C 14- The History of Life Pp. 368- 391

Contents 14-1 The Record of Life 14-2 The Origin of Life

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

History in Rocks Oldest rocks 3.9BY Fossils offer clues to extinct life 95% species extinct Paleontologists study ancient life, climate, & geography

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

Relative Dating Top layers are most recent while deeper layers are older.

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

A Trip Through Geologic Time Geologic Time Scale Divided into 4 large sections between mass extinctions Earth formation 4.6BYA

Precambrian Life Resembled modern cyanobacteria Stromatolites show existence of photosynthetic organisms early on First prokaryotic life; later eukaryotic

Diversity During Paleozoic Cambrian explosion brought teeming ocean life Fishes with backbones, ferns & seeded plants appeared Amphibians & reptiles appear

Life in the Mesozoic Geologic changes Early mammals appear during this age of reptiles Birds evolve Mass extinction of 2/3 species 65 MYA

Changes During Mesozoic Continental drift Supercontinent broke up & drifted Plate tectonics explains how the plates move Affects climate change

The Cenozoic Era Age of mammals Primate appear Modern humans appear 200,000YA

14-2 The Origin of Life Early ideas Spontaneous generation- nonliving things produce life Francesco Redi disproved this

Pasteur’s Experiments Louis 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 Life Modern Ideas Simple organic molecules formed, then more complex molecules like protein, carbohydrates & nucleic acids Alexander Oparin hypothesized life began in the ocean

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

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

The Evolution of Cells Anaerobic prokaryotes Heterotrophs Autotrophs evolved Archaebacteria prokaryotic extremophiles

Photosynthesizing Prokaryotes Release oxygen from water Concentration of oxygen in atmosphere increases Aerobes evolve Ozone layer formed & allowing eukaryotes to evolve

Endosymbiont Theory Proposed by Lynn Margulis in 1960s Eukaryotes evolved through a symbiotic relationship between prokaryotes Chloroplasts & mitochondria have ribosomes