Chapter 14 The Origin of Species Chapter 14 The Origin of Species Theories behind “Why” new species develop and “How” new species develop Examples of supporting evidence of biological diversity

14.1 The origin of species is the source of biological diversity Microevolution = gradual change in a population overtime Speciation = the origin of new species, is at the focal point of evolution Macroevolution = evolutionary change on a grand (LARGE) scale Replacement of one species with another Increases biodiversity Figure 14.1

14.2 What is a species? Carolus Linnaeus, a Swedish physician and botanist, used physical characteristics to distinguish species Developed the binomial system of naming organisms Scientific name = the genus and species names; Should be italicized or underlined Homo sapiens Homo = genus sapien = species Linnaeus’ system established the basis for taxonomy The branch of biology concerned with naming and classifying the diverse forms of life

Similarities between some species and variation within a species can make defining species difficult. Figure 14.2A Figure 14.2B

Different Views for Identifying Species The Biological Species Concept defines a species as: A population or group of populations whose members can interbreed and produce fertile offspring Other Species Concepts The morphological species concept: Classifies organisms based on observable phenotypic traits Primary way of classifying organisms The ecological species concept: Defines a species by its ecological role The phylogenetic species concept: Defines a species as a set of organisms representing a specific evolutionary lineage Uses physical characteristics and DNA sequencing

14.3 Reproductive barriers keep species separate Serve to isolate a species’ gene pool and prevent interbreeding  create new species Are categorized as prezygotic or postzygotic Table 14.3

Prezygotic Barriers - prevent mating or fertilization between species Temporal isolation - two species breed at different times Habitat isolation – live in different habitats  don’t meet Behavioral isolation - there is little or no sexual attraction between species, due to specific behaviors Mechanical isolation - female and male sex organs or gametes are not compatible Gametic isolation – gametes die or fail to unite Figure 14.3A Figure 14.3B Figure 14.3C

Postzygotic Barriers - Operate after hybrid zygotes are formed Hybrid inviability – hybrids don’t develop Hybrid sterility - hybrid offspring between two species are sterile and therefore cannot mate (example: mule) Hybrid breakdown – first generation is viable, 2nd generation sterile or feeble Figure 14.3D Animations of Pre Zygotic and Post Zygotic Barriers

MECHANISMS OF SPECIATION (the “HOW”) 14.4 Geographic isolation can lead to speciation In allopatric speciation a population is geographically divided, and new species often evolve A. harrisi A. leucurus Figure 14.4

Many plant species have evolved by polyploidy 14.6 New species can also arise within the same geographic area as the parent species In sympatric speciation new species may arise without geographic isolation Many plant species have evolved by polyploidy Multiplication of the chromosome number due to errors in cell division (genetic mutation) Figure 14.6B Parent species Meiotic error Self-fertilization Offspring may be viable and self-fertile Zygote Unreduced diploid gametes 2n = 6 Diploid 4n = 12 Tetraploid O. gigas O. lamarckiana Figure 14.6A

CONNECTION Many plants, including food plants such as bread wheat are the result of hybridization and polyploidy AA BB AB AA BB DD ABD AA BB DD  Wild Triticum (14 chromosomes) Triticum monococcum (14 chromosomes) Sterile hybrid (14 chromosomes) Meiotic error and self-fertilization  T.tauschii (wild) (14 chromosomes) T.turgidum Emmer wheat (28 chromosomes) Sterile hybrid (21 chromosomes) Meiotic error and self-fertilization Figure 14.7A T.aestivum Bread wheat (42 chromosomes) Figure 14.7B

14.8 Adaptive radiation may occur in new or newly vacated habitats In adaptive radiation, the evolution of new species occurs when mass extinctions or colonization provide organisms with new environments (“Founder Effect”) Island chains (ex. Galapagos Islands) Cactus-seed-eater (cactus finch) Seed-eater (medium ground finch) Tool-using insect-eater (woodpecker finch) 1 2 3 4 5 A B C D Figure 14.8B Figure 14.8A

14.10 The tempo of speciation can appear steady or jumpy According to the gradualism model New species evolve by the gradual accumulation of changes brought about by natural selection Fits Darwin’s view of the origin of species Big changes (speciations) occur by the steady accumulation of many small changes Time Figure 14.10A

The punctuated equilibrium model draws on the fossil record Species change the most as they arise from an ancestral species and then change relatively little for the rest of their existence Time Figure 14.10B

Transparent protective MACROEVOLUTION Many complex structures evolve in many stages from simpler versions having the same basic function, Ex. Eye complexity Other novel structures result from exaptation - the gradual adaptation of existing structures to new functions Ex. Feathers came before flight – possibly for insulation Figure 14.11 Light-sensitive cells Fluid-filled cavity Transparent protective tissue (cornea) Cornea Layer of light-sensitive cells (retina) Nerve fibers Optic nerve Eyecup Retina Lens Patch of light- sensitive cells Simple pinhole camera-type eye Eye with primitive lens Complex Limpet Abalone Nautilus Marine snail Squid

