CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 22 The Origin of Species

© 2014 Pearson Education, Inc.  Speciation - the process by which one species splits into two or more species

© 2014 Pearson Education, Inc.  Microevolution -changes in allele frequency in a population over time  Macroevolution -broad patterns of evolutionary change above the species level

© 2014 Pearson Education, Inc. The Biological Species Concept  biological species concept -a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations

© 2014 Pearson Education, Inc. Reproductive Isolation  Reproductive isolation -barriers that impede two species from producing viable, fertile offspring  Hybrids -offspring of crosses between different species

© 2014 Pearson Education, Inc.  Prezygotic barriers block fertilization from occurring by…  Impeding different species from attempting to mate  Preventing the successful completion of mating  Hindering fertilization if mating is successful

© 2014 Pearson Education, Inc. Figure 22.3a Prezygotic barriers Habitat isolation Temporal isolation Behavioral isolation MATING ATTEMPT (a) (c) (d) (b) (e)

© 2014 Pearson Education, Inc.  Habitat isolation: Two species occupy different habitats, even though not isolated by physical barriers

© 2014 Pearson Education, Inc. Figure 22.3ab

© 2014 Pearson Education, Inc.  Temporal isolation: Species that breed at different times (time of day, seasons, years …)

© 2014 Pearson Education, Inc. Figure 22.3ac

© 2014 Pearson Education, Inc.  Behavioral isolation: Different courtship rituals and other behaviors

© 2014 Pearson Education, Inc. Figure 22.3ae

© 2014 Pearson Education, Inc. Fig. 19-4c, p.302 Isolating Mechanisms

© 2014 Pearson Education, Inc. Fig. 19-4d, p.302 Isolating Mechanisms

© 2014 Pearson Education, Inc. Fig. 19-4e, p.302 Isolating Mechanisms

© 2014 Pearson Education, Inc. Figure 22.3b Prezygotic barriers Mechanical isolation Gametic isolation FERTILIZATION MATING ATTEMPT (f)(g)

© 2014 Pearson Education, Inc.  Mechanical isolation: Morphological differences prevent successful mating

© 2014 Pearson Education, Inc. Figure 22.3bf

© 2014 Pearson Education, Inc.  Gametic isolation: Sperm not able to fertilize eggs of another species

© 2014 Pearson Education, Inc. Figure 22.3bg

© 2014 Pearson Education, Inc.  Postzygotic barriers prevent hybrid zygote from developing into viable fertile adult by  Reduced hybrid viability  Reduced hybrid fertility  Hybrid breakdown

© 2014 Pearson Education, Inc. Figure 22.3c Postzygotic barriers Reduced hybrid viability Reduced hybrid fertility Hybrid breakdown FERTILIZATION VIABLE, FERTILE OFFSPRING (h) (i) (l) (j) (k)

© 2014 Pearson Education, Inc.  Reduced hybrid viability: Genes of the parent species may interact and impair hybrid’s survival

© 2014 Pearson Education, Inc. Figure 22.3ch

© 2014 Pearson Education, Inc.  Reduced hybrid fertility: hybrids may be sterile

© 2014 Pearson Education, Inc. Figure 22.3ci

© 2014 Pearson Education, Inc.  Hybrid breakdown: Some first-generation hybrids are fertile, but offspring of future generations are feeble or sterile

© 2014 Pearson Education, Inc. Figure 22.3cl

© 2014 Pearson Education, Inc. Concept 22.2: Speciation can take place with or without geographic separation  Allopatric speciation – populations isolated by a physical barrier  Sympatric speciation – speciation with no physical barrier, some other mechanism creates isolation

© 2014 Pearson Education, Inc. Figure 22.7 A. formosus A. nuttingi ATLANTIC OCEAN PACIFIC OCEAN A. panamensis A. millsae Isthmus of Panama

© 2014 Pearson Education, Inc. Figure 22.7a A. formosus A. nuttingi ATLANTIC OCEAN

© 2014 Pearson Education, Inc. Figure 22.7c A. panamensis A. millsae PACIFIC OCEAN

© 2014 Pearson Education, Inc. Concept 22.3: Hybrid zones reveal factors that cause reproductive isolation  hybrid zone -a region in which members of different species mate and produce hybrids  result of incomplete reproductive barriers

© 2014 Pearson Education, Inc. Figure Fire-bellied toad range Fire-bellied toad, Bombina bombina Yellow-bellied toad range Hybrid zone Hybrid zone Fire-bellied toad range Yellow-bellied toad range Distance from hybrid zone center (km) Frequency of B. variegata-specific allele Yellow-bellied toad, Bombina variegata 0.5

© 2014 Pearson Education, Inc. Patterns in the Fossil Record  periods of apparent stasis punctuated by sudden change are called punctuated equilibria  The punctuated equilibrium model contrasts with a model of gradual change in a species’ existence

© 2014 Pearson Education, Inc. Figure (a) Punctuated model (b) Gradual model Time

© 2014 Pearson Education, Inc. Figure A hybrid sunflower species

© 2014 Pearson Education, Inc.  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 years

© 2014 Pearson Education, Inc. From Speciation to Macroevolution  Macroevolution is the cumulative effect of many speciation and extinction events