History of Life

History of LifeChapter 1717.2Earth formed 4.6 billion years agoMolten rock that cooledWater vapor created oceansGases made the atmosphereREVIEW:Spontaneous GenerationLiving organisms can arise from non-living matterEx: fish from mudRedis ExperimentControlUncovered jars of meat=maggots & fliesExperimentalSame jars with netting over top=maggot & fly free

Spallanzanis ExperimentMany thought vital force made organismsHypothesis: microorganisms come from other microorganisms, not airBoiling kills microorganismsObjection: boiled too long and killed vital force

PasteurCurved (s-shaped)flaskPerforms Spallanzanis exp., but no cork neededNo formation of life

Biogenesis=life has to come from other life

How did elements become life?Oparin-Haldane Hypothesis - Primordial SoupEarly atmosphere contained N2, H2, H2O, methaneEarth cools, oceans fill with organic compoundsLightning & UV rays make macromolecules (proteins)Miller & Urey- only support of Oparin (~40 years later)

Lermans Bubble ModelGases were trapped underwater, underwent chemical reactions, put into atmosphere, and fell into oceans as complex compounds

What gave rise to 1st cells?MicrospheresSpherical protein molecules that are organized as a membraneNot cells, but characteristics of living organismsCoacervatesCollection of droplets that contain different types of molecules

DNA/RNA = ????

Brainstorm in Notes:Whats the difference?Prokaryote vs EukaryoteAnaerobic vs AerobicAutotroph vs HeterotrophFirst cells were: anaerobic, prokaryotic, unicellular, and aquatic

Pressure to be autotrophsArchaebacteria-harsh conditions, autotrophsEx: methanogens, halophiles, thermoacidophilesChemosynthesis-use CO2 as source for organic molecules3 billion years ago became photosynthetic1st were cyanobacteriaOxygen levels rise, sunlight splits O2 = formation of ozone layer (O3)Can move onto land- 1st EukaryotesEukaryotesTheory of Endosymbiosis (pg 427)- Lynn MargulisExplains how we got mitochondria & chloroplastsBacteria entered large cells as parasites, began to live inside & performed cellular respiration (mitochondria) or photosynthesis (chloroplasts)Symbiotic relationship: larger cells provide shelter, mitochodria & chloroplasts provide energy

6 KingdomsProkaryotesEubacteria-true bacteria (todays)Archaebacteria- ancientEukaryotesProtistaFungiPlantsAnimalsFirstsMulticellular organisms- fungi living on plantsMycorrhiza live on roots to fix nitrogenAnimals from sea- arthropodsVertebrates- fishInhabit land-amphibians17.1 Fossils- any evidence of an organism that lived long ago1. Petrification- chemicals replace existing hard parts Ex: petrified wood

2. Freezingice man- 5,300 years old, tzi, (tz valley in the Italian Alps) was found by two German tourists between Austria and Italywooly mammoth

3. Casts- impression filled in, an exact replica mold of an organism is formed when it is filled with minerals

4. Mold- impression, formed when an organism is buried, leaving an empty space in the rock the exact shape of the organism

Cast >< Mold5. Trace Fossils- footprints, trails

6. Amber- dried tree sap

7. Asphalt LaBrea Tarpits- LA, CaliforniaTar seeps up & becomes covered with water. Over many centuries, animals that came to drink the water fell in, sank in the tar, and were preserved as bones

8. Dessication- drying out, desert

9. Rat pack middens- collect & store things, urinate on them > crystallizes

10. Coprolites- fossilized excrement, know what they ate

17-1 Relative Dating (pg 419)Determined by layers of sedimentary rockOnly gives idea according to other fossilsRock layers near the bottom of the column are older than those on top

How Do We Determine the Age of Fossils?Radiometric/Radioactive/Absolute DatingAtomic # = protonsMass # - Protons + NeutronsIsotopes- atoms of same element with different # of neutrons, become radioactive (unstable nuclei that release particles or radiant energy)

Carbon- atomic #=6-mass #=12Radioactive Isotopes- C13, C14

Radioactive isotopes commonly used:

Carbon-14 (5,730 yrs.)Potassium-40 (1.227 billion years)Uranium-238(4.5 billion years)Carbon 14 datingUsed for dating fossils less than 50,000 years oldPlants fix atmospheric carbon dioxide (CO2) into organic material during photosynthesis- they incorporate a quantity of 14C that approximately matches the level of this isotope in the atmosphere After plants die or they are consumed by other organisms (for example, by humans or other animals) the 14C fraction of this organic material declines at a fixed exponential rate due to the radioactive decay of 14C. Comparing the remaining 14C fraction of a sample to that expected from atmospheric 14C allows the age of the sample to be estimated.

