Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 14 The Origin of Species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mosquito Mystery Speciation is the emergence of new species How do we know that a distinctly new species has evolved? – In London, two populations of mosquitoes exist with very little overlap in their respective habitats – Evidence indicates that the two species did not diverge from one species

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – In the United States the two species appeared to hybridize into one species, which transmits West Nile virus – How could the mosquitoes behave like two species on one continent and one species on another?

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 14.1 The origin of species is the source of biological diversity Microevolution, gradual adaptation of a species to its environment, does not produce new species Speciation, the origin of new species, is at the focal point of evolution Macroevolution, dramatic biological changes that begin with the origin of new species, has led to Earth's great biodiversity

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONCEPTS OF SPECIES 14.2 What is a species? Taxonomy is the branch of biology concerned with naming and classifying the diverse forms of life – The binomial system was introduced by Linnaeus in the 18th century Similarities between some species and variation within a species can make defining species difficult

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The biological species concept – Defines a species as a population or group of populations whose members can interbreed and produce fertile offspring Reproductive isolation of different species prevents gene flow – Cannot be used as the sole criterion for species assignment

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The morphological species concept – Classifies organisms based on observable phenotypic traits The ecological species concept – Defines a species by its ecological role The phylogenetic species concept – Defines a species as a set of organisms with a unique genetic history

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 14.3 Reproductive barriers keep species separate Reproductive barriers serve to isolate a species' gene pool and prevent interbreeding – Prezygotic barriers prevent mating or fertilization between species Temporal isolation: Species breed at different times Behavioral isolation: There is little or no sexual attraction between species due to specific behaviors

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Mechanical isolation: Female and male sex organs or gametes are not compatible Gametic isolation: After copulation, gametes do not unite to form a zygote

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings – Postzygotic barriers operate after hybrid zygotes are formed Hybrid inviability: Hybrids do not survive Hybrid sterility: Hybrid offspring between two species are sterile and therefore cannot mate Hybrid breakdown: Hybrids that mate with each other or either parent species produce feeble or sterile offspring

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Albatross Courtship Ritual Video: Albatross Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Blue-footed Boobies Courtship Ritual Video: Giraffe Courtship Ritual Video: Giraffe Courtship Ritual

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings MECHANISMS OF SPECIATION 14.4 Geographic isolation can lead to speciation In allopatric speciation, a population is geographically divided – Barriers include geologic processes such as emergence of a mountain or subsidence of a lake – Changes in allele frequencies are unaffected by gene flow from other populations – New species often evolve, but only after reproductive barriers develop

LE 14-4 A. harrisi A. leucurus

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Video: Grand Canyon Video: Grand Canyon

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 14.5 Reproductive barriers may evolve as populations diverge Diane Dodd tested the hypothesis that reproductive barriers can evolve as a by- product of the adaptive divergence of populations in different environments – Fruit flies bred for several generations on a certain food tended to choose mates that were raised on the same food Reproductive isolation was well under way after several generations of evolutionary divergence

LE 14-5a Starch medium Initial sample of fruit flies Results of mating experiments Female StarchMaltose Female Same population Different populations Male MaltoseDifferent Same Starch Mating frequencies in control group Mating frequencies in experimental group Maltose medium

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Geographic isolation in Death Valley led to allopatric speciation of pupfish – By genetic drift or natural selection, the isolated populations evolved into separate species Video: Galápagos Marine Iguana Video: Galápagos Marine Iguana

LE 14-5b A pupfish

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 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 – Not widespread among animals but important in plant evolution Many plant species have evolved by polyploidy, multiplication of the chromosome number due to errors in cell division – First discovered by Hugo de Vries – Most polyploid plants arise from the hybridization of two parent species

LE 14-6a Parent species Meiotic error Self- fertilization 2n = 6 Diploid 4n = 12 Tetraploid Unreduced diploid gametes Zygote Offspring may be viable and self-fertile

LE 14-6b O. lamarckiana O. gigas

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings CONNECTION 14.7 Polyploid plants clothe and feed us 20—25% of all plant species are polyploids – Most result from hybridization between two species – Many of our food and fiber plants are polyploids Bread wheat, Triticum aestivum, is a polyploid with 42 chromosomes that evolved over 8,000 years ago Today, plant geneticists create new polyploids in the laboratory

