CHAPTER 14 How Biological Diversity Evolves Figures 14 1 14 7 PowerPoint Lecture Slides for Essential Biology Second Edition Essential Biology with Physiology Neil Campbell Jane Reece and Eric Simon Presentation prepared by Chris C Romero Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Biological Diversity is Beautiful North America and Europe are drifting apart at a rate of about 2 cm per year Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Biologists estimate that there are 5 30 million species of organisms currently on Earth Microevolution is population level evolution Macroevolution includes multiplication of species p 272 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 1 Our own scientific name Homo sapiens means wise man Globally the rate of species loss may be 50 times higher now than at any time in the past 100 000 years Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings BIOLOGY AND SOCIETY THE IMPACT OF ASTERIODS Many paleontologists Have concluded that a large meteorite hit Earth Believe that the meteor impact contributed to the extinction of the dinosaurs Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Yucat n Peninsula Chicxulub crater Figure 14 1 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 2 MACROEVOLUTION AND THE DIVERSITY OF LIFE Macroevolution Encompasses the major biological changes evident in the fossil record Includes the multiplication of species Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Speciation Is the focal point of macroevolution May occur based on two contrasting patterns Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings In nonbranching evolution a population changes and becomes a new species a Nonbranching evolution Figure 14 2a Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 3 In branching evolution one or more new species branch from a parent species that may continue to exist b Branching evolution Figure 14 2b Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings THE ORIGIN OF SPECIES Species is a Latin word meaning kind or appearance The biological species concept defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups P 273 Individuals within a species can interbreed and produce fertile offspring Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings What Is a Species Ernst Mayr Led an expedition into New Guinea and found a great diversity of birds Distilled his observation into the biological species concept Figure 14 3 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 4 The biological species concept defines species as groups of interbreeding natural populations that are reproductively isolated from other such groups a Similarity between different species b Diversity within one species Figure 14 4 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings The biological species concept cannot be applied in all situations for example with fossils and asexual organisms Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Reproductive Barriers Between Species Pre zygotic barriers impede mating between species or hinder fertilization of eggs Individuals of different species Pre zygotic barriers Temporal isolation Mating or flowering occurs at different seasons or times of day Habitat isolation Populations live in different habitats and do not meet Behavioral Isolation Little or no sexual attraction between males and females Mating Mechanical isolation Structural differences in genitalia or flowers prevent copulation or pollen transfer Gametic isolation Female and male gametes fail to unite in fertilization Fertilization zygote forms Post zygotic barriers Hybrid inviability Hybrid zygotes fail to develop or fail to reach sexual maturity Hybrid sterility Hybrids fail to produce functional gametes Viable fertile offspring Figure 14 5 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 5 Pre zygotic barriers include Temporal isolation Habitat isolation Mechanical isolation Gametic isolation Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Behavioral isolation Figure 14 6 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Courtship rituals or other identification requirements for mates can also function as reproductive barriers behavioral isolation a form of pre zygotic barriers P 274 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 6 Post zygotic barriers Are backup mechanisms that operate should interspecies mating actually occur and produce hybrid zygotes Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Post zygotic barriers include Hybrid inviability Hybrid sterility Horse Mule hybrid Donkey Figure 14 7 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Hybrid inviability is when hybrid offspring die before reaching reproductive maturity P 275 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 7 Mechanisms of Speciation A key event in the potential origin of species occurs when a population is somehow severed from other populations of the parent species Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings The two modes of speciation are Allopatric speciation Sympatric speciation a Allopatric speciation b Sympatric speciation Figure 14 8 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Allopatric Speciation Geological processes Can fragment a population into two or more isolated populations Can contribute to allopatric speciation Figure 14 9 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings 8 Speciation occurs only with the evolution of reproductive barriers between the isolated population and its parent population Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Populations become sympatric again but do not interbreed Geographic barrier Populations become sympatric again and interbreed Population becomes allopatric a Speciation has not occurred b Speciation has occurred Figure 14 10 Copyright 2003 Pearson Education Inc publishing as Benjamin Cummings Sympatric Speciation Sympatric speciation occurs if a genetic change produces a reproductive barrier between mutants and the parent population Polyploidy a mechanism of