Click to edit Master subtitle style 1/7/13 Darwin: Natural Selection & evolution Chapter 6 pgs 172-187 Pgs 728-729

.After Darwin finished public school, he enrolled in college to become a doctor but later studied theology, (religious studies). A professor at Cambridge University in England recommended him for a position on a British Navy survey vessel, the HMS Beagle.Darwin became the naturalist on the voyage which was to last two years. The voyage ended up lasting five years, during which time Darwin was able to explore extensively in South America and numerous islands in the Pacific Ocean, including the Galapagos.Wanting to share his findings, he published a book on his ideas of natural selection and evolution entitled The Origin of Species.

Voyage of HMS Beagle

Darwins ObservationsDiversity each area of the world has very different organismsFossils preserved remains of an organism that lived in the past. The fossils Darwin saw looked different than organisms living at that time. Characteristics of Galapagos Islands organisms organisms were different from organisms elsewhere and from organisms on other Galapagos islands

Diversity each area of the world has very different organismsFossils preserved remains of an organism that lived in the past. The fossils Darwin saw looked different than organisms living at that time. Characteristics of Galapagos Islands organisms organisms were different from organisms elsewhere and from organisms on other Galapagos islands

Galapagos Islands

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Comparisons to organisms On the MainlandGalapagos iguanaSouth American iguana

Comparisons Between organisms on the islandsFinches

AdaptationsAdaptation trait that helps an organism survive & reproduceExamples: The finches beaksThe iguanas clawsPoison & bad tasteBright colors of flowersAnimal coloring

Adaptation trait that helps an organism survive & reproduceExamples: The finches beaksThe iguanas clawsPoison & bad tasteBright colors of flowersAnimal coloring

EvolutionDarwin studied his observations for 20 years after returning to EnglandReasoned that organisms arriving on Galapagos faced conditions different from on the mainland.He hypothesized the species gradually changed over many generations & became better adapted to the new conditions. This gradual change is called evolution. However Darwin could NOT explain how the changes happened.

Darwin studied his observations for 20 years after returning to EnglandReasoned that organisms arriving on Galapagos faced conditions different from on the mainland.He hypothesized the species gradually changed over many generations & became better adapted to the new conditions. This gradual change is called evolution. However Darwin could NOT explain how the changes happened.


Natural SelectionIn 1859, Darwin offered an explanation evolution occurs by natural selection. He published his idea in The Origin of Species


Natural SelectionNatural selection process by which individuals that are better adapted to their environment are more likely to survive & reproduce than other members of the same species

Natural SelectionFactors that can result in natural selection:Overproduction produce more offspring than can surviveCompetition members of a species will compete for resourcesSpecies Variation(aka speciation) any difference between individuals of the same species

Organisms with a helpful variation will survive & reproduce. Poor variations will die out. Over a long time, natural selection will lead to change. Factors that can result in natural selection:Overproduction produce more offspring than can surviveCompetition members of a species will compete for resourcesSpecies Variation(aka speciation) any difference between individuals of the same species

Organisms with a helpful variation will survive & reproduce. Poor variations will die out. Over a long time, natural selection will lead to change.

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Reasons for Species variation aka - speciation 1. Climate changeSnowshoe hare - summerSnowshoe hare - winter


Reasons for Species variation 2. Geographic IsolationKaibab squirrel Grand CanyonAbert squirrel Grand Canyon

Mutualism relationship in which both species benefitCommensalism relationship in which 1 species benefits and the other is neither helped nor harmedParasitism 1 organism lives in or on another organism and harms it

Reasons for species variation

3. Interspecies interactionMutualism relationship in which both species benefitCommensalism relationship in which 1 species benefits and the other is neither helped nor harmedParasitism 1 organism lives in or on another organism and harms it

MutualismParasitismcommensalism


Reasons for Species variation 4. genetic mutation Darwin knew changes happened, but could not explain how. (1850s)Mendel explained how change happens through genetic traits (1850s)

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Click to edit Master subtitle style 1/7/13 Darwin: Natural Selection & evolution Chapter 6 pgs 172-187 Pgs 728-729