Sz2- Students will explain the evolutionary history of animals over the geologic history of Earth. Evolutionary Classification
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 100Million 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 Conical Shells Crustaceans Gastropod Crab Crab Limpet Limpet Barnacle Barnacle Molted exoskeleton Segmentation Tiny free-swimming larva TRADITIONAL CLASSIFICATION CLADOGRAM Go to Section:
Crustaceans Gastropods Molted Exoskeleton Even though they do not look a like, crabs & barnacles are actually related Segmentation Free swimming Larva
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 Domestic Cat Felis 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 Using Cladograms, you can see that crabs and barnacles share similar characteristics because they both molt & are segmented Segmentation Free swimming Larva
Crustaceans Gastropods Molted Exoskeleton You can also see that ALL have a free swimming larval stage Segmentation Free swimming Larva
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.
Modern Evolutionary Classification • Molecular Clocks • A model known as a molecular clock uses DNA comparisons to estimate the length of time that two species have been evolving independently. • Comparison reveals more DNA in common, the more recent the common ancestor
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
Phylogenetic Tree • Shows evolutionary relationships • More historical than cladogram
Uniramia Echinodermata Chelicerata Chordata Lophophorates Crustacea Protochordates Annelida Arthropoda Hemichordata Mollusca Other pseudocoelomates Nemertea Platyhelminthes Ctenophora Nematoda Cnidaria Mesozoa Placozoa Sarcomastigophora Ciliophora Porifera Apicomplexa Microspora Myxozoa
Birds Mammals Reptile Feathers Amphibian Fur Fish Endothermic Amniotic Egg Four Limbs Vertebrae
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
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
Cladogram • Evolutionary relationship of a group of organisms • Each clad (group) share something in common • Ancestral traits are the oldest • Derived traits evolved later
Cladogram for Transportation • Wheels are the most ancestral • Wings are the most derived
Gorilla • Four limbs • Fur • Lost tail
Tiger • Four limbs • Fur • Tail
Lizard • Four limbs • Tail
Fish • Tail
Chimpanzee • Four limbs • Fur • Lost tail
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
Gorilla Chimpanzee Tail Lost Fur Four Limbs Tiger Lizard Fish
Gorilla Tail? • How do we know the gorilla lost its tail?
Human Gorilla’s Vestigial Tail Gorilla