Test 3 Notes- Biological Anthro

# Test 3 Notes- Biological Anthro - Test 3 Notes Chapter 12...

This preview shows pages 1–2. Sign up to view the full content.

1Test 3 Notes Chapter 12: Primate Origins and Evolution The Study of the Fossil Record: Relative Dating: determines which fossils are older then others but not their exact date Chronometric Dating: determines the exact age of fossils or sites Relative Dating Methods: Stratigraphy- cumulative buildup over time of the earth’s surface; the older a site is, the deeper it is under the earth’s surface, lower layers are older; do not know how old the fossil is or the exact amount of time between two fossils, but you know which is older in geologic time Biostratigraphy- method in which sites can be assigned an approximate age based on the similarity of animal remains with those from other dated sites; measure of how old a site is using previously known knowledge about a similar site Paleomagnetic reversals- magnetic field of the earth runs between two poles and the polarity of this field changes at irregular intervals of long periods of time; sedimentary rocks preserve a record of these changes Chemical Methods: Fluorine Dating- looks at the accumulation of fluorine in the bones; allows us to see if two bones found at the same site are the same age Chronometric Dating: -radioactive decay is constant for a given radioactive atom no matter what chemical reaction it is involved in; if we know a certain element decays into another at a constant rate and if we can measure the relative proportions of the original and new elements in some object, then we can mathematically determine the age of the object Carbon-14 Dating- uses the constant rate of decay to determine the age of materials containing carbon; radioactive decay emits particles that can be measured; example: rate of emissions expected from a living organism (15 particles per minute per gram of carbon); if a sample is analyzed and emits 3.75 particles per minute then two half lives have elapsed (15/2 = 7.5, 7.5/2 = 3.75); 5,730 * 2= 11,460 years; if the sample was analyzed in 2005 then its date would be 11,405 because that is 55 years after B.P. (1950 is considered the “Present”); bone tends to not be reliable because there are chemical changes during fossilization; charcoal is the best material to use; this is useful only for sites over the past 50,000 years Half-Life- average length of time it takes for half of a radioactive substance to decay into another form; c14 has a half-life of 5,730 years Potassium-argon Dating- based on the half-life of radioactive potassium (1.31 billion years) decaying into argon; used to date volcanic rock that can be older than 100,000 years old; volcanic rock is best because the heat generated by volcanic eruptions removes any initial argon gas so any found is the result of radioactive decay Argon-argon Dating- decay of an argon isotope in to argon gas; used with very small samples, i.e. a single crystal Dendrochronology- trees accumulate new rings inside for every period of growth; by looking at the width of the rings, archaeologists created a master chart of tree ring changes; if there is a log

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

### Page1 / 8

Test 3 Notes- Biological Anthro - Test 3 Notes Chapter 12...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online