Chapter 5 Macroevolution: Processes of Vertebrate and Mammalian Evolution
Chapter Outline • The Human Place in the Organic World • Principles of Classification • Definition of Species • Vertebrate Evolutionary History: A Brief Summary
Chapter Outline • Mammalian Evolution • The Emergence of Major Mammalian Groups • Processes of Macroevolution
The Human Place in the Organic World • Classification groups life forms into categories showing evolutionary relationships. • Example - human classification • Kingdom: Animalia • Subkingdom: Metazoan • Phyla: Chordata • Subphyla: Vertebrata • Class: Mammalia
Taxonomic Concepts • Homologies - structures shared through descent from a common ancestor. • Analogies - structures used for the same function that developed independently and are not the result of common descent. • Homoplasy - the process by which similarities can develop in different groups of organisms.
Cladistic Taxonomy Groups species according to shared derived characteristics: • Primitive traits reflect the ancestral condition. • Shared derivedcharacteristics are shared traits that weren’t present before the group's appearance.
Cladogram of Relationships of Birds, Dinosaurs, and Other Terrestrial Vertebrates
2 Approaches to Interpretations of Evolutionary Relationships
Geological Eras • 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.
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. • The neocortex, which controls higher brain functions, comprised the majority of brain volume, resulting in greater ability to learn.
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
Early Primate Evolution • Primate origins began in the placental mammal radiation 65 m.y.a. • The earliest undoubted primates appear in the Eocene epoch. • Most of our knowledge of primate Oligocene evolution comes from a site in Egypt, the Fayum.
Fayum Forms: Possible Roots of Anthropoid Evolution • Apidium • Small, primate that may lie near or before the evolutionary divergence of Old and New World anthropoids. • Aegyptopithecus • Largest of the Fayum primates with a small brain, large snout, and none of the traits of Old World monkeys or the hominoids.
Miocene Fossil Hominoids • Marked by a spectacular hominoid radiation and could be called “the golden age of hominoids”. • Grouped geographically: • African forms (23-14 m.y.a.) • European forms (13-11 m.y.a.) • Asian forms (16-7 m.y.a.)
Genus and Species • Species is the most precise taxonomic level. • Genus is a group of species more closely related to each other than to species from another genus. • Members of the same genus share derived characteristics not seen in other genera.