Download Allopatric, Sympatric, Adaptive Radiation

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Allopatric Speciation
Sympatric Speciation
Adaptive Radiation
Objectives
• To define speciation
• To explore the different types of speciation
• To examine real life examples of different types of speciation
Review: ONLY COPY THE LAST POINT
What is a ‘Species’ and the ‘Biological Species Concept’?
• A species is a group of organisms consisting of similar individuals capable of
exchanging genes or interbreeding. Species is the principal natural taxonomic unit,
ranking below a genus and denoted by a Latin binomial.
• The ‘Biological Species Concept’ defines a species as members of populations that
actually or potentially interbreed in nature, not according to similarity of appearance.
Although appearance is helpful in identifying species, it does not define species.
*Most important*- species are an independent evolutionary unit of organisms that do
or could mate with each other if given the opportunity and can produce fertile
offspring.
What is Speciation?
• Speciation is the process where an
ancestral species goes through a
lineage-splitting event that produces
two or more separate species.
• A speciation event the moment in
which the evolutional lineage splits,
starting the history of a new species
Allopatric Speciation
(Geographic Speciation)
• Speciation where a species is
geographically (physically) isolated by
an extrinsic barrier and evolves genetic
reproductive isolation.
• Individuals of the original population
will no longer be able to interbreed
with the new species.
• Allopatric speciation is speculated to be
the most common way of species
formation. Ex: Charles Darwin's
Galápagos Finches.
Sympatric Speciation
• A populations becomes reproductively
isolated into different species within
the same geographic area.
• Factors such as chromosomal changes
(common in plants) and non-random
mating (in animals) alter gene flow.
Sympatric Speciation in Plants ( Polyploidy)
• A Polyploidy organism has three or more sets of
• Small errors in cell division result in a mutant
chromosomes in their nucleus. Most animals are diploid
conditions known as POLYPLOIDY (cell division error
(1 set of chromosomes from each parent) making it rare
that results in an extra set of chromosomes), that can
However in plants it is common because many species
result in a new species in a single generation.
are able to self fertilize and reproduce.
Sympatric Speciation in Animals
• The mechanism of sympatric
speciation for animals generally
occurs when a population starts
to use resources that are
different from the parent
population.
• The use of common resources
different from the parent
populations resources eventually
leads to non-random mating and
eventually speciation.
*Lake Malawi, Africa; over 500 species evolved from one common
ancestor 14,00 years ago.
The Important Stuff…
Adaptive Radiation
• Diversification of a common ancestral
species into a variety of species, all of
which are differently adapted.
• Different ecological niches or
environments allow species to
become specifically adapted to that
specific niche, resulting in specialized
morphology, behaviour, etc.
Example: Speciation of the Galapagos finches occurred
through adaptive radiation.