Presentation on theme: "IQ # 2 Answer the following using the diagram below:"— Presentation transcript:
1 IQ # 2Answer the following using the diagram below:a common ancestor for D & Fmost closely related speciesleast related speciesnew species C arises at this pointcommon ancestor for E & FThe half-life of carbon-14 is about 5600 years. A fossil with ¼ the normal proportion of C14 is probably _______ years old.CDBE34FA251
2 The History of Life on Earth Chapter 26The History of Life on Earth
3 IQ #3What is the age of the Earth and when did prokaryotic and eukaryotic life emerge?Describe the characteristics of the early planet and its atmosphere.How did Miller & Urey test the Oparin-Haldane hypothesis and what did they learned?What are the methods used to date fossils and rocksDescribe the evidence for the endosymbiotic theory.How does continental drift explain the current distribution of species?
5 Earth = 4.6 billion years old First life forms appeared ~3.8 billion years agoHow did life arise?Non-living small organic moleculesSmall molecules macromolecules (proteins, nucleic acids)Packaged into protocells/Protobionts (membrane-containing droplets)Self-replicating molecules allow for inheritanceFirst genetic material most likely RNAFirst catalysts = ribozymes (RNA)
6 Three Proposed Models of how macromolecules formed Pre-Biotic Soup Hypothesis (Oparin & Haldane-independently)**proposed in 1920’s**Iron-Sulfur Hypothesis (Hydrothermal vents)Seeded Meteorite impact
7 Synthesis of Organic Compounds on Early Earth Oparin & Haldane:Early atmosphere = H2O vapor, N2, CO2, H2, H2S methane, ammoniaEnergy = lightning & UV radiationConditions favored synthesis of organic compounds - a “primitive soup”
8 Miller & Urey:(1950’s): (tested primordial soup in lab)water, hydrogen, methane, ammoniaall 20 amino acids, nitrogen bases, & ATP, DNA, and RNA were formed
9 Formation of the first Cells Began as molecular aggregates (microspheres & protobionts)Divide often (binary fission)Grow larger in sizeMaintain a level of homeostasis internallyProduce electrical potential across surfacesAbsorbs materials from the surface (selective permeability)Catalytic activity
11 Molecular Replication Usually involves DNA, RNA and proteinsAll can form on clay surfacesSelf-replication common with DNA & RNAWhich formed first?DNA or RNA?
12 Molecular Replication Most hypothesize that RNA was the first to form. Why?RNA is a versatile molecule and:Able to function both as an enzyme & substrateSingle stranded and easily forms H-bondsHas catalytic propertiesCan direct protein synthesisFolds on itself and from various shapes
13 Molecular cooperation led to the first cells controlled by RNA Oldest fossilized cells widely accepted (2 bya)Layers of Microorganisms & sediment called:StromatolitesFirst cells thought to be anaerobic using glycolysis as its metabolic pathwayHeterotrophs → Photoautotrophs → Aerobes—Euk’s(O2 increases) (endosymbiotic theory)
14 As prokaryotes evolved, they exploited and changed young Earth The oldest known fossils are stromatolites, rocklike structures composed of many layers of bacteria (cyanobacteria) and sedimentStromatolites date back 3.5 billion years agoLiving ones in Shark Bay Australia
19 We humans are, in simple terms, bags of water filled with proteins and prokaryotic bacteria (the bacteria in your body outnumber the cells in your body about 10 to 1). We humans have descended from organisms that adapted to living in a prokaryotic world, and we humans retain (conserved in evolutionary terms) in our mitochondria the cellular machinery to power our cells that we inherited (i.e., endosymbiosis) from the prokaryotes of deep time on earth.
20 Fossil Record: used to reconstruct history Sedimentary rock (layers called strata)Mineralized (hard body structures)Organic – rare in fossils but found in amber, frozen, tar pitsIncomplete record – many organisms not preserved, fossils destroyed, or not yet found
22 Both used to date fossils and determine age Relative DatingRadiometric DatingBoth used to date fossils and determine ageUses order of rock strata to determine relative age of fossilsMeasure decay of radioactive isotopes present in layers where fossils are foundHalf-life: # of years for 50% of original sample to decay
24 The fossil record chronicles macroevolution Macroevolution consists of the major changes in the history of lifeThe fossil record chronicles these changes, which have helped to devise the geologic time scale
25 Geologic Time ScaleEon Era Period Epoch (longest to shortest) Present Day: Phanerozoic Eon, Cenozoic Era, Quaternary Period, Holocene Epoch
27 Key Events in Life’s History O2 accumulates in atmosphere(2.7 bya)Humans(200,000)
28 Endosymbiont TheoryMitochondria & plastids (chloroplasts) formed from small prokaryotes living in larger cellsEvidence:Replication by binary fissionSingle, circular DNA (no histones)Ribosomes to make proteinsEnzymes similar to living prokaryotesTwo membranes
35 Major events during each Era Precambrian: microscopic fossils (stromatolites)Photosynthesis, atmospheric O2Eukaryotes (endosymbiont theory)Paleozoic: Cambrian ExplosionPlants invade land, many animals appearPermian Extinction (-96% species)Mesozoic: “Age of Reptiles”, dinosaur, plantsFormation of Pangaea supercontinentCretaceous Extinction – asteroid off Mexico’s coastCenozoic: PrimatesNote: All end with major extinction & start with adaptive radiation