Bio Assignment 5 PDF

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Hw assignment 5 from textbook, questions and answers included...

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Assignment 5 1. Which type of feedback loop is more common in nature, and which more commonly results from human action? How might the emergence of a positive feedback loop affect a system in homeostasis? Most systems in nature use a negative feedback loop. This is when an output results from a systems input that moves the system in the other direction. For example, as a food supply of a system expands for predators they will eat more prey and this will reduce the total number of prey. Human action like population growth is an example of a positive feedback loop. The more individuals there are the more offspring that can be produced. Another example is the glaciers melting due to global warming. Human actions are primarily responsible for this. Homeostasis is the tendency of a system to maintain constant or stable internal conditions. A positive feedback loop like glaciers melting could affect homeostasis of the oceanic levels could be detrimental. 2. Describe how hypoxic conditions can develop in ecosystems such as the Chesapeake Bay. The hypoxic conditions can develop in an ecosystem like Chesapeake Bay. This may occur because of the excessive growth of phytoplankton or algae in the Bay. It was observed that the oyster species of this Bay is being decreasing in amounts. The oysters can filter the excessive phytoplankton from the water surface thus, less amounts of oyster favors excessive growth of phytoplankton. The runoff of synthetic nitrogen fertilizers from the fields enriches the water body with excessive amounts of nutrients. These nutrients favor the excessive growth of phytoplankton that decreases the amounts of free water for binding oxygen. Thus, the oxygen depletion occurs due to over nutrition of the water body. Hence, in this way the hypoxic conditions may develop in Chesapeake Bay. 3. What is the difference between an ecosystem and a community? An ecosystem is a system that consists of all organisms including nonliving entities and how they interact in a particular area at the same time. A community is the associations of populations of two or more different species that occupy the same geographical area over time. A community does not directly involve living entities.

4. Describe the typical movement of energy through an ecosystem. Now describe the typical movement of matter through an ecosystem. First light energy from the sun fuels photosynthesis for the producers and this starts the transfer of energy of chemical energy among trophic levels and detritus. The energy exits the system through respiration in the form of heat through the different trophic levels. Notice primary consumers feed on producers and energy is exchanged here all the way up to the tertiary consumers with extra energy released as heat. Matter moving through an ecosystem, detritus takes in tertiary, secondary, primary consumers and producers. Producers also feed on detritus and gives food to primary consumers. Primary consumers give food to secondary consumers. Finally, secondary consumers give food to tertiary consumers. Also detritivores and decomposers exchange matter with detritus and also give food to secondary consumers. 5. Explain net primary productivity. Name one ecosystem with high net primary productivity and one with low net primary productivity. Net primary productivity is the rate the productivity occurs and plants convert solar energy to biomass rapidly is an example of this. Fresh wetlands, algal beds and coral reefs tend to have the highest net primary productivities. Areas like desserts, tundra and open ocean have the least net primary productivity. 6. Why are patches in a landscape mosaic often important to people who are interested in conserving populations of rare animals? Scientists who study the loss, protection and restoration of biodiversity have a major concern with fragmentation of habitat into small and isolate patches, which usually occurs with the human development pressures. In turn, many scientists create corridors of habitat to link patches to allow animals to move on among them to maintain biodiversity and protect the extinction of certain animals. 7. What is the difference between evaporation and transpiration? Give examples of how the water cycle interacts with the carbon, phosphorus, and nitrogen cycles. Evaporation is the conversation of a liquid to a gaseous form. Warm temperatures and strong winds affect the rate of evaporation. Transpiration is the release of water vapor by plants through their leaves. Both act as natural processes of distillation and create pure water by filtering out minerals. The water cycle interacts with carbon, nitrogen and phosphorus cycles. First the carbon cycle shows the route that carbon atoms take through

the environment and water is used for the plants to make glucose and also give off water via transportation. The nitrogen cycle occurs and must be fixed in order for specialized bacteria or lightning before plants can use it. Once this is done water can be used for photosynthesis. Finally phosphorus cycle is a key nutrient to plant growth and helps facilitate photosynthesis, which requires water. 8. What role does each of the following play in the carbon cycle?  Cars in the ocean cycle put out carbon dioxide into the atmosphere. This is taken in by plants in the ocean and in forests in order to perform photosynthesis.  Photosynthesis takes carbon dioxide and water and sunlight to create glucose, water and oxygen  The oceans take in carbon dioxide and can either be used by photosynthetic organisms or deposited into the sedimentary rock below and eventually turned into fossils over time.  Earth’s crust contains fossil fuels like coal, oil and natural gas can be converted into energy and carbon dioxide. Also it contains soil and soil biota, which release carbon dioxide into the atmosphere. 9. Distinguish the function performed by nitrogen-fixing bacteria from that performed by denitrifying bacteria. Nitrogen-fixing bacteria must take nitrogen gas N2 and convert it into NH3 using hydrogen. The bacteria live in a mutualistic relationship with many types of plants. First by nitrification specialized bacteria take ammonium ions and first convert them into nitrite ions. Then these nitrite ions NO3-. Plants can take up these ions. Denitrifying bacteria takes these nitrates in the soil or water to gaseous nitrogen via a multistep process. This puts nitrogen back into the atmosphere. 10. How has human activity altered the carbon cycle? The phosphorus cycle? The nitrogen cycle? What environmental problems have arisen from these changes? For the carbon cycle, humans have shifted carbon from lithosphere to atmosphere by mining fossil fuels. Removing carbon from underground over time this is releasing carbon dioxide into the atmosphere and levels that are beyond the natural amount. In addition cutting down forests have also increased carbon dioxide levels in the atmosphere. Humans have influenced the nitrogen cycle. The Haber-Bosch process has enabled people to overcome the limits on the productivity long imposed by the nitrogen scarcity in nature and increasing agriculture

and farming. This alters the nitrogen cycles balance and our species is fixing at least as much nitrogen as is being fixed naturally. Finally the phosphorus cycle by mining rocks that contains phosphorus. Also waste water discharge in high in phosphorus and this runs into waterways and increases algal growth which can lead to murkier waters and alter the aquatic ecosystem....