Module 1 Flashcards
Ardipithecus ramidus
Where do we come from?
fossils to 3.8BYA
Approx. 600 MYA multicellular organisms
comparative anatomy definition
the study of the evolution of the body systems
first teacher of comp. anatomy
Agassiz
Belons book of birds
George cuvier
from a small part of an organism, the whole can be deduced
phylogeny
- a statement of relationships
- evolutionary history
fossils
- allow for better view of evolution
- molecular clock
- estimate when common ancestors might have lived
analoge
correspondence in function, or position b/w organs of dissimilar evolutionary origin or structure
“same function, different origin”
homology
correspondence in evolutionary origin
“same origin, not necessarily same function”
convergence
two unrelated organisms evolving the same structure
- ex: bird wings and bat wings
parallelisms
two sister species evolve same structure independetly
- almost impossible to test
reversals
change to less derived state
- development of the collar bone in primates (small or absent in most other mammals)
phylogeny is expressed in a branching diagram
phylogenetic tree
branch =
lineage
node =
hypothetical common ancestor
clostest relative (sister group)
go to first node and read all taxa above this point
monophyletic group
group consisting of all descendents of the group’s most recent common ancestor
paraphyletic group
group consisting of the group’s most recent common ancestor, but not all descendents.
- bad, doesn’t represent evolution
polyphyletic group
group consisting of two or more groups, but not the group’s most recent common ancestor nor all of its descendents.
why are monophyletic groups the only good ones in taxonomy?
- non monophyletic groups says nothing about the group’s evolution
- naming paraphyletic groups is subjective
- from a proper taxonomy, you can almost recreate the phylogeny
apomorphy
derived characteristics
synapomorphy
shared derived characteristics
plesiomorphy
primitive characteristics
symplesiomorphy
shared primitive characteristics
which one is only useful character for building a tree?
synapomorphies
Principle of Parsimony
Occam’s Razor
- the simplest soution is the best one
- the tree that minimizes the amount of homoplasy is the best
- the fewest steps
taphonomy
the study of fossilization
fossil
any identification of past life
Examples of fossils
- molds
- carbonization
- permineralizations
- replacement
- mummification
- freezing
- amber
internal mold
external mold
permineralization
carbonized lamprey
dinosaur mummy
frozen baby mammoth
amber frog and lizard
amber lizard
fossilization “procedure”
- die of natural causes
- escape scavenging
- near immediate burial in sediments
- undisturbed burial
- survive geological events
- remain in rock until humans evolve and get grants
- be at or near the surface precisely when a paleoontologist is nearby
stratigraphy
relative position in rock layers
- low = older
- not all strata present
- all starte not laid down in same length of time
index fossil
common fossils of known age
Radiometric method
- Complex set of methods using radioactive decay, quantum spin of electrons etc.
- mass spectrometer - counts atoms in very small samples very accurately.
- Radioactive decay
- Longer half-lives can date older samples
half life of uranium-235 to lead-207
713 million years
Zircon
- incorporates uranium into crystalline structure, but excludes lead
- count number of uranium and lead atoms in sample to get age
- internal check, uranium-238 decays to lead-207 with half life of 4.5 biollion years
- good for old stuff
- in a 3 bya sample, error is about 2 million years
half life of potassium-40 to argon-40 is
- 1.3 BYA
- argon is a gas, driven off by volcanic eruptions
- potassium degrades to argon gas, count the atoms of argon vs. potassium
- good for old stuff
