January 27, 2014 – Biology
Exam 1: next week.
Homologies: key for making ancestry tree
• Similarity in characteristics resulting from a shared ancestry
o Wings have developed independently, but within a group they are homologies
(dragonfly, hummingbirds, flying fish, bats)
o Similarity in complex structures (human arm, cat leg, whale fine, bat wing)
o Similarity in developmental pattern
o Molecular similarity (genes and other regions of DNA, shared ancestry)
• Problem: analogy (aka homoplaisy)
o Similarity resulting from convergent evolution rather than ancestry
• Evolution of similar, or analogous, features in distantly related groups
• Analogous traits arise when groups independently adapt to similar environments in
• Does not provide information about ancestry.
o Examples: sugar glider (marsupial, from Australia) Flying squirrel (North
America). Not closely related at all. Similar because they live in similar
• Convergence and mimicry: evolve to mimic others (plants and animals)
• Shifting from the process of evolution to the pattern of evolution
• Phylogeny: is the evolutionary history of a species or group of related species (reality)
• Systematics: classifies organisms according to their evolutionary relationships
o Systematists use fossil, molecular, and genetic date to infer evolutionary
relationship, make the classification that is discovered by phylogeny.
• Taxonomy: is the ordered division and naming of organisms. Understand their
phylogeny by their name.
o in 1700, Linnaeus published a system of taxonomy based on resemblances
o two key features of his system remain useful today: two-part names for species
and hierarchical classification two-part names for species, binomial: first is the genus, second part is the
specific epithet, ex: Ba humbugii (snail)
Hierarchical classification: contained within the higher order, same family
has the same genus
• A taxonomic uni