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 derived characteristics are shared traits that weren’t present before the group's appearance.

Approaches to the Definition of Species

Biological Species Concept

Species are defined by reproductive isolation. Only members of the same species can interbreed

Recognition Species Concept

Key aspect is the ability individuals have to identify members of their own species for mating purposes.

Ecological Species Concept

A species is a group of organisms exploiting a single niche. Natural selection separates species from one another.

Evolutionary “Trees” Showing Development of Vehicles

Cladogram of Relationships of Birds, Dinosaurs, and Other Terrestrial Vertebrates

Evolutionary Relationshipsof Birds and Dinosaurs

2 Approaches to Interpretations of Evolutionary Relationships

Speciation Model: Branching Evolution

Geological Time Scale

ERA PERIODBegan m.y.a. EPOCH

Began m.y.a.

CENOZOIC Tertiary 1.8 HolocenePleistocene

0.011.8

Quaternary 65 PlioceneMioceneOligoceneEocenePaleocene

523345565

Geological Time Scale

ERA PERIOD (Began m.y.a.)

MESOZOIC Cretaceous 136

Jurassic 190

Triassic 225

PALEOZOIC PermianCarboniferous

DevonianSilurian

OrdovicianCambrian

280345395430500570

Continental Drift

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.)

Lateral View of the Brain

Reptilian andMammalian Teeth

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.