Evolutionary Biology - “Evo-devo”- A field that combines evolutionary and developmental biology Many striking evolutionary transformations are the result of a change in the rate or timing of developmental changes Figure 14.12A

Tracing Evolutionary History Chapter 15 Tracing Evolutionary History

MACROEVOLUTION AND EARTH’S HISTORY 15.1 The fossil record chronicles macroevolution The fossil record documents the main events in the history of life In the geologic record: Major transitions in life-forms separate eras Smaller changes divide eras into periods

15.2 The actual ages of rocks and fossils mark geologic time Relative age of fossils is determined by the rock strata in which the fossils appear Radiometric dating (actual age) - Measures the decay of radioactive isotope; Can gauge the actual ages of fossils and the rocks in which they are found Half-life: fixed rate of decay = the amount of time it takes for ½ of the original isotope to decay Carbon-14 used to date younger fossils Potassium-40 can be used for fossils hundreds of millions of years old Half-time emitted Uranium-235 710 million yrs alpha, gamma Plutonium-239 24,000 yrs alpha, gamma

The geologic record – know the Eras and major events that occur in each Table 15.1 p. 298

15.3 Continental drift has played a major role in macroevolution Continental drift (now Plate Tectonics) is the slow, constant movement of Earth’s crustal plates on the hot mantle The formation of Pangaea (~250 mya) altered habitats and triggered extinctions Breakup of Pangaea (~180 mya) created Laurasia and Gondwana Modern continents began to take shape (~65mya) Figure 15.3B 65 135 245 Millions of years ago Paleozoic Mesozoic Cenozoic North America Eurasia Africa South America India Antarctica Australia Laurasia Gondwana Pangaea Edge of one plate being pushed over edge of neighboring plate (zones of violent geologic events) Antarctic Plate Australian Plate Split developing Indian Plate Eurasian Plate North American Plate South American Plate Nazca Plate Pacific Plate Arabian Plate African Plate Figure 15.3A

The separation of the continents affected the distribution and diversification of organisms North America South Europe Asia Africa Australia = Living lungfishes = Fossilized lungfishes Figure 15.3C Lungfish Video Figure 15.3D

15.4 Tectonic trauma imperils local life CONNECTION 15.4 Tectonic trauma imperils local life Volcanoes and earthquakes result from plate tectonics San Andreas Fault North American Plate San Francisco Santa Cruz Los Angeles Pacific California Figure 15.4A, B

15.5 Mass extinctions were followed by diversification of life-forms Mass extinctions occurred at the end of the Permian and Cretaceous periods The Cretaceous extinction (~ 65 mya), which included the dinosaurs, may have been caused by an asteroid which landed near the Yucatan Peninsula A rebound in diversity follows mass extinctions Figure 15.5 North America Chicxulub crater Yucatán Peninsula

PHYLOGENY AND SYSTEMATICS 15.6 Phylogenies are based on homologies in fossils and living organisms Phylogeny, the evolutionary history of a group, is based on identifying homologous and molecular sequences that provide evidence of common ancestry (Phylogenetic tree) Homologous structures – evolved from a common ancestral structure, shows shared ancestry and results from divergent evolution Analogous structures (similarities) – structures of non-related species are similar because they evolved in similar environments, result from convergent evolution Cladogram– a diagram depicting the pattern of shared characters Systematics– the science of classification

15.7 Systematics connects classification with evolutionary history Taxonomists assign a binomial (scientific name) to each species A genus may include a group of related species Genera are grouped into progressively larger categories (know these!) Domain, kingdom, phylum, class, order, family, genus, species *KEY TO REMEMBER: Dear King Philip Came Over From Germany Saturday A phylogenetic tree is a hypothesis of evolutionary relationships Species Felis catus (domestic cat) Mephitis mephitis (striped skunk) Lutra lutra (European otter) Canis familiaris (domestic dog) lupus (wolf) Genus Family Order Felidae Carnivora Mustelidae Canidae Figure 15.7B Species Genus Family Order Class Phylum Kingdom Domain Felis catus Felidae Carnivora Mammalia Chordata Animalia Eukarya

Binomial nomenclature Ursus arctos Genus Species (Grizzly Bear)

Classifying Species into Larger groups

Cladograms are diagrams based on shared characteristics among species Iguana Derived Characteristics (Ingroup) Duck-billed platypus Hair, mammary glands Kangaroo Gestation Beaver Long gestation Phylogenetic Tree

Molecular biology is a powerful tool in systematics Lesser panda Procyonidae Phylogenetic Tree Molecular Clocks are the predictable changes in genes caused by mutations. The changes can be used to determine the amount of time that has passed since two species diverged from a common ancestor. Raccoon Giant panda Spectacled bear Ursidae Sloth bear Sun bear American black bear Asian black bear Polar bear Brown bear 35 30 25 20 15 10 Pleistocene Oligocene Miocene Pliocene Millions of years ago

DOMAINS 15.10 Arranging life into kingdoms is a work in progress Monera Protista Plantae Fungi Animalia Earliest organisms Prokaryotes Eukoryotes Figure 15.10A DOMAINS Bacteria Archaea Eukarya Earliest organisms Prokaryotes Eukoryotes Figure 15.10B