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Lecture

Mesozoic lecture notes.doc


Department
Biology
Course Code
BIO 1130
Professor
Jon Houseman

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Mesozoic: Triassic, Jurassic, Cretaceous
Slide 1:
-when the Permian comes to an end, there is a group that puts amniote eggs up on land and
has a distinct advantage
Slide 2:
Early Triassic
-Pangaea is starting to pull itself apart
Slide 3:
Late Jurassic
-continents continue to drift
Slide 5:
Late Cretaceous
-another mass extinction occurs just before the Jurassic; this seals the fate of the terrestrial
vertebrate form
Slide 6:
Plesiosaurs
-one of the major changes is in the oceans
-diapsids culminate into large swimming, plesiosaurs
-are major predators in the ocean
-a lot of the ocean life is wiped out during the Permian and freshwater organisms move into
the ocean environment and succeed
-Plesiosaurs begin to feed on these newly invading organisms and become huge
Slide 7:
Molluscs and Cephalopods
-when all the agile swimmers invade the oceans, the cephalopods respond by dropping their
shell to become much more agile with jet-propelled water system and develop into the
squids and octopods today
Slide 8:
Amniote Phylogeny
-first vertebrates appear on land
-can feed with their jaws to hold on prey
-in the terrestrial environment, the jaw becomes the main source to get food
-muscles on the jaw become very large to accommodate crushing and tearing
Slide 9:
Oviparous Reproduction
-all of the amniotes are producing eggs at this point and are referred to as oviparous

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Slide 10:
Keratinized Skin
-amniote now has to waterproof their skin
-they take dead skin cells and mesh them together with protein
-protein is keratin which makes its first appearance
-crosslinks form with keratin and outer epithelial skin creates a water-proof membrane
-keratinized material is a major innovation that develops into hair, horns, finger nails, etc.
Slide 11:
-the solution to having jaw muscles attached to skull and expanding and contracting the
skull and brain as a result of eating is to put holes in the skull
-instead of having muscles insert on the inner surface of the skull, the tendons move
through an opening and the muscles are on the surface of the skull
Anapsid
-no openings for jaw muscles
Diapsids
-insertion of muscles through 2 openings in the skull
-diapsid body plan diversifies first; this group colonizes the oceans and start to swim, move
up on land to feed on insects, begin to fly, etc.
-their descendents are the birds, turtles, snakes, crocodiles, etc.
Synapsids
-insertion of muscles through 1 opening in the skull
-don't diversify because the diapsid body plan is the dominant one
Slide 12:
Anapsids
-turtles develop a body plan that is different than all other vertebrate organisms
-fuse all bones together to create a box inside of which they live
-bone is solidified as a protective surface
-the missing opening in the turtle skull is a consequence of this solidifying bone strategy
-the anapsid turtles lost their opening when they solidified their body
-turtles belong in the diapsid category
Slide 13:
Major Diapsid Groups
-there are a huge number that have gone extinct due to the Cretaceous extinction
Slide 14:
Extinct Diapsids
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