GEO 103 Lecture 14: Precambrian Rocks
Document Summary
Phylogenetic trees - express evolutionary relationships as anatomical differences vs time. Cladogram shows relationships among members of a clade - group of organisms including its most recent common ancestor. Cladistics examine derived characteristics - evolutionary novelties - as opposed to primitive or fundamental characteristics. Different interpretations of the relationships among bats, dogs, and birds, Bats and birds flu, suggesting closer relationships than to dogs. Dogs and birds do not appear closely related. Hair and giving birth to live young indicate that bats and dogs are more closely related. Difficult applying to fossils - eg. distinguishing primitive from derived characteristics and with convergent evolution. Mosaic evolution - organisms have both recently evolved and ancestral features. Oldest birds had feathers and fused clavicles, but retained reptile characteristics. However trends may be complex, variable rates, to a degree, and even reversible. Evolutionary trends are series of adaptations to changing environments or exploitation of new habitats.
