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Advanced Ornithology
by
Maryam Riasat
SYSTEMATICS
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
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
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
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
 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
 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
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
 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
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
 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
 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
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
These features indicate that members of the order
Passeriformes evolved from a common ancestor i.e.
they are monophyletic
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
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
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

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Systematics.pptx

  • 1.
  • 3. 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
  • 4. 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
  • 5. 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
  • 6. 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
  • 7.  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
  • 8.  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
  • 9. 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
  • 10.  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
  • 11. 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
  • 12.  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
  • 13.  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
  • 14. 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
  • 15. These features indicate that members of the order Passeriformes evolved from a common ancestor i.e. they are monophyletic
  • 16. 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
  • 17. 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
  • 18. 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