Figure 4.3 (b)

1. Figure 4.3 (b) 24 The Origin of species

2. Species and Speciation • Fundamental unit of classification is the species. • Species = a group of populations in which genes are actually, or potentially, exchanged through interbreeding. • Problems • Reproductive criterion must be assumed based on phenotype and ecological information. • Asexual reproduction • Fossil • Geographical isolation

3. The origin of new species, or speciation • Is at the focal point of evolutionary theory, because the appearance of new species is the source of biological diversity • Evolutionary theory • Must explain how new species originate in addition to how populations evolve

4. Microevolution, Macroevolution, and Evidence of Macroevolutionary change ~ Bacteria gain resistance to antibiotics over time • A change in frequency of alleles in populations over time is called Microevolution. • Over longer timescales, microevolutionary processes result in large scale changes that result in formation of new species called Macroevolution(species level) • Evidence of Macroevolution- patterns of plant and animal distribution, fossils, anatomical structures, and developmental processes

5. Concept 24.1: The biological species concept emphasizes reproductive isolation • Species • Is a Latin word meaning “kind” or “appearance”

6. Reproductive isolation leads to Speciation • the formation of new species • Requirement • Subpopulations are prevented from interbreeding • Gene flow does not occur (Reproductive isolation) • Reproductive isolation can result in evolution • Natural selection and genetic drift can result in evolution

7. Speciation of Darwin’s Finches Warbler

8. Large ground finch

9. Similarity between different species. The eastern and western meadowlark (Sturnella magna, left) (Sturnella neglecta, right) songs and other behaviors are different enough to prevent interbreeding (a) Diversity within a species. As diverse as we may be in appearance, all humans belong to a single biological species (Homo sapiens), defined by our capacity to interbreed. (b) Figure 24.3 A, B

10. Reproductive Isolation • Reproductive isolation • Is the existence of biological factors that impede members of two species from producing viable, fertile hybrids • Is a combination of various reproductive barriers

11. Prezygotic barriers • Impede mating between species or hinder the fertilization of ova if members of different species attempt to mate • Postzygotic barriers • Often prevent the hybrid zygote from developing into a viable, fertile adult

12. Prezygotic barriers impede mating or hinder fertilization if mating does occur Behavioral isolation Habitat isolation Temporal isolation Mechanical isolation Individualsof differentspecies Matingattempt HABITAT ISOLATION MECHANICAL ISOLATION TEMPORAL ISOLATION BEHAVIORAL ISOLATION (g) (b) (d) (e) (f) (a) (c) Figure 24.4 • Prezygotic and postzygotic barriers

13. Gameticisolation Hybridbreakdown Reducehybridfertility Reducehybridviability Viablefertileoffspring Fertilization GAMETIC ISOLATION HYBRID BREAKDOWN REDUCED HYBRID FERTILITY REDUCED HYBRID VIABILITY (k) (j) (m) (l) (i) (h)

14. Limitations of the Biological Species Concept • The biological species concept cannot be applied to • Asexual organisms • Fossils • Organisms about which little is known regarding their reproduction

15. Other Definitions of Species • The morphological species concept • Characterizes a species in terms of its body shape, size, and other structural features • The paleontological species concept • Focuses on morphologically discrete species known only from the fossil record • The ecological species concept • Views a species in terms of its ecological niche • The phylogenetic species concept • Defines a species as a set of organisms with a unique genetic history

16. (a) (b) Sympatric speciation. A smallpopulation becomes a new specieswithout geographic separation. Allopatric speciation. A population forms a new species while geographically isolated from its parent population. Figure 24.5 A, B • Concept 24.2: Speciation can take place with or without geographic separation • Speciation can occur in two ways • Allopatric speciation • Sympatric speciation

17. Allopatric (“Other Country”) Speciation • In allopatric speciation • Gene flow is interrupted or reduced when a population is divided into two or more geographically isolated subpopulations

18. A. harrisi A. leucurus Figure 24.6 • Once geographic separation has occurred • One or both populations may undergo evolutionary change during the period of separation

19. Sympatric (“Same Country”) Speciation • In sympatric speciation • Speciation takes place in geographically overlapping populations

