Chapter 14 The Origin of Species PowerPoint Lectures

Chapter 14 The Origin of Species PowerPoint Lectures

Chapter 14 The Origin of Species PowerPoint Lectures Campbell Biology: Concepts & Connections, Eighth Edition REECE TAYLOR SIMON DICKEY HOGAN 2015 Pearson Education, Inc. Lecture by Edward J. Zalisko DEFINING SPECIES 2015 Pearson Education, Inc.

I can 1. Distinguish between microevolution and speciation. 2. Compare the definitions, advantages, and disadvantages of the different species concepts. 3. Describe five types of prezygotic barriers and three types of postzygotic barriers that prevent populations of closely related species from interbreeding. 2015 Pearson Education, Inc. 14.1 The origin of species is the source of

biological diversity Microevolution is the change in the gene pool of a population from one generation to the next. Speciation is the process by which one species splits into two or more species. Each time speciation occurs, the diversity of life increases.

2015 Pearson Education, Inc. 14.2 There are several ways to define a species The biological species concept defines a species as a group of populations whose members have the potential to interbreed in nature and produce fertile offspring. Thus, members of a biological species are united by being reproductively compatible. 2015 Pearson Education, Inc.

14.2 There are several ways to define a species Reproductive isolation prevents genetic exchange (gene flow) and maintains a boundary between species. Hybrids: clearly distinct species that do occasionally interbreed. An example is the grizzly bear and the polar bear, whose hybrid offspring have been called grolar bears.

2015 Pearson Education, Inc. 14.2 There are several ways to define a species There are other instances in which applying the biological species concept is problematic. There is no way to determine whether organisms that are now known only through fossils were once able to interbreed. Reproductive isolation does not apply to prokaryotes or other organisms that reproduce only asexually. Therefore, alternate species concepts can be

useful. 2015 Pearson Education, Inc. 14.2 There are several ways to define a species The morphological species concept classifies organisms based on observable physical traits and can be applied to asexual organisms and fossils. The ecological species concept defines a species by its ecological niche and focuses on unique adaptations to particular roles in a biological community.

The phylogenetic species concept defines a species as the smallest group of individuals that share a common ancestor and thus form one branch of the tree of life. 2015 Pearson Education, Inc. 14.3 VISUALIZING THE CONCEPT: Reproductive barriers keep species separate Reproductive barriers serve to isolate the gene pools of species and prevent interbreeding.

Reproductive barriers are categorized as Prezygotic: before zygotes form Postzygotic: after zygotes form 2015 Pearson Education, Inc. 14.3 Reproductive barriers keep species separate Five types of prezygotic barriers prevent mating or fertilization between species. 2015 Pearson Education, Inc.

Figure 14.3-1 Habitat isolation (lack of opportunities to encounter each other) The garter snake Thamnophis atratus lives mainly in water. The garter snake Thamnophis sirtalis lives on land. 2015 Pearson Education, Inc.

Figure 14.3-2 Temporal isolation (breeding at different times or seasons) The eastern spotted skunk (Spilogale putorius) breeds in late winter. 2015 Pearson Education, Inc. The western spotted skunk (Spilogale gracilis) breeds in

the fall. 14.3 Reproductive barriers keep species separate Blue footed booby courtship ritual: http://www.arkive.org/blue-footed -booby/sula-nebouxii/video-09a.h tml 2015 Pearson Education, Inc.

Figure 14.3-4 Mechanical isolation (physical incompatibility of reproductive parts) Heliconia latispatha is pollinated by hummingbirds with short, straight bills. Heliconia pogonantha is pollinated by hummingbirds with long, curved bills.

2015 Pearson Education, Inc. Figure 14.3-5 Gametic isolation (molecular incompatibility of eggs and sperm or pollen and stigma) Purple sea urchin (Strongylocentrotus purpuratus) 2015 Pearson Education, Inc.

Red sea urchin (Strongylocentrotus franciscanus) 14.3 VISUALIZING THE CONCEPT: Reproductive barriers keep species separate Three types of postzygotic barriers operate after hybrid zygotes have formed. 2015 Pearson Education, Inc. Figure 14.3-6

Reduced hybrid viability (hybrid development or survival impaired by interaction of parental genes) Some salamander species can hybridize, but their offspring do not develop fully or are frail and will not survive long enough to reproduce. 2015 Pearson Education, Inc. Figure 14.3-7

