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BIOLOGY Chapter 17: pp. 299 - 316 10th Edition Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ensatina eschscholtzi picta Parents 1 Members of a northern ancestral population migrated southward. Ensatina eschscholtzi oregonensis horse donkey mating 2 Subspecies are separated by California’s Central Valley .Some interbreeding between populations does occur. Central Valley Barrier fertilization Ensatina eschscholtzi platensis Ensatina eschscholtzi xanthoptica Sylvia S. Mader Speciation and Macroevolution Ensatina eschscholtzi croceater Usually mules cannot reproduce. If an offspring does result, it cannot reproduce. mule (hybrid) Offspring (Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals Animals/Earth Scenes; Ensatina eschscholtzi eschscholtzii 3 Evolution has occurred, and in the south, subspecies do not interbreed even though they live in the same environment. Ensatina eschscholtzi klauberi PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display 1 Outline Separation of the Species Modes of Separation Allopatic speciation Adaptive radiation Sympatric speciation Macroevolution 2 Separation of the Species Macroevolution is best observed within the fossil record, Requires the origin of species, also called speciation. Speciation is the final result of changes in gene pool allelic and genotypic frequencies. 3 Species Definitions Every species has its own evolutionary history Binomial nomenclature, is used to name various species The two-part scientific name, when translated from the Latin, often tells you something about the organism. Scientific name of the dinosaur, Tyrannosaurus rex, means “tyrant-lizard king.” 4 Species Definitions Evolutionary species concept distinguish species from one another based on: Morphological (structural) traits, Biological species concept relies primarily on reproductive isolation rather than trait differences to define a species. 5 Species Definitions Species Definitions Morphological Can be distinguished anatomically Specialist decides what criteria probably represent reproductively isolated populations Most species described this way 6 Evolutionary Species Concept Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Orcinus orca Hindlimbs too reduced for walking or swimming Rodhocetus kasrani Ambulocetus natans Hindlimbs used for both walking on land and paddling in water Tetrapod with limbs for walking Pakicetus attocki 7 Species Definitions Species Definitions Biological Populations of the same species breed only among themselves Are reproductively isolated from other such populations Very few actually tested for reproductive isolation 8 Biological Species Concept Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. pit-see Acadian flycatcher , Empidonax virescens fitz-bew Willow flycatcher, Empidonax trailli che-bek or che-bek Least flycatcher, Empidonax minimus (Acadian): © Karl Maslowski/Visuals Unlimited; (Willow): © Ralph Reinhold/Animals Animals/Earth Scenes; (Least): © Stanley Maslowski/Visuals Unlimited. 9 Human Populations Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (Left): © Sylvia S. Mader; (Right): © B & C Alexander/Photo Researchers, Inc. 10 Reproductive Isolating Mechanisms Reproductive isolating mechanisms inhibit gene flow between species Two general types: (1) Prezygotic Mechanisms – prevents matting attempts Habitat Isolation - species occupy different habitats, Temporal Isolation - each reproduces at a different time Behavioral Isolation Mechanical Isolation Gamete Isolation 11 Reproductive Barrier Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Prezygotic Isolating Mechanisms Premating Postzygotic Isolating Mechanisms Mating Habitat isolation species 1 Fertilization Zygote mortality Species at same locale occupy different habitats. Fertilization occurs, but zygote does not survive. Mechanical isolation Temporal isolation Genitalia between species are unsuitable for one another. Species reproduce at different seasons or different times of day. hybrid offspring Hybrid sterility Hybrid survives but is sterile and cannot reproduce. species 2 Behavioral isolation Gamete isolation In animal species, courtship behavior differs, or individuals respond to different songs, calls, pheromones, or other signals. Sperm cannot reach or fertilize egg. F2 fitness Hybrid is fertile, but F2 hybrid has reduced fitness. 12 Temporal Isolation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Mating Activity high low March 1 April 1 May 1 June 1 July 1 13 Prezygotic Isolating Mechanism Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. © Barbara Gerlach/Visuals Unlimited 14 Reproductive Isolating Mechanisms Two general types: (2) Postzygotic Mechanisms - Prevent hybrid offspring from developing or breeding Zygote Mortality Hybrid Sterility Reduced F2 Fitness 15 Postzygotic Isolating Mechanism Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Parents horse donkey mating fertilization Usually mules cannot reproduce. If an offspring does result, it cannot reproduce. mule (hybrid) Offspring (Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals Animals/Earth Scenes; 16 Modes of Speciation Speciation: The splitting of one species into two, or The transformation of one species into a new species over time Two modes: (1) Allopatric Speciation Two geographically isolated populations of one species Become different species over time Can be due to differing selection pressures in differing environments 17 Allopatric Speciation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ensatina eschscholtzi picta 1 Members of a northern ancestral population migrated southward. Ensatina eschscholtzi oregonensis 2 Subspecies are separated by California’s Central Valley .Some interbreeding between populations does occur. Central Valley Barrier Ensatina eschscholtzi platensis Ensatina eschscholtzi xanthoptica Ensatina eschscholtzi croceater Ensatina eschscholtzi eschscholtzii 3 Evolution has occurred, and in the south, subspecies do not interbreed even though they live in the same environment. Ensatina eschscholtzi klauberi 18 Allopatric Speciation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lake male River male Lake female River female a. Sockeye salmon at Pleasure Point Beach, Lake Washington b. Sockeye salmon in Cedar River .The river connects with Lake Washington. Salmon that matured at Pleasure Point Beach do not reproduce with those that matured in the Cedar River. 