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Sz2- Students will explain the evolutionary history of animals over the geologic history of Earth. Geologic History Geologic time- time that began when earth was formed until present day Evolution of the Earth with Time: Continental Drift 50 Million Years Ago 200 Million Years Ago 150 Million Years Ago 100 Million Years Ago Present Important Terms Evolution- gradual change in a species over time- sci. theory Theory-well-tested explanation that explains a wide range of observations. Adaptation- any trait that helps an organism survive and reproduce Natural Selection the process by which individuals that are better adapted to their environment are more likely to survive and reproduce. Charles Darwin Natural Selection cont. Over a long time, natural selection can modify a population enough to produce a new species Helpful variations accumulate in a species while unfavorable ones disappear. Speciation When a group of individuals remain separated from the rest of the species long enough to evolve different traits HOW this happens- Pangaea /Continental Drift Landform isolation- river, mountain, water. (ex. Squirrels of N. Grand Canyon) Australia A Problem with Traditional Classification Traditional classification systems relied on body structure comparisons only Due to convergent evolution, organisms that are quite different from each other evolve similar body structures. Convergent Evolution: Process by which unrelated organisms independently evolve similarities when adapting to similar environments. A Problem with Traditional Classification Example: The Crab, The barnacle, & The limpet • The barnacle and the limpet have similarly shaped shells & look alike • The crab has a very different body form • Based on anatomy, the barnacle & limpet could be classified together and the crab in a different group. Related This incorrect because crabs and barnacles are actually related Traditional Classification Versus Cladogram Section 18-2 Appendages Crab Conical Shells Barnacle Limpet Crustaceans Crab Gastropod Barnacle Limpet Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION Go to Section: CLADOGRAM 12 Crustaceans Gastropods Molted Exoskeleton Segmentation Free swimming Larva Even though they do not look a like, crabs & barnacles are actually related Evolutionary Classification Biologists now group organisms into categories that represent lines of evolutionary descent, not just physical similarities Evolution Classification: Is the strategy of grouping organisms together based on their evolutionary history. Genus species If these three species belong to the same genus, they are descended from a common ancestor. Felis domestica domestica Felis Domestic Cat Felis leo leo Lion Felis margarita margarita Sand cat` Classification Using Cladograms Cladogram: A diagram that shows the evolutionary relationships among a group of organisms. Crustaceans Gastropods Molted Exoskeleton Segmentation Free swimming Larva Using Cladograms, you can see that crabs and barnacles share similar characteristics because they both molt & are segmented Crustaceans Gastropods Molted Exoskeleton Segmentation Free swimming Larva You can also see that ALL have a free swimming larval stage Modern Evolutionary Classification Similarities in DNA and RNA The genes of many organisms show important similarities at the molecular level that can be used as criteria to help determine classification. 19 Modern Evolutionary Classification Molecular Clocks A model known as a Comparison reveals more DNA in common, the more recent the common ancestor molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently. 20 Terminology Classification Assigning organisms to different catagories based on their relationship Taxonomy The science of naming organisms Systematics Determining evolutionary relationships of organisms Phylogeny Evolutionary history 21 Phylogenetic Tree Shows evolutionary relationships More historical than cladogram 22 Uniramia Echinodermata Chordata Lophophorates Chelicerata Crustacea Protochordates Arthropoda Annelida Hemichordata Other pseudocoelomates Nematoda Mesozoa Sarcomastigophora Ciliophora Apicomplexa Microspora Mollusca Nemertea Platyhelminthes Ctenophora Cnidaria Placozoa Porifera Myxozoa 23 Birds Mammals Reptile Feathers Amphibian Fish Fur Endothermic Amniotic Egg Four Limbs Vertebrae 24 Monophyletic A group of all the descendants of a common ancestor The common ancestor is in the group Example: Birds and Reptiles Ancestor was a bird like reptile 25 Polyphyletic group that has some similarities Contains organisms that have not descended from a common ancestor Based on physical characteristics instead of evolutionary evidence Example: Flying vertebrates- pterosaurs, birds, mammals 26 Cladogram Evolutionary relationship of a group of organisms Each clad (group) share something in common Ancestral traits are the oldest Derived traits evolved later 27 Cladogram for Transportation Wheels are the most ancestral Wings are the most derived 28 Construct a Cladogram 29 Gorilla Four limbs Fur Lost tail 30 Tiger Four limbs Fur Tail 31 Lizard Four limbs Tail 32 Fish Tail 33 Chimpanzee Four limbs Fur Lost tail 34 Clad With 4 Limbs 35 Clad With Fur 36 Clad With No Tail 37 Characteristics for Constructing Cladogram Tail is the most ancestral Four limbs is the oldest derived trait Fur is a later derived trait Loss of tail is the most derived trait 38 Gorilla Chimpanzee Tiger Lizard Fish Tail Lost Fur Four Limbs 39 Gorilla Tail? How do we know the gorilla lost its tail? 40 Gorilla’s Vestigial Tail Gorilla Human 41 The End.