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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 Mammalian Evolution. Chapter Outline.
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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 • Mammalian Evolution
Chapter Outline • The Emergence of Major Mammalian Groups • Processes of Macroevolution • Issue: Just When We Thought Things Couldn’t Get Any Worse: Bushmeat and Ebola
Classification • Classification is used to order organisms into categories to show evolutionary relationships. • Example - human classification • Kingdom: Animalia • Subkingdom: Metazoan • Phyla: Chordata • Subphyla: Vertebrata • Class: Mammalia
Classification: Definitions • Metazoa • Multicellular animals. • Chordata • The phylum of the animal kingdom that includes vertebrates. • Vertebrates • Animals with segmented bony spinal columns; includes fishes, amphibians, reptiles, birds, and mammals.
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.
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.
Question • The scientific discipline that delineates the rules of classification is • paleontology. • stratigraphy. • homology. • taxonomy.
Answer: d • The scientific discipline that delineates the rules of classification is taxonomy.
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.
Evolutionary “Trees”: Development of Passenger Vehicles • The first divergence is between cars and trucks (I). • A later divergence occurs between luxury cars and sports cars (II).
Evolutionary “Trees”: Development of Passenger Vehicles • SUVs diverge from trucks, but like sports cars, they have a decorative racing stripe. • This is a homoplasy and does not make SUVs sports cars. • Classifications based on a characteristic that can appear independently in different groups can lead to an incorrect conclusion.
Evolutionary Relationships of Birds and Dinosaurs • (a) Traditional view, showing no close relationship. (b) Revised view, showing common ancestry of birds and dinosaurs.
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.
Definition of Species • Biological species concept • Depiction of species as groups of individuals capable of interbreeding, but reproductively isolated from other such groups.
Definition of Species • Recognition species concept • A depiction of species in which the key aspect is the ability of individuals to identify members of their own species for purposes of mating. • This type of selective mating is a component of a species concept emphasizing mating and is therefore compatible with the biological species concept.
Definition of Species • Ecological species concept • The concept that a species is a group of organisms exploiting a single niche. • This view emphasizes the role of natural selection in separating species from one another.
Definition of Species • Phylogenetic species concept • Splitting many populations into separate species based on an identifiable parental pattern of ancestry.
Allopatric • Living in different areas. • This pattern is important in the divergence of closely related species from each other and from their shared ancestral species because it leads to reproductive isolation.
Speciation • Process by which a new species evolves from a prior species. • Speciation is the most basic process in macroevolution.
Recognition of Fossil Species • The minimum biological category we would like to define in fossil primate samples is the species. • Variations • Intraspecific - Variation is accounted for by individual, age, and sex differences seen within every biological species • Interspecific - Variation represents differences between reproductively isolated groups.
Recognition of Fossil Species • Defining where species boundaries begin and end is often difficult. • “Splitters” are researchers who claim speciation occurred frequently during hominid evolution. • “Lumpers” assume speciation was less common and see much variation as being intraspecific.
Recognition of Fossil Genera • A genus is a group of species composed of members more closely related to each other than to species from any other genus. • Species that are members of the same genus share the same broad adaptive zone. • Members of the same genus should all share derived characters not seen in members of other genera.
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.
Continental Drift • The movement of continents on sliding plates of the earth’s surface. • As a result, the positions of large landmasses have shifted drastically during the earth’s history.
Continental drift • The positions of the continents during the Mesozoic (c. 125 m.y.a.). • Pangea is breaking up into a northern landmass (Laurasia) and a southern landmass (Gondwanaland).
Continental Drift • (a) Positions of the continents during the Mesozoic. Pangea is breaking up into a northern landmass (Laurasia) and a southern landmass (Gondwanaland). (b) Positions of the continents at the beginning of the Cenozoic.
Ecological Niches • The positions of species within their physical and biological environments, together making up the ecosystem. • A species’ ecological niche is defined by such components as diet, terrain, vegetation, type of predators, relationships with other species, and activity patterns, and each niche is unique to a given species.
Epochs • Categories of the geological time scale. • In the Cenozoic, epochs include • Paleocene • Eocene • Oligocene • Miocene • Pliocene • Pleistocene • 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.
Reptilian and Mammalian teeth • Mammals are heterodont, they have different kinds of teeth; incisors, canines, premolars, and molars.
Question • The divergence of reptiles into many different forms describes • analogies. • sexual selection. • adaptive radiation. • homologies.
Answer: c • The divergence of reptiles into many different forms describes adaptive radiation.
Heterodont • Having different kinds of teeth; characteristic of mammals, whose teeth consist of incisors, canines, premolars, and molars.
Endothermic • Able to maintain internal body temperature by producing energy through metabolic processes within cells; characteristic of mammals, birds, and perhaps some dinosaurs.
Question • An advantage of heterodont dentition is that it • allows the animal to defend itself more efficiently. • allows for processing a wide variety of foods. • opens up new ways of interacting with potential mates. • allows the animal to grab prey that it could not catch otherwise.
Answer: b • An advantage of heterodont dentition is that it allows for processing a wide variety of foods.
