Download Ch. 22 Descent with Modification

Ch. 22 Descent with Modification
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Enduring Understanding: Evolution is populations changing over time
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Essential Question: How is evolution explained?
http://www.lucidcafe.com/library/96feb/darwin.html
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Who came before Darwin?
Plato ­ believed in 2 worlds:
real = ideal/eternal
illusionary world of imperfection
Aristotle (384­322 B.C.)­
­organisms are arranged in ladder of increasing complexity
­species = permanent, do not evolve
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1700's ­ natural theology = philosophy (religion based) to discover the Creator's plan by studying nature
­adaptations = evidence that God made each organism for a purpose
Carolus Linnaeus (1707­1778)­ founder of taxonomy
­binomial nomenclature
­relationship of organisms is a pattern of creation
http://www.anbg.gov.au/biography/linnaeus.html
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Georges Cuvier (1769­1832)­ paleontologist
­documented succession of fossil species in Pans Basin (Paris)
­older fossils on bottom of sedimentary rock, younger on top
­believed in catastrophism ­ each rock boundary caused by a catastrophe (flood, drought that destroyed species)
­local species died, new from other areas
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James Hutton (1726­1797)
­realized geologic formations formed by processes
­ex. canyons formed by rivers
­believed in gradualism = change occurs slowly & continuously 7
Charles Lyell (1797­1825)
­believed in uniformitarianism ­ processes don't change over time
­ex. forces that build mountains and erode them, forces are same today
http://www.hallencyclopedia.com/topic/Charles%20Lyell.html
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Jean Baptiste Lamarck (1744­1829)
­studied fossils ­ saw relationships
­2 principles:
a. use and disuse of body parts ­ body parts that were used more were stronger and larger
Ex. neck of giraffe got longer because it had to stretch for leaves on trees
b. inheritance of acquired characteristics­ modifications
of an organism can be passed on
­long neck is passed on
Evolution happens because organisms have an innate drive to be more complex
http://hallencyclopedia.com/topic/Jean­Baptiste%20Lamarck.html
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Who was Charles Darwin?
­son of a country doctor
­at 22 (1831) sailed aboard the HMS Beagle on a 5 year voyage
­companion to captain/naturalist ­sailed from England to Argentina, Strait of Magellan into Pacific and around world
­Spent 5 weeks at Galapagos Islands where he documented both visually and written flora and fauna of area
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­influenced by Lyell's work ­ lead Darwin to believe:
1. Earth is older than 6,000 years (theologians belief)
2. slow, subtle processes over long period of time lead
to substantial change
­1844 ­ wrote essay about natural selection ­ did not publish it
­1858 ­ Alfred Wallace sent manuscript to Darwin about theory of natural selection
­ 1859 Published "The Origin of Species"
­uses evolution ("descent with modification") to explain life's unity and diversity
­concept of natural selection
­did not use word "evolution" until end of book
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Ernst Mayr interpretation of Darwin's work on natural selection­made 3 inferences based on 5 observations
Observation 1­ For any species, population sizes would increase exponentially if all individuals that are born reproduced successfully
Observation 2 ­ populations tend to remain stable in size, except for seasonal fluctuations
Observation 3 ­ Resources are limited
Inference #1­ production of more individuals than the environment can support leads to a struggle for existence among the individuals of a population, with only a fraction of their offspring surviving
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Overproduction of offspring
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Observation 4 ­ Members of a population vary extensively in their
characteristics, no two individuals are exactly alike
Asian Lady Beetles
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Observation 5 ­ Much of the variation is heritable
Inference #2 ­ Survival depends in part on inherited traits. Individuals whose inherited traits give them a high probability of surviving and reproducing in a given environment have higher fitness and are likely to leave more offspring than less fit individuals
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Camoflague is an evolutionary adaptation
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Inference #3 ­This unequal ability of individuals to survive and reproduce will lead to gradual change in a population,with favorable characteristics accumulating over generations
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Darwin based other ideas on artificial selection­ selective breeding of domesticated plants and animals
­if change can happen in a short period of time, than can happen long term ("natural selection")
* populations evolve over time, not individuals
* natural selection can amplify or diminish only those traits that are passed on
* a trait that is favorable in one situation, may not be favorable in another
** life evolves through "gradual accumulation of small changes"
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Artificial selection
Diverse vegetables from wild mustard
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What evidence is there for evolution?
Reznick and Endler study in Trinidad
in one pool:
Predator: Killifish ­ eats small guppies
Guppies: larger at sexual maturity in other pool:
Predator: Pike­cichlid ­ eats large guppies
Guppies: smaller at sexual maturity than in killifish pool
in experimental pool:
no guppies, but killifish
introduced guppies from Pike­cichlid pool
conclusion:after 30­60 generations ­ transplanted guppies were average 14% heavier at maturity and average age also increased 21
Drug resistant HIV
HIV resistance to drug 3TC
3TC interferes with reverse transcriptase
3TC molecule is similar to cytosine nucleotide, so 3TC is used instead of cytosine ­ causes termination of elongation of DNA so blocks reproduction of HIV
3TC resistant viruses can distinguish between 3TC and cytosine
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Homologous structures: structures in different species that are similar because of common ancestry
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Comparative embryology­ early stages of development show anatomical homologies
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Vestigial organs­structures within an organism that no longer serve a purpose
ex. In humans:
wisdom teeth
appendix
In snakes: pelvic and leg bones in some species
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Molecular homologies­ similar DNA, RNA, amino acid sequences between organisms
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tetrapod limbs
amnion
feathers
crocodiles are more closely related to birds than lizards
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Convergent evolution­ the independent evolution of similar features in different lineages.
ex. sugar glider ­ marsupial squirrel in Australia and flying squirrel in North America (eutherians­ uterine development)
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ex. Ocotillo in southwestern N.A and the Alluaudia of Madagascar
analogous structures ­ structures that have a similar function but are structurally different
Ex. bird and butterfly wings.
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Biogeography­ geographic distribution
closely related species tend to be found in same geographic region
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Galapagos finches
Islands tend to have endemic species ­ found nowhere else in the world
Darwin found that they have similar species on mainland of other nearby islands
http://encarta.msn.com/media_461517965/Gal%c3%a1pagos_Finches.html
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Fossil Record­
prokaryotes = oldest fossils found
birds from dinosaurs
whales/dolphins from terrestrial animals
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So, what evidence do we have that evolution occurs?
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