 Fossils provide an objective record of Evolution Fossil = A preserved or mineralized remains (bone- petrified tree – tooth – shell) or imprint of an organism that lived long ago. Provide record of Earth’s past life-forms. crinoid (800 million yrs old) pterodactyl ( million yrs old) 13:2 Evidence of Evolution

 1 - Earth is about 4.5 billion years old. 2 – Organisms have inhabited Earth for most of its history. 3 – All organisms living today evolved from earlier, simpler life- forms. 3 Major Points of Scientific Agreement

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 Changes in a gene’s nucleotide sequence build up over time. PROTEINS Analysis of amino acid sequences Species that share a common ancestor in a more distant past (humans/frogs) have many amino acid sequence differences. Species that share a common ancestor more recently (humans/gorillas) have few amino acid sequence differences. Biological Molecules Contain a Record of Evolution

Nucleic Acids Scientists can directly estimate the number of nucleotide changes that have taken place in a gene since 2 species diverged from a common ancestor by comparing the exact nucleotides sequence of genes.

 Diagram that shows evolutionary relationships among groups of organisms. Cladogram

 Diagram that shows how organisms are related through evolution. PHYLOGENETIC TREES

 VESTIGIAL STRUCTURES Structures in different types of organisms that often reveal basic similarities in anatomy, even though the functions may be very different. Cormorant Anatomy and Development Suggest Common Ancestry

  Structures that share a common ancestry. Homologous Structures Forelimbs of vertebrates contain the same kinds of bones.

Embryonic Development

 A: Gradualism – Model in which gradual change over a long period of time leads to species formation.  B: Punctuated Equilibrium – Model in which periods of rapid change in species are separated by periods of little or no change.