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  1. Advanced Ornithology by Maryam Riasat SYSTEMATICS
  2. Systematics  The challenge of reconstructing the history of life belongs to a field of scholarly endeavor called systematics  Systematics are scientists who evaluate evolutionary relationships among organisms through comparisons of fossils, preserved specimens, behavior, and increasingly the genetic code of life itself, DNA
  3. Species and Speciation The diversity of life is a result of three evolutionary processes o Phyletic Evolution: The gradual change of a single lineage o Speciation: The splitting of one phyletic lineage into two or more o Extinction: The termination of a lineage
  4. Species  Species are the fundamental units of biological classification  Species are groups of interbreeding natural populations that are reproductively isolated from other such groups  Birds species have characteristics sizes, shapes, songs, colors, ecological niches, and geographical ranges
  5. Speciation  Speciation is the formation of new and distinct species in course of evolution  The evolutionary legacy of the earliest birds includes roughly 100,000 species of which only 1 in 10 is now with us  Behind this legacy lies the process of speciation: The multiplication of species through the division of one species into two or more as a result of genetic divergence of isolated population
  6.  Geographical separation of populations reduces the exchange of genes, thereby allowing independent divergence and enable speciation  Most species of birds evolve as geographical isolates  Reproductive isolation may sometimes play a role
  7.  Birds populations become geographically isolated in two principal ways o Pioneering individual birds may colonize an oceanic island and thus are separated from their main population o Fragmentation of habitats can also isolate the bird populations  Remnant populations
  8. Classification and phylogeny  Classification is the arrangement of organisms in taxonomic groups in accordance with the observed similarities  Ornithologiae by Francis and John, published in 1676 was the first formal classification of birds  Nearly a century later, Linnaeus used this elementary classification as the model for subsequent classifications
  9.  These early efforts, however, classified birds according to superficial adaptations to aquatic versus terrestrial habitats rather than according to evolutionary relationship  Charles Darwin’s theory of evolution by natural selection transformed the basis of systematics into one based on common ancestries
  10. Taxonomic characters  Reconstruction of the evolutionary history of birds requires the analysis of specific traits, called as characters  In common ancestry these characters are called as shared characters  Conservative characters – that do not easily change in the course of ecological adaptation  These are of greatest value because they retain clues to ancestors  A constant challenge to accurate reconstruction is the possibility of convergence between unrelated species
  11.  Thomas H. Huxley helped to lay the foundation of modern systematics in birds with his study of the arrangement of the bones of the avian bony palate  Skeletal partition between the nasal cavities and the mouth  Succeeding generations of the ornithologists added new characters to the taxonomic tool kit
  12.  Form of the nostrils  Structure of the leg muscles  Tendons of the feet  Arrangement of toes  Morphology of vocal apparatus  Behavior  Vocalization  Protein yielded clues  Plumage patterns
  13. Unique characters Unique characters define related groups of species with common ancestors Song Birds Order Passeriformes have several unique characters i.e. Preen gland with a unique nipple Unique sperms Specialized perching foot with a large hallux Uniquely arranged deep tendons Simplified foot muscles
  14. These features indicate that members of the order Passeriformes evolved from a common ancestor i.e. they are monophyletic
  15. Cladistics  Categorized in groups (clades) based on hypothesis of most recent common ancestry  Cladistics analysis enables ornithologists to separate primitive characters from common derived characters and to sort them rigorously across taxa  Phylogenetic studies require homologous characters which can be traced to the same feature in the immediate common ancestor of both organisms  Exist in both their original and their changed states
  16. Flipper like wings of penguins evolved from the wings of their petrel ancestors o Wings of petrels represent ancestral/primitive character state o Flipper like wings of penguins represent advanced/derived state
  17. If two species have a character state in common, we can hypothesize that they have a common ancestor with the same character state Example: o The flipper like wings common to all penguin species correspond to their common ancestry (Hypothetical ancestor) o We assume that the cladogram with the fewest evolutionary changes is the most likely or most plausible phylogeny