LE 14-7b AABB Wild Triticum (14 chromo- somes) Triticum monococcum (14 chromosomes) AB AA BB DD ABD Sterile hybrid (14 chromosomes) Meiotic error and self-fertilization T. turgidum Emmer wheat (28 chromosomes)   T. tauschii (wild) (14 chromosomes) Sterile hybrid (21 chromosomes) Meiotic error and self-fertilization T. aestivum Bread wheat (42 chromosomes) AA BB DD

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings 14.8 Adaptive radiation may occur in new or newly vacated habitats Adaptive radiation: the evolution of many new species from a common ancestor in a diverse environment – Occurs when mass extinctions or colonization provide organisms with new environments

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Island chains with physically diverse habitats are often sites of explosive adaptive radiation – 14 species of Galápagos finches differ in feeding habits and beak type – Evidence indicates that all 14 species evolved from a single small population of ancestors that colonized one island Video: Galapágos Islands Overview Video: Galapágos Islands Overview

LE 14-8a Cactus-seed-eater (cactus finch) Seed-eater (medium ground finch) Tool-using insect-eater (woodpecker finch)

LE 14-8b AB B B CC C B C C D D D

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings TALKING ABOUT SCIENCE 14.9 Peter and Rosemary Grant study the evolution of Darwin's finches Peter and Rosemary Grant have documented natural selection acting on populations of Galápagos finches – Finch beaks adapted to different food sources through natural selection, as Darwin hypothesized – Occasional hybridization of finch species may have been important in their adaptive radiation

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The tempo of speciation can appear steady or jumpy Gradualism model: New species evolve by the gradual accumulation of changes brought about by natural selection – Darwin's original model – Not well supported by the fossil record, because most new species seem to appear suddenly in rock strata without intermediary transitional forms

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Punctuated equilibrium model: periods of rapid evolutionary change and speciation interrupted by long periods of little or no detectable change – Fossil record shows species changing most as they arise from an ancestral species and then relatively little for the rest of their existence Most evolutionary biologists now see both models as having merit Current research is focused on the tempo of evolution

LE 14-10a Time

LE 14-10b Time

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings MACROEVOLUTION Evolutionary novelties may arise in several ways Darwin's theory of gradual change can account for the evolution of intricate structures – Complex structures may evolve in stages from simpler versions having the same basic function Example: Eyes of molluscs – Existing structures may be gradually adapted to new functions Exaptation: a feature that evolved in one context and was later adapted for another function

LE Light-sensitive cells Nerve fibers Light-sensitive cells Eye cup Nerve fibers Fluid-filled cavity Eye cup Optic nerve Simple pinhole camera-type eye Layer of light-sensitive cells (retina) Optic nerve Transparent protective tissue (cornea) Lens Cornea Retina Optic nerve Eye with primitive lens Complex camera-type eye NautilusMarine snailSquid Patch of light- sensitive cells AbaloneLimpet

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Macroevolution Animation: Macroevolution

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Genes that control development are important in evolution "Evo-devo" combines evolutionary and developmental biology – Studies how slight genetic changes can be magnified into significant phenotypic changes Many striking evolutionary transformations are the result of a change in the rate or timing of developmental changes – Paedamorphosis: retention in adult of features that were juvenile in its ancestors

LE 14-12b Chimpanzee fetus Chimpanzee adult Human fetus Human adult

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Animation: Allometric Growth Animation: Allometric Growth

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Important in human evolution – Large skull and long childhood provide humans with more space for brain and more opportunity to learn from adults – Juvenile physical traits may make adults more caring and protective Example: "evolution" of Mickey Mouse

Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Evolutionary trends do not mean that evolution is goal directed Evolutionary trends reflect the unequal speciation or unequal survival of species on a branching evolutionary tree – Example: lineages of horses that died out Evolutionary trends do not imply an intrinsic drive toward a goal – If environmental conditions change, an apparent trend may cease or reverse

LE Hyracotherium Pachynolophus Orohippus Propalaeotherium Paleotherium Mesohippus Miohippus Parahippus Epihippus Grazers Browsers Merychippus Callippus Hypohippus Archaeohippus Megahippus Anchitherium Sinohippus Equus Hipparion Neohipparion Nannippus Pliohippus RECENT PLEISTOCENE PLIOCENE MIOCENE OLIGOCENE EOCENE Hippidion and other genera