Evolution II1 Chapter 22: The Nature of Species We will also cover some selected topics from Chapters intro to claudistics Chapter Biological classification -- Domains vs kingdoms -- Intro to history of life

Evolution II2 What is a species? Scientific naming of species Scientific binomial – Carolus Linnaeus Genus + Species Homo sapiens vs “humans” Acer rubrum vs “red maple” Writing Conventions Definition “A group of interbreeding organisms that are reproductively isolated” What is ‘reproductive isolation’? Biological classification system: Domain Kingdom Phylum Class Order Family Genus Species Which of these is Acer rubrum? Question

Evolution II3 What are some mechanisms of reproductive isolation? Pre-zygotic Ecological (habitat) e.g., mountain ranges Mechanical e.g. reproductive anatomy Temporal e.g. mating seasons Behavioral e.g., mating rituals Gametic gametes incompatible (many plants) e.g., frogs of Sierra Nevada foothills e.g., bowerbirds of Australia

Evolution II4 Mechanisms of reproductive isolation, con’t. Post-zygotic Hybrid inviability -- embryo / fetus does not develop e.g., cattle and water buffalo Hybrid infertility -- offspring is infertile e.g., colored and pied flycatchers Meet and hybridize in central and northern Europe Question

Evolution II5 The biological species concept has limitations If two species can hybridize, are they separate species? -- plants -- animals Should all dogs be classified in the same species? Native: California Tiger Salamander Invasive: Adult Barred Tiger Salamander Hybrid: Appears to be more fit then native m/2007/09/20/californ ia-barred-tiger- salamanders- interbreed-produce- hybrids/

Evolution II6 How does geographic distribution relate to speciation? Allopatric speciation: geographic isolation mountains, rivers, islands What evolutionary mechanisms can operate? Can Sympatric speciation occur? e.g., “blackbellied seedcracker” Less fit hybrids -  ‘reinforcement’ Reinforcement among European flycatchers Question

Evolution II7 Hawthorn Apple Maggot How can we explain the origin of the apple maggot? Visit Martin G. Kelly’s site at

Evolution II8 Under what conditions does ‘Adaptive Radiation’ occur? -A special case of disruptive evolution Darwin’s Finches -- classic example Can occur regionally or globally -- rise of mammals Adaptations reinforced by “Character Displacement’ Question

Evolution II9 Plotting macroevolution What are some characteristics of evolution that can be diagrammed? Gradualism vs ‘punctuated equilibrium’ Stephen J Gould & Niles Eldredge What are possible mechanisms of rapid speciation? -- polyploidy -- mutations to developmental genes -- geologic time vs ‘human’ time

Evolution II10 Plotting evolutionary relationships (from Chapter 23) The traditional “evolutionary tree” vs Claudistics Clade= all organisms with “Shared derived characteristics”

Evolution II11 Revisiting Classification… (from Chapter 26) Domains and Kingdoms Biological classification system: Domain Kingdom Phylum Class Order Family Genus Species Question

Evolution II12 Highlights of the History of Life (from Chapter 26) Advanced life forms have appeared Late in earth’s geologic history Origin of life ~ 3.8 bya Eukaryotic cells ~ 1.7 bya Multicellular organisms ~ 1.2 bya Humans only ~ 1 mya Origin of life Multicellular organisms

Evolution II13 The origin of major groups of animals The ‘eras’ The Cambrian explosion Vertebrates Invertebrates Age of reptiles Age of mammals Insects most successful of them all

Evolution II14 There have been many mass extinctions! Some small, Some BIG! Question