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What are Ecosystems? of all of the communities within a defined area, along with their nonliving environment. study of ecosystems focuses on the flow of energy and nutrients pathways of energy and nutrients to understand the factors shape interactions within communities, and between communities and the nonliving environment How do Energy and Nutrients move through ecosystems? Nutrients are atoms and molecules that organisms obtain from their living or nonliving environment and that are required for survival constantly cycle and recycle within and among ecosystems change in form and distribution Energy moves in a one-way flow through communities within ecosystems continuously replenished used and transformed in the chemical reactions that power life ultimately converted to heat that radiates back into space HEAT producers Energy from sunlight HEAT NUTRIENTS primary consumers detritus feeders and decomposers HEAT solar energy heat energy higher-level consumers energy stored in chemical bonds nutrients HEAT Fig. 29-1 Energy Flow Through Ecosystems Energy enters ecosystems mainly through photosynthesis energy stored in the chemical bonds of sugar molecules produce food using nonliving nutrients and sunlight autotrophs (or producers) Energy is captured from sunlight Carbon dioxide is absorbed from the air photosynthesis Water is absorbed from soil, used in photosynthesis, and stored in cells Oxygen is released Sugar is synthesized and used in plant tissues plant tissues, growth Inorganic mineral nutrients (nitrate, phosphate) are absorbed from soil and used in plant tissues Producersenergy from sunlight CO2 O2 photosynthesis sugar H2O plant tissues other nutrients Fig. 28-1 Energy Flow Through Ecosystems An ecosystem’s contribution to Earth’s productivity depends upon both the ecosystem’s net primary productivity per unit area and its prevalence. open ocean (125) tundra continental (140) shelf (360) estuary (1,500) tropical rain forest (2,200) coniferous forest (800) temperate deciduous forest (1,200) grassland (600) desert (90) Energy Flow Through Ecosystems Energy passes from one trophic level to another. producers (autotrophs) first trophic level primary consumers (herbivores) second trophic level feed on producers secondary and tertiary consumers third and fourth trophic levels meat-eating predators energy from sunlight heat producers heat Mg O P Ca S H2O H N primary consumers nutrients heat detritus feeders and decomposers higher-level consumers solar energy heat energy energy stored in chemical bonds nutrients heat Fig. 28-2 Energy Flow Through Ecosystems TERTIARY CONSUMER (4th trophic level) PRIMARY CONSUMER (2nd trophic level) SECONDARY CONSUMER (3rd trophic level) PRODUCER (1st trophic level) (a) A simple terrestrial food chain Energy Flow Through Ecosystems SECONDARY CONSUMER (3rd trophic level) Phytoplankton PRODUCER (1st trophic level) Zooplankton PRIMARY CONSUMER (2nd trophic level) TERTIARY CONSUMER (4th trophic level) (b) A simple marine food chain Energy Pyramid for a Grassland Fig. 28-6 biological magnification Because of the inefficiency of energy transfer, certain persistent toxic chemicals become increasingly concentrated in the bodies of animals that occupy increasingly higher trophic levels by a process called Mercury taken up by producers can be highly concentrated in carnivores such as swordfish, and are a health hazard to humans as a result Nutrients Cycles nutrients do not flow down onto Earth in a steady stream from above Macronutrients are required by organisms in large amounts and include water, carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, and calcium Micronutrients, including zinc, molybdenum, iron, selenium, and iodine are required in trace amounts Nutrient cycles (biogeochemical cycles) describe the pathways nutrients follow between communities and the nonliving portions of ecosystems Reservoirs are sources and storage sites of nutrients Major reservoirs are usually in the abiotic environment Hydrologic (water) cycle Water is essential for all terrestrial communities because other nutrients must be dissolved in it before they can be used major reservoir in the oceans travels through the atmosphere, to reservoirs in freshwater lakes, rivers, and groundwater, and then back again to the oceans The oceans contain more than 97% of Earth’s water Solar energy evaporates water, and it comes back to Earth as precipitation The Hydrologic Cycle reservoirs processes water vapor in the atmosphere precipitation over land precipitation over the ocean evaporation from land and transpiration from plants evaporation from the ocean evaporation from lakes and rivers lakes and rivers seepage into soil runoff from rivers and land water in the ocean extraction for agriculture groundwater, including aquifers Fig. 28-7 carbon cycle Chains of carbon atoms form the framework of all organic molecules, the building blocks of life major reservoirs in the atmosphere and oceans Moves through producers and into the bodies of consumers and detritus feeders, and then back to its reservoirs reservoirs CO2 in the atmosphere The Carbon Cycle processes trophic levels burning fossil fuels CO2 dissolved in the ocean respiration fire photosynthesis producers consumers detritus feeders and decomposers decomposition fossil fuels (coal, oil, natural gas) Fig. 28-8 nitrogen cycle Nitrogen is a crucial component of proteins, many vitamins, nucleotides (such as ATP), and nucleic acids major reservoir in the atmosphere reservoirs of ammonia and nitrate in the soil and water, through producers and into consumers and detritus feeders, and then back again to its reservoirs nitrogen gas (N2) makes up 78% of the atmosphere, this form of nitrogen cannot be utilized by plants Plants utilize nitrate (NO3–) or ammonia (NH3) as their nitrogen source N2 is converted to ammonia by specific bacteria during a process called nitrogen fixation Denitrifying bacteria break down nitrate, releasing N2 back to the atmosphere The Nitrogen Cycle reservoirs processes trophic levels N2 in the atmosphere burning fossil fuels lightning application of manufactured fertilizer consumers ammonia and nitrates in water producers uptake by producers detritus feeders and decomposers nitrogen-fixing bacteria in soil and legume roots decomposition denitrifying bacteria ammonia and nitrates in soil Fig. 28-9 phosphorus cycle Phosphorus is a crucial component of ATP and NADP, nucleic acids, and phospholipids of cell membranes; it is also a major component of vertebrate teeth and bones major reservoir in rock bound to oxygen as phosphate moves from phosphate-rich rocks to reservoirs of phosphate in soil and water, through producers and into consumers and detritus feeders, and then back to its reservoirs reservoirs The Phosphorus Cycle phosphate in rock processes trophic levels geological uplift application of manufactured fertilizer runoff from rivers consumers producers detritus feeders and decomposers decomposition runoff from fertilized fields uptake by producers phosphate in water phosphate in soil phosphate in sediment formation of phosphate-containing rock Fig. 28-10 Human Disruption Many of the environmental problems that plague modern society are caused by human disruption of biogeochemical cycles. industrial processes transfer toxic substances such as lead, arsenic, mercury, uranium, and oil into the environment addition of herbicides and pesticides to lawns and shrubs farm fields, gardens, and suburban lawns, ammonia, nitrate, and phosphate are supplied by chemical fertilizers eutrophication – adding nutrients to water combustion of fossil fuels releases sulfur dioxide and nitrogen oxides into the atmosphere acid rain Carbon emmisions Fig. 28-11 Acid Deposition is Corrosive Fig. 28-12 Acid Deposition Can Destroy Forests Fig. 28-13 Greenhouse Gases and Global Warming 5 Most heat is radiated back into space Sun 1 Sunlight energy enters the atmosphere 6 Some atmospheric heat is retained by greenhouse gases 2 Some energy is reflected back into space volcanoes 3 Most sunlight strikes Earth’s surface and is converted into heat vehicle emissions 4 Heat is radiated back into the atmosphere agricultural activities forest fires power plants and factories homes and buildings Fig. 28-14 Global Warming Parallels Atmospheric CO2 Increases Fig. 28-15 Glaciers Are Melting Fig. 28-17