Lecture 16

Lecture 16 - Ecosystems and Global Ecology Nutrient and...

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1 Ecosystems and Global Ecology • Nutrient and energy flows • Nutrient cycles • Global patterns of productivity • Human impacts Why is the ocean blue and the land green? Figure 54.15 Ecosystems • An ecosystem consists of all the organisms living in a community – As well as all the abiotic factors with which they interact • Ecosystems can range from a microcosm, such as an aquarium – To a large area such as a lake or forest Figure 54.1 • Ecosystem ecology emphasizes energy flow and chemical cycling • Ecosystem ecologists view ecosystems – As transformers of energy and processors of matter • This view de-emphasizes the particular species in an ecosystem in favor of studying nutrient cycles and energy flows • Energy flows through an ecosystem • Nutrients cycle within an ecosystem Figure 54.2 Microorganisms and other detritivores Detritus Primary producers Primary consumers Secondary consumers Tertiary consumers Heat Sun Key Chemical cycling Energy flow Trophic Relationships
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2 Trophic Efficiency and Ecological Pyramids • Trophic efficiency – Is the percentage of production transferred from one trophic level to the next – Usually ranges from 5% to 20% • The secondary production of an ecosystem – Is the amount of chemical energy in consumers’ food that is converted to their own new biomass during a given period of time Production Efficiency • When a caterpillar feeds on a plant leaf – Only about one-sixth of the energy in the leaf is used for secondary production Figure 54.10 Plant material eaten by caterpil ar Cel ular respiration Growth (new biomass) Feces 100 J 33 J 200 J 67 J Pyramids of Production This loss of energy with each transfer in a food chain – Can be represented by a pyramid of net production Figure 54.11 Tertiary consumers Secondary consumers Primary consumers Primary producers 1,000,000 J of sunlight 10 J 100 J 1,000 J 10,000 J • Pyramids of biomass – Show a sharp decrease at successively higher trophic levels Figure 54.12a (a) Most biomass pyramids show a sharp decrease in biomass at successively higher trophic levels, as il ustrated by data from a bog at Silver Springs, Florida. Trophic level Dry weight (g/m 2 ) Primary producers Tertiary consumers Secondary consumers Primary consumers 1.5 11 37 809 • Certain aquatic ecosystems Have inverted biomass pyramids Figire 54.12b Trophic level Primary producers (phytoplankton) Primary consumers (zooplankton) (b) In some aquatic ecosystems, such as the English Channel, a smal standing crop of primary producers (phytoplankton) supports a larger standing crop of primary consumers (zooplankton). Dry weight (g/m 2 ) 21 4 Pyramids of Numbers • A pyramid of numbers – Represents the number of individual organisms in each trophic level Figure 54.13 Trophic level Number of individual organisms Primary producers Tertiary consumers Secondary consumers Primary consumers 3 354,904 708,624 5,842,424
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3 • The dynamics of energy flow through ecosystems
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Lecture 16 - Ecosystems and Global Ecology Nutrient and...

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