Ecology 2

  1. biodiversity
    • the distribution and abundance of life on earth, same thing as species diversity
    • Ecologists look for patterns seeking to explain this
  2. 3 kinds of Natural Selection
    • directional
    • stabilizing (normalizing)
    • disruptive
  3. Directional Selection
    • for one extreme and against other extreme
    • results in change in mean and average phenotype
  4. Stabilizing (normalizing) Selection
    • favors the mean, against both extremes (resists change)
    • keeps population phenotype distribution where it is
    • examples: many components of fitness; birth weights, egg #'s in birds nests
  5. David Lack and clutch size experiment in birds
    • egg # and egg survival trade off because of food limitation (quantity vs. quality)
    • 1. average - medium egg #, pretty high survival, fledgling # high
    • 2. above average - high egg #, low survival, fledgling # medium, (too low quantity)
    • 3. below average - low egg #, high survival, fledgling # medium, (too low quality)
  6. Disruptive Selection
    • against mean, for both extremes (opposite of stabilizing)
    • end up with bimodal distribution, average may not change, but there will be two different peaks
  7. Coho salmon
    • females build nests, males fertilize eggs, first two to get there fertilize the most
    • biggest male wards off other big males (hooknose) (largest mean)
    • small males hide nearby ready to sneak in (jack) the smallest is usually the quickest and can sneak into tight places
  8. Ecology vs Evolution
    • Ecology is the short-term, time frame of interactions between organisms and the environment
    • Evolution is the long-term, resulting adaptations that occur over many generations
  9. gill rakers
    • look like little teeth in a rake
    • rakers filter food particles
    • few rakers with space between them filter large particles
    • many rakers cose together filter small particles
  10. pattern with food particle size and raker distance and number
    • food particle size is negatively correlated with raker number (food size up, raker number down)
    • food particle size is positively correlated with distance between rakers (food size up, distance between rakers up)
  11. structuralist vs functionalist approach
    • functionalist - Does raker # evolve in response to diet or food availability?
    • structuralist - Does animal move because of phenotype?
  12. JD McPhail's findings of correlation between lake area and # of rakers on 3 spine sticklebacks
    • positive correlation - large lake, greater # of rakers
    • small lake, fewer # of rakers
    • Bimodal food distribution - larger food (benthos) live on bottom in shallow water, -smaller food (zooplankton) live in open water
  13. benthos
    • larger food that lives on the bottom; insects, snails, isopod, amphipods
    • small lakes have more of this
  14. zooplankton
    • smaller food that lives in open water; copepods, cladocera, arthropods
    • large lakes have more of this
  15. Darwin's theory of natural selection (short version)
    • 1. Individuals within a population vary in phenotype (Vp > 0)
    • 2. Some of this phenotypic variation is genetic, passed on from parent to offspring (h2)
    • 3. Individuals produce more offspring than the environment can support thus there is a "struggle for existence" (the only exclusively Darwinian point)
    • 4. Some individuals, due to phenotypes, survive/reproduce better than others (S)
    • 5. Those favored phenotypes, if heritable (genetic) increase in frequency in the next generation (R)
    • R = h2S
  16. microevolution
    • change in the allele frequencies in a population over generations
    • evolutionary change below the species level
    • *short time scales over several generations
  17. quantitative trait
    • a heritable feature that varies continuously over a range rather than in an either-or-fashon
    • determined by many genes (polygenic) of small effect (like height in humans)
    • will not follow patterns of Mendelian inheritance (monogenic traits)
  18. benthic fish
    • eat benthos
    • have few rakers with space between them
  19. limnetic fish
    • eat zooplankton
    • have many rakers close together
  20. How do we know raker number is a quantitative trait?
    • cross a benthic with a limnetic --> get a hybrid intermediate
    • cross hybrids and recover some of the parent phenotype that was lost in the hybrid generation
    • *overall, hybrids do worse than either benthics or limnetics averaged over both environments
Card Set
Ecology 2
day 2