What are the physiological challenges an organism (such as a waterbug) might experience in a freshwater lake of the following conditions: depth of 200 m, water cold (approx 10 degrees celcius on surface), eutrophic, poor visibility, pH approx. 4?© BrainMass Inc. brainmass.com October 7, 2022, 9:43 am ad1c9bdddf
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What are the physiological challenges an organism (such as a waterbug) might experience in a freshwater lake of the following conditions: depth of 200 m, water cold (approx 10 degrees Celsius on surface), eutrophic, poor visibility, pH approx. 4?
The key to answering this question is to think about the stresses that these conditions would put on an aquatic insect. These stressors could be things that decrease the organism's ability to capture prey or escape from predators or things that alter the organism's homeostasis. Let's look at each condition separately:
Freshwater: When an organism lives in water osmosis and ion transfer is going to occur between the external environment and the organism's cells, until the two environments are isotonic (same concentration of water and ions inside and out). Most organisms' cells can only operate correctly and/or survive in a limited range of osmolarities. When exposed to external conditions not appropriate to their cells they can do a few things: 1. move, 2. osmoregulate (usually through ionic pumps), 3. become isotonic with the environment and deal with it. To address this question specifically you want to find out the osmotic requirements of the waterbug. It is likely that its cells are isotonic to freshwater and then there would be no osmotic and ionic stress, however if there was a larger runoff event that left the lake "saltier" than usual the animal would have to prevent water from leaving its cells.
Depth of 200 m: At this depth the waterbug is going to be exposed to increased pressure. What can pressure do to an organism on a cellular level? A good analogy is to think about scuba diving and decompression illness. When gases are exposed to high pressure they shrink and liquefy, but rapidly expand when the pressure is decreased (i.e. coming to the surface) when this happens gas bubbles can get trapped in the bloodstream and fatty tissue. How would this effect a waterbug? Do waterbugs live at this depth? If they only occupy the surface this is a mute point? However, animals coming from this depth and preying on the waterbug could be a problem.
Water temperature of 10 degrees C: For ectotherms temperature is everything!! Ectotherms do not regulate their own metabolic rate, which saves them lots of energy, but also makes them susceptible to changes in temperature. For an ectotherm cold temperatures equal a low metabolic rate. A low metabolic rate can be seen in decreased ventilation and heart rates. The concept of the temperature coefficient is important here. The temperature coefficient is a ratio of an activity or physiological process at one temperature compared to another temperature. In ectotherms in general a 10 degree C increase in temperature causes a 2-3 fold increase in the measured activity level or physiological process (for more information check out my library solution submission about the temperature coefficient). So at a low temperature, ventilation, heart rate, metabolism and activity levels would be low. How will this affect the waterbug?
Eutrophic: When a body of water is said to be eutrophic the available levels of oxygen in the water are very low. This is because the overabundant growth of algae (usually because of pollution) depletes oxygen levels, algae booms also decrease the amount of light getting to the depths of a lake. What effects would decreased oxygen levels (and light) have on a waterbug? Remember most aquatic insects breath dissolved oxygen in the water.
Poor visibility: The first question you need to answer is do waterbugs use vision as a primary sensory modality? If so poor visibility would have huge implications for all sorts of behaviors, for example predator-prey interactions. Are there any other senses the insect could rely on instead?
pH of 4: pH is the standard measure of the concentration of hydrogen ions. A pH of 4 is rather acidic (think acid rain or tomato juice). Bodies of freshwater with low pHs are often the result of bacterial decay, which causes a lot of carbon dioxide to be produced. This carbon dioxide is converted into carbonic acid in the water column and increases the acidity of the water. The pH of the lake is going to determine which organisms can survive there, for example most fish are limited to pH levels of 5-9. In addition low pH levels can aggravate pollution levels in a lake as sediments tend to release toxicants into the water in acidic conditions (source: http://www.scorecard.org/env-releases/def/cwa_cause_class_def.html). You need to find out what pH constraints aquatic insects have. Could a waterbug survive? If so a low pH could be advantageous as it may decrease fish predators. However, increased pollution in the water would have deleterious effects.
With this information you should be able to think through how each condition would effect an aquatic insect. Use your text book, class notes and reliable internet sources (i.e. university sites and government sites) to figure out how an insect specifically may be affected. Remember the main goal of the organism is to maintain internal balance (homeostasis), while minimizing energy use. Also being able to eat and escape predation are keys to survival. Besides surviving the ultimate goal is to reproduce and pass on genetic material. Think about how these conditions may effect reproduction.
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