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Ecology Section Study Questions

Ecology Section Study Questions - 3 Stratification in lakes...

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Questions 1. What is the difference between autocthonous and allochthonous forms of food, and what are examples of each in streams? 2. When do dead end adaptations in organisms occur? 3. Explain water stratification and seasonal turnover in lakes. Answers 1. Autochonous sources of food are energy within the habitat, such as primary producers like diatoms or algae that live in the stream. Allochthonous forms of food come from energy outside the system, such as leaves that fall into the stream from trees growing along the bank. 2. Dead end adaptations occur in organisms that inhabit ponds or lakes, because they will tend to fill and eventually disappear, leaving the organism without a habitat. Organisms in rivers will not have dead end adaptations because streams and rivers persist in geological time.
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Unformatted text preview: 3. Stratification in lakes occurs when there are layers of water at different temperatures. Seasonal turnover is caused by the fact that the density of water is heaviest at 4 degrees C. In the winter, the water is stratified, with the coldest water at the bottom. In the spring, the top of the water heats up until it reaches 4 degrees. This makes the water at the top denser than the water at the bottom, causing the water to mix. In the summer, the top of the water heats up to greater than 4 degrees, and the water is stratified again, with the coldest water at the bottom. In the fall, the water at the top cools until it reaches 4 degrees, which leads to mixing of the water again due to the density of water at 4 degrees....
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