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AGENDA – 2/11/15 • Today’s Objective: • We will discuss how fossils, anatomical structures, DNA, and embryology show evidence in evolution and evolutionary relationships. • Bell-Ringer – Homology vs Analogy • Finish Fossils and Evidence notes • Natural Selection Test Corrections AGENDA – 2/11/15 • Today’s Objective: • We will discuss how fossils, anatomical structures, DNA, and embryology show evidence in evolution and evolutionary relationships. • 4.1 --- Test Scores • Fossils and Evidence notes EVIDENCE OF CHANGE OVER TIME • There are several places we can see evidence of evolution/evolutionary relationships: -fossils, -studying similarities in anatomy, - biochemistry/DNA, -and embryology. • Fossils are evidence of organisms that lived long ago that are preserved in Earth’s rocks. TYPES OF FOSSILS Fossils Types Formation A trace fossil is any indirect evidence Trace fossils Casts left by an animal and may include a footprint, a trail, or a burrow. When minerals in rocks fill a space left by a decayed organism, they make a replica, or cast, of the organism. A mold forms when an organism is Molds Petrified fossils Amber-Preserved or frozen fossils buried in sediment and then decays, leaving an empty space. Petrified-minerals sometimes penetrate and replace the hard parts of an organism At times, an entire organism was quickly trapped in ice or tree sap that hardened into amber. • Paleontologists, scientists who study ancient life, are like detectives who use fossils to understand events that happened long ago. • They use fossils to determine the kinds of organisms that lived during the past and sometimes to learn about their behavior. • For fossils to form, organisms usually have to be buried in mud, sand, or clay soon after they die. • Fossils are not usually found in other types of rock because of the ways those rocks form. • Most fossils are found in sedimentary rocks. rocksthe form at relatively low temperatures and pressures • These For example, conditions under which metamorphic rocks form often that may damage to the organism. destroy anyprevent fossils that were in the original sedimentary rock. • Few organisms become fossilized because, without burial, bacteria and fungi immediately decompose their dead bodies. • Occasionally, however, organisms do become fossils in a process that usually takes many years. How fossils form • Scientists use a variety of methods to determine the age of fossils. • Relative dating • This method basically indicates that the fossils found closer to the surface are younger, and the fossils found in deeper strata are more primitive (older). (in undisturbed ground) • This method does not give a specific age of the fossil or rock. • Using this principle, scientists can determine relative age and the order of appearance of the species that are preserved as fossils in the layers. • To find the specific ages of rocks, scientists use absolute dating, also called Radiometric Dating. • In this type of dating scientists use radioactive atoms to determine the absolute age of objects. As specific atoms decay they emit radiation and lose electrons, which causes them to turn into a different element. So- these atoms change from one thing into something else over time- and they do this at a constant rate. • The half-life of a radioactive atom is the time it takes for half of that atom in a sample to decay and turn into another element. One form of evidence in the unity of life….. Anatomical evidence Science sees structural similarities as evidence that organisms evolved from a common ancestor. Crocodile forelimb Bird wing Whale forelimb Homologous parts are similar in structure, but may be very different in specific function. Structural features with a common evolutionary origin are called homologous structures. The body parts of organisms that do not have a common evolutionary origin but are similar in function are called analogous structures. Analogous parts are very different in structure, but perform similar functions. Pre-AP Bell-Ringer: 2/11/15 1. What are homologous structures? 2. What are analogous structures? 3. Give an example of each type of structure. ANATOMY • Vestigial structure—a body structure in a present-day organism that no longer serves its original purpose, but was probably useful to an ancestor. Video clip BIOCHEMISTRY Scientists believe that the fact that ALL LIVING THINGS have A,T,C, and G in their DNA and all use the same coding for proteins means we are all related in some way. EMBRYOLOGY • The study of how similar embryos are for different organisms (may be evidence of relation) • An embryo is the earliest stage of growth and development of both plants and animals. EMBRYOLOGY • Scientists believe the shared features in the young embryos of different species suggest evolution from a distant, common ancestor. Pharyngeal pouches Pharyngeal pouches Tail Fish Tail Reptile Bird Mammal Chicken Rat Turtle