Rock ID Interactive

RELATIVE DATING-NOT DATING YOUR COUSIN! GEOLOGIST noticed that certain types of rock could always be found in the same vertical order –If they knew the type of rock and how old it was then … The age of the rock can be estimated by its position in the rock layers. Newer layers Older layer

RADIOACTIVE DATING-YOU HAVE A GLOW ABOUT YOU! Uranium Uranium The age of rocks can be determined by what element(s) it is made from As you recall, many elements are radioactive (isotopes) ATOMS DECAY OVER TIME SO…

URANIUM 238 HALF LIFE is 4.5 Billion years When URANIUM decays it becomes LEAD Scientist determine ROCK AGE by comparing Uranium to Lead RATIO If the ratio of uranium:lead is higher then, is the rock younger or older? –younger

Radioactive Dating is More Exact Dating of Fossils When the atoms decay they become new elements because the number of sub atomic particles has been reduced. The decay rate of an element is called HALF LIFE. HALF LIFE Is the time it takes for half the atoms of a molecule of an element to decay. Half life animationanimation

C14, CARBON DATING of ONCE LIVING ORGANISMS The element Carbon exists as radioactive Carbon14 & non-radioactive Carbon12 Living cells take in BOTH forms. When cells die they no longer take in C14. The longer an organism is dead, the lower the ratio of C14 :C12 C14 CARBON’s half life is 5,730 YEARS So after 5,730 years ½ is left, –11,460 2 half lives ¼ is left, –17,190 3 half lives 1/8 is left, –22,920 4 half lives 1/16 is left Can date clothing, bones, some prehistoric items, etc

FOSSIL RECORD Information of the GEOLOGICAL RECORD of EARTH. Can tell us about climate, life forms. SEA CREATURES IN ARIZONA, –COASTLINE CHANGES GIANT FERNS IN N. AMERICA –WARMER CLIMATE WHAT DOES A PALEONTOLOGIST STUDY? –Fossils, bones

FORMATION OF FOSSILS /es2901page01.cfm?chapter_no=visualization /es2901page01.cfm?chapter_no=visualization MOST FOSSILS ARE FOUND IN WHICH TYPE OF ROCK? –SEDIMENTARY ROCK -SEDIMENT FORMS WHEN SAND & SILT FROM WATER SETTLE TO THE BOTTOM OF A BODY OF WATER Animals & plants that die in the water are compressed by pressure from sediments and water

FORMATION OF FOSSILS BONES & TEETH can be preserved by SAND, MUD OR VOLCANIC ASH. Footprints or soft tissue can be preserved by ash, but this is very rare. They have no hard parts so they are harder to make impressions and molds. Sap from trees can trap insects, & plants and preserve them. The sap is preserved is called Amber.

FORMATION OF FOSSILS PETRIFICATION can occur when the remains are covered with water DISSOLVED MINERALS from the water replace the decaying tissues & hardens like stone.

Petrified wood

GAPS IN THE FOSSIL RECORD Why are there gaps in the fossil record? –CONDITIONS TO FORM FOSSILS NOT PRESENT –SOME TISSUES ARE TOO SOFT TO FORM FOSSILS-JELLY FISH, WORMS –EROSION DESTROYS FOSSILS –FOSSILS CAN BE BURIED AND NOT FOUND

How to determine Ancestry COMPARISON OF LIVING ORGANISMS Video Video EMBRYOLOGY CHARACTERISTICS LOST IN ADULTHOOD are present in unrelated embryo species ALL VERTEBRATE EMBRYOS HAVE GILL POUCHES-NECK FOLDS –IN FISH DEVELOP INTO GILLS –IN HUMANS-EAR BONES This is evidence of inheritance from a fish-like ancestor. The common ancestor of these organisms passed on a gene for development in the embryonic stage. Mutations passed on changes to the adult form to create differences in anatomy and evolvement to new species.

COMPARATIVE ANATOMY HOMOLOGOUS STRUCTURES -SIMILAR STRUCTURES DUE TO A COMMON ANCESTOR

COMPARATIVE ANATOMY ANALOGOUS STRUCTURES -Similar looking but not from a recent, common ancestor.

COMPARATIVE ANATOMY VESTIGIAL STRUCTURES -INHERITED from an ancestor, but no longer used –Whale pelvisWhale

COMPARATIVE BIOCHEMISTRY big pictureBIOCHEMISTRYpicture COMPARISON OF GENETIC SEQUENCES among organisms. –HOW CLOSELY RELATED ORGANISMS ARE TO EACH OTHER comparing their genes Organisms with a recent COMMON ANCESTOR –HAVE SIMILAR GENE SEQUENCES This has caused re-thinking of the ancestry of some animals.

OLD SCHOOL THINKING NEW SCHOOL

OLD SCHOOL NEW SCHOOL

CLADOGRAM-shows ancestral relationships, timeline