Bryant University
Energy Management Strategies (Sci355)
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Week 1-2: Energy Systems: An Overview
  Energy in Nature
Production/Consumption in Ecosystems
Photosynthesis - plants/algae can capture sunlight, converting light to chemical energy
Dependent on pigments like chlorophyll
Production of carbohydrates
Respiration - ability of living cells to convert carbohydrates to ATP units
Production/Consumption in Ecosystems (continued)
Formula for Photosysnthesis
(chlorophyll & sunlight)
CO2 + H20 ----------> C6H1206  +  02
Formula for Respiration
C6H1206  +  02 ----------> CO2 + H20 + ATP
World Energy Budget
Annual Insolation (equivalent to 15,000 times the 1990 world energy supply)
30% reflected back to space (albedo)
50% Absorbed, converted to heat and reradiated
20% creates wind, powers water cycle and drives photosynthesis
Trophic Dynamics
Ability to photosynthesize
Algae and plants (some bacteria)
Usually small in size; exist in large numbers
Base of food chains
Responsible for primary productivity
Generate carbohydrates for respiration
Primary Consumers (Herbivores)
Organisms that consume plants or algae
Usually small in size
Examples: Zooplankton, snails, cows, horses, insects, zebras, ciliated protozoa
Contribute to secondary productivity
Secondary Consumers (Carnivores)
Consume herbivores
Usually larger in size
Examples: wolves, lions, sharks, reptiles, hawks, shrews, spiders, amoebae
Many layers of carnivores in an ecosystem
Contribute to secondary productivity
May act as herbivores or carnivores
Varied feeding habits (versatile consumers)
Include humans, pigs and many insects
Contributed to secondary productivity
Detrivores (consume decaying material)
Very important to detrital food chains; recycle nutrients
Found in large numbers in forest litter, marine and aquatic benthos
Examples: fungi, some invertebrates, bacteria, protozoa
Grazing vs. Detrital Food Chains
Grazing food chains based on producers (photosynthesis)
Detrital food chains based on detrivores (breaking down detritus and wastes)
Grazing food chains important in marine and aquatic ecosystems
Detrital chains important in forest litter
Trophic Pyramid
Show feeding patterns
Smaller to larger size
Many to fewer in numbers
Levels vary from one ecosystem to another
Ecosystem Energetics
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Gaytha A. Langlois, Ph.D., 1999
Bryant University, Smithfield, RI, USA
Last Updated: August 2006