BIOLOGY CONCEPTS CONNECTIONS Fourth Edition Neil A Campbell

BIOLOGY CONCEPTS & CONNECTIONS Fourth Edition Neil A. Campbell • Jane B. Reece • Lawrence G. Mitchell • Martha R. Taylor CHAPTER 14 The Origin of Species Modules 14. 3 – 14. 9 From Power. Point® Lectures for Biology: Concepts & Connections Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

MECHANISMS OF SPECIATION 14. 3 Geographic isolation can lead to speciation • When a population is cut off from its parent stock, species evolution may occur – An isolated population may become genetically unique as its gene pool is changed by natural selection, genetic drift, or mutation – This is called allopatric speciation Figure 14. 3 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. 4 Islands are living laboratories of speciation • On the Galápagos Islands, repeated isolation and adaptation have resulted in adaptive radiation of 14 species of Darwin’s finches Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14. 4 A

• Adaptive radiation on an island chain 1 A Species A from mainland

14. 5 New species can also arise within the same geographic area as the parent species • In sympatric speciation, a new species may arise without geographic isolation – A failure in meiosis can produce diploid gametes – Self-fertilization can then produce a tetraploid zygote Parent species Zygote Meiotic error Selffertilization 2 n = 6 Diploid Offspring may be viable and self-fertile 4 n = 12 Tetraploid Unreduced diploid gametes Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14. 5 A

• Sympatric speciation by polyploidy was first discovered by Dutch botanist Hugo de

14. 6 Connection: Polyploid plants clothe and feed us • Many plants are polyploid – They are the products of hybridization – The modern bread wheat is an example Figure 14. 6 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

• The evolution of wheat AA BB Wild Triticum (14 chromosomes) Triticum monococcum (14 chromosomes) AB Sterile hybrid (14 chromosomes) Meiotic error and self-fertilization AABB DD T. turgidum EMMER WHEAT (28 chromosomes) T. tauschii (wild) (14 chromosomes) ABD Sterile hybrid Meiotic error and self-fertilization AA BB DD T. aestivum BREAD WHEAT (42 chromosomes) Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14. 6 B

14. 7 Reproductive barriers may evolve as populations diverge • This has been documented by Starch medium Maltose medium Results of mating experiments 8 20 Mating frequencies in experimental group Same 9 Different 22 Male populations Female Starch Maltose Starch – laboratory studies (fruit flies) Initial sample of fruit flies Female populations Same Different 18 15 12 15 Mating frequencies in control group Figure 14. 7 A Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

– examples in natural populations (pupfish in Death Valley) Figure 14. 7 B Copyright

14. 8 The tempo of speciation can appear steady or jumpy • According to the gradualist model of the origin of species – new species evolve by the gradual accumulation of changes brought about by natural selection • However, few gradual transitions are found in the fossil record Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14. 8 A

• The punctuated equilibrium model suggests that speciation occurs in spurts – Rapid change occurs when an isolated population diverges from the ancestral stock – Virtually no change occurs for the rest of the species’ existence Figure 14. 8 B Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

14. 9 Talking About Science: Peter and Rosemary Grant study the evolution of Darwin’s finches • The occasional hybridization of finch species adds to the genetic variation of parent populations – This may have been important in the adaptive radiation of finch species Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 14. 9