© 2012 john wiley & sons, inc. all rights reserved. overview of chapter 3 energy &...
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© 2012 John Wiley & Sons, Inc. All rights reserved.
Overview of Chapter 3
• Energy & Ecosystems– Photosynthesis and Cellular Respiration
• Flow of Energy Through Ecosystems– Producers, Consumers & Decomposers– Ecological Pyramid– Ecosystem Productivity
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy• The ability or capacity to do work
– Chemical, – Thermal, – Mechanical, – Nuclear, Electrical, and – Radiant/Solar BASIS OF MOST ECOSYSTEMS
• Stored energy = potential energy• Energy of motion = kinetic energy
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy Rules (laws of thermodynamics)
– Energy cannot be created or destroyed; it can be changed/converted from one form to another
• 1st law of thermodynamics• Producers capture energy of sun• Consumers must eat other living things (or their waste)
– When energy is converted form one form to another, some of it is degraded to heat
• Second Law of Thermodynamics• Energy is lost as it passes from one trophic level to next
© 2012 John Wiley & Sons, Inc. All rights reserved.
Trophic level• Based on main source of nutrition/energy
– Producers (fix energy from sun)– Primary consumers (herbivores)– Secondary consumers (predators or detrivores/decomposers)– Tertiary consumers (predators or detrivores/decomposers)– Quartinary consumers (predators or detrivores/decomposers)
© 2012 John Wiley & Sons, Inc. All rights reserved.
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecosystem Productivity• Gross Primary Productivity (GPP)
– Total amount of energy plants capture by photosynthesis• Net Primary Productivity (NPP)
– Energy captured by photosynthesis minus energy “spent” during cellular respiration
• GPP (photosyn) – cellular respiration = NPP– Plant growth per unit area per time– Only NPP is available as food to higher trophic levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Variation in NPP by Ecosystem
© 2012 John Wiley & Sons, Inc. All rights reserved.
Ecosystem Productivity• Aquatic Ecosystems:
• Nutrients--#1• Nitrogen & phosphorus
• Limited by light penetration--#2
• Terrestrial ecosystems• Temperature and water availability -- #1• Nutrients -- #2
• Nitrogen & phosphorus
© 2012 John Wiley & Sons, Inc. All rights reserved.
Energy Flow Through Ecosystems
© 2012 John Wiley & Sons, Inc. All rights reserved.
Food Chains
© 2012 John Wiley & Sons, Inc. All rights reserved.
Food Web
© 2012 John Wiley & Sons, Inc. All rights reserved.
Food Web
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Energy• Amount of energy at each trophic level
– (and how much is transferred to the next level)
Most energy is lost between trophic levels Limits number
of levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Average 10% efficiency(ranges from 5-20%)
© 2012 John Wiley & Sons, Inc. All rights reserved.
© 2012 John Wiley & Sons, Inc. All rights reserved.
Number of tropic levels is limited by amount of energy available in ecosystem (i.e., productivity)
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Biomass• The amount of living material (biomass) at each
level 90% reduction in
biomass between trophic levels Why?
© 2012 John Wiley & Sons, Inc. All rights reserved.
© 2012 John Wiley & Sons, Inc. All rights reserved.
Pyramid of Numbers
• Number of individuals at each trophic level Fewer organisms
occupy each successive level
Does not indicate: biomass of organisms
at each level amount of energy
transferred between levels
© 2012 John Wiley & Sons, Inc. All rights reserved.
Controls on trophic levels
• Bottom up:– Trophic levels are limited by nutrient availability and
biomass of next lower level– Nutrientproducers1 consumers (herbivores) 2 consumers (predators)…
• Top Down (trophic cascade)– Consumption by higher levels limits next lower level– Predation herbivores producers
© 2012 John Wiley & Sons, Inc. All rights reserved.
Bioaccumulation• The buildup of a persistent toxic substance in an
organism’s body, often in fatty tissues – Synthetic chemical do not metabolize well– They remain in the body for extended periods of time
• DDT• Lead• Mercury• PBDE (flame retardants)
• Dioxins• PCB• Phthalates• BPA
© 2012 John Wiley & Sons, Inc. All rights reserved.
Biomagnification• The increased
concentration of toxic chemicals in the tissues of organisms that are at higher levels in food webs
• Diagram (right) is example of biomagnification of DDT
• LD50of 113 mg/kg in rats
© 2012 John Wiley & Sons, Inc. All rights reserved.
Effect of DDT on Bald Eagles
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