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 caterpillar Cellular 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 illustrated 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 small 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 Have important implications for the human population Eating meat
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