I. Changes Through Time

A. The Beginning of Life

1. Origin of the Universe (13.7 BYA)Many theories existb) Scientists favor the Big Bang Theory which state that the universe began as a dense concentration of matter smaller than a speck of dust which exploded outward violently

Great Explanations of The Big Bang Theory appear in these books:

2. Origin of the Sun (10 BYA)Clouds of molecules, made of hydrogen gas, began to grow in mass which increased their gravity, which in turn, attracted more hydrogen to increase their mass

b) These clouds increased to such a huge mass, that its gravity smashed hydrogen molecules together, triggering a Fusion Reaction. We call these fusion reactions clouds Stars and one formed our Sun

3. Origin of EarthClouds of matter caught in the Suns gravitational field began forming PlanetsSolid matter collected into a dense core and radioactive decay melted the matter into a ball of molten rock that we call Earth

Earth at Birth (4.5 BYA)

c) Earth could not support life at this time.Tidal waves of LavaPoison gas atmosphereDeadly ultraviolet raysConstant meteorite bombardmentFrequent earthquakes

Relative Size of Inner Planets

Relative Size Outer Planets

Size of Planet Relative to the Sun

Size of Sun Relative to Other Stars

Our Sun Relative to the Largest Stars

4. Origin of Life (3.5 BYA)a) The heat of the earth slowly radiated away and the atmosphere cooled below the boiling point. Rain formed the oceans

Abiogenesis- Spontaneous generation of Life. Russian Biochemist Alexander Oparin introduced a plausible theory of chemical development of life in 1927Abiogenesis is NOT evolution

b) Oparins Hypothesis The early atmosphere contained hydrogen, Methane, Ammonia and Water vaporViolent atmospheric conditions caused much lightning; heat from molten rock, and ultraviolet radiation from the sun provided energy for chemical reactions to take placeOrganic molecules such as Amino acids, lipids and nucleic acids accumulated in the oceans forming an organic soupThe organic compounds developed into the first cells which might have resembled anaerobic bacteria

5. Global Famine and Toxic Waste The first cells had plenty to eat; however, as population size increased, food decreased (Global Famine) Fortunately, high amounts of ultraviolet radiation caused a high rate of mutation and cells capable of photosynthesis developedThese cynobacteria changed the earths atmosphere by adding oxygenPure oxygen is toxic and highly reactive and it built up in the atmosphere until it threatened all live on earth (toxic waste)Mutations created cells capable of respiration which converted the oxygen to water

B. Evidence for Oparins Hypothesis 1. Stanley Millers ExperimentMiller created an apparatus to simulate the conditions on early earth After running his primitive earth machine for a few days, miller found his ocean teeming with amino acids the building blocks of protein!

2. Sidney Fox ExperimentFox heated and cooled amino acids. And found they formed cell-like clump called coacervates. Coacervates carry on limited enzyme activity

3) Leslie OrgelOrgel proved that nucleotides of DNA and RNA can assemble under the conditions of earlyProposed that RNA was the first genetic material because its can be auto catalytic

4) David DeamerDeamer mixed lipid with DNA and dehydrated them and rehydrated them and found that they would form membranes around the DNA

What does DNA and RNA polynucleotides with protein catalyzing chemical reactions in a lipid membrane remind you of? But, scientists have only produced Coacervates in the labA cell of course!

DNA replication requires enzymes and DNA is required to make enzymes.Therefore, current theory suggests that the first genetic material was RNA because it can be auto catalytic (RNA could catalyze its own replication.) But, replication produces a complementary strand, not a coding strand, so two replications would be required.

C. Evidence of Evolution1. Direct evidence of Evolution comes from the fossil recordScientists who interpret the fossil record are called paleontologists

Fossil RecordFossils- any evidence of a once living thingFossil formation (a sequence of improbable events) most often occurs in sedimentary rock, where sand under great pressure turns to rock

Types of FossilsImprintsPetrifiedCastsMolds

3) Types of FossilsImprints- formed by impressions in rockMolds- depressions in rocks shaped like the organismsCasts- where molds are filled with other material leaving a fossil shaped like the original structurePetrified fossils- where parts of an organisms are replaced by minerals

b) Determining the Age of FossilsBy their position in the layers of sedimentary rockBy using radioactive isotopes- materials that decompose into decay elements at a constant rate called a half-life Carbon 14 half-life 5730Uranium 238 half life 4.5 billion

2. Indirect Evidence of Evolution

a. Comparative BiochemistryOrganisms with similar protein structure and similar DNA sequences are more closely related than organisms with different protein structure and different DNA sequences

Examine the following DNA sequences. Which two of the three organisms is most closely related? Organism A: GGT CTC AAT GTA ATC CAA TCC AGGOrganism B: GGT CAC ATT GTA ATG CAA TCG AGGOrganism C: GGA CTC ATT GTA ATC CGG TCC AGC

A & B Matches: 20A & C Matches: 19B & C Matches: 17A & B are most closely related

b. Homologous Bone StructuresSimilar structures found in different organisms suggests a common ancestry

c. Embryological EvidenceOrganisms that develop similarly have common genetic material which controls development which in turn suggest common ancestry

3. Geologic Time Scale