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BIO 203L- Lecture 8

by: Karissa Sandoval

BIO 203L- Lecture 8 BIOL 203L 005

Karissa Sandoval
GPA 3.5

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About this Document

Speciation and Species
Ecology and Evolution Laboratory
Dr. Kelly Miller and Dr. Scott Collins
Class Notes
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This 5 page Class Notes was uploaded by Karissa Sandoval on Tuesday February 16, 2016. The Class Notes belongs to BIOL 203L 005 at University of New Mexico taught by Dr. Kelly Miller and Dr. Scott Collins in Spring 2016. Since its upload, it has received 10 views. For similar materials see Ecology and Evolution Laboratory in Biology at University of New Mexico.


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Date Created: 02/16/16
BIO 203: Evolution Lecture 8 Speciation and Species • Isolating Mechanism – Cause a population to be isolated from each other and will reproduce and eventually diverge from the main population into two different species (they don’t interact with each other and do not have the same phenotypes either) • Common ancestor is the branch the species share • Scales of evolutionary study – Species create an inflection point between macro and micro evolution •    Isolating mechanisms – Hybrid – offspring produced from mating between two different populations or species (ex: mule is a hybrid of a horse and a donkey) – Isolating mechanisms – any factor that impedes two populations from producing viable, fertile hybrid offspring (reproductive barriers) • Sexual reproduction – Isolation of gene pools preventing gene flow • Prezygotic • Postzygotic • Prezygotic isolating mechanisms – before the production of a zygote – Impede mating or hinder fertilization • Geographic isolation – populations live in different geographic regions (they cant engage in gene flow due to isolation in different locations) BIO 203: Evolution Lecture 8 • Habitat isolation – populations live in different habitats in the same area (ex: one lives in forest and the other in the desert they will never interact) • Behavior isolation – mate attraction signals, courtship differences (ex: sexual selection can be a factor if a female requires a specific courtship and one species has it the other doesn’t than the female will mate with the one that acquires the specific courtship) • Temporal isolation – breed at different times of day, different seasons or different years • Mechanical isolation – anatomical differences don’t allow for mating (anatomy does not fit together to mate) • Gametic isolation – gametes are unable to fuse to form a zygote (two sets of species from different populations may not be able to fuse gametes into zygotes) • Postzygotic isolating mechanisms – after the production of a zygote • Prevent zygote from developing in viable, fertile adult • Reduced hybrid viability – genetic incompatibility may abort development (zygote is formed by chromosomes do not match and the proteins released from each cannot work together so the zygote is aborted) • Reduced hybrid fertility – hybrids are sterile because of chromosomal differences (fully in tack hybrids cannot reproduce so species that make hybrids are making dead ends) • Hybrid breakdown – first generation of hybrids is viable, but future generations deteriorate • On the origin of species – Speciation – the origin of new species • In asexual taxa may occur with new mutations • In sexual taxa, occurs when the gene pool of a population is permanently isolated from the gene pool of another population • Different mutations in each arise and go to fixation either through drift or selection – Types of speciation defined by degree of geographic isolation • Allopatric • Allopatric – occupying different geographic distributions (long distance relationship) BIO 203: Evolution Lecture 8 • Allopatric speciation Allopatric speciation  Original population Geographic isolatingmechanism Accumulationofdifferences from microevolution Resultingseparatespecies – Vicariance – division of the original distribution of a species by a geographic barrier • E.g. Mountain range • As the mountain range increases a species may become more isolated • E.g. Body of water • A body of water can split land into two regions and species will form from a common ancestor – Dispersal – Colonization of a new geographic area by members of a population • E.g. founding populations • Has the potential for dispersal because there is new gene flow BIO 203: Evolution Lecture 8 • E.g. range extensions • Species are always changing their ranges so it can lead to speciation • Adaptive radiation – Adaptive radiation – evolution of many diversely adapted species from a single common ancestor • E.g. colonization of an island chain provides opportunity for species to diversify • Many ecological opportunities available, little competition • Sympatry – Sympatric – occupying the same or overlapping geographic distributions • Sympatric speciation Sympatric speciation  Original population Concentratedgenetic frequency differences (polymorphism) Accumulationofdifferences from microevolutionincludingisolating mechanism Resultingseparatespecies BIO 203: Evolution Lecture 8 – Highly contentious – how can speciation occur in the presence of gene flow – Polymorphisms may be due to disruptive selection (e.g. selection against heterozygotes so they are selected out – Natural selection must counteract gene flow


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