Evolution 101
Learn About Evolution
What is a Theory?
The Theory of Evolution
History of Evolution
4.6 billion years ago: the earth forms and is bombarded by meteorites and comets
3.8 billion years ago: replicating molecules (precursors of DNA) form
3.5 billion years ago: unicellular life evolves; photosynthetic bacteria begin to release oxygen into the atmosphere
500 million years ago: fish-like vertebrae evolve
420 million years ago: land-plants evolve, changing landscape and creating habitats
360 million years ago: four-limbed vertebrates move onto the land as seen plants and large forests appear; vast reef systems
250 million years ago: the super continent Pangea forms; conifer-like forests, reptiles, ancestors of mammals are common
225 million years ago: dinosaurs and mammals evolve; Pangea begins to separate into continents
65 million years ago: a massive asteroid hits the Yucatan Peninsula, and ammonities an non-avian dinosaurs go extinct; birds and mammals are among survivors
4 million years ago: in Africa, an early hominid (Lucy) lives
130 thousand years ago: modern humans evolve
Ways Scientists Date Fossils and Rocks
- the configure the order the layers of sediment were deposited
- if a fossil is found in rock, it gives a good estimate of how old the rock is
Absolute Dating
- tells exact age
- carbon dating
- by studying the proportion of Carbon-14 atoms, compared to the other Carbon atoms, we can find out how old rocks and fossils are
Fossils
Examples:
Transitional Fossils
Examples:
Apes to Humans
Fish to Tetra-pods
Dinosaurs to Birds