The fossil record

What is a fossil? A trace from a long dead organism. A trace from a long dead organism. Biogeography – study of the geographical distribution of fossils and living organisms. Biogeography – study of the geographical distribution of fossils and living organisms.

How fossils form Hard parts such as shells, bones, or teeth, are long-lasting and may become preserved as fossils. Hard parts such as shells, bones, or teeth, are long-lasting and may become preserved as fossils. Under the right conditions, minerals dissolved in groundwater seep into the tissues of a dead organism and replace its organic material. The remains become petrified—they turn to stone. Under the right conditions, minerals dissolved in groundwater seep into the tissues of a dead organism and replace its organic material. The remains become petrified—they turn to stone.

What types of fossils are there? Mold – an imprint Mold – an imprint Cast- molds that are eventually filled with minerals. Cast- molds that are eventually filled with minerals.

Dating fossils: Relative Ages Law of superimposition – sucessive layers of rock and soil are layered on top of one another. The lowest stratum (layer) would have the oldest fossils.

Dating fossils: Absolute Ages Radiometric dating - method most often used to determine the absolute ages of rocks and fossils. Radiometric dating - method most often used to determine the absolute ages of rocks and fossils. Radiometric dating Radiometric dating Based on the measurement of certain radioactive isotopes in objects. Based on the measurement of certain radioactive isotopes in objects.

What we can learn Species that existed and then became extinct. There were several mass extinctions – brief periods where large number of species disappeared.

Evolution All the changes that have transformed life over an immense time. All the changes that have transformed life over an immense time.

Lamarck Proposed that life evolves of changes. Proposed that life evolves of changes. Adaptation – an inherited characteristic that improves an organism’s ability to survive and reproduce in an environment. Adaptation – an inherited characteristic that improves an organism’s ability to survive and reproduce in an environment.

Voyage of the Beagle When: December 1831 When: December 1831 Mission: Chart unmapped stretches of South America’s coastline. Mission: Chart unmapped stretches of South America’s coastline. Charles Darwin was on this trip to study the geology and plant and animal life encountered. Charles Darwin was on this trip to study the geology and plant and animal life encountered.

Uniformitarianism Earth’s geological structure results from observable processes that cycle. Earth’s geological structure results from observable processes that cycle. Darwin: Modification of environment is a very slow process. Darwin: Modification of environment is a very slow process.

What did Darwin see? Plants in South America were quit distinct from the plants in Europe. Plants in South America were quit distinct from the plants in Europe. Fossils found were distinct – appeared to be gigantic versions of modern animals. Fossils found were distinct – appeared to be gigantic versions of modern animals. Supported the thought that species living on the continent were decedents from ancestral species that used to live on the continent. Supported the thought that species living on the continent were decedents from ancestral species that used to live on the continent.

Darwin’s Main Points: Descent with Modification Today’s species descended from ancestral species. Depending on where the modern species ended up they adapted to that environment.

Modification with Natural Selection Individuals with more favorable characteristics leave more offspring than other individuals. Individuals with more favorable characteristics leave more offspring than other individuals.

Adaption to environment The number of favorable characteristics in an organism increases The number of favorable characteristics in an organism increases An organism’s contribution to next generation – fitness. An organism’s contribution to next generation – fitness.

Your task Take this animal and draw how it would adapt to one of the following climates. You must include 5 adaptations – label and explain: Take this animal and draw how it would adapt to one of the following climates. You must include 5 adaptations – label and explain: –Swamp –Desert –Tropical forest –North Pole –Mars –Your choice

What are homologous structures? Structural similarities found in more than one species that share a common ancestor. Structural similarities found in more than one species that share a common ancestor.

Explain how these homologous structures suggest a common ancestor. Homologous structures show how different animals can use their very similar forelimb bones in different ways. This suggests a common ancestral species whose forelimb bone structure was modified as those forelimbs took on new functions.

Contrast the size and shape of the bones of the whale flipper and the bat wing. The whale bones are thick and flat which provide a paddle like surface. The bones of the bat are thin and light which is a necessary adaptation for flight.

Analogous Structures Structures that serve the same function but do not share a common ancestor. Structures that serve the same function but do not share a common ancestor.

Vestigial Structures remnant of a structure that may have had an important function in a species' ancestors, but has no clear function in the modern species

Similarities in Embryology

Which one of the four species do the cytochrome c data suggest is most closely related to humans? The hemoglobin data? MONKEYS

Which one of the four species do the cytochrome c data suggest is least related to humans? The hemoglobin data? FROGS

More evolution Evidence Similarities in macromolecules: Similarities in macromolecules: –DNA & amino acid sequences The more similar the proteins are in 2 organisms, the closer related they are. The more similar the proteins are in 2 organisms, the closer related they are.

Patterns in Evolution Coevolution Coevolution Convergent Evolution Convergent Evolution Divergent Evolution Divergent Evolution

Coevolution 2 or more species changing together 2 or more species changing together

Convergent Evolution The environment selects similar phenotypes. The environment selects similar phenotypes. Ancestors are very different. Ancestors are very different.

Divergent Evolution 2 or more related populations/species become more and more different 2 or more related populations/species become more and more different Adaptive Radiation – related species evolve from a common ancestor Adaptive Radiation – related species evolve from a common ancestor Artificial selection Artificial selection