Transcript Slide 1
Evolution • is change in the inherited traits of a population of organisms from one generation to the next (over VAST amounts of time). These changes are caused by a combination of three main processes: variation, reproduction, and selection. The Record of Life A. Earth is believed to be about 4.6 billion years old • This age was determined from meteorites and moon rocks • The earliest atmosphere contained H2 (hydrogen) CH4 (methane), NH3 (ammonia) and H2O (water vapor) • B. Fossils and Ancient Life • A fossil is any evidence of previous life Ex: amber, trace fossils, molds & casts, imprints, tracks • Fossils are usually found in sedimentary rocks – Made from particles of sand, silt, and clay • The simplest dating method is called RELATIVE DATING, where the rocks closer to the surface are considered younger and the deeper layers are older. C. Radioactive Dating •Radiometric dating involves using radioactive isotopes to detect the amount of decay. Ex: C14 dating D. Geologic Time Scale • A scale which is a kind of calendar that communicates all the events of the Earth since its formation is known as the Geologic Time Scale. II. Origin of Life E. Origin of Life • Spontaneous generation process by which life was thought to be produced from non-living matter. • Fransesco Redi partially disproved this, but not until the experiments of Louis Pasteur was the theory of spontaneous generation totally disproved. • Biogenesis – living organisms come only from other living organisms. • The beginning of life is thought to have originated in the oceans from protocells. All the ingredients for life were present in the atmosphere and oceans. • Primitive life forms are considered to most closely resemble Archaebacteria (most primitive kind) • Cyanobacteria – type of photosynthetic bacteria believed to have been the earliest group of organisms to evolve. cyanobacteria stromatolites III. First Organic Molecules • Atoms today do not assemble themselves – Because atmospheric O2 is reactive and would destroy any organic molecules – Bacterial organisms would consume for source of energy • Early Earth’s atmosphere is more conducive to molecular assemblage – Stanley Miller and Harold Urey questioned composition of early atmosphere Miller-Urey Experiment (Abiotic Synthesis) Made Amino Acids (mostly GLYCINE) History of Life Timeline • Earth formed – 4.6 bya • Earth cooled, LIQUID water is present – 3.8 bya • Organic molecules form, including simple carbs, lipids, proteins, and RNA – 3.7 bya • Prokaryotic cells arise – 3.5 bya • Photosynthesis arises, oxygen added to atmosphere – 2.8 bya • Eukaryotic cells arise – 2.1 bya • Sexual reproduction and multicellular organisms arise – 1.5 bya • Plants colonize land – 1.2 bya Important Milestones 1. Photosynthesis releases O2 into the atmosphere a. Kills all anaerobic organisms exposed to O2 Leads to aerobic processes being selected for (precursor to cellular respiration) Important Milestones 2. Prokaryotic eukaryotic a. Provided compartmentalization for the cell, more diverse functionality b. Endosymbiotic theory – eukaryotes were created when one prokaryote engulfed another but did not digest it Important Milestones 3. Sexual Reproduction a. Leads to more genetic diversity in a population, increases long-term survival of a species (gene shuffling) 4. Multicellular organisms a. Bigger organisms b. Cell differentiation (driven by gene regulation) c. Not constrained to limits of simple diffusion