Chapter 54 Review Questions

Chapter 54 ? Ecosystems and the Biosphere Ecosystems have two sets of interacting parts: the living, or biotic component and the nonliving, or abiotic component. Ecosystems are also the basic units of ecology and encompass all the interactions among organisms living together and interacting with their abiotic environment Energy Flow Through an Ecosystem: How does the flow of energy through an ecosystem obey the 2nd Law of Thermodynamics? How is energy transferred and where is it lost? (Fig 54-2) Trophic relationships within an ecosystem occur as one way trophic systems, but the interrelationship of those levels within the ecosystem is far more complicated ? discuss this statement with respect to the predator-prey relationship and feedback loops that are characteristic of any given ecosystem?s food web. In an ecological pyramid of numbers, each trophic level is reliant on the number of organisms at the successive level ? what does this mean, and why is it so important to successive trophic levels that the primary producers be in large numbers (supply) at the bottom level? How do ecologists use trophic pyramids that represent biomass and energy at each trophic level? How can they be used to assess the equilibrium of relationships between species in any given ecosystem? Productivity (Capturing energy during photosynthesis) (Fig 54-5) What is gross primary productivity; what does it measure and how does it differ to net primary productivity? How do we measure it ? per gm, per liter, each year, every day, per person, per population? When primary productivity increases, what happens to species richness and why? What if the environment is less productive? Vitousek suggests that human dominance could lead to extinction, even genetic impoverishment of certain species. Why does he say this? Biological Magnification (Bioaccumulation through the food chain) Fig 54-6 What is bioaccumulation? Give an example of how industrialization might be hurting the environment with respect to the use of such agents as nitrates, pesticides, insecticides? Carbon Cycle (Fig 54-7): matter moves in numerous cycles from one part of an ecosystem to another (biogeochemical cycles) ostensibly for reuse: Describe the carbon cycle; why is it vital to have a balanced CO2 output to the atmosphere? Name and describe the 5 steps in the nitrogen cycle (Fig 54-8). Why do the organisms that fix nitrogen need to be in an anaerobic environment (Fig 54-9)? What are the roles of the decomposers in the nitrogen cycle? How does nitrogen recycle back to the atmosphere? Which stage of the nitrogen cycle produces the greatest amount of nitrogen per year? Fertilizers and Fossil Fuels disturb the nitrogen cycle: Why is the use of nitrates in fertilizers for agricultural production so detrimental to the environment? What role does the burning of fossil fuels have in the alteration of soil chemistry? Phosphorus Cycle (Fig 54-10): Describe the phosphorus cycle; how is it used in the body biochemistry? Animals and plants differ in their use of phosphorus, how? why? When phosphorus washes out into the ocean it can get lost for centuries buried on the sea floor. How does it get released back for use by the ecosystem? Hydrologic Cycle (Fig 54-11) Describe the hydrological cycle. How does water get into and leave the atmosphere? What are aquifers and why is it ecologically important when they get depleted? What role do they play in the hydrological cycle Ecosystems (Fig 54-12) are regulated from the top down or from the bottom up What do we mean when we say this and which exerts more influence on an ecosystem. Why? Abiotic Factors: Solar energy (Fig 54-13): which part of the world is the solar energy most concentrated? Why does the energy/solar concentration vary across the earth?s geography? What causes these variations? How does the variation in solar energy affect ecosystems? In large measure, differences in temperature are due to variations in the amount of solar energy at different locations on earth ? and this drives the circulation of the atmosphere.(Fig 54-15) How does this relate to temperature changes during the seasons ? why? What is an equinox, and a solstice? What moderates the temperatures over the earth?s surface? Persistent prevailing winds blowing over the ocean are responsible for the production of mass movements of surface ocean water and the surface ocean currents ? how? How does the presence of an El Nino effect change the patterns of upwelling and why is that important to coastal communities? What is a rain shadow? (Fig 54-19) how does it form and how can this contribute to desertification and dust storms? How have these threatened certain populations like China and what have they done to try to help the situation? Why is it so important to world populations like China?s to reduce desertification? Besides as a result of rain shadows, where else would you expect to find desertification? Fire can be a valuable tool (Fig 54-20). Why are controlled burns (fires) ecologically beneficial and when might they not be? Name a couple of ecosystems where fires have resulted in fire-adaptation of the various species in the area PAGE PAGE 1