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Evolution L-318 > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

Charles Darwin

A
  • graduated 1831
  • naturalist on Beagle on round the world trip
  • 22 when left, returned when 27 in 1836
  • last long trip
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2
Q

South America

A
  • Darwin saw giant mammal fossils
  • important, did not recognize importance until he got home and identified the specimens
  • read Malthus in 1838 clearly looking for a mechanism
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3
Q

Darwin’s tools to study evolution

A
  • travel, collections, observation
  • geographic distribution of organisms
  • morphology and classification
  • geology
  • simple experiments
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4
Q

Biogeography

A
  • the study of geographic distribution of organisms
  • in his early reasoning based on his travels this is what he used
  • key to making him realize that evolution had to have occurred
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5
Q

Role of biogeography in establishing evolution

A

-Darwin: relationships of living and extinct South American mammals. Species distributions in the Galapagos Islands-birds and tortoises
Wallace: Wallace’s line in East Asia
-biogeography plus paleontology were crucial to Darwin’s inference of evolution

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6
Q

Key point from South America

A

-fossil glyptodons-related to living armadillos

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7
Q

Ground sloths

A
  • related to living tree sloths
  • groups native to South America
  • fossil species not identical to the living
  • fossils are related to living groups native to same region which indicates a genetic link between the extinct and living species in regions of the world (ground sloth DNA is similar to that of living tree sloths)
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8
Q

Other examples of genetic link

A

-cacti new world vs. euphorbs old world

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9
Q

Other example from biogeography

A
  • Tasmanian wolf
  • dog-like but not related to dogs
  • has a pouch and is a marsupial related to possums and kangaroos
  • DNA links it to other Australian marsupials
  • all other original mammals in Australia are marsupials
  • how do we account for this dog like carnivore–>Darwin (and) Wallace fact best explained by the hypothesis of local evolution in various regions of the Earth
  • resemblance to wolf is convergence between unrelated carnivores
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10
Q

Mexican blind cave fish

A
  • analogous case under modern study
  • not relate to blind cave on other continents
  • related to fish with eyes that linve in above ground streams near the caves-can be hybridized in lab
  • eye loss is linked to genes that enlarge the jaws for feeding on cave floor. loss of eyes is incidental
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11
Q

Conclusion

A

-evolution is taking place locally, with direct genetic link between an ancestral population and a derived population

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12
Q

Generalizations from biogeography

A
  • fossil forms related to the living in various regions
  • similar environments have similar forms, but related to local species
  • island faunas have peculiarities that can only be explained by migrations of ancestors from elsewhere, followed by local evolution and speciation
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13
Q

Darwin in the Galapagos

A
  • disharmony: reptiles in mammalian roles
  • species unique to the islands but closest relatives in South America
  • species unique to each island, but closely related to those on the other Galapagos islands
  • Adaptive spectrum of birds but within a small group of finches, rather than among several bird groups (these other groups are absent from the islands
  • Conclusion: these observations make more sense given evolution than creation
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14
Q

Tortoises in Galapagos

A

-every island in the Galapagos had a different species of tortoise and very few species survived. All related to each other and all related to tortoises in South America in the new world

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15
Q

Alfred Russell Wallace

A
  • also made disturbing observations like Darwin
  • travels to Indonesian island ins 1850’s
  • Bali and Lombok are 20 miles apart
  • Bali: tigers, monkeys, orangs, rhinos, bears, Asian birds
  • Lombok: marsupials, birds of paradise, cocatoos
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16
Q

Why do evolutionary biologists study islands?

A
  • semi isolated evolutionary laboratories
  • fewer species, simpler evolutionary histories
  • products of colonization followed by speciation
  • each island is unique, but general rules apply across islands
  • e.g. accidental sampling of colonists that may not represent outside world (reptiles dominate Galapagos), islands effects like dwarfing, evolution of endemics, convergence
17
Q

Island biogeography

A
  • dispersal
  • species/area
  • adaptive radiation and convergence
18
Q

Effects of geography on past life

A
  • plate tectonics
  • paleobiogeography
  • vicariance
19
Q

Results of low dispersal rates to islands

A
  • disharmony of faunas e.g. no mammals on the Galapagos Islands. Mammals never got there , so reptiles dominate what would be mammalian niches
  • endemics: colonizing species evolve into unique forms in isolation
20
Q

Area effect

A
  • area of an island determines the number of species that are present (so of course so does dispersal)
  • number of species on an island is an interaction between number of new species introduced and number of species that go extinct
21
Q

Archipelago Effect:

A

-species coming from outside survives on an island and gives rise to a new species which then migrates to a new island and gives rise to a new species which then migrates back to the first island and so on

22
Q

Adaptive radiation and convergence

A
  • colonizing organisms evolve to fill empty niches
  • convergence results when unrelated organisms in different locations evolve similar adaptations or structures
  • islands provide numerous examples of both, and have been viewed as evolutionary laboratories
23
Q

Plate tectonics

A
  • has rearranged positions of contacts between continents over time
  • ancient distribution of animals and plants provide evidence
  • influences evolution, and the present distribution of some organisms has resulted from continental movement-called vicariance e.g. flightless bird
24
Q

-endemics

A

colonizing species evolve into unique forms in isolation

Evolution L-318 (28 decks)

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