Presentation on theme: "THE HISTORY OF LIFE SC STANDARD B-5 Students will demonstrate an understanding of the basis of evolution."— Presentation transcript:
THE HISTORY OF LIFE SC STANDARD B-5 Students will demonstrate an understanding of the basis of evolution
CN: page 54 notebook Topic: The History of Life EQ: What are the 4 important patterns of macroevolution?
FOSSILS Paleontologist: scientists who study fossils Fossil Record: information about past life, including the structure of organisms, what they ate, in what environment they lived, & order in which they lived
This species lived 7700 years ago This species lived 7700 years ago The fossil record provides evidence about the history of life on Earth. It also shows how different groups of organisms, have changed over time. Extinct: term used to describe a species that has died out
Lists of Extinct Animals nct_mammals.htm
How Fossils Form Formation of any fossil depends on a precise combination of conditions
Evolution of Whales Why is the fossil record described as an incomplete record of lifes history?
Interpreting Fossil Evidence Erosive forces cut through sedimentary rock wearing away the youngest layers first, exposing any fossils embedded in them.
Paleontologists reconstruct extinct species from few fossil bits to entire bodies. They look for similarities & differences with living organisms
Relative Dating In relative dating, the age of a fossil is determined by comparing its placement in the layers of sedimentary rock
Index fossils: distinctive fossil used to compare relative ages of fossils
Radioactive Dating half-life: is the length of time required for 50% of the sample of radioisotopes to decay radioactive dating: calculating the age of a fossil based on the remaining radioactive isotopes assumption is: the amount of C-14, for example, has remained constant C-14 can only be used for fossils <60,000 yrs because of its short half-life (not enough specimen left to measure)
Radioactive Decay of K-40
Geologic Time Scale
Formation of Earth Geologic evidence suggests that Earth formed over millions of years Process began ~4.6 billion years ago This process involved multiple collisions and temperatures so high anything solid melted While melted substances arranged themselves by densities Less dense substances floated to surface and gradually cooled forming Earths crust
Earths Early Atmosphere Hydrogen & Nitrogen formed early atmosphere hydrogen cyanide carbon dioxide carbon monoxide sulfide water ~ 4 billion years ago Earth had cooled enough to allow 1 st solid rocks to form still being bombarded by comets, asteroids, etc. too hot for water to exist in liquid form
~ 3.8 billion years ago Earths surface cooled down enough for water to stay in liquid phase Oceans covered most of planet Oceans brown due to dissolved iron Oldest sedimentary rock deposited in water
The 1 st Organic Molecules Miller & Urey tried to reproduce conditions on early Earth in a lab: CH 4, H 2, NH 3, H 2 O in a flask to represent early atmosphere passed electric shocks through it to simulate lightening Over a few days several amino acids began to accumulate Results suggests how mixtures of organic cpds necessary for life could have arisen from simpler cpds present on primitive Earth
Endosymbiotic Theory Proposes that eukaryotic cells arose from living communities formed by prokaryotic organisms Mitochondria Chloroplasts