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Figure 4.3 (b)

Figure 4.3 (b)

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Figure 4.3 (b)

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  1. Figure 4.3 (b) 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. 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. • 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 • 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 • In cichlid fish • Sympatric speciation has resulted from nonrandom mating due to sexual selection

  22. 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

  23. Systematics and Clades • 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

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

  25. 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

  26. 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

  27. 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

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

  29. Outgroups • Systematists use a method called outgroup comparison • To differentiate between shared derived (unique to a clade but not found in beyond that taxon) and shared primitive (ancestral) characteristics

  30. As a basis of comparison we need to designate an outgroup • which is a species or group of species that is closely related to the ingroup, the various species we are studying • Outgroup comparison • Is based on the assumption that homologies present in both the outgroup and ingroup must be primitive characters that predate the divergence of both groups from a common ancestor

  31. TAXA Lancelet(outgroup) Salamander Leopard Lamprey Turtle Tuna Hair 0 0 0 0 0 1 CHARACTERS 0 0 0 0 1 1 Amniotic (shelled) egg 0 0 0 1 1 1 Four walking legs 0 0 1 1 1 Hinged jaws 1 0 1 1 1 1 1 Vertebral column (backbone) (a) Character table. A 0 indicates that a character is absent; a 1 indicates that a character is present. Leopard Turtle Hair Salamander Amniotic egg Tuna Four walking legs Lamprey Hinged jaws Lancelet (outgroup) (b) Cladogram. Analyzing the distribution of these derived characters can provide insight into vertebrate phylogeny. Vertebral column • The outgroup comparison • Enables us to focus on just those characters that were derived at the various branch points in the evolution of a clade Figure 25.11a, b