4Evolution of the Earth with Time: Continental Drift 50 Million Years Ago200 Million Years Ago150 Million Years Ago100 Million Years AgoPresent
5Important TermsEvolution- gradual change in a species over time- sci. theoryTheory-well-tested explanation that explains a wide range of observations.Adaptation- any trait that helps an organism survive and reproduce
6Natural Selection-the process by which individuals that are better adapted to their environment are more likely to survive and reproduce.Charles Darwin
7Natural Selection cont. Over a long time, natural selection can modify a population enough to produce a new speciesHelpful variations accumulate in a species while unfavorable ones disappear.
8Speciation Pangaea /Continental Drift When a group of individuals remain separated from the rest of the species long enough to evolve different traitsHOW this happens-Pangaea /Continental DriftLandform isolation- river, mountain, water. (ex. Squirrels of N. Grand Canyon)Australia
9A Problem with Traditional Classification Traditional classification systems relied onbody structure comparisons onlyDue to convergent evolution, organisms thatare quite different from each other evolvesimilar body structures.Convergent Evolution: Process by which unrelated organisms independently evolve similarities when adapting to similar environments.
10A Problem with Traditional Classification Example: The Crab, The barnacle, & The limpetThe barnacle and the limpet have similarly shaped shells & look alikeThe crab has a very different body formBased on anatomy, the barnacle & limpet could be classified together and the crab in a different group.
11This incorrect because crabs and barnacles are actually related
12Traditional Classification Versus Cladogram TRADITIONAL CLASSIFICATION Section 18-2AppendagesConical ShellsCrustaceansGastropodCrabBarnacleLimpetCrabBarnacleLimpetMolted exoskeletonSegmentationTiny free-swimming larvaTRADITIONAL CLASSIFICATIONCLADOGRAMGo to Section:
13Segmentation Free swimming Larva CrustaceansGastropodsMolted ExoskeletonEven though they do not look a like, crabs & barnacles are actually relatedSegmentationFree swimming Larva
14Evolutionary Classification Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similaritiesEvolution Classification: Is the strategy of grouping organisms together based on their evolutionary history.
15Felis Genus species domestica leo margarita If these three species belong to the same genus, they are descended from a common ancestor.Felis domesticadomesticaDomestic CatFelisFelis leoleoLionFelis margaritamargaritaSand cat`
16Classification Using Cladograms Cladogram: A diagram that shows the evolutionary relationships among a group of organisms.
17Segmentation Free swimming Larva Molted Exoskeleton CrustaceansGastropodsMolted ExoskeletonUsing Cladograms, you can see that crabs and barnacles share similar characteristics because they both molt & are segmentedSegmentationFree swimming Larva
18You can also see that ALL have a free swimming larval stage CrustaceansGastropodsMolted ExoskeletonYou can also see that ALL have a free swimming larval stageSegmentationFree swimming Larva
19Modern Evolutionary Classification Similarities in DNA and RNAThe genes of many organisms show important similarities at the molecular level that can be used as criteria to help determine classification.
20Modern Evolutionary Classification Comparison reveals more DNA in common, the more recent the common ancestorMolecular ClocksA model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently.
21Terminology Classification Taxonomy Systematics Phylogeny Assigning organisms to different catagories based on their relationshipTaxonomyThe science of naming organismsSystematicsDetermining evolutionary relationships of organismsPhylogenyEvolutionary history
22Phylogenetic Tree Shows evolutionary relationships More historical than cladogram
25Monophyletic A group of all the descendants of a common ancestor The common ancestor is in the groupExample: Birds and ReptilesAncestor was a bird like reptile
26Polyphyletic group that has some similarities Contains organisms that have not descended from a common ancestorBased on physical characteristics instead of evolutionary evidenceExample: Flying vertebrates- pterosaurs, birds, mammals
27Cladogram Evolutionary relationship of a group of organisms Each clad (group) share something in commonAncestral traits are the oldestDerived traits evolved later
28Cladogram for Transportation Wheels are the most ancestralWings are the most derived