http://www.uwo.ca/biology/images/undergraduate/trilobite.jpg
Oldest fossils – 3.5 byo prokaryotes 1st life forms are probably older
What is evolution? The scientific theory that explains how species change over time
Today, species have changed both structurally & physiologically from what they were.
Remains/traces of once living organisms that no longer exist.
Usually found in sedimentary rock – the formation process is quick, preventing bacteria from decaying the organism.
Usually consists of ‘hard’ parts of the organism.
Minerals may replace remains, preserving microscopic structures.
Freezing – i.e. Mammoths Imprints – film of carbon left after decay Casts – sediments fill mold of organism Kinds of fossils =-
Whole organisms, bones, plants; feathers; pollen grains
http://images.google.com/imgres?imgurl=http://notexactlyrocketscience.files.wordpress.com/2007/01/800px-microraptor_fossil1.jpg&imgrefurl=http
Relative age – position in layers of sedimentary rocks.
Absolute age – radioisotopes w/unstable nucleii & a constant (known) rate of decay
Half-life – length of time it takes ½ of radioactive material to decay
http://razd.evcforum.net/Pictures/CvE/carbon14decay.jpg
Atom with a different # of neutrons 12C and 13C= 6P, 6N (7N) and are stable 14C = 6P & 8N, unstable, ½ life = 5730 yrs
How does dating work? 1) ratio of 14C production/decay in atmosphere is
constant 2) organisms take in 12C & 14C at a constant rate
3) organism dies – 12C & 14C in atmosphere remain constant14C in organism decays12C : 14C ratio in organism changes
4) compare 12C : 14C ratio in organism to atmospheric ratio
5) scientists can date organisms up to 50K years using carbon dating.
Use different isotopes – i.e. 40K (potassium 40), ½ life = 1.28 billion
years So…….
How is all of this information applied to fossils we find in the dirt?
http://images.usatoday.com/tech/_photos/2006/11/07/fossil472.jpg
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