2Essential Knowledge1.b.2 – Phylogenetic trees and cladograms are graphical representations (models) of evolutionary history that can be tested ( ).1.d.2 – Scientific evidence from many different disciplines supports models of the origin of life (26.6).
3Phylogeny Phylon = tribe, geny = genesis or origin The evolutionary history of a species or a group of related speciesFound in fossils and the fossil record
4Fossils Any preserved remnant or impression of a past organism. Types: 1. Mineralized2. Organic matter3. Trace4. Amber
5Mineralized Fossils Organic Matter Fossils Found in sedimentary rock. Minerals replace cell contents.Ex: bone, teeth, shellsOrganic Matter FossilsRetain the original organic matterEx: plant leaves trapped in shaleComment – can sometimes extract DNA from these fossils
6Trace FossilsFootprints and other impressions No organic matter presentAmberFossil tree resinPreserve whole specimenUsually small insects, etc
7Fossils - LimitationsRare eventHard to findFragmentaryDating
8Fossil Dating Methods1. Relative - by a fossil's position in the strata relative to index fossilsAbsolute - approximate age on a scale of absolute time2 types:1. RadioactiveEstimated from half-life productsEx: Carbon 14, Potassium 402. Isomer Ratios
9What do fossils tell us?That the geographical distribution of organisms has changed over timeReason? – The land formations of the earth have changed through continental drift
10Continental Drift The movement of the earth's crustal plates over time Drift is correlated with events of mass extinctions and adaptive radiations of life
11Pangaea 250 million years ago One super continent Many life forms brought into contact with each otherResult:Geographic isolationNew environments formed, others lostAs environments changed, so did life!
12Mass Extinctions The sudden loss of many species in geologic time May be caused by asteroid hits or other disastersResult:Area open for surviving species to exploitRapid period of speciation (adaptive radiation)Many new species are formed in short amount of time
13Systematics The study of biological diversity. Uses evidence from the fossil record and other sources to reconstruct phylogeny.Goal:To have Taxonomy reflect the evolutionary affinities or phylogeny of the organisms.
14Areas of Systematics1. Phylogeny- tracing of evolutionary relationships 2. Taxonomy- the identification and classification of species
15Taxonomy Natural to humans. Modern system developed by Linnaeus in the 18th century.Includes:Binomial nomenclature: naming systemEx: Homo sapiensHierarchical system: arranges life into groupsEx: Kingdom species
17Question? How do we relate Taxonomy to evolution? Not all “likeness” is inherited from a common ancestor.Problem is of homology vs. analogy
18Homology and AnalogyHomology – likeness attributed to shared ancestry (divergent and parallel evolution)Ex: forelimbs of vertebratesAnalogy – likeness due to convergent evolution (not necessarily a shared ancestral lineage)Ex: wings of insects and birds
19Convergent EvolutionWhen unrelated species have similar adaptations to a common environmentEx: Sharks and dolphins fins; wings of bats, butterflies and birds
20Taxonomy and Evolution We need methods to group organisms by anatomical similarities and phylogeniesOne possible method is Molecular SystematicsCompares similarities at the molecular levelEx: DNA, Proteins
21DNA Comparisons A direct measure of common inheritance The more DNA in common, the more closely relatedMethods:Restriction MappingDNA Sequencing
22Protein ComparisonsExamines the Amino Acid sequence of homologous proteins.Ex: Cytochrome C Study
23Molecular Clock Compares molecular differences to fossil records Result is a way to estimate divergence in species where the fossil record is missing
25Essential Knowledge1.a.4 – Biological evolution is supported by scientific evidence from many disciplines, including mathematics (25.2).1.b.1 – Organisms share many conserved core processes and features the evolved and are widely distributed among organisms today (25.1, 25.3).1.c.1 – Speciation and extinction have occurred throughout the Earth’s history (25.4).
26Essential Knowledge, Continued 1.d.1 – There are several hypotheses about the natural origin of life on Earth, each with supporting scientific evidence (25.1 & 25.3).4.b.4 – Distribution of local and global ecosystems changes over time (25.4).
27Fossil Record Earliest - 3.5 billion years old Earth billion years oldPoint - Life on earth started relatively soon after the earth was formed
28Chemical EvolutionDef – the evolution of life by abiogenesis Steps: 1. Monomer Formation 2. Polymer Formation 3. Protobiont Formation 4. Origin of Heredity
29Primitive Earth Conditions Reducing atmosphere presentSimple moleculesEx: H2O, CH4, H2, NH3Complex molecule formation:Requires an energy sourceUVRadioactivityHeatLightning/Electricity
30Oparin and Haldane, 1920sHypothesized steps of chemical evolution from primitive earth conditions
31Miller and Urey, 1953 Tested Oparin and Haldane’s hypothesis Experiment - to duplicate primitive earth conditions in the labResults: Organic monomers formed (include amino acids)
32Other Investigator's Results All 20 Amino Acids foundOthersSugarsLipidsNucleotidesATP
33HypothesisEarly earth conditions could have formed monomers for life's originsThese early monomers eventually joined together to form large, complex polymers
34Genetic Information DNA RNA Protein Too complex for early life Were there other forms of genetic information?
35RNA Hypothesis RNA as early genetic information Rationale RNA polymerizes easilyRNA can replicate itselfRNA can catalyze reactions including protein synthesis
36Ribozymes RNA catalysts found in modern cells Could be a possible relic from early evolutionary processes
37DNA hypothesis Developed later as the genetic information Why? More stable than RNA
44Other SystemsMultiple Kingdoms – split life into as many as 8 kingdomsDomains – a system of classification that is higher than kingdomBased on molecular structure for evolutionary relationshipsGaining wider acceptance
453 Domains1. Bacteria – prokaryotic 2. Archaea – prokaryotic, but biochemically similar to eukaryotic cells 3. Eucarya – the traditional eukaryotic cells
46Summary Identify the steps of Chemical Evolution Recognize the conditions on early Earth.Recognize the limitations of the fossil record.Recognize some of the key events in the history of Earth.