Evolution

California 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.

What is Evolution? Evolution The gradual change of a species through adaptations over a period of time. Adaptation A structure, behavior, or internal process that makes an organism better suited to their environment.

Change Over Time The Earth has changed over time Temperature Climate Eruptions Earthquakes Change in sea level Change in land masses due to Continental Drift Pangea

Continental Drift The 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.

Evidence of Evolution Fossils Comparative Anatomy Comparative Embryology Comparative Biochemistry

Fossils 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.

How 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.

The 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.

An 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.

Types of Fossils Imprint Fossils Mold & Casts Fossils Petrified Fossils Preserved Fossils

Imprint Fossils Imprint fossils, also called trace fossils, are any evidence left by an organism, such as a footprint, trail, or burrow.

Mold & Cast Fossils A 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.

Petrified Fossils In petrified fossils, minerals sometimes penetrate and replace the hard parts of an organism.

Preserved Fossils A preserved fossil is an entire organism trapped and preserved in ice, tar, or amber, which is hardened sap.

The Age of Fossils Scientists 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.

Relative Age The lower layer contains fossils that are older and less complex. The upper layer contains fossils that are younger and more complex.

The Fossil Record

Absolute Age Radioactive 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.

Potassium-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.

Geologic Time Scale By 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.

Other Evidence of Evolution Comparative Anatomy The comparison of body structures from different species. Homologous Structures Analogous Structures Vestigial Structures

Homologous Structures Organs or body parts that are similar in structure, function, or both. Organisms with homologous structures have a common ancestor.

Homologous Structures

Analogous Structures Organs or body parts that have a similar function, but a different structure. Organisms with analogous structures do not share a common ancestor.

Analogous Structures

Vestigial Structures Organs 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.

TOP 10 Vestigial Organs 10. The wings on flightless birds 9. Hind leg bones in whales & snakes 8. Erector pili and body hair 7. The human tailbone 6. The eyes of a blind fish 5. Wisdom teeth in humans 4. Sexual organs of dandelions 3. Reproduction of whiptail lizards 2. Male breast tissue and nipples 1. The human appendix

Comparative 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

Evidence from Embryology An Elephant Embryo 58 days old  166 days old 4 mm long  6 cm long

Comparative Biochemistry Studying the similarities of organisms at a biochemical level, for example DNA, ATP, and enzymes.

Evidence from Biochemistry Blood, DNA, RNA, amino acids, enzymes, and other proteins (Example Cytochrome C) Comparison of Organisms Percent Substitutions of Amino Acids in Cytochrome c Residues Two orders of mammals Birds vs. mammals Amphibians vs. birds Fish vs. land vertebrates Insects vs. vertebrates Algae vs. animals 5 and 10 8-12 14-18 18-22 27-34 57

Scientists 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.