20. Habitat Differentiation and Sexual Selection • Sympatric speciation • Can also result from the appearance of new ecological niches

21. Monochromatic orange light Researchers from the University of Leiden placed males and females of Pundamilia pundamilia and P. nyererei together in two aquarium tanks, one with natural light and one with a monochromatic orange lamp. Under normal light, the two species are noticeably different in coloration; under monochromatic orangelight, the two species appear identical in color. The researchers then observed the mating choices of the fish in each tank. Normal light EXPERIMENT P. pundamilia P. nyererei Under normal light, females of each species mated only with males of their own species. But under orange light, females of each species mated indiscriminately with males of both species. The resulting hybrids were viable and fertile. RESULTS The researchers concluded that mate choice by females based on coloration is the main reproductive barrier that normally keeps the gene pools of these two species separate. Since the species can still interbreed when this prezygotic behavioral barrier is breached in the laboratory, the genetic divergence between the species is likely to be small. This suggests that speciation in nature has occurred relatively recently. CONCLUSION Figure 24.10 • In cichlid fish • Sympatric speciation has resulted from nonrandom mating due to sexual selection

22. Allopatric and Sympatric Speciation: A Summary • In allopatric speciation • A new species forms while geographically isolated from its parent population • In sympatric speciation • The emergence of a reproductive barrier isolates a subset of a population without geographic separation from the parent species

23. Figure 24.11 Adaptive Radiation • Adaptive radiation • Is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities (typical for long-distance dispersal) Black noddy tern Australian coast

24. N 1.3 million years Dubautia laxa MOLOKA'I KAUA'I MAUI 5.1 million years Argyroxiphium sandwicense O'AHU LANAI 3.7 million years HAWAI'I 0.4 million years Dubautia waialealae Dubautia scabra Dubautia linearis Figure 24.12 • The Hawaiian archipelago • Is one of the world’s great showcases of adaptive radiation

25. Time (b) (a) Gradualism model. Species descended from a common ancestor gradually diverge more and more in their morphology as they acquire unique adaptations. Punctuated equilibrium model. A new species changes most as it buds from a parent species and then changes little for the rest of its existence. Figure 24.13 • The punctuated equilibrium model • Contrasts with a model of gradual change throughout a species’ existence

26. 25 Phylogeny and Systematics

27. Overview: Investigating the Tree of Life • This chapter describes how biologists trace phylogeny • The evolutionary history of a species or group of related species

28. Biologists draw on the fossil record • Which provides information about ancient organisms Figure 25.1

29. Biologists also use systematics • As an analytical approach to understanding the diversity and relationships of organisms, both present-day and extinct

30. Currently, systematists use • Morphological, biochemical, and molecular comparisons to infer evolutionary relationships Figure 25.2

31. Concept 25.1: Phylogenies are based on common ancestries inferred from fossil, morphological, and molecular evidence

32. 1 Rivers carry sediment to the ocean. Sedimentary rock layers containing fossils form on the ocean floor. 2 Over time, new strata are deposited, containing fossils from each time period. 3 As sea levels change and the seafloor is pushed upward, sedimentary rocks are exposed. Erosion reveals strata and fossils. Younger stratum with more recent fossils Older stratum with older fossils The Fossil Record • Sedimentary rocks • Are the richest source of fossils • Are deposited into layers called strata Figure 25.3

33. The fossil record • Is based on the sequence in which fossils have accumulated in such strata • Fossils reveal • Ancestral characteristics that may have been lost over time

34. (c) Leaf fossil, about 40 million years old (b) Petrified tree in Arizona, about 190 million years old (a) Dinosaur bones being excavated from sandstone (d) Casts of ammonites, about 375 million years old (f) Insects preserved whole in amber (e) Boy standing in a 150-million-year-old dinosaur track in Colorado (g) Tusks of a 23,000-year-old mammoth, frozen whole in Siberian ice Figure 25.4a–g • Though sedimentary fossils are the most common • Paleontologists study a wide variety of fossils

35. Morphological and Molecular Homologies • In addition to fossil organisms • Phylogenetic history can be inferred from certain morphological and molecular similarities among living organisms • In general, organisms that share very similar morphologies or similar DNA sequences • Are likely to be more closely related than organisms with vastly different structures or sequences

