bio 117 lecture2
Terms
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- land uplift and subsidence
- through time with strata always formed underwater and the gaps between successive strata being times of uplift above sea level
- factors that favor preservation
- 1) rapid burial, 2) possession of hard parts
- genetic homology
- common strands of DNA across many organisms
- how are fossils formed
- 1) organic (entire) preservation [a) antiseptic burial, b) freezing], 2) mineral profusion, 3) molds and casts, 4) footprints and trails, 5) coprolites
- indirect dating
- uranium-lead method (half-life of U235 decay to Pb207, radio isotope dating volcanic intrusions running through the fossil bearing strata, the stratum is older than the intrusion
- A study on Daphne Major (island) with Geospiza fortis
- a) vary in beak shape and size, b) tribulus fruit pits are tough to crack and avoided when other seeds are available, c) rain stopped largest beak sizes survived best, other seeds became available-bills smaller, chose males with large beaks as mating partners (sexual selection)
- oscillating selection
- evolutionary changes with the ebb and flow of weather and differential food availability
- structural homology
- traits in two organisms that are similar because they were derived from a single trait in a common ancestor (vertebrate limb bones)
- weather induced food availability
- classic case of microevolution in Darwin's finches on Galapagos Isles
- geological record
- record of geological activity as appearing in the layers of rocks and sediment over geological time
- fossil record
- record or history of life forms preserved from the past and occurring in the geological record
- silent mutations
- changes in amino acid sequences that do not affect protein function, increase to fixation in populations at a steady rate
- direct dating
- a) carbon-14 or radio carbon (half life of C14 decay to N14=5,568 years), b) potassium-argon (half-life of K40 decay to Ca40+argon gas= 1.3BYA
- background on darwn's finches
- a) originated from a mainland "grassquit" ground finch, b) 14 different species now eat seeds, buds and insects on the galapagos islands, c) bills differ in relation to food type, d) only a few species occupy each island
- what geological events affect the fossil record
- 1) continental drift, 2) land uplift and subsidence, 3) volcanic activity, 4) weathering/erosion
- freezing
- woolly mammoth found in siberian permafrost
- coprolites
- fossilized excrement
- fossils
- any recognizable structure of organic origin(once living) preserved from the geological past
- embryology (developmental homology)
- the pouches of higher vertebrates disappear during development, as do the necessity of gills but the presence of pouches in the embryo suggest a common ancestor to all vertebrates
- direct enumeration
- a) growth rings (trees), b ) varves (anual deposit patterns), 1) seasonal runoff [corse slit vs fine clay], 2) snow accumulation [layering of fine winter vs coarse summer]
- volcanic activity
- ash (favors fossil formation), lava (destroys organisms and formations)
- antiseptic burial
- in oil seeps and asphalt bogs, mastodon found in a peat bog
- footprints and trails
- dinosaur footprints, worm burrows
- how fossils are dated
- 1) direct enumeration (counting the years), 2) direct dating (radioisotope dating of fossil or the strata touching it, 3) indirect dating
- invasive species
- causes local changes in phenotypes and gene frequency of native species because of sudden increases in competition
- molecular clock
- the fossil record can be supplemented with the information on the amino acid and DNA sequences in living species
- weathering and erosion
- land uplift carries dead animals into adjacent lakes and seas for rapid burial, but also destroys some of the most recent records in strata
- macroevolution
- the change from one major taxonomic group into another
- microevolution
- changes in gene frequency within a species that produce differences in characteristics from one population to the next
- Generalities from the fossil record
- a) major increases in structure/species complexity requires millions/billions of years, b) life began in the sea, c) rapid burial in aquatic sediment is the most important way that fossils are formed
- vestigial traits
- non-functional trait in one species that is homologous to a functional trait in an ancestral species (coccyx=tailbone and appendix)
- brief history of geological principles, the geological record and fossil record
- geologist Charles Lyell, provided evidence of the geological processes responsible for establishing the fossil record, Darwin was influenced by the research of Lyell, who published the book in 1830 entitled
- molds and casts
- sediment around buried organism becomes hardened before the organism disintegrates forming a mold
- mineral perfusion
- replacement of original tissue of buried organism, petrified forest
- antibiotic resistance
- tuberculosis had a single gene mutation
- continental drift
- land masses have broken up, drifted adn collided over millions of years, more ancient the organism the more likely you are to find similar species separated by vast distances