Transcript Taxonomy & Phylogeny - Blue Valley Schools

Species & Speciation
Morphological Species
Concept
• Species are based on comparison and
differences existing in the physical
characteristic between organism
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
shouldn’t be (fish and whales)
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
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)
Evolutionary
Species 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)
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)
Recognition Species Concept
• A species is the most inclusive
population of individual biparental
organisms that share a common
fertilization system. (Paterson, 1985)
Cohesion Species Concept
• A species is the most inclusive
population of individuals having the
potential for phenotypic cohesion
through intrinsic cohesion mechanisms.
(Templeton, 1989)
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)
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)
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
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…).
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.
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
Continental Drift & Speciation
• Alfred Wegener
• In the 1930’s 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
Evidence for Continent Drift
• Continental Geography
• Paleontology and Climate
• Past Glacial Events
Continental Geography
• The eastern coast of
South America and
the western coast of
Africa appear to fit
nicely together like
pieces of a puzzle
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
Past Glacial Events
• Mapping of the
extent of glacial rock
remains on the
different continent
suggests particular
connections
between the
continents in the
past
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
1970’s
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
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 Earth’s largest feature is the
Mid-Atlantic Ridge running down the
middle of the Atlantic Ocean
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
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
• As magma in the
Earth’s 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.
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)
• Mapping of the
distribution of
Earthquakes across
the globe correlates
well with places
were plates are
coming together
• http://pubs.usgs.gov/publications/text/
Information on Continental Drift and
Plate Tectonics