Half- life- time it takes for of a sample of isotope to decayCarbon= 1 half-life = 5730 years 2 half-lives = 11460 years 3 half-lives = 17190 years 4 half-lives = 22920 years 5 half-lives = 28650 years 6 half-lives = 34380 years

Work your way down dividing in half and then count arrows.

Ex: Living specimen= 8gm of C14Fossil specimen= 2 gm of C14 How old?

=8>4>2 is 2 half-lives so fossil is 11,460 years old

Ex: Living specimen= 24gm of C14Fossil = 3gm of C14How old?

=24>12>6>3 So, fossil is 17,190 years old

Review:Who were the three scientists who worked to disprove spontaneous generation? What were their experiments?What is Biogenesis?Describe the first cells found on Earth?What is the Theory of Endosymbiosis?What are 10 types of fossils?17.3 Geologic Time ScaleBased on different types of living organismsEons > Eras(divided by mass extinctions) > Periods > Epochs > Ages

Precambrian EraNo life for a long time and then very simple life appears.Early life influenced by volcanoes and mountain building87% of all of Earths historyThe oldest rock known on our planet is the Acasta Gniess, which is found in Arctic Canada. Radiometric dating of isotopes trapped in zircon crystals in the rock have shown that this is an incredible 4030 million years old.Radiometric dating showed, in 1956, that the Canyon Diablo meteorite is around 4550 million years ago (hence why we know Earth is around 4.6 billion years old)Cyanobacteria- photosynthetic prokaryotes (3.5bya)Released O2 > atmosphere ozone layerPaleozoic Era- 544 to 245 myaCambrian Period- explosion of lifeInvertebrates- worms (420mya)Vertebrates-fish (500mya)Plants-ferns & gymnosperms (non-flowering plants) (475mya)Amphibians (380mya) & reptiles (300mya)Tropical climates allowed growth of new speciesMass extinction at end most marine invertebrates disappeared.

Mesozoic Era- 245-66myaTriassic Period- small mammals (200mya), dinosaurs(end 225mya)Jurassic Period- age of dinosaurs, birds(end 150mya)Cretaceous Period- change of mammals, more flowering plants (130mya)Late mass extinction by asteroid or climate change that caused dinosaurs to go extinct.

Cenezoic Era- 65mya to presentThe Era we are currently in!!!Mammals, flowering plants, humans.Age of Mammals Australopithecus the first human (because it could stand and walk fully upright as we do)Homo erectus appeared 2 mya and immigrated out of Africa into Asia. Approx 1mya humans reached Europe. Neanderthal man existed in the cold ice ages of Europe from about 100,000-35,000 myaGeologic Time Music video https://www.youtube.com/watch?v=7PQURsc2SYs

Mass extinction wide spread and rapid decrease in the amount of life on Earth.

Background extinction

smaller, normal extinctions that provide turnover in the ecosystem.

Major Extinctions:Ordivician440 myaDevonian365 myaMajor Extinctions:Ordivician440 myaDevonian365 myaPermian245 mya (90% Marine Sp. & 75% Land Sp.)Major Extinctions:Ordivician440 myaDevonian365 myaPermian245 myaTriassic210 myaCretaceous 65 myaMajor Extinctions:Ordivician440 myaDevonian365 myaPermian245 myaTriassic210 myaCretaceous 65 myaToday: 20% in last 50 years(habitat loss)Possible Causes for Mass Extinction:

Most relate to a rapid climate change

Shifting continents & ocean currents;Volcanic activity; Solar flares;Nearby supernovas (gamma rays);Ocean methane gas belching;Asteroids hitting earth

Does Extinction Increase Biodiversity?