Reduced hybrid fertility (vigorous hybrids that cannot produce viable offspring) A mule is the sterile hybrid offspring of a horse and a donkey. 2015 Pearson Education, Inc. Figure 14.3-8 Hybrid breakdown (viable and fertile hybrids with feeble

or sterile offspring) The rice hybrids on the left and right are fertile, but plants of the next generation (middle) are sterile. 2015 Pearson Education, Inc. MECHANISMS OF SPECIATION 2015 Pearson Education, Inc. I can 1. Explain how geologic processes can fragment

populations and lead to speciation. 2. Explain how reproductive barriers might evolve in isolated populations of organisms. 3. Explain how sympatric speciation can occur. 4. Describe the circumstances that led to the adaptive radiation of the Galpagos finches. 2015 Pearson Education, Inc. 14.4 In allopatric speciation, geographic isolation leads to speciation A key event in the origin of a new species is the separation of a population from other populations

of the same species. With its gene pool isolated, the splinter population can follow its own evolutionary course. Changes in allele frequencies caused by natural selection, genetic drift, and mutation will not be diluted by alleles entering from other populations (gene flow). 2015 Pearson Education, Inc. 14.4 In allopatric speciation, geographic isolation leads to speciation In allopatric speciation, the initial block to gene

flow may come from a geographic barrier that isolates a population. 2015 Pearson Education, Inc. 14.4 In allopatric speciation, geographic isolation leads to speciation Several geologic processes can isolate populations. A mountain range may emerge and gradually split a population of organisms that can inhabit only lowlands. A large lake may subside until there are several

smaller lakes, isolating certain fish populations. Continents themselves can split and move apart. How large must a geographic barrier be to keep allopatric populations apart? depends on the ability of the organisms to move 2015 Pearson Education, Inc. 14.5 Reproductive barriers can evolve as populations diverge How do reproductive barriers arise? As a result of natural selection acting on preexisting variations (or as a result of genetic drift

or mutation), a populations traits may change in ways that also establish reproductive barriers. http://www.hhmi.org/biointeractive/anole-lizards-ex ample-speciation (3 min) 2015 Pearson Education, Inc. 14.6 Sympatric speciation takes place without geographic isolation Sympatric speciation occurs when a new species arises within the same geographic area as its parent species.

How can reproductive isolation develop when members of sympatric populations remain in contact with each other? Gene flow between populations may be reduced by Polyploidy (usually plants), habitat differentiation or sexual selection (usually animals) . 2015 Pearson Education, Inc. 14.6 Sympatric speciation takes place without geographic isolation Many plant species have originated from sympatric speciation that occurs when accidents during cell

division result in extra sets of chromosomes. New species formed in this way are polyploid, in that their cells have more than two complete sets of chromosomes. 2015 Pearson Education, Inc. 14.6 Sympatric speciation takes place without geographic isolation Sympatric speciation can result from polyploidy

within a species (by selffertilization) between two species (by hybridization). 2015 Pearson Education, Inc. 14.7 EVOLUTION CONNECTION: The origin of most plant species can be traced to polyploid speciation Plant biologists estimate that 80% of all living plant species are descendants of ancestors that formed

by polyploid speciation. Hybridization between two species accounts for most of these species, perhaps because of the adaptive advantage of the diverse genes a hybrid inherits from different parental species. 2015 Pearson Education, Inc. 14.7 The origin of most plant species can be traced to polyploid speciation Polyploid plants include

cotton, oats, potatoes,

bananas, peanuts, barley, plums, apples, sugarcane, coffee, and wheat. 2015 Pearson Education, Inc. 14.8 Isolated islands are often showcases of speciation

Isolated island chains are often inhabited by unique collections of species. Islands that have physically diverse habitats and that are far enough apart to permit populations to evolve in isolation but close enough to allow occasional dispersions to occur are often the sites of multiple speciation events. The evolution of many diverse species from a common ancestor is known as adaptive radiation. 2015 Pearson Education, Inc. 14.8 Isolated islands

are often showcases of speciation The Galpagos Islands currently have 14 species of closely related finches. These birds differ in their feeding habits and their beaks, specialized for what they eat, and arose through adaptive radiation. http://www.hhmi.org/biointeracti ve/origin-species-beak-finch (16 min)

2015 Pearson Education, Inc. 2015 Pearson Education, Inc. I can 1. Explain how new species of fish have evolved in Lake Victoria. 2. Explain how hybrid zones are useful in the study of reproductive isolation. 3. Compare the gradual model and the punctuated equilibrium model of evolution. 2015 Pearson Education, Inc.

14.9 SCIENTIFIC THINKING: Lake Victoria is a living laboratory for studying speciation Biologists are still studying the process of speciation. Cichlid fish populations They come in all colors of the rainbow. Live in the large lakes of East Africa with more than a thousand species of cichlids in less than 100,000 years. In the largest of these lakes,

Lake Victoria, roughly 500 species evolved in about 15,000 years. 2015 Pearson Education, Inc. 14.9 SCIENTIFIC THINKING: Lake Victoria is a living laboratory for studying speciation In Lake Victoria, there are pairs of closely related cichlid species that differ in color but nothing else. Breeding males of Pundamilia nyererei have a bright red back and dorsal fin. Breeding males of Pundamilia pundamilia males are metallic blue-gray.

