10 13 Lecture Summary Species What is a species Domain Kingdom Phylum Class Order Family Genus Species 1 Typological species each kind of organism is fixed and immutable and can be represented by an 2 Biological def of species reproductively isolated group of actually interbreeding natural pops ideal individual the type specimen that produce fertile offspring Sympatric species ranges overlap easy to determine if 2 organisms are diff species or not Allopatric Species ranges do not overlap hard to determine Problems with identifying species 1 Polymorphic species 2 Sibling Species 3 Ring species 4 Asexual species 5 Fossil species Species with many different types of individuals virtually identical species but they don t breed Continuous gradual shift in phenotype over a large range end pops cant breed can t use biological definition can t use bio def b c you can t see breeding What keeps species from interbreeding Reproductive isolating mechanisms 1 Pre zygotic mechanisms 2 groups that share territory but occupy different regions Ecological Barriers Temporal isolation Behavioral Barriers Mechanical barrier distinct reproductive parts Gametic barriers mating occurs but egg and sperm are incompatible 2 Post sygotic barriers Hybrid inviability fertilixation occurs but zygot embro or larva dies Hybrid sterility healthy hybrid unable to reproduce due to abnormal gametes mules Populations do not strive to become different species How are species formed Microevolution A Allopatric speciation geographic speciation Happens in 2 steps 1 Geographic separation of species that was once continuous Dispersal successful species that spreads out over large area Barriers Continental Drift 2 Reproductive isolation during genetic drift or isolation Original population physical barrier reproductive isolation Differentiation speciation Ecological Speciation Speciation within a population occurring the same habitat 1 Instantaneous speciation polyploidy common in plants tends to produce offspring that cannot mate with eachother 1 generation new species mutation not probable