

• Monera

• Protista

• Plantae

• Fungi

• Animalia

Six kingdom system

Archae‑bacteria

Eu‑bacteria

Protista

Plantae

Fungi

Animalia

Three domain system

Bacteria (eubacteria)

Archaea (archaebacteria)

Eucarya (eukaryotes)

Eight kingdom system

Eubacteria

Archaebact

Archaezoa

promista

Protista

Plantae

Fungi

Animalia