Observational collect date by seeing what"s happening. How you think the world works -> verbalize it. Comparative collect from # of species see if robust. Experimental test preceding obs, theory, comparative data. James: species diversity: number of species in particular place. Idea that species: also have populations genetically variable. From gene -> pop -> species -> genre -> family. Trait = character/characteristic of org feature -> contributes to fitness how many genes you pass on to next generation vs another indivi in pop, pass more gene = more fit better able to survive/reproduce in env. Verb: process, evo process leads to origin of maintenance of traits (above) Pics of ppl and know who ppl are. Used fruit fly as model system for understanding population genetics, mutation, etc. Organisms have genes that are transferred to next generation. How well they do that depends on env they"re in + traits they have. Studying adaptations, speciation, process that give rise to diversity.