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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.