Ch 16 Ecosystems Vocabulary Words Habitat: the place where an organism or population of organisms lives Biodiversity: the number of species living in an ecosystem Primary productivity: the rate at which organic material is produced by photosynthesis Food web: complicated, interconnected group of food chains Energy pyramid: a diagram that shows the flow of energy from the sun through all trophic levels Water: of abiotic factors, this has the greatest influence on an ecosystems inhabitants Nitrogen: cycled throughout the living world primarily by bacteria Essays Why are both bacteria and fungi important organisms in an ecosystem? Without bacteria and fungi, dead organisms would not decompose, and the nutrients within their bodies would be unavailable to other living organisms. Describe the process of primary succession that occurred following the retreat of the glacier at Glacier Bay, Alaska. As the glacier retreated, seeds and spores of pioneer species, including lichens, and mosses, were carried in by wind and landed on exposed rock and gravel. After about ten years, alder seeds were able to take root. Alder roots can fix nitrogen, so willows and cotton wood were able to grow in the richer soil. Why are producers an essential component of an ecosystem? Producers capture from the sun all the energy for an ecosystem. Concepts to Know The ultimate source of energy for producers and all consumers is the sun. In a marine food web, there is far more total biomass in algae than in all the killer whales because it takes a massive amount of algae to support a food web with a killer whale at the top. In a meadow food chain, grass –mouse –snake –hawk is the correct path of energy flow. In 1866, the German biologist Ernst Haeckel named the study of how organisms fit in their environment, calling it ecology. When succession occurs in areas where previous growth has occurred, it is called secondary succession. A typical ecosystem might include large and small mammals, microscopic eukaryotes, and birds, trees, and flowers. Five kingdoms of life are represented by the most accurately descriptive statement about the biodiversity I one square kilometer of pine forest in the southeastern United States. In a living portion of the water cycle, water passes through plants and evaporates into the atmosphere through the process of transpiration. The carbon in the remains of organisms that lived long ago is released in the burning of fossil fuels. Nitrogen-fixed bacteria live in soil and plant roots. Humans cannot digest cellulose. Heat can be used to do mechanical work, but it is not useful in biological systems. Water is required in the greatest quantity in all ecosystems. Marine organisms use carbon dioxide dissolved in seawater to make calcium carbonate shells. Nitrogen-fixing bacteria, decomposers, and denitrifying bacteria all play a significant role in the nitrogen cycle.