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Transcript
Chapter 19: MacroEvolution and the Evidence AP Biology 2006-2007 Macro-evolution Looking at the big picture. Looking at what drives the diversity and unity of life cells DNA AP Biology One form of evidence in the unity of life….. Anatomical evidence AP Biology Science sees structural similarities as evidence that organisms evolved from a common ancestor. 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. AP Biology The body parts of organisms that do not have a close evolutionary origin but are similar in function are called analogous structures. Analogous parts are very different in structure, but perform similar functions. AP Biology AP Biology Vestigial organs Thesewhales are Why would remnants of have pelvis & leg bones ifstructures they were that alwayswere sea functional creatures? in ancestral species AP Biology These are structures that used to have a function, but no longer do….therefore suggesting evolution based on new behaviors Video clip or environments AP Biology Embryology is the study of organisms in embryonic stages. The embryo is one of the earliest stages of growth and development of both plants and animals. The shared features in the embryos suggests evolution from a distant common ancestor. AP Biology Shared Common Features: • a tail posterior to the anus • spinal cord • muscles arranged in bundles • cartilage dorsal notochord (becomes the vertebral column) • Pharyngeal gill slits Pharyngeal pouches Pharyngeal pouches Tail Fish AP Biology Tail Reptile Bird Mammal BIOCHEMISTRY All living things have A,T,C,G in their DNA and use the same codon chart to code for the same amino AP Biology acids. The biochemistry (DNA) of a bat is much closer to that of a whale, than that of a bird. Why? The same technology used to determine paternity can be done to determine shared ancestry. Because bats and whales are mammals! Therefore, more closely related….. AP Biology Bat Whale Bird AP Biology Another form of evidence that evolution occurs…. Fossil record 550 500 Body size (kg) 450 Equus 400 350 300 250 Merychippus 200 150 Mesohippus Hyracotherium 100 50 Nannippus 60 55 50 45 40 35 30 25 20 15 10 5 0 AP Biology Millions of years ago Fossils are usually formed when an organism is covered by sediments that then harden into sandstone, slate, mudstone or flint. Most of the time, organisms die in locations that are not conducive to fossilization. Most organisms do not fossilize and those that do are usually destroyed by geological processes or they never surface for examination. We have only discovered about 250,000 fossilized species. This tells us that there are many gaps in the fossil record. AP Biology 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 AP Biology 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 AP Biology organisms that lived during the past and sometimes to learn about their behavior. • Relative Dating Techniques Law of superposition (Nicolaus Steno) You cannot use this technique to get the actual AP Biology age of a specimen Most Complex Most Primitive The first fossilized fish appear buried below the first fossilized amphibians which appear below the first fossilized reptiles which appear below the first fossilized birds and mammals. This is consistent with the Darwinian model of origins which says that birds and mammals evolved from earlier reptile ancestors, which evolved from amphibian ancestors which evolved from fish ancestors. AP Biology Fossil evidence for evolution concerns transitional fossils. Transitional fossils are fossils which are thought to document the evolutionary change, or transition, of one species into another. The Mesohippus, Merychippus, and Pliohippus are all thought to be transitional fossils, documenting the evolution of the Eohippus into the modern horse. Perhaps one of the most famous “transitional fossils” of all time was the archaeopteryx [ahr-kee-op-tuh-riks], which shows evidence of transitioning between a reptile and a bird. AP Biology Evolution of birds Archaeopteryx lived about 150 mya links reptiles & birds Smithsonian Museum, AP Biology Washington, DC Evolution of land animals 2006 Fossil Discovery “Tiktaalik” “missing link” from sea to land animals from swimming (0 legs) to walking (4 legs) AP Biology Evolution of marine mammals Land Mammal ? ? ? ? But then, they actually found my fossil! At first, I was just a joke! AP Biology Aquatic Mammal • Radiometric Dating Techniques To find the specific age of rocks, scientists use radiometric dating. By using the radioactive isotopes present in rocks, and understanding the rates at which these isotopes decay, scientists can determine approximate age of the rocks. Atoms of the same element with differing atomic weights can be naturally found in the environment, and are called isotopes. AP Biology Radioactive isotopes are atoms with unstable nuclei that break down, or decay, over time, giving off radiation. The isotope is eventually changed into, or replaced by another element over time. AP Biology 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. AP Biology If you know what the unstable atom is (Carbon 14) and you know what it turns into as it decays (Nitrogen 14). And you know the rate at which the unstable atom decays/turns into something else It takes 5,730 years for ½ of Carbon 14 to turn into Nitrogen 14 You can measure the amount of the unstable parent atom in the rock….and compare that to the amount of the new atom This will tell you the age of the sample rock. AP Biology 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. AP Biology • The element potassium-40 decays to argon-40 and has a halflife of approximately 1.25 billion years AP Biology • The element carbon-14 decays more rapidly into Nitrogen-14, and has a half-life of only 5,730 years. Because Carbon 14 has such a short half-life, it can only be used to date things that died recently in geologic history (under 70,000 years ago). • You can only date organic remains using carbon 14 If you need to date rocky material from farther back in our geologic past, you must use another method, such as Potassium/Argon, which has a much longer half-life. AP Biology Most radioactive isotopes have rapid rates of decay (that is, short half-lives) and lose their radioactivity within a few days or years. Some isotopes, however, decay slowly, and several of these are used as geologic clocks. The parent isotopes and corresponding daughter products most commonly used to determine the ages of ancient rocks are listed below: Parent Isotope Stable Daughter Product Uranium-238 Lead-206 4.5 billion years Uranium-235 Lead-207 704 million years Thorium-232 Lead-208 14.0 billion years Rubidium-87 Strontium-87 48.8 billion years Potassium-40 Argon-40 1.25 billion years Samarium-147 Neodymium-143 106 billion years AP Biology Currently Accepted Half-Life Values 256 14C atoms How many carbon-14 atoms and how many nitrogen-14 atoms will this rock have in 5,730 yrs. AP Biology After 5730 years or 1 half-life 128 14C and 128 14N atoms AP Biology After 11,460 yrs or 2 half-lives 64 14C and 192 14N atoms AP Biology After 17,190 yrs or 3 half-lives 32 14C and 224 14N atoms AP Biology After 22,920 yrs or 4 half-lives 16 14C and 240 14N atoms AP Biology After 28,650 yrs or 5 half-lives 8 14C and 248 14N atoms AP Biology After 34,380 yrs or 6 half-lives 4 14C and 252 14N atoms AP Biology After 40,110 yrs or 7 half-lives 2 14C and 254 14N atoms AP Biology