1. Why is X
1.1. 2 types of answers
1.1.1. proximate explanations
1.1.1.1. mechanisms responsible for the trait
1.1.1.2. within lifetime of organism
1.1.2. ultimate explanations
1.1.2.1. fitness consequences of the trait
1.1.2.2. over many generations
1.2. examples
1.2.1. why do waxwings migrate south in the winter
1.2.1.1. proximate (ST)
1.2.1.1.1. a mechanism in their brains senses days are getting shorter/colder
1.2.1.2. ultimate (LT)
1.2.1.2.1. those migrating south have been better at surviving the winter
1.2.2. Humans crying
1.2.2.1. proximate (ST)
1.2.2.1.1. cold
1.2.2.1.2. hunger
1.2.2.1.3. wants attention
1.2.2.1.4. high levels of stress hormone
1.2.2.1.5. neural signal for pain
1.2.2.2. ultimate (LT)
1.2.2.2.1. babies that dont cry when they need help are less likely to survive
2. Fossils and Fossilization
2.1. Geological context
2.1.1. 3 major classes of rocks
2.1.1.1. sedimentary rocks
2.1.1.1.1. formed by particles(mineral/organic) gradually settling out of solution>compact then to form rock
2.1.1.2. igneous
2.1.1.2.1. from magma and lava
2.1.1.2.2. formed by cooling of magma
2.1.1.3. Metamorphic
2.1.1.3.1. in between
2.1.1.3.2. modification of existing rocks under high pressure and heat
2.1.2. fossils only in sedimentary rocks
2.1.2.1. deposited on oceanic shorelines,lake beds,flood plains
2.1.2.2. weathering/erosion exposes older layers
2.1.2.3. 2 main ways fossils can be formed
2.1.2.3.1. permineralization
2.1.2.3.2. natural cast process
2.1.2.3.3. example of fossil formation
2.1.2.4. most fossil bearing rocks are sedimentary
2.1.2.4.1. the older the rock the less likely it will harbor fossils
2.2. fossils
2.2.1. body parts such as
2.2.1.1. shells
2.2.1.2. bones
2.2.1.3. teeth
2.2.1.4. hard parts =best parts for fossilization
2.2.2. include remains of the activity of living things
2.2.2.1. burrows/footprints (trace fossils)
2.2.3. include remains of organic chemicals formed
2.2.3.1. form chemical fossils
2.3. process of fossilization=taphonomy
2.3.1. death of organism
2.3.2. processes b4 burial
2.3.3. after burial
2.4. factors that affect fossilization
2.4.1. body construction
2.4.1.1. organisms that consist mainly of soft parts r less likely to leave fossils than organisms that have hard parts
2.4.1.1.1. worms and plants
2.4.1.2. hard parts may be crushed by rocks,stones,or wave action,or broken up by scavengers
2.4.1.3. fossil plants
2.4.1.3.1. coal contains a huge number of compressed fossil fern
2.4.1.3.2. majority of fossils are of hard parts
2.4.2. environment
2.4.2.1. animals that normally live within sediments more likely to be buried in sediment b4 being destroyed
2.4.2.1.1. more likely to leave fossils
2.4.2.2. animals that live on surface of the sediment more likely to be fossilized than those that swim in water column
2.4.3. predators
2.4.3.1. Terrestrial species least likely to be fossilized
2.4.3.1.1. likely to be dead on the ground so exposed to scavengers and not rapidly buried
2.5. fossilization is rare
2.5.1. fossils don't form often
2.5.2. predators, scavengers, insects consume the corpse
2.5.3. bacteria and fungi might decompose the remains
2.5.4. decomposition faster in tropics
2.5.4.1. acid
2.5.4.2. soil
2.5.4.3. humidity
2.5.4.4. warm
2.5.5. example
2.5.5.1. leemar fossils are rare
2.5.5.1.1. only ones found dated from 25,000 years ago
2.5.6. fossils can be lost
2.5.6.1. mountains
2.5.6.1.1. lots of erosion
2.5.6.2. metamorphosis and subduction of rocks destroys fossils
2.5.6.3. most underground and difficult to find
2.5.6.4. most still buried and not exposed
2.5.6.4.1. 4 fossil in rock to be exposed
2.5.6.4.2. Earth must open either by a fracture or by the knifing action of a river
2.6. fossil preservation
2.6.1. hard parts most likely to remain
2.6.2. soft part less likely to form fossils
