BILD 3 Chapter 5: Reading Notes 18:10:12
26 Oct 2018
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BILD3 Reading Notes 10/12/18
Chapter 22: Descent with Modification: A Darwinian View on Life
- 22.3: Evolution is supported by an overwhelming amount of scientific evidence
o direct observations of evolutionary change
▪ natural selection in response to introduced species
• what happens when herbivores switch to new food source with different
characteristics?
o Soapberry bugs use beak to feed, which usually corresponds with plant
depth. Southern Florida soapberry bugs feed on seed in balloon vine. Central
Florida lacks balloon vines, so soapberry bugs instead feed on goldenrain tree
seeds. Balloon vines are deeper than goldenrain trees, so natural selection
predicted that Southern Florida bugs expected to have longer beaks than
Central, and this was true
o Conclusion: change in size of food source result in evolution by natural
selection for corresponding change in beak size
o In Louisiana, Oklahoma, and Australia, introduced plants larger than native,
so species evolved longer beaks
o Rapid evolution: 35 years
▪ Evolution of drug-resistant bacteria
• Bacteria and viruses can produce new generations in short time, so resistant
strains can proliferate very quickly
• Ex: Staphylococcus aureus evolved drug resistance (MRSA)
o Treated with penicillin, but some had enzymes that could destroy penicillin
o Treated with methicillin (works to deactivate enzyme that helps synthesize
cell walls), but within 2 years, developed enzyme not affected by methicillin
o Developed resistance to multiple antibiotics due to bacterial gene exchange
• Drug doesn’t create resistant pathogens, just selects for resistant individuals
already present in the population
▪ Natural selection is process of editing, not creating. Can occur rapidly, from few
years to few decades
▪ Natural selection depends on time and place. What may be advantageous in one
location, may be detrimental in another
o Homology: similarity resulting from common ancestry
▪ Anatomical and molecular homologies
• Forelimbs of all mammals (humans, cats, whales, bats) show same arrangement
of bones from shoulder to digits, though appendages have different functions
• homologous structures: variations on structural theme present in common
ancestor
• all vertebrate embryos have tail on posterior and pharyngeal (throat) arches,
which ultimately develop into structures with very different functions
• vestigial structures: remnants of features that served a function in the
organism’s ancestors, but have marginal importance to the current organism
