Bio 3400 1nd Edition Lecture 20 Outline of Last Lecture I Mechanisms of speciation II Signatures of sympatric speciation III Secondary contact IV Reinforcement V Isolating mechanisms VI Adaptive radiations Outline of Current Lecture I Levels of evolutionary biology II Beginning of life III LUCA IV Universal tree of life Current Lecture I II Levels of Evolutionary Biology a Microevolution changes in gene frequencies and trait distributions that occur within populations and species b Macroevolution large evolutionary change typically refers to the evolution of differences among populations that would warrant their placement in different genera or higher level taxa How did life begin a 1 Simple organic molecules formed b 2 Replicating molecules evolved and began to undergo natural selection i Until 1982 all known enzymes were protein ii Altman and Cech discovered ribozymes RNA enzymes iii Early life is hypothesized to consist of an RNA world self replicating RNA that also performs biological functions iv Evidence for ancient roots of RNA 1 Central role of rRNA and ribosomes 2 Critical cell metabolism components are structurally similar to RNA c Can RNA evolve via natural selection i Variation in a trait 1 Sequence ii Variation is heritable 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 III IV 1 Self replication iii Differential reproductive success 1 Variation in speed of replication iv Relationship between the trait and reproductive success 1 Do some sequences replicate faster d Replicating molecules then became enclosed within a cell membrane i Enclose genetic material ii Control internal environment iii Allow different actors to take on different tasks within the cells e Some cells began to evolve modern metabolic processes and out competed those with older forms of metabolism Evidence for a single common ancestor LUCA a The genetic code is shared among all organisms i The same triplets specify the same amino acids start and stop codons b All cells use ribosomes and tRNA to synthesize proteins from amino acids c rRNA exists in all living cells and is highly conserved among all organisms d Biochemical processes only use L amino acids Building a Universal tree of life a Genes that exist in all organisms b Genes that do not change quickly c E g small subunit rRNA d Lateral gene transfer complicates the bacteria and archaea clades
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