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Evolution L-318 > Lecture 3 > Flashcards

Lecture 3 Flashcards

1
Q

Fossils-What are they, what do they tell us, examples

A
  • remains of former life
  • give a view of extinct morphologies, species, ecosystems, and evolutionary transitions between now clearly separate forms
  • include bacteria, algae, plants, invertebrates, and vertebrates
  • also include tracks, traces, burrows, that give us a view of the activities of extinct life
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2
Q

Modes of preservation

A
  • actual remains, such as frozen mammoth, wood, shells, bone
  • mineral replacement “petrified”
  • impressions
  • casts
  • special modes like amber
  • chemical fossils-event ancient DNA
  • trails and other trace fossils
  • coprolites
  • eggs, nests, fossil fetuses
  • environmental traces, including fossil raindrops, ripples, dunes, mud cracks, glacial scrape marks
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3
Q

Pre-modern interpretation of fossils

A

-generally seen as items created in place and mimicking shells, teeth, or bones

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4
Q

Leonardo da Vinci and Nicklaus Steno

A
  • realized that fossils were remains of former life
  • da Vinci speculated that shells on mountains showed that they were once covered by the sea
  • most famous demonstration was of fossil tongue stones to teeth of living sharks
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5
Q

John Woodward

A

-by 1680 fossils are seen as remains from the Deluge (flood of Noah)

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6
Q

George Curvier

A
  • introduces reality of extinction, long history of life, repeated catastrophes and re-population by new organisms
  • use of biostratigraphy and index fossils
  • invented archeology
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7
Q

Modes of preservation

A
  • sediments-almost all fossils in sedimentary rocks

- biases: these affect what we see as fossils

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8
Q

conglomerate

A

-rocks cemented

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9
Q

sandstone

A

-sand cemented

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10
Q

shale

A

-mud cemented

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11
Q

limestone

A

-shell bits

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12
Q

chert

A

-silica

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13
Q

Environmental Bias

A
  • fossilization requires sedimentation

- best sites: shallow marine basins, reefs, lakes, river flood plains

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14
Q

Preservational bias

A

-hard parts of large creatures best; small creatures with soft bodies least likely to leave fossils

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15
Q

Depositional environmental bias

A

-fossilization unlikely if scavengers are present, soil is acidic, there are high O2 levels which encourage decah, strong water currents or bioturbation moves things around

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16
Q

How do fossils come to be?

A
  • have to know how rocks are made
  • sediment and these things get stuck under layers and layers of sediment over thousands of years make a fossil
  • most of the time what dies rots away so no fossil is made
  • so the fossil record is kind of sparse, not a complete record of everything that ever lived
17
Q

Sampling biases and gaps

A
  • over and under representation by environment (shallow water marine–>good, mountains–>poor)
  • by taxon: mollusks, brachiopods, corals, echinoderms, all well represented while insects, spiders are poorly represented and flatworms, nematodes, rotifers, and ctenophores are almost not at all represented
  • by geological time period
  • by continent: Australia is a poor record of invertebrates
18
Q

taphonomy

A

-do experiments to determine how dead things get preserved

19
Q

Nematodes

A
  • most diverse species

- only have fossils of 5 kinds

20
Q

gaps

A
  • missing rock sequenes common in geological record
  • due to non-deposition, non-preservation, destruction by tectonic forces
  • destruction by erosion
  • the higher you go in the taxonomic category the more representation you get so you can see the big picture
21
Q

Importance of fossil record

A

-without it we would know that whales are mammals but we wouldn’t know how they got there

22
Q

special and unusual preservation in fossil record

A
  • most valuable kinds of fossils
  • unusual deposition, fast, fine sediment, no O2 microbial action to replace and mineralize soft tissue
  • entire small soft bodied animals, hair, feathers, dinosaur eggs with embryos, body tissue of frogs and mammals, wings/internal ears of bats
23
Q

Cabrian

A

-Burgess shale, Chengjiang

24
Q

Pennsylvanian

A

-Mason Creek

25
Q

Jurassic

A

-Solnhoffen

26
Q

Eocene

A

-Messel

27
Q

Mesozoic/Cenozoic

A

-Ambers

28
Q

What we learn from fossil record

A
  • sampling-how complete is our view of life history in the fossil record?
  • extinct diversity
  • times of origination and extinction-confidence intervals and data to use for determining evolutionary rates
  • observe evolutionary transitions
  • rates and patterns of evolution in the past
  • paleobiogeography
  • paleoclimate
  • paleoecology
29
Q

Sampling

A
  • if we look at living marine animals, only 20% would leave fossils under normal circumstances
  • gaps in deposition/erosion
  • if only a tiny minority of extinct species is known, how good can our record of the major patterns of evolution be?
  • ex: for animal fossil record should recover nearly all phyla, most classes and proportionally fewer lower taxonomic categories
30
Q

Extinct diversity

A
  • reveals former life on earth. Trilobites, dinosaurs, strange Cambrian animals all known only via the fossil record
  • patterns change through time
31
Q

Kinds of questions

A
  • was live always as divers as now?
  • does the record reveal trends or underlying regularities? (past extinctions only known this way)
  • is there progress?
  • can we find transitional forms in evolutionary series?
32
Q

Evolutionary transitions

A
  • to observe speciation
  • to observe macroevolution, transitions between major groups: fish to amphibian, reptile to mammal, reptile to bird, land mammal to whale
  • to test theories of evolution: gradual vs. punctuational
33
Q

Vertebrates in the fossil record

A
  • origins and new structural features (jaws, lungs, legs)
  • rise and fall in diversity
  • transition to land life
  • meaning of extinctions-competition vs. convergence
34
Q

Species origins

A

-difficult to pick up in fossil record because of the sampling problem. However some species to species transitions are known from the fossil record

35
Q

Transitional forms between distinct groups

A
  • several

- fish to amphibian, dinosaur to bird, land mammal to whale, lizard to snake, hominid to human

Evolution L-318 (28 decks)

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