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where are fossils found
near water, where oxygen is low, so that bacteria can't decompose organism as quickly
what method of fossilization keeps soft tissues?
soft parts may be preserved through distillation under heat and pressure which preferentially removes hydrogen and oxygen
how are fossils biased?
- hard parts
- some environments
- limited anatomical snapshot
- stratigraphic incomplete and pull to present
- taxonomy (more complex organisms, we can gain more info)
shark teeth discovered by steno
which dinosaurs gave parental care?
how to genome size of animal?
looking at cell size
why is fossil dating difficult?
composed of products of erosion of other rocks (chimeras), not amenable to isotope based dating techniques
how is the ideal formation for dating rocks?
fossil bearing sedimentary strata are sandwiched between layers of volcanic rock that can be dated using isotopic means
what does fossils tell us
- extinction events
- once closely related species lived together, but land drifted apart
what are mass extinctions?
- when at least 50% of organisms go extinct
- trigger by climate
ordovician silurian extinction
- 25% of marine families and 60% of marine genera
- Gondwana shift, temp decrease, sea level decrease
- 2/3 brachiopod and bryozoans disappeared
- 374 mya
- 19% families, 50% genera, 75% of species
- corals, protoamphibians
- plants colonized the land, CO2 and temp decreased
- 250 mya
- 53% marine families
- 84% marine genera
- 95% of marine species, 70% land species
- increase in volcanic activity in Siberian Traps, release of methane from sea floor, shifts in ocean currents, anoxia, increased temp
- 200 mya
- 23% of families, 48% of genera
- increased volcanic activity
- decrease in speciation, but plants and dinosaurs did well
- 65 mya
- extinction of 50% of genera, 75% of species
- decline in body size (delidaput)
Paleocene Eocene Thermal Maximum extinction
- increase in temp and CO2
- lost rhino, passenger pigeon
- happening now
- first known chordate
- has notocord: flexible rod shaped body
what was cope's rule?
population lineages tend to increase in body size over evolutionary time
largest land animal ever
what is one problem of cope's rule?
selective reading of artifact?
what are reasons for mammals to get bigger?
- sexual competition
- energetic efficiency
what caused the cambrian explosion?
- increase in oxygen (increase in size and metabolic rates)
- origin of hard parts
- evolution of eyes
- genetic changes (activation of homeotic genes for transcription factors that control body plans)
adaptive radiation by Mayr
evolutionary divergence of members of a single phyletic line into a series of rather diff niches or adaptive zones
who proposed punctuate equilibrium
- Gould and Eldredge
- to account for gaps in fossil record
- sedimentary deposit with exceptionally good fossils from anoxic environments and minimal bacteria decomposition
- soft parts preserved
what does a taxonomic bias mean?
more complex animals we can get more info from
what does hallucigenia looks like
pointy stuff in the back, legs on bottom to move
with teeth in back
which animal had 40 ft wingspan
what are some other things going extinct now
Mexican grizzly bear, passenger pigeon, caribbean monk seal, western black rhino, tasmanian tiger, stellar sea cow
what is interesting about probability of extinction over time
constant over time
what is the significance of edicacaran fauna
predate the cambrian explosion
what are three biases in the fossil?
geographic, taxonomic and temporal
what was significant about burgess shale
- all but one of the 35 existing phyla appeared
- walcott 520 mya
when did ediacaran fauna appear
560 soft bodied
what was great about increased oxygen content in seawater?
- allowed organisms to achieve increased sizes and metabolic rates
- prerequisite for evolution of predators
where did eyes first appear
trilobites 543 MYA
what are two characteristics of punctuated equilibrium
- periods of rapid morphological change with rapid speciation
- after species have formed, they exhibit stasis
how does PE explain stasis compared to PG?
- genetic homeostasis and/or developmental constraint.
- PG explains in terms of stabilizing selection
how does evolutionary change come to play between PE and PG?
- significant evolutionary change occurs in association with speciation
- PG says change within lineages
what is the difference in speciation between PE and PG?
- speciation is non-adaptive process entailing some kind of genetic revolution
- while PG, speciation is simple corollary of adaptive change
what is adaptation
genetic change in an environment