C 14- The History of Life

C 14- The History of LifePp. 368- 3911Contents14-1 The Record of Life14-2 The Origin of Life

14-1 The Record of LifeEarly earth probably hot with colliding meteorites & radioactive mineralsBy 4.4 BYA cooled enough for water to condense & lightening storms

History in RocksOldest rocks 3.9BYFossils offer clues to extinct life95% species extinctPaleontologists study ancient life, climate, & geography

Fossil FormationOrganisms are buried in sand, mud or clay & compressed & hardened into fossils.

Relative DatingTop layers are most recent while deeper layers are older.

Radiometric DatingUses radioactive isotopes & half-life to determine age of rock or other organic matter

A Trip Through Geologic TimeGeologic Time ScaleDivided into 4 large sections between mass extinctionsEarth formation 4.6BYA

Precambrian LifeResembled modern cyanobacteriaStromatolites show existence of photosynthetic organisms early onFirst prokaryotic life; later eukaryotic

Diversity During PaleozoicCambrian explosion brought teeming ocean lifeFishes with backbones, ferns & seeded plants appearedAmphibians & reptiles appear

Life in the MesozoicGeologic changesEarly mammals appear during this age of reptilesBirds evolveMass extinction of 2/3 species 65 MYA

Changes During MesozoicContinental driftSupercontinent broke up & driftedPlate tectonics explains how the plates moveAffects climate change

The Cenozoic EraAge of mammalsPrimate appearModern humans appear 200,000YA

14-2 The Origin of Life

Early ideasSpontaneous generation- nonliving things produce lifeFrancesco Redi disproved this

Pasteurs ExperimentsLouis Pasteur used a crook neck flask to boil a nutrient broth. Air could get in but microorganisms could not.Biogenesis became accepted in biology after that.

The Origin of LifeModern IdeasSimple organic molecules formed, then more complex molecules like protein, carbohydrates & nucleic acidsAlexander Oparin hypothesized life began in the ocean

The Origin of LifeStanley Miller & Harold Urey (1953) tested Oparins idea by simulating early conditions on Earth in the lab.Amino acids, sugar & other small organic molecules were produced

Formation of ProtocellsStanley Fox 1992Large ordered structure with a membrane that carries out some life activities such as growth and division

The Evolution of CellsAnaerobic prokaryotesHeterotrophsAutotrophs evolvedArchaebacteria prokaryotic extremophiles

Photosynthesizing ProkaryotesRelease oxygen from waterConcentration of oxygen in atmosphere increases Aerobes evolveOzone layer formed & allowing eukaryotes to evolve

Endosymbiont TheoryProposed by Lynn Margulis in 1960sEukaryotes evolved through a symbiotic relationship between prokaryotesChloroplasts & mitochondria have ribosomes