For questions 1–3, Consider the following graph showing threshold irradiance lev

Question

For questions 1–3, Consider the following graph showing threshold irradiance levels by temperature for four species of rockfish that inhabit shallow waters off the Pacific coast. This indicates the level of light necessary for each fish species to be able to see. A lower threshhold value (more negative value on the log scale) indicates more sensitive vision in low light. The horizontal dotted line shows the irradiance level of moonlight during full moon at 10 m depth. Olive rockfish and kelp rockfish are generally nocturnal, while the other two species are diurnal, therefore these two groups generally do not compete. Rockfish are visual sit-and-wait predators. For these questions, assume that rockfish do not show plastic (developmental) responses nor acclimation responses in threshold irradiance.

For these questions, you can ignore the blue vertical lines showing error around the mean values.

Remember that light decreases with depth, so species adapted to different light levels area adapted to different depths.

[4 pts] Describing the biology depicted by this figure. What are the main factors influencing vision sensitivity and how does the figure help explain which species are diurnal vs nocturnal.

[4 pts] In some areas, increased light pollution from coastal cities has raised the nighttime light level to 10?4 W/m2 at 10 m depth. What are some possible consequences of this light pollution for rockfish ecology?

[4 pts] If the Pacific waters warm by several degrees, what are possible consequences for rockfish ecology?

[3 pts] Your book mentions that evaporative cooling is not a viable cooling method for plants in deserts. Why?

[5 pts] Butterflies, which are ectothermic and diurnal, are found from the tropical rainforest to the Arctic. They can elevate their body temperature by basking in sunlight. Draw a graph predicting how the percentage of time butterflies spend basking versus flying changes with latitude. Think about what the axes should be, make a prediction, and draw the predicted relationship. Label your axes carefully and describe your graph.

Explanation / Answer

1. Main factors influencing vision sensitivity is temperature and irradiation.

2. Light pollution caused upon organism is highly variable, ranging form beneficial to fatal. It can change the population frequency of the ecosystem.

3. At warmer temperatures the smaller rock fish grows well than the larger ones. Below 10 degrees the growth rate for larger fish is higher than the smaller one. This suggest that based on temperatures the fish moves to larger depths.

4. In CAM plants water saving is obtained by closed stomata during day time and open stomata in night time. They can tolerate extreme high temperatures in day time due to lack of evaporative cooling which impacts on the carbon di oxide accumulation.

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