The Human Place in the Organic World Principles of Classification Vertebrate Evolutionary History: A Brief Summary Mammalian Evolution The Emergence of Major Mammalian Groups Classification Classification is used to order organisms into categories to show evolutionary relationships. Example - human classification Kingdom: Animalia (multicellular; heterotrophs) Subkingdom: Metazoan (all animals except protozoans) Phyla: Chordata (a hollow nerve cord in the dorsal side of the body) Subphyla: Vertebrata (skull and a backbone containing vertebrae, a series of segmented units that enclose the nerve cord) Class: Mammalia (endothermic; hair; mammary glands; efficient circulatory systems with a four chambered heart, a well-developed brain, and four limbs.) Classification Classification is used to order organisms into categories to show evolutionary relationships. Example - human classification Kingdom: Animalia (multicellular; heterotrophs) Subkingdom: Metazoan (all animals except protozoans) Phyla: Chordata (a hollow nerve cord in the dorsal side of the body; a notochord, or flexible rod between the nerve cord and the digestive tract; gill structures in the pharynx; the digestive tube located just behind the mouth; and a post-anal tail Principles of Classification The field that specializes in establishing the rules of classification is called taxonomy. Organisms are classified first on the basis of physical similarities. Basic physical similarities must reflect evolutionary descent in order for them to be useful. Principles of Classification Homologies Similarities based on descent from a common ancestor. Analogies Similarities based on common function, with no assumed common evolutionary descent. Homoplasy The separate evolutionary development of similar characteristics in different groups of organisms. Homologies Analogies Homology or Analogy? Ancestral and Modified Characters Ancestral characters Refers to characters inherited by a group of organisms from a remote ancestor and thus not diagnostic of groups (lineages) that diverged after the character first appeared. Derived characters Refers to characters that are modified from the ancestral condition and thus are diagnostic of particular evolutionary lineages. Two Approaches to Classification Evolutionary systematics A traditional approach in which presumed ancestors and descendants are traced in time by analysis of homologous characters. Cladistics Attempts to make rigorous evolutionary interpretations based solely on analysis of certain types of homologous characters Cladogram Shows relationships of birds, dinosaurs, and other terrestrial vertebrates. There?s no time scale, and both living and fossil forms are shown along the same dimension. Ancestor- descendant relationships aren?t indicated. Evolutionary Systematics vs Cladistics Geological Eras: Deep Time Paleozoic The first vertebrates appeared 500 m.m.y.a. Mesozoic Reptiles were dominant land vertebrates. Placental mammals appeared 70 m.Y.A. Cenozoic Divided into two periods: Tertiary and Quaternary and 7 epochs: Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene and Holocene. Geologic Time Geological Time Scale ERA PERIOD Began m.y.a. EPOCH Began m.y.a. CENOZOIC Tertiary 1.8 Holocene Pleistocene 0.01 1.8 Quaternary 65 Pliocene Miocene Oligocene Eocene Paleocene 5 23 34 55 65 Epochs Categories of the geological time scale. In the Cenozoic, epochs include Paleocene Eocene Oligocene Miocene Pliocene Pleistocene Holocene Probably Every Old Man Plays Pool Horribly Mammalian Evolution The Cenozoic era is known as the Age of Mammals. After dinosaurs became extinct, mammals underwent adaptive radiation, resulting in rapid expansion and diversification. 70 mya The neocortex, which controls higher brain functions, comprised the majority of brain volume, resulting in greater ability to learn Adaptations Flexible behaviors,larger brain,expanded neocortex Oviparous vs Viviparous Reptilian and Mammalian teeth Reptilian teeth (homodont) and mammalian teeth (heterodont). Having different kinds of teeth; characteristic of mammals, whose teeth consist of incisors, canines, premolars, and molars. A heterodont arrangement allows mammals to process a wide variety of foods. Endothermic Able to maintain internal body temperature by producing energy through metabolic processes within cells; characteristic of mammals, birds, and perhaps some dinosaurs. Major Mammalian Groups Monotremes Primitive, egg laying mammals Marsupials Infants complete development in an eternal pouch Placental Longer gestation allows the central nervous system to develop more completely