Question

in higher latitudes where lakes freeze over in winter, how do cool fall temperatures help fish make it through the winter?
the cooling water slows fish metabolisms down and allows them to go into hibernation in winter.
water from the bottom of the lake raises and provides oxygen to the cooler waters on the surface.
cool water at the surface traps nutrients deep in the lake to provide food during the winter.
the water in contact with the air sinks and mixes with the less oxygenated water in the deeper levels.
question 16(multiple choice worth 4 points)
(04.03 hc)
for the past 20 years, the population of the invasive asian carp in the mississippi river has skyrocketed while populations of native species have declined. which of the following conclusions provides the best explanation for this phenomenon?
the carp out - competed the native species for food and space.
the food sources preferred by the carp increased.
the native species migrated to new areas, while the carp remained.
the native species contracted a virus that the carp were immune to.

Explanation:

For the first question:

• Fish do not hibernate in the way described in the first option.
• Water from the bottom does not raise in the way described in the second option.
• Cool water at the surface does not trap nutrients in the way described in the third option.
• In fall, as water cools, it becomes denser and sinks. This mixing (the water in contact with the air sinks and mixes with the less - oxygenated water in the deeper levels) helps to oxygenate the deeper water which is important for fish survival in winter.

For the second question:

• If the carp out - competed native species for food and space (a common outcome of invasive species), it would lead to an increase in carp population and a decline in native species.
• If only the food sources preferred by carp increased, it does not fully explain the decline of native species.
• If native species migrated, it is not clear why the carp population would skyrocket in the same area.
• There is no indication in the problem statement about a virus.

Answer:

First question: The water in contact with the air sinks and mixes with the less oxygenated water in the deeper levels.
Second question: The carp out - competed the native species for food and space.