Download - Biology 100 Chapter 18
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Systematics
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Biological Classification
taxonomy: naming organisms
2 part name: Genus species (Homo sapiens,
Felis concolor)
phylogeny: classification based on
evolutionary history
systematics: discovering those evolutionaryrelationships
clade: family tree of groups of organisms
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hierarchical:
domain: Eukarya
kingdom: Plantae
phylum: Echinodermata
class: Aves, Reptilia
order: Lepidoptera
family: Gekkonidae
genus: Sceloporus
species: sapiens
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How do we decide?
homologous structures: similar
structures show similar evolutionary
historyeven when similar structures have
different functions (wings, flippers, and
legs)forelimbs of birds and mammals
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vestigial structures: maintaining structures
that dont serve any purpose
hind limb bones where no hind limbs exist whale and snake pelvic structures
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watch out for convergent evolution and
analogous structures!!!!!
convergent evolution: anatomicalsimilarities not derived from common
ancestry (antifreeze proteins)
analogous structures: structures withsimilar function, but dissimilar anatomy
bird wings, grasshopper wings, and sting
ray wings not derived from common ancestry, but
similar environment
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Evolutionary Biology:
Reconstructing Evolutionary Trees and Classification
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the BIGpicture
We dont have a directmeasure of evolutionary
history, so we must
reconstruct it.
Classification based onphylogeny is powerful.
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Classification Types
Trivial classification: an organizing system ofconvenience which does not reflect anything beyondthe criterion used for Classification CD collection: Megadeath|Motab, Pavarotti|Pink Floyd
Stamp, coin collections, classifying organisms by colors,shapes sizes, etc.
Non-trivial Classification: An organizing system whichreflects something in addition to the criterion onwhich it was organized Periodic table of the elements
Based on proton & electron number; predictive
Is organismal classification trivial?
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Species can be arranged into sets of nested
hierarchies
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Monophyletic Group
A group comprised of an ancestor and all of itsdescendants.
All the members of that group can trace their ancestry to
a single, most recent common ancestor (MRCA).
The ancestor must be the progenitor of all the species inthe group, and none outside of it.
A EDCB F
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Non-monophyletic Groups
Paraphyly/Polyphyly: A group which includessome, but not all, descendants of a common
ancestor.
A EDCB F
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So What? What can you do with reconstructed
evolutionary history?
It can be used to solve riddles
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Hair
Hair
To solve the riddle, we need to build an
evolutionary tree (a phylogeny)
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hair
hairscales
amnion
scales
amnion
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hair
hairscales
amnion4 limbs
4 limbs
scales
amnion
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The egg came here
The turkey came here
The EGG came first!!
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Plastic Organisms
groups of three
decide how to group organisms based on
shared traits
build clade or tree based on your decisions
defend your grouping decisions and speciation
events (tell me why you did what you did)
GO!