Species

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Species Speciation
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Morphological Species Concept

• Species are based on comparison and differences
  existing in the physical characteristic between
  organism

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Morphological Problems

• Two organisms that appear to be different species
  may be the same species
• Likewise, organism with similar characteristics
  may be place in the same taxonomic groups when
  they shouldnt be (fish and whales)

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Evolution Phylogeny

• After the publication of On the Origin of Species
  in 1859 by Charles Darwin classification took on
  new meaning.
• Phylogeny is a form of classification with the
  goal of representing the evolutionary
  relationships and history of living organisms

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Biological Species Concept

• Species are groups of actually or potentially
  interbreeding natural populations that are
  reproductively isolated from other such groups.
  (Mayr, 1942)
• A species is a group of individuals fully
  fertile, but barred from interbreeding with other
  similar groups by its physiological properties.
  (Dobzhansky, 1935)

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EvolutionarySpecies Concepts

• A species is a single lineage of populations or
  organisms that maintains its identity from other
  such lineages and which has its own evolutionary
  tendencies and historical fate (Wiley, 1978)

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Phylogenetic Species Concept

• A species is an irreducible cluster of organisms
  that is diagnosably distinct from other such
  clusters, and within which there is a parental
  pattern of ancestry and decent. (Cracraft, 1989)
• A species is the smallest monophyletic group of
  common ancestry. (de Queiroz and Donoghue, 1990)

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Recognition Species Concept

• A species is the most inclusive population of
  individual biparental organisms that share a
  common fertilization system. (Paterson, 1985)

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Cohesion Species Concept

• A species is the most inclusive population of
  individuals having the potential for phenotypic
  cohesion through intrinsic cohesion mechanisms.
  (Templeton, 1989)

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Ecological Species Concept

• A species is a lineage that occupies an adaptive
  zone minimally different from that of any other
  lineage in its range and which evolves separately
  from all lineages outside its range. (Van Valen,
  1976)

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Internodal Species Concept

• Individual organisms are conspecific by virtue of
  their common membership in a part of the
  genealogical network between two permanent
  splitting events or between a permanent split and
  an extinction event. (Kornet, 1993)

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Speciation

• Process by which
• a) subpopulations of one species diverge
  becoming adapted to different environments and
  reproductively isolated
• b) descendants of a species become adapted
• to an environment different than the one in
  which it was originally adapted such that they
  are qualitatively distinct from their ancestor

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Allopatric Speciation

• Mode of speciation in which the subpopulations
  diverge because they are separated by a
  geographic barrier
• Common barriers include water (oceans to rivers),
  landforms (canyons and mountains), climate
  (glacial periods), and habitats (deserts,
  tropics, etc).

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Geographic Separation

• Once populations of a species are geographically
  separated the genes that determine their
  characteristics can no longer be shared (gene
  flow stops).
• If the environment in the different geographic
  regions is not the same, then each population may
  diverge in their characters through natural
  selection.
• If these populations are segregated long enough
  the populations may become new species.

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Reproductive Isolation

• Pre-Zygotic Mechanisms
• 1) Temporal
• 2) Behavioral
• 3) Mechanical
• 4) Ecological
• 5) Gametic Mortality

• Post-Zygotic Mechanisms
• 1) Hybrid Inviability
• 2) Hybrid Sterility
• 3) Low Fitness Hybrids

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Continental Drift Speciation

• Alfred Wegener
• In the 1930s suggested that continents were (and
  are currently) moving relative to each other and
  that at some time in the past they were joined
  together forming a super continent Pangea

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Evidence for Continent Drift

• Continental Geography
• Paleontology and Climate
• Past Glacial Events

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Continental Geography

• The eastern coast of South America and the
  western coast of Africa appear to fit nicely
  together like pieces of a puzzle

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Paleontology Climate

• The ranges of fossil plant and animal specimens
  of similar age appear to correlate well across
  current continental boundaries
• Tropical fossils exist in Antarctic sediment
  suggesting that this continent has not always
  existed in its current location

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Past Glacial Events

• Mapping of the extent of glacial rock remains on
  the different continent suggests particular
  connections between the continents in the past

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Plate Tectonics

• Continental Drift was not taken seriously by the
  geological community until a mechanism that could
  explain the movement of the continents could be
  developed
• Technical developments associated with WWII
  allowed a better understanding of the Ocean Floor
  and subsequent development of the mechanism of
  Plate Tectonics in the 1970s

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Evidence for Plate Tectonics

• Ruggedness and Age of the Ocean Floor
• Oceanic Ridges and the process of Sea Floor
  Spreading
• Oceanic Trenches and the process of Mountain
  Formation, Volcanoes, and Earthquakes

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Ruggedness of the Ocean Floor

• Through development of sonar and more extensive
  use of submarines a picture of a rugged sea floor
  emerged (previously it was thought that the ocean
  floor was flat)
• In fact, the Earths largest feature is the
  Mid-Atlantic Ridge running down the middle of the
  Atlantic Ocean

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Oceanic Ridges

• At ocean ridges new crust arises from magma
  within the Earth forcing the existing plate out
  while a new border for the plate is being made

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Magnetic Striping

• As new magma cools magnetic crystals within it
  line up with the magnetic poles of the Earth
• The north end facing north and the south end
  facing south

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• As magma in the Earths core circulates magnetic
  or polar reversals occur
• Our current north and south flip such that the
  magnetic crystal line up opposite of what they
  would be normally.

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Oceanic Trenches

• Where two plates come together one is subducted
  under the other forming a trench
• Tension builds up in the plate laying on top
  while heat may generate magma below (Mts
  Volcanoes)

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• Mapping of the distribution of Earthquakes across
  the globe correlates well with places were plates
  are coming together

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• http//pubs.usgs.gov/publications/text/
• Information on Continental Drift and Plate
  Tectonics