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BIOLOGY 1M03 Study Guide - Midterm Guide: Tooth Enamel, Homininae, Human Taxonomy

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Jon Stone
Study Guide

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Biology 1M03 Test Two Notes
Key Terms
Primitive: There is no such thing as “higher” or “lower” organisms
Population: Individuals in the same species that live in the same area
Therapsids: A group with mammalian traits that disappeared at the end of the Triassic period; one group
evolved and diversified, constituting mammals
Hominoids: Clade containing gibbons, orangutans, gorillas, chimps, and humans; apes
Plesiadapiforms: A taxon containing extinct animals; experts disagree as to whether they should be included
in the primate order; if they possess some primate-like traits
Platyrrhines: New world monkeys; comprise 5 primate families in Central and South America
Hominin: Refers to any of the below three groups
Homininae: Gorillas, chimps, humans
Hominini: Chimps, humans
Hominina: Humans, relatives
Geological Time Scale
- The origin of the human lineage is a late event in Earth history
Cenozoic era: Saw a spectacular mammal radiation, following extinction of the dinosaurs (except birds)
Early Triassic Period
Therapsids (warm-blooded, fur-covered ‘synapsids’)
Late Triassic, Early Jurassic Period
First mammals, dinosaurs rule
End of Cretaceous
“Dinosaurs” extinct; mammal radiation
Reconstructing Ancient Environments
Continental drift
- Continents have moved significantly in the past 200 million years from Pangaea to Laurasia and
Gondwanaland to seven continents
- Effects evolution by putting up barriers that isolate species
- Effects climate change
Climate change
- Gradual cooling and drying trend in the last 20 million years
- Climate changed substantially during the last 65 million years
- First becoming warmer and less variable (Eocene and early Miocene), then cooling (Pleistocene), and finally
fluctuating in temperature
- Changing environments lead to adaptations
Dating Techniques
Taking the Global Temperature
- Deep sea cores
- Oxygen isotopes
- O16 lighter (evaporates into snow and rain); gets trapped in glaciers and poles during cold times; high
O18/O16 ratio during cold periods
- Can be radioactive
- Decay at a constant rate
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- Half-life
- Half-life for carbon-14 is 5730 years (used for cells, tissues etc.)
Potassium-argon dating
- Used for volcanic rocks
- Fossils dated indirectly
- Can date ancient fossils (half-life is 1.25 billion years)
- More recent technique is Ar-Ar dating
Uranium-lead dating
- Flowstones in caves
Other methods of dating: Thermoluminescence (objects), Electron-spin resonance (teeth), Paleomagnetic
dating, biostratigraphy
How to Identify a Fossil Primate
- Grasping hands and feet
- Nails instead of claws
- Forward-facing eyes encased in bone
- Hind limb-dominated locomotion
- Relatively large brain
- Generalized teeth (2-1-3-3) formula
Why are Teeth Useful?
- They are complex structures, meaning they’re useful for phylogenetic analysis
- Tooth enamel remains intact through an individual lifetime (contains individual’s record)
- Grow through precise developmental sequence, allowing paleontologists to make inferences about
processes in long dead organisms
- Tooth form relates to dietary specialization
The Rarity of Fossils causes us to…
- Overestimate origin of lineage
- Underestimate time of extinction
- Oversimplify relationship between fossil taxa
- Underestimate divergence times (age for common ancestor)
Apes vs Monkeys
- Apes have no tail
- Forelimb suspension
- Short stiff lower back
- Mobile joints
- Long arms and fingers
Early Primate Evolution
- Ancestors to modern primates were small, nocturnal, quadrupeds, similar to modern shrews
- Earth warm and wet
- Tropical forest spread into North America and Europe
- Fossils discovered in North America, Africa, Europe, and Asia
- Classified into two families:
Adapidae: small eye orbits (diurnal); lemurlike in teeth, skull, nasal and auditory regions
- Larger, diurnal, and quadrupedal
Omomyidae: Enlarged eye orbits (nocturnal), galagolike and tarsierlike
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- Nocturnal, some leapers
Oligocene (34-23 mya)
- Climate became cooler, with greater annual temperature fluctuations, and drier
- Tropical, evergreen forests became replaced with deciduous forests in NA and Europe
- Climate remained warm and tropical in SA and Africa
- Egypt used to be forest like
- 2-1-2-3
- Fruit eater
- Sexually dimorphic
- Arboreal quadruped
- Diurnal
- Relatively small brain
Miocene (23-5 mya)
- Warm and wet, became cool and dry over time
- Found in Uganda
- 20 million years old
- Oldest ape?
- Face and teeth are apelike
- Mobility at shoulder
- Stiff lower back
- Femur indicates slow climbing
- Mid Miocene deposits reveal a primate radiation and expansion into Eurasia
- Africa (23-17 mya)
- Frugivorous
- Forest environments
- Apelike skull and teeth
- Monkey-like postcrania (quadrupedal, non-suspensory)
Pierolaptithecus (Middle Miocene)
- Spain (13 mya)
- Apelike face and teeth
- Wide torso, stiff lower back, mobile, wrist
- Short palm and fingers (unlike modern apes)
- Last common ancestor for African apes lived 8-10 mya in Africa
- Climatic changes in late middle Miocene reduced hominoid diversity in Asia and Europe
- Late Miocene apes are rare in Africa
- No clear candidates for ape ancestors
- Many ape species became extinct and were replaced by monkeys
What Makes Humans Unique?
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