-modern scientific thought -influences on darwin's theory of … · 2019. 6. 21. ·...

-Modern scientific thought

-Influences on Darwin's theory of natural selection

-Natural selection

-Examples of natural selection

Textbook progress: ch. 2 and some ch. 3

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Pre-scientific thinking

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Common views before the 18th century

Fixity of species

Young Earth

Pre-scientific thinkingChanges before the 18th century

-discovery of the New World

-new tools (e.g., telescope)

-heliocentrism

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Precursors to evolutionary theoryJohn Ray:

species: a group of organisms that are reproductively isolated

Carolus Linnaeus: binomial nomenclatureE.g., Homo sapiens = Genus species

Precursors to evolutionary theoryGeorges-Louis Buffon: posited a correlation between changes in the environment and changes in an organism

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Precursors to evolutionary theoryJean-Baptiste Lamarck: emphasized organism-environment interaction

First to try and explain evolution...Inheritance of acquired characteristics

-traits altered through use or disuse-altered traits are inherited

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Precursors to evolutionary theoryJean-Baptiste Lamarck: emphasized organism-environment interaction

First to try and explain evolution with:Inheritance of acquired characteristics

-traits altered through use or disuse-altered traits are inherited

Problem: says traits are altered during the lifetime of an individual

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Georges Cuvier: tried to explain geology with catastrophism-first to say species go extinct

Charles Lyell: Uniformitarianism explains geology points to an old Earth

https://youtu.be/o_wmulBtWlk

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Thomas Malthus: populations grow exponentially but resources grow linearly

-leads to competition for resources

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-learned about Lamarck, Buffon, etc.-BFFs with Lyell-a 5-year voyage around the world inspired his theory of natural selection

Charles Darwin (1809-1882)

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Artificial selection-All dogs share a common ancestor-Explains the extreme variation between breeds

Natural selection: artificial selection analogy

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Individuals with favorable traits have higher reproductive success compared to individuals with less favorable traits.

(1) all species produce offspring faster than the food supply

(2) there's biological variation in all species

(3) each generation more offspring are born than survive

Natural selection in detail - Eight processes

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(4) more favorable traits lead to more fit individuals

(5) environment determines which traits are favorable

(6) traits are inherited and passed on to yield greater reproductive success

Natural selection in detail - Eight processes

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(7) over time, changes accumulate leading to new species

(8) geographical isolation leads to new species through selective pressure

Natural selection in detail - Eight processes

Reproductive success: # of reproductively viable offspring produced

Fitness: relative measure of reproductive success

Selective pressures: environmental factors determining reproductive success.

https://youtu.be/Uf-mOCN7rUUhttp://peppermoths.weebly.com/

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Important terms for evolution by natural selection

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Natural selection

Examples of natural selection: Galapagos finches-Local environmental conditions varied from island to island

SO: NS led to different populations to diverge from each other

*beak size and structure differ between species

Heavy beaks = exploit seeds and leaves

Long stout beaks = exploit insects in trees (like a woodpecker)

Long thin beaks = exploit flying insects

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NS ex: Antibiotic resistance in bacteria

Environmental pressure: use of antibioticsSelection for: higher resistance to antibiotics-Over many generations, a new resistant bacteria emerges.

https://youtu.be/CUslKICi5mc(antibiotics as evidence)

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Examples highlight important conditions needed for natural selection

i. Only acts on heritable traits

ii. Only acts on already existing variation

iii. Fitness is relative to environmental changes

iv. Only acts on traits that affect reproduction

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Constraints on Darwin's theory of natural selectionConstraint: Didn't know why biological variation occurs

Constraint: Didn't know how traits were inherited traits

Overcame constraints due to:-advancements in technology, cell biology, and genetics-the rediscovery of Mendel's principles of inheritance

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Examples of natural selectionhttps://www.pbs.org/wgbh/nova/video/evolution-in-action

https://youtu.be/lIEoO5KdPvg(Whale evolution)

https://youtu.be/mZt1Gn0R22Q(misconceptions about evo)

https://youtu.be/CdzmH3jNkU0

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Examples highlight important conditions needed for natural selection

i. Only acts on heritable traits

ii. Only acts on already existing variation

iii. Fitness is relative to environmental changes

iv. Only acts on traits that affect reproduction

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