EVOLUTION: Part 1: The Fossil Record Evolution = (change in # of alleles in a population) / time Evolution = descent with modification

Archeopteryx - a transitional fossil between non-avian dinosaurs and birds

T/F Original tissues can be preserved as fossils Organisms become extinct only in mass extinction events Environmental change causes variation in populations Variations can lead to adaptations Living species contain no evidence that they are related to each other Plants and animals share similar genes

What can be learned from Fossils? When did this organism live? How did it move or grow? How did this organism die? To what other organisms is this organism related?

The Fossil Record = all the fossils discovered on Earth (millions of species representing thousands of species) INCOMPLETE – the record only represents a small fraction of all the organisms that have lived on Earth

Fossil Formation Tissue: similar cells that work together and perform a function. Tissues that are not eaten eventually get broken down by bacteria. Only the bones, shells, and teeth remain. Under rare conditions, they become fossils. Fossils of tissues are EXTREMELY rare.

Fossil Formation Mineralization – minerals in the water replace organism’s original material (bones, maybe tissue, fossilized wood). Carbonization – compression squeezes out liquids and gases, leaving only carbon. Molds and Casts – mold = impression of an organism (in mud or sand), tiny rocks fill in to form a cast = fossil copy of an organism in a rock Trace Fossils – preserved evidence of the activity of an organism (footprints, for example) (How did it move or grow?) Original Material - most are less than 10,000 years old (mammoths frozen in ice), though dinosaur tissues and insects stuck in amber have been found

Determining a Fossil’s Age Relative-Age Dating - the science of determining the relative order of past events (i.e., the age of an object in comparison to another) Absolute-Age Dating - provides a numerical age or range in contrast with relative dating

Relative-Age Dating The relative order in which rock layers were deposited (added to the location by water, wind, etc.). The bottom layers are the oldest, the top layers are the youngest.

Absolute-Age Dating More precise than relative-age dating. Determines age by examining radioactive decay in rocks (a natural, clocklike cycle of equilibrium in rocks) Radioactive decay results in higher and higher ratios of one type of chemical material to another The older the rock, the higher the ratio.

Geologic Time Scale used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history Evidence from radiometric dating indicates that Earth is about 4.54 billion years old. Different spans of are usually marked by major geological or paleontological events, such as mass extinctions.

GEOLOGIC TIME SCALE

Earth’s History in 24 hours https://www.youtube.com/watch?v=H2_6cqa2cP4 The Earth is 4.54 billion years old (if the average person lives 75 years, that would be over 60 million lifetimes!)

Colorado and Fossils Green River Formation Picketwire Canyonlands Fossil Lake Fossil Beds