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History of Life
(Chapter 14)
The Record & Origin of Life
Earth’s
History
Geologic Timescale –
calendar of Earth’s
history based on
rocks & fossils
4 Eras:
• Precambrian
• Paleozoic
• Mesozoic
• Cenozoic
http://lifeasahuman.com/files/2011/01/geological-time-scale.jpg
Plate Tectonics – movement of land
masses
• Helps to explain why similar fossils are found
on different continents
• May account for speciation
• VERY gradual
• http://www.ucmp.berkeley.edu/geology/anim1.html
Fossils – evidence of an organism from
long ago
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Provide record of life on Earth
Imprint, burrow, actual bone
Demonstrate diversity
Evidence of behavior
Photography by J. Botz & K. Williams
Biogenesis vs Spontaneous Generation
http://www.expertsmind.com/questions/theory-of-biogenesis-30116598.aspx
How did life begin?
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Divine Origins (theology)
Meteorites (semantics)
Primordial Soup (re-create organic molecules)
Bubbles (1986, supports Primordial Soup)
“An RNA World” (self-replicating molecules
preceded self-replicating organisms)
Primordial Soup
• A.I. Oparin – energy + (N, CH4, NH3) =
oraganic molecules (like amino acids)
• Harold Urey & Stanley Miller – experimental
evidence supports Primordial Soup Theory
• Amino acids form proteins when heated w/o
O2
• ATP & nucleic acids form similarly
• Sidney Fox & protocells
Bubbles
• Louis Lerman (1986) suggest primordial soup
occurred in tiny bubbles of lipid molecules.
• Wind, waves, rainfall created bubbles
• Bubbles provided environment to speed
reactions of primordial soup
“An RNA world”
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Self-replicating molecules preceded cells
DNA, RNA (perhaps a precursor?)
RNA probably predated DNA
Difficult to obtain data to support this idea
because RNA is more complex than a protein
(like what was produced in Primordial Soup
experiments)
“First” is still a mystery, but early
development well supported…
• Small organic molecules can form complex
organic molecules
• Earliest: anaerobic, heterotrophic, prokaryotes
• Next: chemosynthetic prokaryotes (similar to
archaebacteria)
• Then: photosynthetic prokaryotes (produced
O2)
• Evolution of aerobic cells & eukaryotes
(endosymbiont hypothesis)
Evolution & Natural Selection
(Chapter 15)
Natural Selection
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Charles Darwin
Artificial selection (breeding)
Mechanism for change in populations
Adaptations (structural, behavioral)
“survival of the fittest”
Camouflage
Mimicry
Evidence for Evolution
• Field observations (some laboratory, too)
• Fossil record
• Anatomy
– Homologous structures
– Vestigial structure (no current function, but
functioned in ancestor)
– Analogous structures (not direct support)
• Biochemistry
• Embryology (tail & gill slits in embryos)
Haekel’s drawings
http://ncse.com/book/export/html/11831
Mechanisms for Evolution
• A gene pool w/ allelic frequencies that remain constant
through generations demonstrates genetic equilibrium
• Evolution occurs only when genetic equilibrium
changes
– Mutation (when useful, gains prominence in gene pool)
– Genetic drift (chance events alter allelic frequency)
– Gene flow (individuals move in & out of population)
• Natural selection acts on variation and usually factors
into changes in established gene pools
• Speciation
– Isolation: Geographic, reproductive
– Gradualism & Punctuated Equilibrium
Selection & Patterns of Evolution
• Natural Selection
– Stabilizing selection (favors average)
– Directional selection (favors one extreme)
– Disruptive selection (favors extremes)
• Diversity
– Adaptive radiation (“branches”)
– Divergent evolution (distinct from ancestor)
– Convergent evolution (distant relatives evolve
similar traits)
Primate Evolution
(Chapter 16)
Primate Adaptation & Evolution
Human Ancestry
Primate Adaptation & Evolution
• Primate = arboreal mammals
• Primate Adaptations:
– Binocular vision
– Opposable thumbs
– Flexible joints (hips & shoulders)
– Complex brains
– How might these adaptations be beneficial for life
in the trees?
Primate Adaptation & Evolution
• Primates appear in fossil record 65-70 mya
• Trends:
– Increasing brain size
http://www.athenna.com/dr-peppers-evolution-joke-on-facebookriles-up-creationists/athenna/web_design/teoria-de-design/
– Walking upright
Primate Adaptation & Evolution
(two groups)
Prosimians
• Small, noctournal
• Tropical environments
• Lemurs
• Tarsiers
Anthropoids
• Monkeys
– New World
• Prehensile tail
– Old World
• No tail
• Hominoids (apes & humans)
– Long-term parental care
– Social
Human Ancestry
• Humans developed over time
– Brain & body size increased
– Bipedalism more efficient
– Jaws & teeth decrease in size
Human Ancestry (great pic 445)
• Earliest hominids arose in Africa
• (hominids = primates that can walk upright on
2 legs – gorillas, chimps, bonobos, humans)
– 5-8 mya (last common ancestor w/ apes 5-10 mya)
– Old world monkeys became adapted to global
cooling (new climate conditions)
– Probable order
• Gibbons
• Orangutans
• Chimps & gorillas (likely share human ancestor)
Human Ancestry
• Sahelanthropus tchadensis – oldest known hominid
(or near hominid) 6-7 mya (2002)
• Ardipithecus ramidus 4.4 mya (1994) – indicate
bipedalism evolved in forested areas, not open
savannah
• Australopithecus anamensis ~ 4 mya (1995)
• Australopithecus afarensis 3-4 mya (1974) “Lucy”
• *other Australopithecus species lived between
4 and 1 mya (http://www.talkorigins.org/faqs/homs/species.html)
Human Ancestry
• Homo habilis 2.5-1.1 mya, “handy man”
rudimentary speech?
• Homo erectus 1.8 million – 300K yrs ago
“upright human” hunting & fire?
• Homo antecessor 780 K yrs ago (1977)
earliest European hominid
Human Ancestry
• Homo sapiens appeared in Europe, Africa,
Middle East, Asia (400-100 kya, book)
• Homo sapiens (archaic) (also Homo
heidelbergensis) 500-200 kya (H. erectus similar)
• Homo sapiens neanderthalensis (also Homo
neanderthalensis) 230-30 kya
• Homo sapiens sapiens (modern) 195 kya
– Continue to see trends toward small molars & less
robust
Human Ancestry
• Stone tools coincide w/ genus Homo in fossil
record
– Homo Habilis – first evidence of tool use
– Neanderthal
• Genetic evidence suggested NOT evolve to Cro-Magnon
(may have interbred, however)
– Cro-Magnon – spread throughout Europe 35-40
kya
• 200 kya: Africa, Europe, Asia
• 12 kya: North America
• 8-10 kya Native Americans had agriculture &
domestication