Biol 100 - Lecture 28 PDF

Mark Brigham LB 257 [email protected] EVOLUTION Most important topic in all of biology Most misunderstood topic in all of biology Understanding evolution and the mechanism(s) by which it occurs unites the sub-disciplines of biology Thus, evolution is the foundation for all of modern biol...

Mark Brigham LB 257 [email protected] EVOLUTION Most important topic in all of biology Most misunderstood topic in all of biology Understanding evolution and the mechanism(s) by which it occurs unites the sub-disciplines of biology Thus, evolution is the foundation for all of modern biology "Evolution" is really two concepts 1. Change evolution is - organic -> happens in populations change and english in -> Evolution of living means something changes. organisms species· 2. The mechanism causing change -> Happens at -> Happens at -> Natural level of diff scale selection -> organisms jobs is individuals to than causes change individual survive and change . reproduce Professor Farnsworth 1. Variation 2. Differences can be inherited 3. Different environments have different effects on different phenotypes 4. Some genotypes; those who produce the favoured phenotypes, will be selected for by the environment Biological or Organic Evolution Change in properties of living organisms that transcend the lifetime of a single individual = Descent with modification -> Evolution over time INDIVIDUALS do not evolve! In essence, Natural Selection is simply “Differential reproductive success of individuals” NS has NO purpose, NO goal. It is NOT directed, even towards the survival of the species NOTE: Being favoured does NOT mean that all “good” genotypes survive and reproduce and all “bad” genotypes die, only that the “good” ones have a better chance. CHANCE in part determines which individuals will survive and reproduce Professor Farnsworth “Screwdriver Sam” If the environment changes, so does the advantage for certain genotypes. This can account for the reshuffling of the proportions of different phenotypes in a population from generation to generation but does it account for new species? To get new species, must generate new alleles These come from mutations or gene duplications in cells that produce gametes Typically mutations in well adapted organisms tend to be negative but on occasion…. Remember there is no deliberate attempt at progress or moving towards a goal. Chance drives the process The effect of a chance event can LOOK purposeful. In the fossil record of animals, simple ones are often first and more complex ones later. This tempts the conclusion: “Clearly evolution is progressive, moving towards greater perfection. Someone must have designed it”. It is tempting given the amazing diversity of plants and animals to think that “this could not happen by chance alone”. “Someone or something must have designed or created them.” This is a perfectly reasonable explanation but reasonable does not necessarily mean “true”. So to put the idea that jumps to mind to rest: Does the theory of organic evolution disprove that a God created all plants and animals? NO!! What the theory does is provide a plausible and more importantly, a TESTABLE alternative. We can collect evidence for or against evolution. We can’t directly test the idea that a God did it. Creationism is a belief not a theory. When Darwin proposed the idea of Natural Selection he was thinking primarily of simple survival: You can’t have kids if your dead! Professor Farnsworth “Sexual selection and summary” But there is more to Natural Selection than just survival. Overall FITNESS (e.g., survival, feeding, finding a mate, parental care etc.) Thus SURVIVAL OF THE FITTEST. Natural Selection does not favour the fittest, it determines the fittest. Survival is determined in part by chance (an idea Darwin really didn’t deal with) but he did pick up on “sexual selection” or the attractiveness idea. That is “Is the likelihood of survival the only factor which determines who you get a date with this Friday” - NO! Characteristics important for survival are not necessarily good for securing a mate Survival is determined in part by chance (an idea Darwin really didn’t deal with) but he did pick up on “sexual selection” or the attractiveness idea. That is “Is the likelihood of survival the only factor which determines who you get a date with this Friday” - NO! Characteristics important for survival are not necessarily good for securing a mate