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

(a)

The low-light sensitivity of individual retinae is inversely depent on temperature decreasing 10 fold with a 100C increase in temperature.

In all four species temperature had a similar effect on sensitivity, but the absolute sensitivity levels are different.

Based on the sensitivity measurements (from the figure) we can divide the four species into 2 groups.

1. Kelp and olive rockfish form a high sensitivity group capable of responding to light levels approximately 50 fold lower than blue and black rockfish, so kelp and olive fishes are nocturnal.

(c)

From the fig. we can say that, for all four species the threshold sensitivity significantly affect by temperature, so that habitat utilization will differ at different environmmental temperatures. So If the Pacific waters warm by several degrees, the sensitivity will decrease by the same degrees and hence affects the rockfish ecology.

(d)

The evaporative cooling is not a viable cooling method for plants in deserts, because evaporation process in the plant increases the temperature of the plants. [already we know that in desert the temperature is very high]. So the evaporation process is critacal for the plants in desert.

(e)

Butterflies have overlapping anterior and posterior wings.

Basking should be most extensive among butterflies in cooler climates at higher latitudes. Butterflies should also be more likely to bask in early morning, as they transition from inactive night-time to active day-time modes, and to avoid basking midday, when the risk of overheating would increase.

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