19 Modes of Speciation Two modes: (2) Sympatric Speciation One population develops into two or more reproductively isolated groups No prior geographic isolation It involves polyploidy (a chromosome number beyond the diploid [2n] number) Tetraploid hybridization in plants Results in self fertile species Reproductively isolated from either parental species 20 Modes of Speciation (2) Sympatric Speciation A polyploid plant can reproduce with itself, but cannot reproduce with the 2n population because not all the chromosomes would be able to pair during meiosis. Two types of polyploidy are known: Autoploidy - diploid plant produces diploid gametes due to nondisjunction during meiosis. If diploid gamete fuses with a haploid gamete, a triploid plant results. A triploid (3n) plant is sterile and cannot produce offspring because the chromosomes cannot pair during meiosis. Alloploidy - more complicated process than autoploidy Requires two different but related species of plants Hybridization is followed by doubling of the chromosomes. 21 Alloploidy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. seeds diploid banana (2n) no seeds polyploid banana 22 Autoploidy Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2n = 14 2n = 10 Clarkia concinna Clarkia virgata hybrid doubling of chromosome number 2n = 24 Clarkia pulchella (C. pulchella): © J. L. Reveal; (C. concinna): © Gerald & Buff Corsi/Visuals Unlimited; (C. virgata): ©: Dr. Dean Wm. Taylor/Jepson Herbarium, UC Berkeley 23 Adaptive Radiation Adaptive Radiation When members of a species invade several new geographically separate environments The populations become adapted to the different environments Many new species evolve from the single ancestral species This is an example of allopatric speciation 24 Adaptive Radiation Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. * Lesser Koa finch Palila Laysan finch * Greater Koa finch Ou * Kona finch Maui parrot bill Akiapolaau * Kauai akialoa Nukupuu * Akialoa Genus Loxops Great amakihi Anianiau (green (lesser solitaire) amakihi) * Extinct species or subspecies Alauwahio (Hawaiian creeper) Akepa Amakihi 25 Principles of Macroevolution Macroevolution Evolution at the species or higher level of classification Occurs gradually Evolutionists support a gradualistic model Speciation occurs after populations become isolated Each group continuing its own evolutionary pathway The gradualistic model suggests that it is difficult to indicate when speciation occurred 26 Principles of Macroevolution Macroevolution Some paleontologists believe that Species can appear quite suddenly Remain essentially unchanged phenotypically during a period of stasis (sameness) until they undergo extinction. Based on these findings, they developed a punctuated equilibrium model to explain the pace of evolution. 27 Gradualistic and Punctuated Equilibrium Models Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. new species 1 new species 1 ancestral species ancestral species transitional link ancestral species new species 2 Time a. Gradualistic model stasis new species 2 Time b. Punctuated equilibrium 28 Developmental Genes and Macroevolution Genes can bring about radical changes in body shapes and organs. Gene Expression Can Influence Development A change in gene expression could stop developmental process or continue it beyond its normal time. Using modern technology researchers discovered genes whose differential expression can bring about changes in body shapes and organs. 29 Pax6 Gene and Eye Development Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (Left): © Carolina Biological Supply/Photo Researchers, Inc.; (Center): © Vol. OS02/PhotoDisc/Getty Images; (Right): © Aldo Brando/Peter Arnold, Inc. 30 Study of Pax6 Gene Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Courtesy Walter Gehring, reprinted with permission from Induction of Ectopic Eyes by Target Expression of the Eyeless Gene in Drosophila, G. Halder, P. Callaerts, Walter J. Gehring, Science Vol. 267, © 24 March 1995 American Association for the Advancement of Science 31 Hox6 Gene Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. (Both): © A. C. Burke, 2000 32 Macroevolution Is Not Goal-Oriented The evolution of the horse (Equus) Studied since the 1870s Model for gradual, straight-line evolution Modern horse, had been achieved as a goal Three trends were particularly evident during the evolution: Increase in overall size, Toe reduction, and Change in tooth size and shape. 33 Simplified Family Tree of Equus Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 2 MYA 4 MYA Equus Neohipparion Hipparion 12 MYA Dinohippus Megahippus 15 MYA Merychippus 17 MYA 23 MYA 25 MYA 35 MYA Miohippus 40 MYA Palaeotherium 45 MYA 50 MYA Hyracotherium 55 MYA 34 Review Separation of the Species Modes of Separation Allopatic speciation Adaptive radiation Sympatric speciation Macroevolution 35 BIOLOGY Chapter 17: pp. 299 - 316 10th Edition Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Ensatina eschscholtzi picta Parents 1 Members of a northern ancestral population migrated southward. Ensatina eschscholtzi oregonensis horse donkey mating 2 Subspecies are separated by California’s Central Valley .Some interbreeding between populations does occur. Central Valley Barrier fertilization Ensatina eschscholtzi platensis Ensatina eschscholtzi xanthoptica Sylvia S. Mader Speciation and Macroevolution Ensatina eschscholtzi croceater Usually mules cannot reproduce. If an offspring does result, it cannot reproduce. mule (hybrid) Offspring (Stallion): © Superstock, Inc.; (Donkey): © Robert J. Erwin/Photo Researchers, Inc.; (Mule): © Jorg & Petra Wegner/Animals Animals/Earth Scenes; Ensatina eschscholtzi eschscholtzii 3 Evolution has occurred, and in the south, subspecies do not interbreed even though they live in the same environment. Ensatina eschscholtzi klauberi PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor Copyright © The McGraw Hill Companies Inc. Permission required for reproduction or display 36