36. Sorting Homology from Analogy • A potential misconception in constructing a phylogeny • Is similarity due to convergent evolution, called analogy, rather than shared ancestry

37. Convergent evolution occurs when similar environmental pressures and natural selection • Produce similar (analogous) adaptations in organisms from different evolutionary lineages Marsupial Australian mole Eutherian North Am. mole Figure 25.5

38. 1 Ancestral homologous DNA segments are identical as species 1 and species 2 begin to diverge from their common ancestor. C C A T C A G A G T C C 1 C C A T C A G A G T C C 2 Deletion 2 Deletion and insertion mutations shift what had been matching sequences in the two species. 1 C C A T C A G A G T C C C C A T C A G A G T C C 2 Insertion G T A 3 Homologous regions (yellow) do not all align because of these mutations. C C A T C A A G T C C 1 C C A T G T A C A G A G T C C 2 4 Homologous regions realign after a computer program adds gaps in sequence 1. C C A T C A A G T C C 1 Figure 25.6 C C A T G T A C A G A G T C C 2 • Analogous structures or molecular sequences that evolved independently • Are also called homoplasies

39. Concept 25.2: Phylogenetic systematics connects classification with evolutionary history • Taxonomy • Is the ordered division of organisms into categories based on a set of characteristics used to assess similarities and differences

40. Binomial Nomenclature • Binomial nomenclature • Is the two-part format of the scientific name of an organism • Was developed by Carolus Linnaeus 1707-1778 (Father of Taxonomy or Systematics)

41. The binomial name of an organism or scientific epithet • Is latinized • Is the genus and species

42. Panthera pardus Species Panthera Genus Felidae Family Carnivora Order Mammalia Class Chordata Phylum Animalia Kingdom Eukarya Domain Hierarchical Classification • Linnaeus also introduced a system • For grouping species in increasingly broad categories Figure 25.8

43. Panthera pardus(leopard) Mephitis mephitis (striped skunk) Canis familiaris (domestic dog) Canislupus (wolf) Lutra lutra (European otter) Species Genus Panthera Lutra Canis Mephitis Family Felidae Mustelidae Canidae Carnivora Order Linking Classification and Phylogeny • Systematists depict evolutionary relationships • In branching phylogenetic trees Figure 25.9

44. Leopard Domestic cat Common ancestor • Each branch point • Represents the divergence of two species

45. Concept 25.3: Phylogenetic systematics informs the construction of phylogenetic trees based on shared characteristics • A cladogram • Is a depiction of patterns of shared characteristics among taxa • A clade within a cladogram • Is defined as a group of species that includes an ancestral species and all its descendants • Cladistics • Is the study of resemblances among clades

46. Cladistics • Clades • Can be nested within larger clades, but not all groupings or organisms qualify as clades

47. Grouping 1 E J K D H G F C I B A (a)Monophyletic. In this tree, grouping 1, consisting of the seven species B–H, is a monophyletic group, or clade. A mono-phyletic group is made up of an ancestral species (species B in this case) and all of its descendant species. Only monophyletic groups qualify as legitimate taxa derived from cladistics. • A valid clade is monophyletic • Signifying that it consists of the ancestor species and all its descendants Figure 25.10a

48. Grouping 2 G J K H E D C I F B A (b)Paraphyletic. Grouping 2 does not meet the cladistic criterion: It is paraphyletic, which means that it consists of an ancestor (A in this case) and some, but not all, of that ancestor’s descendants. (Grouping 2 includes the descendants I, J, and K, but excludes B–H, which also descended from A.) • A paraphyletic clade • Is a grouping that consists of an ancestral species and some, but not all, of the descendants Figure 25.10b

49. D E J G H K I F C B A (c)Polyphyletic. Grouping 3 also fails the cladistic test. It is polyphyletic, which means that it lacks the common ancestor of (A) the species in the group. Further-more, a valid taxon that includes the extant species G, H, J, and K would necessarily also contain D and E, which are also descended from A. • A polyphyletic grouping • Includes numerous types of organisms that lack a common ancestor Grouping 3 Figure 25.10c

50. Shared Primitive and Shared Derived Characteristics • In cladistic analysis • Clades are defined by their evolutionary novelties (new chars)