BIOL 152 9thEdition Lecture 5 Outline of Last Lecture I Why Define a Species II Reproductive Isolation Outline of Current Lecture I Extrinsic Mechanisms II Geographic Separation III NO Geographic Separation IV Review Current Lecture 1 Two genetically similar individuals had potential to make and produce viable offspring but never did because one was nocturnal other diurnal TEMPORAL ISOLATION 2 List the following from most general to most specific a Reproductive Isolating Mechanism b Pre zygotic isolating mechanism c Gametic isolation d Sperm egg incompatibility in sea urchins I EXTRINSIC MECHANISMS Broadly the Biological Species Concept BSC is defined by whether or not GENE FLOW can occur The former intrinsic mechanisms PREVENT gene flow Over time CAN lead to speciation o NOT ALWAYS II GEOGRAPHIC SEPARATION o Allopatric Allos other Patris fatherland Barrier intercepts gene flow III NO GEOGRAPHIC SEPARATION o Sympatric Less common than allopatric species Gene flow is STILL disrupted Polyploidy o Extra sets of chromosomes Nondisjunction These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute IV o Plants vs Animals o Autopolyploid vs Allopolyploid o Other mechanisms Habitat differentiation Sexual selection REVIEW In ALLOPATRIC SPECIATION geographic isolation restricts gene flow between populations Reproductive isolation may then arise by natural selection genetic drift or sexual selection in the isolated population Even if contact is restored between populations In SYMPATRIC SPECIATION a reproductive barrier isolates a subset of a population without geographic separation from the parent species Sympatric speciation can result from polyploidy natural selection OR sexual selection