ANT 102 1st Edition Lecture 6Outline of Last Lecture I. Forces of evolutionII. VocabularyIII. Founder EffectOutline of Current Lecture I. Speciation and CladisticsII. Biological Species Concept (BSC)III. Problems with BSCIV. Modes of SpeciationCurrent LectureSpeciation and Cladistics:What is a species?It’s easy to tell the difference between an elephant and butterfly, but when it comes to two different types of elephants, what makes them different?If organisms from different populations are capable of breeding naturally and can produce viable (fertile) offspring, they are considered part of the same species. Organisms must be capable of interbreedingMust do so naturally, not captivity (not like lion and tiger crossbreed)Offspring must also be fertile (unlike crossbreed between horses and donkeys)Problems with the Biologic Species Concept (BSC):Not testable in organisms that are separated geographically (allopatric)Not testable in organisms that are separated chronologically (allochronic)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.How does this apply to organisms that reproduce asexually?Problematic when talking about the fossil record….they’re dead…hard to reproduce when you’re dead.BSC argument: Ernst Mayr (1904-2005) species are groups of actually or potentially interbreeding natural pops, which are reproductively isolated from other groupsEcological Species Concept (EcSC), Psychological Species Concept (PhySC), Phenetic Species Concept (PheSC)Applicable is not always testable!BSC can be empirically tested, even if only in sympatric and synchronic (geographically and chronologically contiguous) organismsOnly BSC deals with a natural isolating mechanism of populations that ultimately may lead to divergence of lineage (lack of reproduction or viable offspring)How do we apply BSC to fossils?We can’t since they are not livingHow are new species formed?Speciation is a process, not an eventGoes from microevolution to macroevolutionSpeciation is one of the more convincing arguments for evolutionSince it is a process, it is impossible and pointless to “draw a line in the sand” between where one species ends and the other beginsModes of speciation:Anagenesis: evolution in a straight lineCladogenesis: formation of one or more species from another over timeMechanisms of Cladogenesis:Allopatric speciation: populations become physically isolated from each other (islands, mountains, etc. get in the way)They remain isolated long enough for accumulation of genetic changes to render them incapable of producing viable offspring, even if the groups reconnectTwo step process:1. Reproductive isolation: elimination or drastic reduction of gene flow between populations2. Genetic divergence: once gene flow is eliminated or minimized, the other three forces of evolution come into play (genetic drift, mutations or natural selection)Sympatric speciation: speciation within the same environment. Within a single population in a single environment, two or more distinctly different adaptations to the environment are selected Natural selection is keyEssentially disruptive selection over a longer period of timeParapatric speciation: speciation between neighboring environments. An ancestral population colonizes a new environment with different selective pressures. Natural selection is keyHybrid offspring between these populations are at a disadvantage to survive in either environment, therefore selected against, inhibiting gene flow.Ex: northern white rhino six left, can’t crossbreed with southern white rhino because two different eating habits, would push them into