TAILIEUCHUNG - Lecture Biology: Chapter 55 - Niel Campbell, Jane Reece

Chapter 55 - Ecosystems, this chapter explain how the first and second laws of thermodynamics apply to ecosystems; define and compare gross primary production, net primary production, and standing crop; explain why energy flows but nutrients cycle within an ecosystem; explain what factors may limit primary production in aquatic ecosystems;. | Chapter 55 Ecosystems Overview: Observing Ecosystems An ecosystem consists of all the organisms living in a community, as well as the abiotic factors with which they interact Ecosystems range from a microcosm, such as an aquarium, to a large area such as a lake or forest Regardless of an ecosystem’s size, its dynamics involve two main processes: energy flow and chemical cycling Energy flows through ecosystems while matter cycles within them Fig. 55-1 Figure What makes this ecosystem dynamic? Fig. 55-2 Figure A cave pool Concept : Physical laws govern energy flow and chemical cycling in ecosystems Ecologists study the transformations of energy and matter within their system Conservation of Energy Laws of physics and chemistry apply to ecosystems, particularly energy flow The first law of thermodynamics states that energy cannot be created or destroyed, only transformed Energy enters an ecosystem as solar radiation, is conserved, and is lost from organisms as heat The second law of thermodynamics states that every exchange of energy increases the entropy of the universe In an ecosystem, energy conversions are not completely efficient, and some energy is always lost as heat Conservation of Mass The law of conservation of mass states that matter cannot be created or destroyed Chemical elements are continually recycled within ecosystems In a forest ecosystem, most nutrients enter as dust or solutes in rain and are carried away in water Ecosystems are open systems, absorbing energy and mass and releasing heat and waste products Energy, Mass, and Trophic Levels Autotrophs build molecules themselves using photosynthesis or chemosynthesis as an energy source; heterotrophs depend on the biosynthetic output of other organisms Energy and nutrients pass from primary producers (autotrophs) to primary consumers (herbivores) to secondary consumers (carnivores) to tertiary consumers (carnivores that feed on other carnivores) .

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