The Origin of Species Speciation in real time 11 min Chapter 14 The Origin of Species Speciation in real time 11 min

Mosquito Mystery Speciation is the emergence of new species In England and North America Two species of mosquitoes exist and spread West Nile virus

Speciation The emergence of a new species Occurs if the members of a species are isolated from each other for so long that they evolve differently.

14.1 The origin of species is the source of biological diversity Speciation, the origin of new species Is at the focal point of evolution Each time speciation occurs, biological diversity increases. Figure 14.1

Macroevolution Earth’s incredible biological diversity is the result of macroevolution (dramatic changes that occur over long periods of time) which begins with the origin of new species

What is the difference between microevolution and Macroevolution?

Appearance alone does not always define a species 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 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

4 key concepts in Identifying Species The Biological Species Concept Morphological species concept Ecological species concept Phylogenic species concept

The Biological Species Concept The biological species concept defines a species as A population or group of populations whose members can interbreed and produce fertile offspring

What are the advantages/disadvantages of these classifications? Other Species Concepts The morphological species concept Classifies organisms based on observable phenotypic traits The ecological species concept Defines a species by its ecological role in a community The phylogenetic species concept Defines a species as a set of organisms representing a specific evolutionary lineage. i.e unique set of genetic history. Biologist trace the history of a species by comparing its physical characteristics or its DNA sequence to the corresponding data for other species. What are the advantages/disadvantages of these classifications?

What prevents species that are closely related from interbreeding?

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

Prezygotic Barriers Prezygotic barriers Prevent mating or fertilization between species There are five main typed of prezygotic barriers: Temporal isolation Habitat isolation Behavioral isolation mechanical isolation Gametic isolation

In temporal isolation Two species breed at different times Different seasons; different years, different times of the day Figure 14.3A

Habitat isolation Two species live in the same general area, but not in the same kind of places They never meet.

In behavioral isolation There is little or no sexual attraction between species, due to specific behaviors. Courtship rituals video Figure 14.3B

In mechanical isolation Female and male sex organs or gametes are not compatible Many species of plants have flower structures that are adapted to specific insects or animal pollinators Figure 14.3C

Gamete Isolation The egg and sperm of different species do not unite to form a zygote. In many organisms, the sperm cannot servive in the reproductive tract of a female of a different species

Postzygotic Barriers Postzygotic barriers Operate after hybrid zygotes are formed There are three forms of postzygotic barriers Hybrid inviability Hybrid sterility Hybrid breakdown

One postzygotic barrier is hybrid sterility Where hybrid offspring between two species are sterile and therefore cannot mate. Hybrid Inviability In other cases the hybrid does not survive Hybrid Breakdown 1st generation is fertile, 2nd generation is either sterile or produce feeble offspring. Figure 14.3D

Two closeley related tropical birds species live in the same forest, but one feeds and mates in the forest canopy and the other on the forest floor. This is an example of ___________________isolation , which is a_______zygotic reproductive barrier.

MECHANISMS OF SPECIATION 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

How do geological processes fragment populations and lead to speciation? Review: Gene pool Become isolated → evolutionary course Genetic drift Changed in allele frequency caused by natural selection Mutations Random changes in the alleles All of these are unaffected by the gene flow in other populations

Allopatric speciation Populations separated by geographic barriers. Mountain ranges A land bridge separates marine life Allopatric speciation increases when a population is both small and isolated Small population lead to genetic drift and natural selection Speciation does not occur unless the genetic changes lead to reproductive barriers.

New species will not arise just because populations become geographically isolated. For _______________speciation to occur, changes in the gene pool must produce __________ __________.

Freshman biology skip to slide 33

population populations 14.5 Reproductive barriers may evolve as populations diverge Laboratory studies of fruit flies Have shown that changes in food sources can cause speciation Starch medium Maltose medium Initial sample of fruit flies Results of mating experiments Female Starch Maltose Same Different population populations Maltose Starch Male Different Same Mating frequencies in experimental group in control group 22 9 20 8 12 18 15 Figure 14.5A

Geographic isolation in Death Valley Has led to the evolution of new species of pupfish Figure 14.5B A pupfish

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 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 14.7 Polyploid plants clothe and feed us 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

Island chains Provide examples of adaptive radiation In the Galapagos, the islands were formed by underwater volcano’s. They gradually were occupied by plants and other organisms. video 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

Why would allopatric speciation be less common on an island close to a mainland than a more isolated island of the same size? Mainland populations promote continued gene flow for those islands closer to them. The further away a the island is to the main land, the smaller the gene pool.

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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 Figure 14.9

The occasional hybridization of finch species May also have been important in their adaptive radiation

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 Time Figure 14.10A

The punctuated equilibrium model draws on the fossil record Where 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 14.11 Evolutionary novelties may arise in several ways Many complex structures evolve in many stages From simpler versions having the same basic function 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

Other novel structures result from exaptation The gradual adaptation of existing structures to new functions

14.12 Genes that control development are important in evolution “Evo-devo” Is 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

Changes in the timing and rate of growth Have also been important in human evolution Figure 14.12B Chimpanzee fetus Chimpanzee adult Human fetus Human adult

Stephen Jay Gould, an evolutionary biologist Contended that Mickey Mouse “evolved” Figure 14.12C Copyright Disney Enterprises, Inc.

14.13 Evolutionary trends do not mean that evolution is goal directed Evolutionary trends reflect species selection The unequal speciation or unequal survival of species on a branching evolutionary tree A general trend in evolution of mammals was toward larger brain size relative to body size. Use the species model to explain how such a trend could occur Hippidion and other genera Nannippus Neohipparion Hipparion Sinohippus Megahippus Archaeohippus Callippus Hypohippus Anchitherium Miohippus Parahippus Paleotherium Propalaeotherium Pachynolophus Orohippus Epihippus Equus Pliohippus Merychippus Mesohippus Hyracotherium Grazers Browsers EOCENE OLIGOCENE MIOCENE PLIOCENE E RECENT PLEISTOCEN Figure 14.13

A general trend in evolution of mammals was toward larger brain size relative to body size. Use the species model to explain how such a trend could occur.