absorb more oxygen.\nsome cichlids live in polluted water with low levels of oxygen. if these cichlids have…

absorb more oxygen.\nsome cichlids live in polluted water with low levels of oxygen. if these cichlids have gills with smaller surface areas, they may not be able to absorb enough oxygen to survive. but if their gill surface areas are too large, they may absorb too many harmful pollutants or parasites.\nthe graph below describes an isolated population of east african cichlids over a time period long enough for natural selection to occur. the graph shows gill surface area measurements for a representative sample of the population at the start of this period and for another representative sample at the end. at the start of this time period, the east african cichlids environment changed.\ndescribe how the east african cichlid population changed over this time period. use the theory of natural selection to construct a possible explanation for this change.\nthe average gill surface area in the population. this suggests that cichlids with greater gill surface areas were likely to survive and reproduce after the populations environment changed. this may have occurred because the number of parasites in the cichlids environment. cichlids with larger gill surface areas were less likely than before to absorb too after the environment changed.

absorb more oxygen.\nsome cichlids live in polluted water with low levels of oxygen. if these cichlids have gills with smaller surface areas, they may not be able to absorb enough oxygen to survive. but if their gill surface areas are too large, they may absorb too many harmful pollutants or parasites.\nthe graph below describes an isolated population of east african cichlids over a time period long enough for natural selection to occur. the graph shows gill surface area measurements for a representative sample of the population at the start of this period and for another representative sample at the end. at the start of this time period, the east african cichlids environment changed.\ndescribe how the east african cichlid population changed over this time period. use the theory of natural selection to construct a possible explanation for this change.\nthe average gill surface area in the population. this suggests that cichlids with greater gill surface areas were likely to survive and reproduce after the populations environment changed. this may have occurred because the number of parasites in the cichlids environment. cichlids with larger gill surface areas were less likely than before to absorb too after the environment changed.

Answer

Brief Explanations:

  1. Analyze the box - and - whisker plots: The "Sample at start" has a lower range of gill surface area (around 350 - 600) and the "Sample at end" has a higher range (around 500 - 650). The median (the line inside the box) of the "Sample at end" is also higher than that of the "Sample at start". So the average gill surface area increased.
  2. Natural selection logic: In natural selection, organisms with traits that are more favorable in the new environment are more likely to survive and reproduce. Since the average gill surface area increased, it means that cichlids with greater gill surface areas were more likely to survive and reproduce.
  3. Parasite and oxygen balance: The problem states that if gill surface area is too large, they absorb too many parasites, but if the number of parasites decreased, then larger gill surface areas would be more favorable (as they can absorb more oxygen). Also, with larger gill surface areas, they are less likely to absorb too few oxygen (since the environment change might have made oxygen absorption more critical, and larger gills help with that, and with fewer parasites, the downside of large gills (too many parasites) is reduced). So the number of parasites likely decreased, and cichlids with larger gills were less likely to absorb too few oxygen (or too many pollutants/parasites? Wait, the last blank: the problem says "absorb too..." - from the initial text, when gills are too large, they absorb too many harmful pollutants or parasites. But if the environment changed, maybe the pollutants/parasites decreased, so larger gills are less likely to absorb too many pollutants/parasites. But also, they need to absorb enough oxygen. So putting it all together:
    • The average gill surface area increased.
    • Cichlids with greater gill surface areas were more likely to survive and reproduce.
    • The number of parasites in the cichlids' environment decreased.
    • Cichlids with larger gill surface areas were less likely than before to absorb too many parasites (or pollutants) after the environment changed.

Answer:

  1. The average gill surface area (\boldsymbol{\text{increased}}) in the population.
  2. This suggests that cichlids with greater gill surface areas were (\boldsymbol{\text{more}}) likely to survive and reproduce after the population's environment changed.
  3. This may have occurred because the number of parasites in the cichlids' environment (\boldsymbol{\text{decreased}}).
  4. Cichlids with larger gill surface areas were less likely than before to absorb too (\boldsymbol{\text{many parasites (or pollutants)}}) after the environment changed.