2015 Pearson Education, Inc. 14.9 Lake Victoria is a living laboratory for studying speciation Pundamilia females prefer brightly colored males. Mate-choice experiments performed in the laboratory showed that P. nyererei females prefer red males over blue males, P. pundamilia females prefer blue males over red males,

the vision of P. nyererei females is more sensitive to red light than blue light, and the vision of P. pundamilia females is more sensitive to blue light than red light. Researchers also demonstrated that this color sensitivity is heritable. 2015 Pearson Education, Inc. 14.9 Lake Victoria is a living laboratory for studying speciation As light travels through water, suspended particles selectively absorb and scatter the shorter (blue) wavelengths, so light becomes increasingly red with

increasing depth. Thus, in deeper waters, P. nyererei males are pleasingly apparent to females with red-sensitive vision but virtually invisible to P. pundamilia females. When biologists sampled cichlid populations in Lake Victoria, they found that P. nyererei breeds in deep water, while P. pundamilia inhabits shallower habitats where the blue males shine brightly. As a consequence of their mating behavior, the two species encounter different environments that may result in further divergence. 2015 Pearson Education, Inc.

14.10 Hybrid zones provide opportunities to study reproductive isolation What happens when separated populations of closely related species come back into contact with each other? Biologists try to answer such questions by studying hybrid zones, regions in which members of different species meet and mate to produce at least some hybrid offspring. 2015 Pearson Education, Inc. 14.10 Hybrid zones provide opportunities to study reproductive isolation

Species may interbreed in a hybrid zone. There are 3 possible hybrid zone outcomes Reinforcement: when reproductive barriers are strengthened and keep species separate. Fusion: when reproductive barriers are weakened or eliminated and speciation is reversed. Stability: when a few hybrids continue to be produced. 2015 Pearson Education, Inc. When hybrid offspring are less fit than members of both parent species,

natural selection to strengthen, or reinforce, reproductive barriers barriers between species should be stronger where the species overlap (sympatric). The closely related collared flycatcher and pied flycatcher are an example of reinforcement. 2015 Pearson Education, Inc.

14.10 Hybrid zones provide opportunities to study reproductive isolation Fusion Reproductive barriers between species are not strong and the species come into contact in a hybrid zone. So much gene flow may occur that the speciation process reverses, causing the two hybridizing species to fuse into one. Such a situation has been occurring among the cichlid species in Lake Victoria.

2015 Pearson Education, Inc. 14.10 Hybrid zones provide opportunities to study reproductive isolation Pollution caused by development along the shores of Lake Victoria has turned the water murky. What happens when P. nyererei or P. pundamilia females cant tell red males from blue males? The behavioral barrier crumbles. Many viable hybrid offspring are produced by interbreeding. The once isolated gene pools of the parent species are combining, with two species fusing into a single hybrid

species. 2015 Pearson Education, Inc. 14.10 Hybrid zones provide opportunities to study reproductive isolation Stability Many hybrid zones are fairly stable and hybrids continue to be produced. Example: the islands inhabited by two finch species occasionally interbreed. 2015 Pearson Education, Inc.

Speciation of California Salamanders and Hybrid Zones https://www.youtube.com/watch?v=aDIQFQOCGaI (3.5 min) Is this an example of reinforcement, fusion, or stability? 2015 Pearson Education, Inc. 14.11 Speciation can occur rapidly or slowly There are two models for the tempo of speciation. 1. The punctuated equilibria: long periods of little

apparent morphological change (equilibria) interrupted (punctuated) by relatively brief periods of sudden change. 2. Other species appear to have evolved more gradually. 2015 Pearson Education, Inc. Figure 14.11 Punctuated pattern

Gradual pattern Time 2015 Pearson Education, Inc. Crash Course: Speciation https://www.youtube.com/watch?v=2oKlKmrbLoU 10:25 min 2015 Pearson Education, Inc. 2015 Pearson Education, Inc. Figure 14.UN05

Zygote Gametes Prezygotic barriers Habitat isolation Temporal isolation Behavioral isolation Mechanical isolation Gametic isolation 2015 Pearson Education, Inc. Postzygotic barriers Reduced hybrid

viability Reduced hybrid fertility Hybrid breakdown Viable, fertile offspring Figure 14.UN06 Original population

a. 2015 Pearson Education, Inc. b. Figure 14.UN07 Species may interbreed in a a. outcome may be

b. c. when d. when when are

a few hybrids continue to be produced reproductive barriers are e. 2015 Pearson Education, Inc.

f. keeps and species separate speciation is reversed

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