Presentation on theme: "Darwin on the HMS Beagle"— Presentation transcript:
1 Darwin on the HMS Beagle Section 1EvolutionDarwin’s Theory of Natural SelectionDarwin on the HMS BeagleDarwin’s role on the ship was as naturalist and companion to the captain.His job was to collect biological and geological specimens during the ship’s travel.
2 Darwin’s Theory of Natural Selection Section 1EvolutionDarwin’s Theory of Natural Selection
3 Section 1EvolutionDarwin’s Theory of Natural SelectionThe Galápagos IslandsDarwin began to collect mockingbirds, finches, and other animals on the four islands.He noticed that the different islands seemed to have their own, slightly different varieties of animals.Almost every specimen that Darwin had collected on the islands was new to European scientists.Populations from the mainland changed after reaching the Galápagos.
4 The Galápagos Islands Darwin’s Theory of Natural Selection Section 1 EvolutionDarwin’s Theory of Natural SelectionThe Galápagos Islands
5 Darwin Continued His Studies Section 1EvolutionDarwin’s Theory of Natural SelectionDarwin Continued His StudiesDarwin hypothesized that new species could appear gradually through small changes in ancestral species.Darwin inferred that if humans could change species by artificial selection, then perhaps the same process could work in nature.Like Persian cat would survive in nature?
6 Section 1EvolutionDarwin’s Theory of Natural SelectionPersian Cat
7 Individuals in a population show variations. Section 1EvolutionDarwin’s Theory of Natural SelectionNatural SelectionIndividuals in a population show variations.Variations can be inherited.You don’t inherit an injury.Organisms have more offspring than can survive on available resources.Variations that increase reproductive success will have a greater chance of being passed on.Acts to select the individuals that are best adapted for survival and reproduction
8 Natural Selection Darwin’s Theory of Natural Selection Section 1 EvolutionDarwin’s Theory of Natural SelectionNatural Selection
11 Section 2EvolutionEvidence of EvolutionThe Fossil RecordFossils provide a record of species that lived long ago.Fossils show that ancient species share similarities with species that now live on Earth.The ancient Glyptodont have been compared to modern day armadillos.No species today are found in the fossil record over a million years ago!!Glyptodont
12 Section 2EvolutionEvidence of EvolutionDerived traits are newly evolved features, such as feathers, that do not appear in the fossils of common ancestors.Ancestral traits are more primitive features, such as teeth and tails, that do appear in ancestral forms.Anatomically similar structures inherited from a common ancestor are called homologous structures.
13 Homologous Structures Section 2EvolutionEvidence of EvolutionHomologous Structures
14 Section 2EvolutionEvidence of EvolutionVestigial StructuresStructures that are the reduced forms of functional structures in other organisms.Appendix and hip bones in whalesEvolutionary theorypredicts that features of ancestors that nolonger have a function for that species willbecome smaller over time until they are lost.
15 Section 2EvolutionEvidence of EvolutionVestigial Structures
16 Section 2EvolutionEvidence of EvolutionAnalogous structures can be used for the same purpose and can be superficially similar in construction, but are not inherited from a common ancestor.Show that functionally similar features can evolve independently in similar environmentsExamples include dorsal fins of dolphins vs. sharks or wings of birds vs. insectsAnalogous Structures
17 Comparative Embryology Section 2EvolutionEvidence of EvolutionComparative EmbryologyVertebrate embryos exhibit homologous structures during certain phases of development but become totally different structures in the adult forms.All vertebrates have a:post anal taildorsal nerve cord (becomes the spinal cord)pharyngeal slits (gills)notochord (becomes the spine)
18 Comparative Embryology Section 2EvolutionEvidence of EvolutionComparative Embryology
19 Comparative Biochemistry Section 2EvolutionEvidence of EvolutionComparative BiochemistryCommon ancestry can be seen in the complex metabolic molecules that many different organisms share.
20 Comparative Biochemistry Section 2EvolutionEvidence of EvolutionComparative BiochemistryAs species evolved, one change after another should have become part of their genetic instructions.Therefore, more and more changes in a gene’s nucleotide sequence should build up over time.
21 Geographic Distribution Section 2EvolutionEvidence of EvolutionGeographic DistributionEvolution is intimately linked with climate and geological forces.If environments never changed, then the traits best suited to survive would continue and mutations would not be beneficialExamples are alligators, swamps haven’t changed in many years.As climates change, new mutations may now be beneficial.
22 Section 2EvolutionEvidence of EvolutionTypes of AdaptationAn adaptation is a trait shaped by natural selection that increases an organism’s reproductive success.Organisms cannot change “adapt” to their environment.Either they have the genetic traits to survive or they do not.Fitness is a measure of the relative contribution an individual trait makes to the next generation.
23 Allows organisms to become almost invisible to predators Section 2EvolutionEvidence of EvolutionCamouflageAllows organisms to become almost invisible to predatorsMimicryOne species evolves to resemble another species.
24 Shaping Evolutionary Theory Section 3EvolutionShaping Evolutionary TheoryMechanisms of EvolutionHardy-Weinberg principle states that when allelic frequencies remain constant, a population is in genetic equilibrium.In order for populations to remain constant, the five components of Hardy-Weinberg must occur:No natural selectionMating is randomNo mutationsLarge populationNo gene flow - migration
25 In larger populations, the alleles tend to remain more stable Section 3EvolutionShaping Evolutionary TheoryGenetic DriftA change in the allelic frequencies in a population that is due to chanceIn larger populations, the alleles tend to remain more stableIn smaller populations, the effects of genetic drift become more pronounced, and the chance of losing an allele becomes greater.Genetic drift reduces genetic variation!!!
26 Genetic Drift - Founder Effect Section 3EvolutionShaping Evolutionary TheoryGenetic Drift - Founder EffectOccurs when a small sample of a population settles in a location separated from the rest of the population.Alleles that were uncommon in the original population might be common in the new population.
27 Genetic Drift - Founder Effect Section 3EvolutionShaping Evolutionary TheoryGenetic Drift - Founder EffectFor example, one of the founding members of a small group Germans that began an Amish community in Pennsylvania had an allele for polydactylism (more than 5 fingers or toes)After 200 years of isolation, the 8000 Amish have a much higher % of polydactylism than the rest of the world
29 Genetic Drift - Bottleneck Section 3EvolutionShaping Evolutionary TheoryGenetic Drift - BottleneckOccurs when a population declines to a very low number and then rebounds.Certain traits may become more prevalent while others may die out because of the traits that survived.Caused by floods or hurricanes
30 Section 3EvolutionShaping Evolutionary TheoryGene FlowIncreases genetic variation within a population and reduces differences between populationsCaused by migrationsNonrandom MatingPromotes inbreeding and could lead to a change in allelic proportions favoring individuals that are homozygous for particular traits
31 Section 3EvolutionShaping Evolutionary TheorySexual selection operates in populations where males and females differ significantly in appearance.Qualities of sexual attractiveness appear to be the opposite of qualities that might enhance survival.Sexual selection will effect natural selection by increasing certain traits in a population such as big pretty feathers on peacocks