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review questions 1-35

review questions 1-35 - 1 Humans change the hydraulic cycle...

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1) Humans change the hydraulic cycle in freshwater systems by increasing the amounts of phosphorus levels through high use of detergents, fertilizers, agriculture and development. This exposes new soil and rocks and makes the water less clear. It also limits the amount of nitrogen the system receives. This affects the species by increasing primary productivity and making it difficult for the primary consumers to control their prey. It affects humans because it causes species at the bottom of the floor to die which is economically harmful to many fisheries. No. changes in the hydraulic cycle have to do with diverting water. I gave examples from the Sacramento River, Mono Lake and the Everglades. See lecture notes from Freshwater Ecology to answer this question (April9th) 2) Three important abiotic factors in freshwater ecosystems are the sun, dissolved chemicals, and sediment. In the bottom up control the dissolved nutrients are key. They decide how many nutrients are available for primary producers which decides what consumers will be found in that ecosystem. Perfect, Although I think saying sunlight available for photosynthesis for primary producers would be more correct. You could have also said temperature or movement (lakes vs. streams) 3) Two major sources of phosphorus in freshwater systems are newly disturbed soil and rocks and from human inputs such as agricultural runoff. Three human activities that cause too much phosphorus to be released are washing clothes with detergents high in phosphorus, lawn care with fertilizers also potent with the chemical and constructions exposing soils to water. 4) Two major contributors to the nutrient pollution causing the dead zone are fertilizer runoff which increases nitrogen levels and runoff from animal waste, urban runoff and sewage pollution. We could reduce or eliminate the Dead Zone by planting perennial crops which uses less fertilizer and we could improve the storage areas that hold fertilizer. Another thing we could do is restore wetlands to the area. The major impact of the Dead Zone on aquatic ecosystems is that it is killing all the organisms on the bottom of the floor (benthic organisms) and it also destroys fisheries. 5) A shifting baseline is when you count the amount of a population based on a certain time period. For example biologists may think a species at equilibrium of 20,000 if they look back 20 years but when they look back 40 years or more they may notice that they used to be stable at a population size of 40,000. In other words it is the process of basing a species original state or natural state at a different or certain time. This is not a good definition. Consult slides on shifting baselines, and also the slides on marine systems. A baseline is a standard, so a standard for what? How does it shift? Why?
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6) It is important to know the history of an ecosystem to correctly diagnose an ecological problem because without it people may only solve half the problem which is not enough.Or may not solve the problem at all because
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review questions 1-35 - 1 Humans change the hydraulic cycle...

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