BIOL 152 9thEdition Lecture 4 Outline of Last Lecture I Genetic Drift Can Result In Outline of Current Lecture I Why Define a Species II Reproductive Isolation Current Lecture I Why define a species Why are species the key evolutionary unit A What is a species o Groups of actually or potentially interbreeding natural populations which are reproductively isolated from other groups What s key to the biological species concept o Reproductive Isolation What types of organisms would the BSC NOT apply to o Dinosaurs extinct asexual bacteria and ring species B How else can we identify a species o Morphospecies You find two bacteria that reproduce asexually and look alike how might you determine if they are different species o Grow them under different environmental conditions grow them on different nutrient sources AND analyze their DNA for similarities C How can populations be reproductively isolated Intrinsic Mechanisms o Internal characteristics Extrinsic Mechanisms external factors II Reproductive Isolation a Ecological Isolation o Occupy different habitats b Temporal Isolation o Mating times are different c Behavioral Isolation 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 o Courtship or mating displays differ d Mechanical Isolation o Parts don t fit e Gametic Isolation o Egg AND sperm are not compatible f Hybrid Inviability or Infertility Two species of garter snakes live in the same geographic area One lives mainly n water while the other lives mainly on land They do not interbreed What type of reproductive isolation is this o Ecological and Pre zygotic Pre zygotic Barrier impedes mating between species or hinders fertilization Post zygotic Barrier prevents hybrid zygotes produced by two different species from developing into viable fertile adults