Evolution Charles Darwin Giant tortoise- Galapagos Islands.
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Transcript of Evolution Charles Darwin Giant tortoise- Galapagos Islands.
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EvolutionEvolution
Charles Darwin
Giant tortoise-Galapagos Islands
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• Evolution: gradual change in a species over time• Scientific theory: a well tested concept that explains
a wide range of observations• Darwin came up with the theory of evolution based
on observations & evidence he collected from the Galapagos Islands.
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Observations made by Darwin:
Observations made by Darwin:
1. Tortoise shell shape2. Finches (sizes & shapes of their beaks)3. Iguanas’ claw size-larger so they can grip on slippery rocks to eat seaweed
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Animals of the Galapagos Islands
Iguana
Different finches
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Natural Selection
• . Natural selection: process by which individuals that are better adapted to their environment are more likely to survive & reproduce successfully
• Darwin said evolution happened as a result of natural selection.
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Overproduction
• Species produce way more offspring than can survive.
• There are not enough resources (food, water, space) to support them.
• Why does this happen?
Baby turtles
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Variation
• Any difference between individuals of the same species
• Ex. Brown labrador retriever & a black labrador retriever
• How can variation such as color affect the process of natural selection?
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Competiton (survival of the fittest)
• Members of a species compete for: food, water, space, ability to get away from predators
•
Turtle eating a mayfly Alligator eating a
fish
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Selection
• Some variations make individuals better adapted to their environment
• These individuals are more likely to survive and reproduce (pass favorable traits onto their offspring)
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Environmental Change
• A change in the environment can affect an organism’s ability to survive.
• This change can lead to selection.
Monkey flower
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Evidence of Evolution:
• 1. fossils-comparing animals from millions of years ago to the alive today
• 2. Similarities in early development• 3. Similarities in body structure (homologous-
structures that are similar because of a common ancestor)
• 4. Similar DNA
Elephant shrew
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Selective Breeding (genetic engineering)
• Breeding plants & animals for a particular trait.
• Ex. Thoroughbred horses are bred for sped in racing.
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Charles DarwinCharles Darwin
• Influenced by Charles LyellInfluenced by Charles Lyell who published “Principles of Geology”.“Principles of Geology”.
• This publication led DarwinDarwin to realize that natural forces gradually change Earth’s surface and that the forces of the past are still operating in modern times.
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Charles DarwinCharles Darwin
• Darwin set sail on the H.M.S. BeagleH.M.S. Beagle (1831-1836) to survey the south seas (mainly South America (mainly South America and the Galapagos Islands)and the Galapagos Islands) to collect plants and animals.
• On the Galapagos Islands, Galapagos Islands, Darwin observed species that lived no where else in the world.
• These observations led Darwin to write a book.
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Charles DarwinCharles Darwin
• Wrote in 1859Wrote in 1859: “On the Origin of Species by “On the Origin of Species by Means of Natural Selection”Means of Natural Selection”
• Two main points:Two main points:
1.1. Species were not created in their present Species were not created in their present form, but evolved from ancestral species.form, but evolved from ancestral species.
2.2. Proposed a mechanism for evolution:Proposed a mechanism for evolution: NATURAL SELECTIONNATURAL SELECTION
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Natural SelectionNatural Selection• IndividualsIndividuals with favorablefavorable traitstraits are more
likely to leave more offspring better suited for their environmentenvironment.
• Also known as “Differential Reproduction”“Differential Reproduction”
• Example:Example:
English peppered moth (English peppered moth (Biston betularia))
- light and dark phases- light and dark phases
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Artificial SelectionArtificial Selection
• The selective breedingselective breeding of domesticated plants and animals by man.
• Question:Question:
What’s the ancestor of the domesticated dog?
• Answer:Answer: WOLFWOLF
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Evidence of EvolutionEvidence of Evolution
1.1. Biogeography: Biogeography:
Geographical distribution of species.Geographical distribution of species.
2. Fossil Record:2. Fossil Record:
Fossils and the order in which they Fossils and the order in which they appear appear in layers of sedimentary rock in layers of sedimentary rock (strongest (strongest evidence).evidence).
