topic 4-1 Flashcards
what eon is most geological timeline within? what isnt included
Phanerozoic
pre cambrian not included - it is its own eon and era
what are the four eras oldest to newest
pre cambrian, paleozoic, mesozoic, cenozoic
what are the three periods/epochs in the pre cambrian era ((oldest to newest)
hadean (4600 mya- 3800), archean (3800 mya - 2500), Proterozoic (2500 mya - 540 mya)
what periods are included in the paleozoic era oldest to newest (540 mya - 250 mya)
Cambrian, ordovician, silurian, devonian, carboniferous (missippian, pennsylvanian), permian
periods in mesozoic oldest to newest (250 mya- 65 mya)
triassic, jurassic cretaceous
periods of cenozoic oldest to newest
paleogene (65 mya-23 mya), neogene (23- 1.5 mya), Quaternary (1.5 mya - now)
epochs in the paleogene (cenozoic) oldest to newest (65 mya to 23)
paleocene, eocene, oligocene
epochs in the neoogene (cenozoic) oldest to newest (23 mya to 1.5 mya)
miocene, pliocene
epochs in the quaternary (cenozoic) oldest to newest (1.5 mya to present)
pleistocene, holocene `
what is needed for radiometric dating?
• Absolute ages
○ Based mostly on radioactive decay
○ Need unstable elements with half-lives of appropriate length
○ Only igneous rocks can be dated; therefore, fossil bearing sedimentary rocks must be bracketed between younger and older igneous rock
○ Method not available until mid 20th century
○ Exs. Carbon 14, uranium 235
what can radiometric dating be used to calculate? how old are meteorites? oldest?
• Can use to calculate the age of earth and the solar system
○ Dating of meteorites
§ Most meteorites are 4.5 or slightly more byo
§ The earth and other planets must be the same age
□ A few meteorites came from other planets and are a bit younger
The oldest rocks on earth are from northern Canada
+Nuvvuagittuq Greenstone Belt, exposed on the Eastern shore
Of Hudson Bay, Northern Quebec
*Approx. 4.4 billion years Old
oldest fossil of living things?
○ The oldest fossils of living things are approx. 3.8 byo
§ Stromatolites from shark bay, western australia
three biases in the fossil record. describe them.
• Geographic bias
○ Majority of compression and impression fossils come from marine sediments, lake beds, and floodplains
○ Terrestrial environments, especially tropical ones, are poorly
represented
• Taxonomic bias
○ Fossil record is dominated by marine species possessing shells
○ approx-95% of all fossil animals are marine invertebrates
•
• Temporal bias
○ Older rocks are much rarer than newer rocks
describe contiental drift. look at example in notes
- Theory proposed by German geophysicist and meteorologist Alfred Lothar Wegener in 1912
- All continents were connected as one large land mass (he named it Pangea) about 200 mya; continents are slowly drifting around the earth
- Evidence: matching coastlines, similarity of fossils - south america and africa
when were plate tectonics discovered? describe it
• Discovered in the 1950s • Earth's crust divided into plates • Plates move relative to one another - tectonic activity • Plate movements cause continents to move also North America is moving west at about 2cm/year • Europe is moving northeast at about 3cm/year • Most ocean basins are not older than about 200 million years (Jurassic Period)
geoloical time summary/ conclusions
Geological Time: Conclusions
Cosmic distances and cosmic time are known
independently of the dating of earth events.
The solar system including earth is about 4.5 billion years
old, estimated from ages of meteorites and moon rocks.
The surface of the earth is composed of plates that
o
move. The ocean basins are relatively young, nowhere
older than Jurassic.
Plate movement rates are measured directly by satellite-
born laser devices, confirming the radiometric ages of
the rocks forming the ocean basins.
The 4.5 billion-year old age of the earth, the
approximate 13 billion-year old age of the universe, and
the ages of many, many earth events are scientific facts.
changes with lineages in fossil records examples
• Changes within lineages
○ Foraminiferans, trilobites, sticklebacks,, and suckers
• Origin of higher taxa
○ Tetrapods, birds, mammals, whales, humans
describe the change in lineage reharding foraminiferan shells
• Study by kucera and malmgren 1998
○ Increasingly cone shaped shells over a period of approx 3 million years
○ Gradual evolution (likely anagenesis)
○ Note first 2.5 my of stasis - no change
describe the changes within trilobite lineages
• they Can be documented in continuous, fosiliferous sections of sedimentary rock
• e.g. trilobites - study by sheldon, 1987
Various species in different genera changing gradually in the
same feature: number of ribs on the rear dorsal part of the
exoskeleton over about three million years
describe changes in lineage with sticklebacks
- Samples 5-10,000 years apart in annulally layered lake beds
- Several features of the sticklebacks changed gradually but not always In the same direction
- One feature might increase in number of parts while another might decrease
describe changes in stickleback lineage
- Study of fossil sticklebacks (Gasterosteus) by M. Bell 1985
- Samples 5-10,000 years apart in annulally layered lake beds
- Several features of the sticklebacks changed gradually but not always In the same direction
- One feature might increase in number of parts while another might decrease
Change within lineage: Amyzon sucker
• Studies of amyzon by mark Wilson and Doug Barton 1996, Barton and wilson 1999
○ Eocene (50 my old) suckers from B.C.
○ Preserved in annual layers called varves
- changes in vertebrae over 600 years
changes in fin rays over 8,000 years
exhibit in UofA
slow drop in dorsal vertebrae, more varying in dorsal fin rays
fossils came from a very narrow window of time
origin of terapods from lobe finned fish ex and features. look at specimens found in quebec
e.g., Eusthenopteron
- a rhipidistian
- Devonian
• Internal nostrils
• Lungs and gills
• Limbs with bony
axis
• Labyrinthodont
teeth
• Skull with
tetrapod pattern of bones
what discovery helped us better understand the origin of tetrapods? who discovered and where
a discovery in 2004 of a Late Devonian tetrapod-like fish ○ By Dr. Neil Shubin of the University of Chicago & his colleagues ○ From Ellesmere Island in the Canadian Arctic ○ Provides important insights into the transition between sarcopterygians and tetrapods ○ Tiktaalik roseae
describe tiktaalik and its features. how many specimens found
○ Tiktaalik roseae
○ Has a mix of fish and amphibian traits
○ Looked like a cross between the primative fish and amphibians
○ Lived amongst the first tetrapods
○ Tiktaalik - shallow water fish
○ Transitional form from late devonian ○ Termed "fishapod" as it intermediates between fish (eusthenopteron) and early tetrapods (acanthostega and ichthyostega) ○ More than 10 specimens, 3-9 feet ○ Eyes located dorsally ○ Crocodile-like flattened head with sharp teeth ○ Well developed lungs
describe skeletal modifications of tiktaalik
Pectoral girdle z Like a lobe finned fish but also a distinct shoulder, elbow, & wrist Fish like fins (no toes) Neck could move independent Of body (unlike other fish)
tik taalik rib cage and pelvic girdle features
• Rib cage
○ Well developed and tetrapod llike
○ Suggests benthic (shallow H2O) habit: could move on land for short periods
• Pelvic girdle
○ Primitive features: no ischium; no
attachment for sacral rib
○ Advanced features: enlarged; paired with
broad iliac processes, flat & elongate pubes (bone)
tiktaalik summary
• Closed 10 my gap between sacropteryian ancestors and their tetrapod descendants
Fish-like: gills, scales/fin rays, caudal fin
Fishapod-like: limb bones & joints
Tetrapod-like: ribs, neck, lungs