2.6.3. best locations
2.6.3.1. deserts
2.6.3.2. places with little O2
2.6.3.3. underwater
2.6.3.4. cold
2.6.3.5. arid
2.6.3.6. example
2.6.3.6.1. Madagascar= huge diversity hotspot
2.7. rarely DNA can be extracted from fossils
2.7.1. Neanderthal skull
2.7.1.1. Iraq
2.7.1.2. 50,000 yrs ago
2.7.1.3. DNA can rarely be extracted and sequenced from sub fossils
2.8. Fossil examples
2.8.1. plesiosaur fossil
2.8.1.1. aquatic reptile
2.8.1.2. not dinosaur
2.8.1.3. mesozoic era
2.8.1.4. typical fossil skeleton
2.8.2. Akmonistion Zangerli
2.8.2.1. parts of head and anvil/brush
2.8.2.2. more typical fossil
2.8.2.3. shark from Carboniferous Scotland
2.8.2.4. maybe brush used 4 sexual selection
2.8.3. Belemnites
2.8.3.1. very common in mesozoic era
2.8.3.2. fossils
2.8.3.2.1. like bullets
2.8.4. ammonites
2.8.4.1. very common
2.8.4.1.1. Devonian-Cretaceous period
2.8.4.2. similar to nautilus
2.8.4.2.1. Triassic -present
2.8.4.3. index fossils
2.8.4.3.1. fossils used to date other fossils
2.8.5. Archaeopteryx
2.8.5.1. late jurassic (150 mya)
2.8.5.2. some soft parts and feathers usually don't fossilize
2.8.5.3. they leave an impression in the earth they are buried
2.8.5.3.1. impressions of feathers in the rock around skeleton
2.8.5.4. feathers not suitable 4 flight
2.8.5.4.1. probably lived in trees
2.8.6. fuzzy raptor (dromaeosaur)
2.8.6.1. had feathers
2.8.6.1.1. probably for insulation
2.8.6.2. 2 legs
2.8.6.3. found in China 2001
2.8.6.4. dates to late Triassic period
2.8.7. eutherian mammal
2.8.7.1. eomaia scansoria
2.8.7.1.1. ancestor of modern eutherians
2.8.7.1.2. climbing mammal from lake shore environment
2.8.7.1.3. lower cretaceous China
2.8.7.2. leptictidium tobieni
2.8.7.2.1. Paleogene
2.8.7.2.2. bipedal extinct mammal
2.8.7.2.3. soft tissues and gut contents preserved
2.8.7.2.4. Shahl Germany
2.8.8. Dinosaur footprint
2.8.8.1. informed us about locomotion of animal
2.8.8.2. behaviour of vertebrates and how they ambled across ancient landscapes is implied by spacing of fossilized footprints
2.8.8.3. from sequential spacing of dinosaur tracks
2.8.8.3.1. speed of animal can be calculated at the time tracks were made
2.8.8.4. probably formed when the footprint was made in soft mud which hardened over time
2.9. fossilization can also occur in
2.9.1. amber
2.9.1.1. e.g. insects in amber
2.9.1.1.1. mosquito imbedded into tree sap that hardened into amber
2.9.1.2. fossil resin from trees
2.9.1.3. tree sap traps insects and hardens into amber over time
2.9.1.3.1. preserves external structure
2.9.2. by mammification
2.9.2.1. A few mummified remains of animals have been found in some caves where the conditions are dry and sterile
2.9.2.2. not true fossilization
2.9.2.2.1. pause in disintegration process
2.9.2.3. usually only bone but occasionally tissue and other remains as well
2.9.3. in ice
2.9.3.1. discovery of frozen whole Woolly mammoths in Alaska and Siberia
2.9.3.2. thawed and yielded
2.9.3.2.1. actual hair
2.9.3.2.2. muscle
2.9.3.2.3. viscera
2.9.3.2.4. digested food
2.9.3.3. very rare
2.9.3.3.1. soft parts usually decay quickly after death and so rarely fossilized
3. Fossil dating methods
3.1. geologists date events in the past by relative and absolute techniques
3.1.1. absolute
3.1.1.1. the item itself is dated
3.1.1.2. absolute time
3.1.1.2.1. a date expressed in years
3.1.2. relative
3.1.2.1. strate above (younger) and below(older) an the item is expressed relative to these
3.1.2.2. relative time
3.1.2.2.1. is time relative to some other known event
3.1.3. best method depends on context and age
3.2. 3 methods
3.2.1. radiometric dating
3.2.1.1. use C12 and C14 radio isotopes
3.2.1.1.1. found in organisms
3.2.1.1.2. when organism dies
3.2.1.2. based on decay of radioactive isotopes
