Biology 100 Chapter 18

8/13/2019 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!

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Biology 100 Chapter 18