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Eastern Long Necked Turtle
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Evidence of EvolutionEvidence of Evolution
3. Taxonomy:3. Taxonomy:
Classification of life forms.Classification of life forms.
4. Homologous structures:4. Homologous structures:Structures that are similar because Structures that are similar because
of of common ancestry common ancestry (comparative (comparative anatomy)anatomy)
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Evidence of EvolutionEvidence of Evolution
5. Comparative embryology:5. Comparative embryology:
Study of structures that appear Study of structures that appear during during embryonic development.embryonic development.
6. Molecular biology:6. Molecular biology:
DNA and proteins (amino acids)DNA and proteins (amino acids)
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Population GeneticsPopulation Genetics
• The sciencescience of genetic changegenetic change in population.
• Remember:Remember: Hardy-Weinberg equation.
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PopulationPopulation
• A localized group of individualsindividuals belonging to the same speciessame species.
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SpeciesSpecies
• A group of populationspopulations whose individualsindividuals have the potential to interbreedinterbreed and produce viableviable offspring.
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Gene PoolGene Pool
• The total collection of genescollection of genes in a population at any one time.
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Hardy-Weinberg PrincipleHardy-Weinberg Principle
• The conceptconcept that the shuffling of genesshuffling of genes that occur during sexual reproduction, by itself, cannot changecannot change the overall genetic makeup of a population.
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Hardy-Weinberg PrincipleHardy-Weinberg Principle
• This principleprinciple will be maintained in nature only if all fivefive of the following conditions are met:
1.1. Very large populationVery large population
2.2. Isolation from other populationsIsolation from other populations
3.3. No net mutationsNo net mutations
4.4. Random matingRandom mating
5.5. No natural selectionNo natural selection
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Hardy-Weinberg PrincipleHardy-Weinberg Principle
• Remember:Remember:
If these conditions are met, the population is at equilibriumequilibrium.
• This means “No Change” or “No “No Change” or “No Evolution”.Evolution”.
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MacroevolutionMacroevolution
• The origin of taxonomic groups higher higher than the species levelthan the species level.
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MicroevolutionMicroevolution
• A change in a population’s gene poolpopulation’s gene pool over a secession of generations.
• Evolutionary changesEvolutionary changes in species over relatively brief periods of geological timegeological time.
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Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
1. Genetic drift:1. Genetic drift:
Change in the gene pool of a Change in the gene pool of a small small population due to chance.population due to chance.
• Two examples:Two examples:
a. Bottleneck effecta. Bottleneck effect
b. Founder effectb. Founder effect
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a. Bottleneck Effecta. Bottleneck Effect
• Genetic driftGenetic drift (reduction of alleles in a population) resulting from a disasterdisaster that drastically reduces reduces population sizepopulation size.
• Examples:Examples:
1.1. EarthquakesEarthquakes
2.2. Volcano’sVolcano’s
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b. Founder Effectb. Founder Effect
• Genetic driftGenetic drift resulting from the colonizationcolonization of a new location by a small number of individuals.
• Results in random changerandom change of the gene pool.
• Example:Example:
1.1. Islands (first Darwin finch)Islands (first Darwin finch)
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Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
2. Gene Flow:2. Gene Flow:
TThe gain or loss of allelesgain or loss of alleles from a population by the movementmovement of individuals or gametes.
• Immigration or emigrationImmigration or emigration.
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Five Mechanisms of MicroevolutionFive Mechanisms of Microevolution
3. Mutation:3. Mutation:
Change in an organism’s DNA thatChange in an organism’s DNA thatcreates a new allele.creates a new allele.
4. Non-random mating:4. Non-random mating:
The selection of mates other thanThe selection of mates other thanby chance.by chance.
5. Natural selection:5. Natural selection:
Differential reproduction.Differential reproduction.
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Modes of ActionModes of Action
• Natural selectionNatural selection has three modesthree modes of action:
1.1. Stabilizing selectionStabilizing selection
2.2. Directional selectionDirectional selection
3.3. Diversifying selectionDiversifying selection
Number ofIndividuals
Size of individualsSmall Large
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1.1. Stabilizing SelectionStabilizing Selection
• ActsActs upon extremesextremes and favorsfavors the intermediateintermediate.
