2California State Standard Biological evolution accounts for the diversity of species developed through gradual processes over many generations.Independent lines of evidence from geology, fossils, and comparative anatomy provide the bases for the theory of evolution.
3What is Evolution? Evolution The gradual change of a species through adaptations over a period of time.AdaptationA structure, behavior, or internal process that makes an organism better suited to their environment.
4Change Over Time The Earth has changed over time Temperature Climate EruptionsEarthquakesChange in sea levelChange in land massesdue to Continental DriftPangea
5Continental DriftThe theory of continental drift, suggests that in the Earth’s history, continents have moved due to plate tectonics, and are still moving today at a rate of about six centimeters per year. Pangea refers to the supercontinent that connected all of the land masses.
7Evidence of Evolution Fossils Comparative Anatomy Comparative EmbryologyComparative Biochemistry
8Fossils Fossils Evidence of an organism that once existed. The study of Paleontology uses fossils to understand events that happened long ago, ancient climates, and ancient geography.
9How are fossils formed?Fossils are formed by being buried in mud, sand, or clay after they die.Most fossils are found in sedimentary rocks. These rocks form at relatively low temperatures and pressures that may prevent damage to the organism.
10The Fossilization Process Few organisms become fossilized because, without burial, bacteria and fungi immediately decompose (break down) the dead bodies.Occasionally, organisms do become fossils in a process that usually takes many years.
11An organism or its body are washed into a body of water. Sediments rapidly cover the body.Over time, additional layers of sediments compress the area around the body.Earth movement or erosion may expose the fossil many years after it formed.
13Imprint FossilsImprint fossils, also called trace fossils, are any evidence left by an organism, such as a footprint, trail, or burrow.
14Mold & Cast FossilsA mold forms when an organism is buried in sediment and then decays, leaving an empty space.When the empty space is filled in with minerals, a replica or cast is made.
15Petrified FossilsIn petrified fossils, minerals sometimes penetrate and replace the hard parts of an organism.
16Preserved FossilsA preserved fossil is an entire organism trapped and preserved in ice, tar, or amber, which is hardened sap.
17The Age of FossilsScientists use a variety of methods to determine the age of fossils. One method is relative dating.If the rock layers have not been disturbed, the relative age can be determined by the position in the soil and rock layers.
18Relative AgeThe lower layer contains fossils that are older and less complex.The upper layer contains fossils that are younger and more complex.
20Absolute AgeRadioactive dating is used to find the specific ages of rocks, which may contain fossils.Radioactive isotopes are atoms that are unstable and break down or decay over time, giving off radiation and forming a new isotope.Every radioactive isotope has a characteristic decay rate, scientists use the rate of decay as a type of clock, called half-life.
21Potassium-40 decays to Argon-40 to half its original amount in 1 Potassium-40 decays to Argon-40 to half its original amount in 1.3 billion years.Carbon-14 decays to half its original amount in 5730 years and is used to date fossils less than 70,000 years old.
22Geologic Time ScaleBy examining and dating sedimentary rock and fossils, scientists have put together a chronology, or calendar, of Earth’s history, called the geologic time scale.Time frames in evolution are based on the geologic time scale.
23Other Evidence of Evolution Comparative AnatomyThe comparison of body structures from different species.Homologous StructuresAnalogous StructuresVestigial Structures
24Homologous Structures Organs or body parts that are similar in structure, function, or both.Organisms with homologous structures have a common ancestor.
29Vestigial StructuresOrgans or body parts that do not have a current function, but may be useful in other organisms.A body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor.
30TOP 10 Vestigial Organs 10. The wings on flightless birds 9. Hind leg bones in whales & snakes8. Erector pili and body hair7. The human tailbone6. The eyes of a blind fish5. Wisdom teeth in humans4. Sexual organs of dandelions3. Reproduction of whiptail lizards2. Male breast tissue and nipples1. The human appendix
31Comparative Embryology The comparison of the early stages of development of different species.The shared features in the young embryos suggest evolution from a distant, common ancestor.fish reptile bird mammal
32Evidence from Embryology An Elephant Embryo58 days old days old4 mm long 6 cm long
33Comparative Biochemistry Studying the similarities of organisms at a biochemical level, for example DNA, ATP, and enzymes.
34Evidence from Biochemistry Blood, DNA, RNA, amino acids, enzymes, and other proteins (Example Cytochrome C)Comparison of OrganismsPercent Substitutionsof Amino Acids inCytochrome c ResiduesTwo orders of mammalsBirds vs. mammalsAmphibians vs. birdsFish vs. land vertebratesInsects vs. vertebratesAlgae vs. animals5 and 108-1214-1818-2227-3457
35Scientists have constructed evolutionary diagrams that show levels of relationships among species. Scientists combine data from fossils, comparative anatomy, embryology, and biochemistry in order to interpret the evolutionary relationships among species.