Evolution: the Evidence Biology Evolution: the Evidence

Do Now 3/21/16 List 2 pieces of evidence for evolution https://youtu.be/lIEoO5KdPvg

Evolution: The Evidence Fossil Record Geographic Distribution Similarities in Structure Similarities in Development Molecular Biology

Fossil Record Fossils = preserved remains or markings left by organism that lived in the past Found in sedimentary rock Buildup of sand and silt over long period of time Deposited by rivers and compress sediment below

Sink to bottom and are buried in sediment Aquatic organism Sink to bottom and are buried in sediment Land organism Swept into rivers, lakes or swamps Others covered by dust, sand or volcanic ash

Rock layers Younger rock strata on top of older ones Position of fossils with the layers determine relative age Chronological record life’s remains

Fossil Record Provides evidence of Earth’s changing life Oldest fossil evidence = chemical traces in rocks 3.8 billion years old Prokaryotes (bacteria & archaebacterial) have been found in rocks 3.5 billion years old Data fits with evidence that prokaryotes are the oldest life forms Younger fossils record evidence of eukaryotic organisms

Fossils provide evidence to link past to present Ex: Whales evolved from land-dwelling ancestors that had 4 limbs

Geographic Distribution Darwin noted that there are similarities and differences among species located in different parts of the world Suggests these organism evolved from common ancestor

Geographic distribution Why do some species share similar characteristic to other species found in a different ecosystem Why are there so many marsupials in Australia verses placental animals

Geographic distribution Just as fossil records provide evidence to the past Geographic distribution provides clues to how organisms may have evolved

Similarities in Structure Similarities in structure among species provide clues to evolutionary history Forelimb of mammals consist of same skeletal parts Same parts but different functions Called homologous structures

Homologous structures Homologous structures = similar structures in species that share a common ancestor

Homologous structures Homologous structures provide evidence that evolution is a remodeling process Structures that functioned one way in an ancestral species changes over time as it takes on new functions Darwin called this “descent with modification”

Vestigial structures Vestigial structures Are remnants of structures that may have had important functions in ancestral species but no clear function today’s species Goosebumps Dewclaws in dogs and cats Appendix

Vestigial structures

Vestigial structure of Human

Similarities in Development Development of organisms and the similarities provide clues to evolutionary history Embryos of similar closely related organisms have similar stages of development Supports homologous structures

embryology

Molecular Biology DNA sequencing Reading genetic codes enable closer comparison of organism The more similarities or matches the closer the organisms are related The more differences among the DNA sequence the less related and less likely they share a common ancestor

Molecular biology

Evidence for Evolution Molecular Biology Similariities in Develop-ment Evidence for Evolution Similariities of Structure Geographic distribution Fossil Record