3.2.1.3. a technique that takes advantage of the natural transformation over time of an unstable elemental isotope to a more stable form/product
3.2.1.3.1. such decay occurs at a constant rate
3.2.1.3.2. expressed as half life
3.2.2. stratigraphy
3.2.2.1. older fossils likely to be lower down
3.2.2.2. e.g. of relative time measurement
3.2.2.3. a method that places fossils in relative sequence to each other
3.2.2.4. Arduino 1970
3.2.2.4.1. proposed that rocks can be arranged from oldest to youngest based on depth
3.2.2.5. Charles Lyell
3.2.2.5.1. Principles of Geology
3.2.2.5.2. principle
3.2.2.5.3. correlation
3.2.2.5.4. allows us to determine which fossil species arose first and which later relative to other fossils
3.2.3. Index fossils
3.2.3.1. diagnostic fossil species that help date new finds
3.2.3.2. an organism usually a hard shelled invertebrate animal that previous work has shown to occur only within one specific time horizon of rock
3.2.3.3. presence of index fossil in rock layer indicates that the stratigraphic layer belongs to the same time horizon as strata that contains the same fossil
3.2.3.4. absence of index fossils at location 3
3.2.3.4.1. layer B does not exist at that location
3.2.3.4.2. rock forming processes never reached area / layer was eroded
3.2.3.5. e.g. Grand Canyon
3.2.3.5.1. 1.7 mya
3.2.3.5.2. grouping together of fossils and info of where they are from helps to figure out age
4. Interpreting fossils
4.1. fossils can indirectly/directly tell us a gr8 deal about the behaviour of an organism/lifestyle
4.2. 3 hominids footprints
4.2.1. preserved in volcanic ash that hardened to stone
4.2.2. 3.6 mya
4.2.3. discovered in Tanzania by Mary Leakey
4.2.4. footprints of lrg individual, small individual, and still smaller individual
4.2.4.1. could be a family
4.2.5. told us that our ancestors 3 mya walked upright on two hind legs
4.2.5.1. bipedal
4.2.6. can tell a lot from footprints
4.2.7. numerous other mammals as well
4.2.8. Australopithecus afarensis
4.3. fossil eggs
4.3.1. clutch of dinosaur eggs
4.3.2. dates 70 mya
4.3.3. from Segnosaur
4.3.3.1. enigmatic carnivorous/omnivorous species that we know little about
4.3.4. found in China
4.3.5. laid together in pits/holes in the ground lined by plant material
4.3.6. each egg = 6cm diameter
4.3.7. info on development and social reproductive behaviour
4.3.7.1. eggs near to each other>breeding colonies
4.3.7.2. analysis of rock sediments
4.3.7.2.1. location of colony
4.3.7.3. presence of bones nearby
4.3.7.3.1. young stayed near nest until grown
4.3.7.3.2. care of young by parents
4.4. Fossil Ichthyosaur
4.4.1. small skeletons seen within adult's body and next to it
4.4.2. may fossilized a birth and one young already born,one in birth canal, and several more in uterus
4.4.3. such special preservations suggest the reproductive pattern and live birth process in species
4.5. interpretation
4.5.1. careful interpretation
4.5.1.1. helps makes sense of fossilized remains
4.5.2. analysis of hard parts can tell something about soft anatomy ( e.g muscle structure)
4.5.3. geological environment
4.5.3.1. freshwater, marine ,swamp
4.5.4. more info can be inferred from living relatives and organisms
4.5.5. examples
4.5.5.1. Hallucigenia
4.5.5.1.1. member of morphologically diverse group of animals
4.5.5.1.2. found in the Burgess Shale fossil bed in the Canadian rockies
4.5.5.1.3. soft bodied animal fossil
4.5.5.1.4. 375 mya
4.5.5.1.5. most similar living organism today is the velvet worm ( onychoporon)
4.5.5.2. changing pictures of iguanadon
4.5.5.2.1. everything very hypothetical
4.5.5.2.2. Sir Richard Owen 1830
4.5.5.2.3. Louis Dollo 1870s
4.5.5.2.4. David Norman 1980s
4.5.5.3. colours dont fossilize
4.5.5.3.1. few evidence suggests they do
4.5.5.3.2. discovered fossilized melanosomes