During an ecology field trip to a lake, your professor asks you to take temperature readings at various depths and record your data. At 5 meters, you note a temperature of 25°C and at 10 meters you record a temperature of 10°C. Readings at 20 meters and below stay fairly consistent around 8°C. The temperature readings of 25°C, 10°C, and 8°C represent the:
A. epilimnion,thermocline, and hypolimnion.
B. epilimnion,hypolimnion, and thermocline.
C. hypolimnion, epilimnion,and thermocline.
D. hypolimnion, thermocline,andepilimnion.
E. thermocline,epilimnion, and hypolimnion.
Clarify Question
· What is the key concept addressed by the question?
· What type of thinking is required?
Gather Content
· What do you already know about thermal stratification?
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
A. epilimnion,thermocline, and hypolimnion.
Clarify Question
· What is the key concept addressed by the question?
o This question addresses thermal stratification.
· What type of thinking is required?
o This question is asking you to take what you already know and apply it to this unfamiliar situation.
Gather Content
· What do you already know about thermal stratification?
o Thermal stratification is characteristic of many lakes and large ponds. In summer, water warmed by the Sun forms a layer known as the epilimnion at the surface—because warm water is less dense than cold water and tends to float on top. Colder, denser water, called the hypolimnion, lies below. Between the warm and cold layers is a transitional layer, the thermocline. Although here we are focusing on freshwater, a similar thermal structuring of the water column occurs also in many parts of the ocean.
o In a lake, thermal stratification tends to cut off the oxygen supply to the bottom waters; a consequence of the stratification is that the upper waters that receive oxygen do not mix with the bottom waters. The concentration of oxygen at the bottom may then gradually decline over time as the organisms living there use oxygen faster than it is replaced. If the rate of oxygen use is high, the bottom waters may run out of oxygen and become oxygen-free be-fore summer is over. Oxygen-free conditions, if they occur, kill most animals in a lake.
Choose Answer
· Given what you now know, what information and/or problem solving approach is most likely to produce the correct answer?
o The warmest reading at the top represents the top, warm layer – the epilimnion.
o The middle reading represents the middle, transitional layer – the thermocline.
o The coldest reading represents the bottom, cold layer – the hypolimnion.
Reflect on Process
· Did your problem-solving process lead you to the correct answer? If not, where did the process break down or lead you astray? How can you revise your approach to produce a more desirable result?
o The question required you to take what you already know and apply it to this unfamiliar situation.
o Did you recognize that lakes become stratified during the summer, with a warm epilimnion on top, a cold hypolimnion on the bottom, and a thermocline between?
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