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Chapter 9

BIOLOGY 1M03 Chapter 9: Chapter 9

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Ben Evans

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CHAPTER9:FromTreeShrewto Ape Overview • human’s evolution in its entirety began with the origin of cellular life (3.8billion yrs ago) • very recent portion is what we will be focussed on • -100 MYA until present First true Mammals • Cenozoic era (65 mya-present)  Radiation of mammals, extinction of dinosaurs • Probably linked to diversification of angiosperm/flowering plants Angiosperms o vascular plant that has flowers o have endosperm within seeds o fruit that contain the seeds (ovules that have a cover-the ovary) o Testa: the fruit coating the seed coat o most diverse group of land plants o seeds are innovation that evolved in the ancestor of gymnosperm and angiosperm o before seeds, they had spores ex. Ferns o spores have not little food resources gymnosperms o produce ovules no cover o “naked seed” Diversification of Angiosperms • by the late Cretaceous (65 mya), angiosperms dominated habitat formerly occupied by ferns and cycads • large canopy-forming angiosperms replaced conifers as the dominant trees Relationships between angiosperms and animals • angiosperms need animals for pollination, defense, and dispersal • they reward animals with nectar, fruit, shelter • angiosperms are not first plant to have mutualistic relationship with animals -ex. Some pines require animals to open the pine cones • but these interactions of angiosperms did become more elaborate compared to conifers, ferns, and cycads primates had to compete with the animals for angiosperm resources • in primates, binocular vision, grasping hands and feet, nails on fingers and toes, changes in dentition were favored by natural selection to: • enhance ability to predate arboreal insects • facilitate foraging on fruit, nectar, and leaves • facilitate locomotion what was the climate when animals were diversified? 16 • This means that snow/rain and glaciers have a higher O concentration than oceans • When there is extensive glacial coverage (cold climate) this causes the ratio of O :O in the ocean to drop because O16 is trapped in glaciers • examine ocean cores for ratio of oxygen isotopes • the concentration of O is higher in oceans during periods with cold climate • climate changed substantially during the last 65 million years • this means that snow and rain, glaciers have higher O concentration than oceans • during warm periods of Miocene, palm trees grew in Alaska, most of Antarctica was not glaciated • cold = O higher in oceans as O is in glaciers How can we relate changes in climate over time to changes in biological diversity over time? Dating Fossils: Absolute dating with radiometric methods • Potassium Argon Dating o Argon is absent from lava do any argon in a volcanic rock is derived from the decay of potassium o Works for ages of 500,000+ years, requires lava o KA • C-14 Dating 14 12 o Live animals have the same level of C and C as t14 atmosphere because they eat plants that consume CO2 that contains C o After death, C begins to decay into N so the amount of C be used to estimate age o Works for cells or tissues younger than 40,000 years o The C :C ratio has decreased substantially since industrialization (late 1800s) due to burning fossil fuels, which depletes of C and release more C 12 14 o Corrections are also needed due to extra C form bomb testing in 1960’s • Thermoluminescence dating: requires burned material • Electron-spin resonance dating: requires fossilized teeth • Uranium-lead dating: requires speleothem mineral deposits from caves Radiometric methods can have large confidence intervals or may not be appropriate for a particular site They are often supplemented with relative dating methods: • Magnetic reversals • Extinct and distinct species of animals Primate • Adaptations for climbing and locomotion (leaping, walking on 2-4 limbs, knuckle walking, brachiation) • Opposable thumbs • Prehensible tails (can grab) • Hind limb dominated posture • Grasping hands • Short snouts • Grasping hands • Increased reliance on stereoscopic vision forward eyes • 3 coloured vision in some species • eyes encased in bony orbit • nails instead of claws • relatively large brains Claws - curved, pointed, compressed sideways - 5 digits on hands - nails may be correlated with small branch foraging Colugo • Arboreal gliding mammal from southeast Asia • Has flaps of skin between legs used for gliding • Also known as “flying lemurs” Primate Phylogeny Prosiminans • small brain • large olfactory lobes • bicornuate uterus • reflective layers in eyes • nocturnal Tarsiers • enormous eyes (big as brain) • great hearing • distinctive auditory cortex • long feet/fingers New world monkeys • prehensile tails • no 3 colour vision • excellent howlers • monogamous pair bonds • most not opposable thumbs • twinning common in some species Old world monkey/ape • no prehensile tails • grasping hands • sexual dimorphism • not monogamous • diurnal • blue testes Apes o lesser apes are gibbons o greater apes are chimps, humans, Middle Eocene (54-34 mya) • no primates found on south America (it was isolated) New World Monkeys • monkeys reached south America 30 mya (late Oligocene) to evolve into new world monkey (“flat nosed” primates) • morphological features linked between new and old monkey (primates) • by Late Oligocene, South America and Africa were separated by 3,000 km • In north America, there are no fossils of anthropoid primates only prosimians (and NWM are definitely anthropoids) • anthropoid primates somehow dispersed across southern Atlantic Ocean • not only primates dispersed across the Atlantic Ocean • a dispersal scenario: ocean was around before the animals Teeth • reflect dietary specialization (fruit, meat, leaf, insects) • can tell well defined developmental sequences (how old) • preserve better than other bones • good for DNA studies Terms: anthropoids: NWM and OWM, including apes (humans too) hominoid: apes (including humans, gibbons) hominins: human linages after divergence from chimps and bonobos Hominoids/Apes • includes gibbons, orangutans, gorillas, chimpanzees, and humans • differ from other monkeys in dental/skeletal traits, brain size, and life history patterns • NWM and OWM sit on tops of branches to feed - Have sitting pads: “ischial callosities” • Apes often feed while hanging below branches, lacking ischial callosities • Apes have… o long arms o long fingers o short legs o Short stiff lumbar spine o Lack tails • Some OWN have small tails (convergence not synaptimorphy) • Long arms to reach to branch to branch • First evidence for adaptations to suspensory locomotion  fossil of Miocene • Some Miocene hominoids were quadrupedal and frugivorous but lacked tails (similar to modern apes) • These fossils have been found over much of Africa and Eurasia • Gibbons only occur in southeast Asia o 17 species • orangutans also occur in southeast Asia o 2 species o very far range • Chimpanzees species are in south east Africa • Bonobo only in south of Congo river Africa • Gorilla
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