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Understanding Ecosystems: Energy Flow, Nutrient Cycles, and Ecological Dynamics

This chapter delves into the intricacies of ecosystems, emphasizing energy flow through various trophic levels from producers to decomposers. It explores essential nutrient cycles, including carbon, nitrogen, phosphorus, and hydrologic cycles, detailing their processes and ecological significance. The significance of ecological pyramids in demonstrating biomass and energy reduction is discussed, along with the impact of external factors like sunlight and climate on ecosystem dynamics. Additionally, the chapter highlights the role of fire in nutrient release and ecosystem adaptation, offering insights into the balance of nature.

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Understanding Ecosystems: Energy Flow, Nutrient Cycles, and Ecological Dynamics

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  1. Chapter 53 Ecosystems and the Biosphere

  2. Energy flow through an ecosystem • Linear • Sun to producer to consumer to decomposer • Trophic relationship may be expressed as food chains or as food webs

  3. Energy flow through an ecosystem

  4. Ecological pyramids • Express the progressive reduction in numbers of organisms, biomass, and energy found in successive trophic levels

  5. Pyramids of biomass

  6. Gross primary productivity (GPP) • Rate at which photosynthesis captures energy • Net primary productivity (NPP) • Energy that remains after plants and other producers carry out cellular respiration

  7. NPP for selected ecosystems

  8. Carbon cycle • Carbon dioxide is the most important gas • Carbon enters plants, etc., as CO2 • Cellular respiration, combustion, and erosion of limestone return CO2 to the environment

  9. Carbon cycle

  10. Nitrogen cycle • Five steps • Nitrogen fixation • Nitrification • Assimilation • Ammonification • Denitrification

  11. Nitrogen cycle

  12. Phosphorus cycle • Phosphorus erodes from rock as inorganic phosphate • Animals obtain it from their diet

  13. Phosphorus cycle

  14. Hydrologic cycle • Renews the supply of water • Involves an exchange of water between the land, ocean, atmosphere, and organisms • Water enters the atmosphere by evaporation and transpiration • Water leaves the atmosphere as precipitation

  15. Hydrologic cycle

  16. Bottom-up processes • Availability of resources such as nutrient minerals controls the number of producers, which controls the number of herbivores, etc. • Top-down processes • An increase in top predators cascades down the food web

  17. Sunlight primary source of energy • Combination of Earth’s spherical shape and its axis tilt concentrate solar energy at the equator • Inclination of Earth’s axis primarily determines the seasons

  18. Seasonal changes in temperature

  19. Visible light and infrared radiation warm the surface and lower part of the atmosphere • Atmospheric heat produces air movement, which moderates the climate

  20. Atmospheric circulation

  21. Major surface ocean currents

  22. Coriolis effect • Tendency of moving air or water to be deflected • Right in the Northern Hemisphere • Left in the Southern Hemisphere

  23. Regional precipitation differences • Influenced by latitude, elevation, topography, vegetation, distance from large bodies of water, and location • Precipitation greatest where warm air passes over the ocean and then cools

  24. Rain shadow

  25. Effect of fire on certain ecosystems • Fire frees the nutrient minerals locked in organic matter, removes plant cover, and increases erosion • Many ecosystems, such as savanna, chaparral, grasslands, and certain forests, contain fire-adapted organisms

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