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BIOC50H3 Study Guide - Final Guide: Theropoda, Spinosaurus, Hoatzin

Biological Sciences
Course Code
Jason Weir
Study Guide

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Macroevolution Final Notes
Lecture 10: Theropods and the Evolution of Birds
Sister group to saurapodomorphs
Bipedal, all small
From small forms, we get the various groups radiating from it
Small body sizes evolve and once they get to large sizes they die out and do not
continue to evolve small ones produce the major radition of dinosaurs
Spinosaurs largest of theopods
Q: Why might the largest of the Theropods represent evolutionary dead-ends?
When you specialize to become so big it will be difficult to reverse that, giant bone
densities etc
Much easier for a generalist to evolve
Giant skull adapted to catching fish
Possible that it was eating other dinosaur in marine environments
Teeth serrated along edges for cutting meat
Serrated teeth
Theropods and evolution of birds
Darwin talked about origin of birds
Feather came from Jurassic
o Missing link had feathers
o Had more similar features with theropods
Two hypotheses for origin of birds
o Archaeopteryx
Concluded it was related to dinosaurs based on skeletal features
Lack Pgyostyle
Claws on its arms (hoatzin chick is an exception) genetic expression
must have been turned off in modern birds
Digits have been adapted for flight feathers to attach to
Lacked beak and had teeth, shape like a dinosaur
Had a theropod dinosaur pelvis
o Birds arose from a pre-dinosaur reptile group
Focused on wishbone found in birds
Had advanced in phylogenetic analysis, which saw that birds were radiated from birds
1996 found fossil of sinosaurapteryx
o proto feathers
o banded pattern of feathers
o melanosomes lack or don’t lack colour

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conclusion: birds are a higly derived clade of feathered theropod dinosaurs
Evolution of Feathers
o Large bodied donisuars and many large bodied mammals lack obviously hair lik
o Chicks of theropods may have had feathers but loss them later in life
o Branching life feathers downy feathers possible for thermoregulation
o Contoured feather
o Contoured feather with asymmetrical shape adaptation for flight
o Need to know summary slide with types of feathers, list not phylogeny
o Feathers did not evolve initially for flight
Early on used for thermoregulation
o Contoured feathers
Used for protection of chicks from elements or predation
3 hypotesis for evolution of flight
o Cursorial model
Evolved through a series of short umps to catch insects
Feathers get longer and body gets lighter, we get from jumping to gliding
o Pouncing Model
Contoured feathers help break its fall, or positioning itself to catch prey
o Arboreal Model
Evolved from ancestor to climb trees and glided down
Microraptor gui fossil
Has long contour feather on hind legs
Forearms also have contoured feathered
o Come from china
o Some parts of china are these isolated islands
o Birds may have evolved in complete geographic isolation
Asymmetrical feathes
o Microraptor gui has primary asymmetrical feathers
o Asym feathers found on all flight birds, most aerodynamic capabilities and best
shape for flight
Loss of teeth? Do modern birds use gizzards for food digestion?
Evolution of beak shape?
Once birds who lose flights can adapt to flying again?

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LECTURE 11: Mass Extinction and Cenozoic Diversification
Species naturally rise and go extinct
Graph speciation rates have been greater from 200 million years ago
Five major mass extinction events
Late ordovincian
Late Devonian
Late Permian
Late Triassic
Late Cretaceous
Late Devonian
o Not clear, die off of coral reefs and other faunas
o Largest mass extinction event
o So large that detected by fossils by scienets
o Extinction marked paeozoic and Mesozoic eras
o Rapid event
o Coal forming forsts stopped in fossil record suggests significant drop in
o Volcano provides possible explanation Siberian traps
o Plume tectonics rise of magma towards surface that results in series of volcanic
eruptions in an area
o Resulted in hundreds of ash and gases being released which would have blocked
sunlight, killing off both terrestrial plants
o Bloom of fungi in fossil record, short peak lot of decomp
o Global cooling initially, aftermath is global warming due to co2
Late Triassic
o Large amphibians and reptiles go extinct paved way for dinosaurs
o Opens up ecological opportunites for new species to survive
o Dinosaurs and pterosaurs (non avian dinosaurs) go extinct
o Mammals and birds become dominant life forms
o Asteriod impact
Layer in geological strata bn certaceuous and tertiary
Spike in iridium rare on earth but plentiful in asteroids
Asteroids sends out lot of ejecta
Resulted in earthquakes tsumanis
Dust released into air block sunlight, preventing photosynthesis
Heated up ejecta comes down and caused forest fires
Part 2: Evolution of Mammals
Evolutionary events
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