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Warm-upList and explain the three ways in which sympatric speciation occurs.Important dates1. Exam is this Tuesday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test.2. Finish Clover Case Study for bonus on exam. Due Tuesday, 9-16 before exam. 10% points extra credit.3. Lab Write-up due Thursday, September 18You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday this week. Write up will be in your lab notebook.4. Binder check on exam day

Sympatric (Same Country) SpeciationIn sympatric speciation, speciation takes place in geographically overlapping populationsCould occur via:PolyploidyHabitat differentiationSexual selection4PolyploidyPolyploidy is the presence of extra sets of chromosomes due to accidents during cell divisionPolyploidy is much more common in plants than in animals

5Habitat DifferentiationSympatric speciation can also result from the appearance of new ecological nichesFor example, the North American maggot fly can live on native hawthorn trees as well as more recently introduced apple treesNative habitat: hawthorne treeApple tree introduced by Europeans

6Sexual Selection-Sexual selection can drive sympatric speciation-Sexual selection: type of selection in which individuals with certain inherited traits are more likely than others to obtain mates-Sexual selection for mates of different colors has likely contributed to speciation in cichlid fish in Lake Victoria, which led to about 600 species of cichild within the one lakehttp://evolution.berkeley.edu/evolibrary/news/090301_cichlidspeciation

7Figure 24.12

Normal lightMonochromaticorange lightP. pundamiliaP. nyerereiEXPERIMENT8Figure 24.12 Inquiry: Does sexual selection in cichlids result in reproductive isolation?Hybrid zones reveal factors that cause reproductive isolationA hybrid zone is a region in which members of different species mate and produce hybridsHybrids are the result of mating between species with incomplete reproductive barriers9Patterns Within Hybrid ZonesA hybrid zone can occur in a single band where adjacent species meetFor example, two species of toad in the genus Bombina interbreed in a long and narrow hybrid zone10Figure 24.13

EUROPEYellow-belliedtoad, BombinavariegataFire-belliedtoad rangeHybrid zoneYellow-belliedtoad rangeFire-bellied toad, Bombina bombinaFrequency ofB. variegata-specific alleleYellow-belliedtoad rangeHybridzoneFire-belliedtoad rangeDistance from hybrid zone center (km)400.990.90.50.10.013020100102011Figure 24.13 A narrow hybrid zone for Bombina toads in Europe.Hybrid Zones over TimeWhen closely related species meet in a hybrid zone, there are three possible outcomes:Reinforcement of reproductive barriers by less fit hybridsFusionStability12Reinforcement: Strengthening Reproductive BarriersThe reinforcement of barriers occurs when hybrids are less fit than the parent speciesOver time, the rate of hybridization decreases

13Fusion: Weakening Reproductive Barriers-If hybrids are as fit as parents, there can be substantial gene flow between species-If gene flow is great enough, the parent species can fuse into a single species

14Figure 24.12

Normal lightMonochromaticorange lightP. pundamiliaP. nyerereiEXPERIMENT15Figure 24.12 Inquiry: Does sexual selection in cichlids result in reproductive isolation?Figure 24.16

Pundamilia nyerereiPundamilia pundamiliaPundamilia turbid water,hybrid offspring from a locationwith turbid water16Figure 24.16 Fusion: The breakdown of reproductive barriers.Stability: Continued Formation of Hybrid IndividualsWhen hybrid populations are stable because they are as fit or fitter than the parent populations

17Speciation can occur rapidly or slowly and can result from changes in few or many genes 18The Time Course of SpeciationBroad patterns in speciation can be studied using the fossil record, morphological data, or molecular data19Patterns in the Fossil RecordThe fossil record includes examples of species that appear suddenly, persist essentially unchanged for some time, and then apparently disappearNiles Eldredge and Stephen Jay Gould coined the term punctuated equilibria to describe periods of apparent stasis punctuated by sudden changeThe punctuated equilibrium model contrasts with a model of gradual change in a species existence

20Figure 24.17

(a)PunctuatedpatternTime(b)Gradualpattern21Figure 24.17 Two models for the tempo of speciation.Speciation RatesThe punctuated pattern in the fossil record and evidence from lab studies suggest that speciation can be rapidFor example, the sunflower Helianthus anomalus originated from the hybridization of two other sunflower species

22Studying the Genetics of SpeciationA fundamental question of evolutionary biology persists: How many genes change when a new species forms?Depending on the species in question, speciation might require the change of only a single allele or many allelesFor example, in Japanese Euhadra snails, the direction of shell spiral affects mating and is controlled by a single gene

23Morphological evidence for speciation?Examples weve discussed so far?From Speciation to MacroevolutionMacroevolution is the cumulative effect of many speciation and extinction events

The interval between speciation events can range from 4,000 years (some cichlids) to 40 million years (some beetles), with an average of 6.5 million years25Important dates1. MasteringBiology HW due this Friday night, 11:59 PM!2. Exam is Monday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test.3. Finish Clover Case Study for bonus on exam. Due Monday, 9-15 before exam. 10% points extra credit.4. Lab Write-up due Thursday, September 18You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday next week.Write up will be in your lab notebook.

Important dates1. Exam is this Tuesday. Study guide is up on MasteringBiology. It is listed as homework that is due Tuesday, but it is NOT homework. This is just for you to practice for the test.2. Finish Clover Case Study for bonus on exam. Due Tuesday, 9-16 before exam. 10% points extra credit.3. Lab Write-up due Thursday, September 18You will finish the lab on your own, since we did not finish in lab. I will include a write up with specific directions by Saturday! If you need help, see me after school Monday-Wednesday this week. Write up will be in your lab notebook.4. Binder check on exam day