7.2

7.2Evidence for Evolution

I. Fossil EvidenceA. Texas fossils proved it was once

covered by seaB. Kinds of Fossils

a. Fossil – any evidence of life from an earlier geological time

b. Imprint of a leaf, feather, or organism in rock

c. Cast made of minerals that fills in the follows of an animal track, mollusk shell, or other parts of an organism

d. A piece of wood or bond replaced by minerals

e. An organism frozen in icef. An insect or other organism trapped

in amberg. Sedimentary Rock – a rock type

formed from particles of preexisting rocks

II. The Fossil RecordA. Scientists developed a geologic Time

ScaleB. Relative Dating

a. Estimate of how old a fossil isb. Based on the idea that the lower it is,

the older it will be.C. Radiometric Dating

a. Radioactive elements – give off radiation due to an unstable nucleus

b. Compares radioactive to non radioactive material to determine dating

c. Several samples to obtain consistent results

d. Uranium

D. Fossils Show Evolution Occurreda. Simple life forms from past times

I. Other Evidence for EvolutionA. Homologous – body parts that are

similar in origin and structureB. Homologous structures indicate that

two or more species might share a common ancestor

a. Dolphin flipper and bird wing

C. Vestigial Structuresa. Vestigial structure – a body part that

doesn’t seem to have a functionb. Whales and snakes with hip bones

D. Embryologya. Embryology – study of the

development in organismsb. Gills in all mammals

A. DNAa. Closely related organisms have

similar DNAb. Bears and Dogsc. All primates have a common ancestor

i. Share hemoglobin, a protein in red blood cells that carries oxygen