AP Biology Chapter 19: MacroEvolution and the Evidence

AP Biology Macro-evolution  Looking at the big picture.  Looking at what drives the diversity and unity of life cells DNA

AP Biology Anatomical evidence One form of evidence in the unity of life…..

AP Biology Science sees structural similarities as evidence that organisms evolved from a common ancestor. Structural features with a common evolutionary origin are called homologous structures. Homologous parts are similar in structure, but may be very different in specific function.

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.

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Vestigial organs Why would whales have pelvis & leg bones if they were always sea creatures? These are remnants of structures that were functional 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 or environments Video clip

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 Section 15.1 Summary – pages Fish ReptileBirdMammal Pharyngeal pouches Pharyngeal pouches Tail 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

AP Biology All living things have A,T,C,G in their DNA and use the same codon chart to code for the same amino acids. BIOCHEMISTRY

AP Biology 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….. BatWhaleBird

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Another form of evidence that evolution occurs…. Fossil record Millions of years ago Equus Hyracotherium Mesohippus Merychippus Nannippus Body size (kg)

AP Biology Fossils are usually formed when an organism is covered by sediments that then harden into sandstone, slate, mudstone or flint. 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. Most of the time, organisms die in locations that are not conducive to fossilization.

AP Biology Section 14.1 Summary – pages  Fossils are evidence of organisms that lived long ago that are preserved in Earth’s rocks. TYPES OF FOSSILS Fossils TypesFormation Trace fossils Casts Molds Petrified fossils Amber-Preserved or frozen fossils A trace fossil is any indirect evidence 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 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.

AP Biology Section 14.1 Summary – pages  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.

AP Biology Relative Dating Techniques Law of superposition (Nicolaus Steno) You cannot use this technique to get the actual age of a specimen Most Primitive Most Complex

AP Biology 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 Smithsonian Museum, Washington, DC  Archaeopteryx  lived about 150 mya  links reptiles & birds

AP Biology 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 ? ? ? ? Where are the transitional fossils? Land Mammal Aquatic Mammal At first, I was just a joke! Evolution of marine mammals But then, they actually found my fossil!

AP Biology 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  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. It takes 5,730 years for ½ of Carbon 14 to turn into Nitrogen 14

AP Biology Section 14.1 Summary – pages  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 half- life of approximately 1.25 billion years The element carbon-14 decays more rapidly into Nitrogen-14, and has a half-life of only 5,730 years.

AP Biology 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). 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. You can only date organic remains using carbon 14

AP Biology 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: Most radioactive isotopes have rapid rates of decay (that is, short half-lives) and lose their radioactivity within a few days or years. Parent Isotope Stable Daughter Product Currently Accepted Half-Life Values Uranium-238Lead billion years Uranium-235Lead million years Thorium-232Lead billion years Rubidium-87Strontium billion years Potassium-40Argon billion years Samarium-147Neodymium billion years

AP Biology C 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 C and N atoms

AP Biology After 11,460 yrs or 2 half-lives C and N atoms

AP Biology After 17,190 yrs or 3 half-lives C and N atoms

AP Biology After 22,920 yrs or 4 half-lives C and N atoms

AP Biology After 28,650 yrs or 5 half-lives 8 14 C and N atoms

AP Biology After 34,380 yrs or 6 half-lives 4 14 C and N atoms

AP Biology After 40,110 yrs or 7 half-lives 2 14 C and N atoms