BIOL 152 9thEdition Lecture 5Outline of Last Lecture I. Why Define a Species?II. Reproductive IsolationOutline of Current Lecture I. Extrinsic MechanismsII. Geographic SeparationIII. NO Geographic SeparationIV. Review Current Lecture1) Two genetically similar individuals had potential to make and produce viable offspring but never did because one was nocturnal; other diurnal = TEMPORAL ISOLATION2) List the following from most general to most specific:a. Reproductive Isolating Mechanismb. Pre-zygotic isolating mechanismc. Gametic isolationd. 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 speciationo NOT ALWAYSII. GEOGRAPHIC SEPARATION o Allopatric- “Allos” = other “Patris” = fatherland- Barrier intercepts gene flowIII. NO GEOGRAPHIC SEPARATIONo Sympatric- Less common than allopatric species- Gene flow is STILL disrupted- Polyploidyo Extra sets of chromosomes NondisjunctionThese 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.o Plants vs. Animalso Autopolyploid vs. Allopolyploido Other mechanisms Habitat differentiation Sexual selectionIV. 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