Wednesday, April 30, 2008
Wednes-Day 2
Bio- we discussed the mechanism of antibiotic resistance evolution in a population of bacteria. We used the tenets of the Theory of Evolution to show that overpopulation (of bacteria) leads to competition for resources which leads to the "selection" of those bacteria that have the best traits/adaptations for their particular environment. The (artificial) selecting agent in our case was PENICILLIN, which selected against (killed) those bacteria that had no natural resistance to the antibiotic (they lacked the allele that gives them the penicillin-resistant phenotype). Those bacteria that had natural resistance to penicillin (they were "born" that way whether or not they would ever be in a penicillin-containing environment!!!) were selected FOR by the penicillin-environment because these bacteria survived the antibiotic, were able to reproduce and pass on their penicillin-resistant alleles to their asexually reproduced offspring.
We then discussed the incompleteness/weakness of Darwin's Theory: he could not explain the CAUSES of variation within a species and also he did not know that environmentally "acquired traits" could not be passed on to offspring.
Darwin's Theory has been modified and continues to be developed in the Modern Synthetic Theory of Evolution. This theory retains/keeps most of Darwin's tenets but has much more explanatory power and supporting evidence. A source of variation are genetic mutations that produce new alleles that cause new phenotypes; also, sexual reproduction/genetic recombination
can result in new combinations of alleles that cause new phenotypes that may be advantageous in a given environment.
Chem 7/8: we took the Solutions unit exam and then we completed our precipitate lab.
Chem 9: we took the Solution unit exam.
We then discussed the incompleteness/weakness of Darwin's Theory: he could not explain the CAUSES of variation within a species and also he did not know that environmentally "acquired traits" could not be passed on to offspring.
Darwin's Theory has been modified and continues to be developed in the Modern Synthetic Theory of Evolution. This theory retains/keeps most of Darwin's tenets but has much more explanatory power and supporting evidence. A source of variation are genetic mutations that produce new alleles that cause new phenotypes; also, sexual reproduction/genetic recombination
can result in new combinations of alleles that cause new phenotypes that may be advantageous in a given environment.
Chem 7/8: we took the Solutions unit exam and then we completed our precipitate lab.
Chem 9: we took the Solution unit exam.
# posted by C @ 7:20 PM 