Number ofIndividuals
Size of individualsSmall Large
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2.2. Directional SelectionDirectional Selection
• FavorsFavors variants of one extremeone extreme.
Number ofIndividuals
Size of individualsSmall Large
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3.3. Diversifying SelectionDiversifying Selection
• FavorsFavors variants of opposite extremesopposite extremes.
Number ofIndividuals
Size of individualsSmall Large
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SpeciationSpeciation
• The evolutionevolution of new species.
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Reproductive BarriersReproductive Barriers
• Any mechanismmechanism that impedesimpedes two species from producing fertile and/or viable hybrid fertile and/or viable hybrid offspringoffspring.
• Two barriers:Two barriers:
1.1. Pre-zygotic barriersPre-zygotic barriers
2.2. Post-zygotic barriersPost-zygotic barriers
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1.1. Pre-zygotic BarriersPre-zygotic Barriers
a. Temporal isolation:a. Temporal isolation:
Breeding occurs at different times for different species.
b. Habitat isolation:b. Habitat isolation:
Species breed in different habitats.
c. Behavioral isolation:c. Behavioral isolation:
Little or no sexual attraction between species.
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1.1. Pre-zygotic BarriersPre-zygotic Barriers
d. Mechanical isolation:d. Mechanical isolation:
Structural differences prevent gamete exchange.
e. Gametic isolation:e. Gametic isolation:
Gametes die before uniting with gametes of other species, or gametes fail to unite.
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2.2. Post-zygotic BarriersPost-zygotic Barriers
a. Hybrid inviability:a. Hybrid inviability:
Hybrid zygotes fail to develop or fail to reach sexual maturity.
b. Hybrid sterility:b. Hybrid sterility:
Hybrid fails to produce functional gametes.
c. Hybrid breakdown:c. Hybrid breakdown:
Offspring of hybrids are weak or infertile.
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Allopatric SpeciationAllopatric Speciation
• Induced when the ancestralancestral population becomes separatedseparated by a geographical geographical barrier.barrier.
• Example:Example:
Grand Canyon and ground squirrels
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Adaptive RadiationAdaptive Radiation
• Emergence of numerous speciesEmergence of numerous species from a common ancestorcommon ancestor introduced to new and diverse environments.
• Example:Example:
Darwin’s FinchesDarwin’s Finches
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Sympatric SpeciationSympatric Speciation
• Result of a radical change in the genome that produces a reproductively isolated sub-reproductively isolated sub-populationpopulation within the parent population (rare).
• Example: Plant evolution - polyploidExample: Plant evolution - polyploid
A species doubles it’s chromosome #chromosome # to become tetraploid.
reproductive sub-population
Parent population
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Interpretations of SpeciationInterpretations of Speciation
• Two theories:Two theories:
1.1. Gradualist Model (Neo-Darwinian):Gradualist Model (Neo-Darwinian):
Slow changes in species overtime.
2.2. Punctuated Equilibrium:Punctuated Equilibrium:
Evolution occurs in spurts of relatively rapid change.
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Convergent EvolutionConvergent Evolution
• SpeciesSpecies from different evolutionary branchesevolutionary branches may come to resemble one another if they live in very similar environments.very similar environments.
• Example:Example:
1.1. Ostrich (Africa) and Emu (Australia).Ostrich (Africa) and Emu (Australia).
2.2. Sidewinder (Mojave Desert) andSidewinder (Mojave Desert) and
Horned Viper (Middle East Desert)Horned Viper (Middle East Desert)
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CoevolutionCoevolution
• Evolutionary changeEvolutionary change, in which one species act as a selective forceselective force on a secondsecond species, inducing adaptations that in turn act as selective force on the firstfirst species.
• Example:Example:
1.1. Acacia ants and acacia treesAcacia ants and acacia trees
2.2. Humming birds and plants with Humming birds and plants with flowers flowers with long tubeswith long tubes
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