Lecture 1 Lecture 1 Outline of Current Lecture I. The Drunkards Walk II. E. Coli & Evolution Current Lecture The Drunkards Walk Toward Complexity •as organisms get more complex —> fewer of them •as time goes by organisms get more complex and varied •only bacteria in precambrian period (no complex organisms) •multicellular organisms evolve —> more complex •transition to land (fish —> dinosaur) •impossible to get less complex than bacteria—organisms are randomly evolving but they can only become more complex •not progress—just adaptation !**Clicker Question** !Does the mode (most common value on the x axis) change? •No — “peak” represents the most common (most organisms are still bacterial) and it does not change over time !!!**Clicker Question** Biology 152 1Edition!!!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. !!Are present bacteria genetically identical to those from the pre-cambrian era? •No, probably not •because of poor DNA replication, bacteria will mutate—become genetically different **Clicker Question** What does the “Drunkards Walk” refer to? •The random changes that underlie evolution !E.Coli & Evolution What is E. coli? •facultative anaerobic •makes up less than 0.1% of flora in our guts •can easily be grown in culture—it doubles every 15 minutes **Clicker Question** If E.coli cells were grown in a liquid broth with limited glucose but supplemented with citrate serially for 35,000 generations (re-cultured every day & each sample frozen). What do the data suggest? •at 33,000 the E. coli were able to reproduce faster because of a change in the bacteria’s energy production and
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