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Lecture

ANT203 October 11.pdf


Department
Anthropology
Course Code
ANT203Y1
Professor
Xueda Song

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LECTURE 4: MACROEVOLUTION
Macroevolution relates to how new species are formed and how they changed
must consider:
geological history
systems of classifications
modes of evolutionary change
Linnaean Classification
taxonomy
classification of humans:
Kingdom Animalia
eukaryotic
motile
heterotrophic (depend on other organisms as food source)
Precambrian Era (~610 Ma)
ex. stromatolite, trilobite
Phylum Chordata
notochord: flexible jointed rod, bent by surrounding muscles
gill slits at some stage in development
muscles, respiration
Cambrian Period, Paleozoic Era (~570 Ma)
ex. amphioxus, a translucent, fishlike but finless organisms
that lives in the shallow parts of seas; source of info on
vertebrate development b/c still living but has been around
since about 520 Ma
Subphylum Vertebrata
jawless and bony fishes, sharks, and rays; amphibians, reptiles,
mammals, birds
segmented spinal column
closed circulatory system (heart + blood vessels)
developed brain, paired sensory structures (balance, sight, olfaction)
heads and tails
Upper Cambrian Period (~510 Ma)
ex. agnathans (lampreys and hagfish) - means "lack jaw" -
have a notochord, light-sensitive eyes, and 2-chambered <3
Class Mammalia
sweat glands (incl. those modified to produce milk, mammary)
hair
auditory ossicles (3 tiny bones for transmission of sound from outer
to inner ear)
larger more complex brain and esp. neocortex (sense perception,
motor functions, conscious thought, language)
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longer period of ontogeny in and out of utero (req'd for big brain)
viviparous (live young, usually)
specialized dentition - heterodont
human dental formulation is: 2, 1, 2, 3
in mammalian ancestors it was: 3, 1, 4, 3
endothermic
Jurassic period, mesozoic era (~199-145 Ma)
the time when dinosaurs spread, but there were some
mammal-like species:
Dimetrodon (mammal-like reptile)
Steropodon (first monotremes; egg-laying like a
platypus)
Sinodelphis (first pouched/marsupial mammal) and
Eomaia (first placental mammal)
Order Primates
originated around the time of the dinosaur extinction, which opened
niches for the radiation of mammals
lemurs, lorises, tarsiers, monkeys, apes, humans
generalized structures shared with mammals in general:
pentadactyly
longer gestation/ontogony
generalized dentition (this does not conflict with heterodont -
it means that the morphology is general enough for the
consumption of a variety of food types)
limb structure: morphology allows for movement in a variety
of different habitats (arboreal, ground, etc.)
binocular (eyes positioned in front of skull, resulting in
overlapping fields of vision) and steroscopic (3D) vision
opposable thumbs (and in some primates, semi-opposable feet)
divergent big toes in non bipedal primates for foot grasping
nails, not claws
originated ~65 Ma, but recognizing the first primates in the fossil
record is difficult
Plesiadapis (~58-55 Ma in Europe and North America)
very reptilian body layout
Smilodectes (~55 Ma onwards, North America)
To note re the above fossils: the distribution is different from what
we see today (no primates in Europe or North America)
Family Hominidae
Genus Homo
Species sapiens (Homo sapiens)
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