Transcript INTRODUCTION

Energy and Nutrient Relations
Chapter 6
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Outline
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Energy Sources
Solar-Powered Biosphere
Photosynthetic Pathways
Using Organic Molecules
Chemical Composition and Nutrient
Requirements
Using Inorganic Molecules
Energy Limitation
Food Density and Animal Functional
Response
Optimal Foraging Theory
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Energy Sources
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Organisms can be classified by trophic levels.
 Autotrophs use inorganic sources of carbon
and energy.
 Photosynthetic: Use CO2 as carbon
source, and sunlight as energy.
 Chemosynthetic: Use inorganic
molecules as source of carbon and
energy.
 Heterotrophs use organic molecules as
sources of carbon and energy.
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Fig. 6.2
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Solar - Powered Biosphere
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Light propagates through space as a wave.
 Photon: Particle of light bears energy.
 Infrared (IR) Long-wavelength, low energy.
 Interacts with matter, increasing motion.
 Ultraviolet (UV) Short wavelength, high
energy.
 Can destroy biological machinery.
 Photosynthetically Active Radiation (PAR)
 Between two extremes (visible light).
 Wave length between about 400 and 700 nm
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Solar - Powered Biosphere
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PAR
 Quantified as photon flux density.
 Number of photons striking square meter
surface each second.
 Expressed in µmole, where 1 mole is
Avogadro's number of photons 6.023X10²³.
Chlorophyll absorbs light as photons.
 Landscapes, water, and organisms can all
change the amount and quality of light
reaching an area.
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Photosynthetically Active Radiation
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Photosynthetic Pathways
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C3 Photosynthesis
 Used by most plants and algae.
 CO2 + ribulose bisphosphate (5 carbon
sugar) = phosphoglyceric acid (3 carbon
acid)
 To fix carbon, plants must open stomata
to let in CO2 .
 Water gradient may allow water to
escape.
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C3 Photosynthesis
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Photosynthetic Pathways
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C4 Photosynthesis
 Reduce internal CO2 concentrations.
 Increases rate of CO2 diffusion inward.
 Need fewer stomata open.
 Conserving water
 Acids produced during carbon fixation
diffuse to specialized cells surrounding
bundle sheath.
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C4 Photosynthesis
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Photosynthetic Pathways
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CAM Photosynthesis
 (Crassulacean Acid Metabolism)
 Limited to succulent plants in arid and
semi-arid environments.
 Carbon fixation takes place at night.
 Reduced water loss.
 Low rates of photosynthesis.
 Extremely high rates of water use
efficiency.
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CAM Photosynthesis
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Using Organic Molecules
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Three Feeding Methods of Heterotrophs:
 Herbivores: Feed on plants.
 Carnivores: Feed on animal flesh.
 Detritivores: Feed on non-living organic
matter.
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Chemical Composition
and Nutrient Requirements
Five elements make up 93-97% of biomass
of plants, animals, fungi and bacteria:
 Carbon
 Oxygen
 Hydrogen
 Nitrogen
 Phosphorus
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Fig. 6.7
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Essential Plant Nutrients
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Potassium
Calcium
Magnesium
Sulfur
Chlorine
Iron
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Manganese
Boron
Zinc
Copper
Molybdenum
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Fig. 6.9
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Fig. 6.10
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Herbivores
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Substantial nutritional chemistry problems.
 Low nitrogen concentrations.
Must overcome plant physical and chemical
defenses.
 Physical
 Cellulose; lignin; silica
 Chemical
 Toxins
 Digestion Reducing Compounds
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Fig. 6.11
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Detritivores
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Consume food rich in carbon and energy,
but poor in nitrogen.
 Dead leaves may have half nitrogen
content of living leaves.
Fresh detritus may still have considerable
chemical defenses present.
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Fig. 6.12
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Carnivores
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Consume nutritionally-rich prey.
 Cannot choose prey at will.
 Prey Defenses:
 Aposomatic Coloring - Warning colors.
 Mullerian mimicry: Comimicry among
several species of noxious organisms.
 Batesian mimicry: Harmless species
mimic noxious species.
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Fig. 6.13
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Carnivores
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Predators are usually selection agents for
refined prey defense.
 Usually eliminate more conspicuous
members of a population (less adaptive).
 Must catch and subdue prey - size
selection. (mountain lion Puma concolor)
Predator and prey species are engaged in a
co-evolutionary race.
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Fig. 6.14
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Fig. 6.15
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Fig. 6.16
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Using Inorganic Molecules
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1977 - Organisms found living on sea floor.
 Near nutrients discharged from volcanic
activity through oceanic rift.
 Autotrophs depend on chemosynthetic
bacteria.
 Free-living forms.
 Living within tissue of invertebrates.
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Fig. 6.17
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Fig. 6.18
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Energy Limitation
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Limits on potential rate of energy intake by
animals have been demonstrated by
studying relationship between feeding rate
and food availability.
Limits on potential rate of energy intake by
plants have been demonstrated by studying
response of photosynthetic rate to photon
flux density.
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Photon Flux and Photosynthetic
Response Curves
Rate of photosynthesis increases linearly
with photon flux density at low light
intensities, rises more slowly with
intermediate light intensities, and tends to
level off at high light intensities.
 Response curves for different species
generally level off at different maximum
photosynthesis rates.
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Fig. 6.20
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Food Density and Animal Functional Response
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Functional response: when amount of food
available to animal is increased, its rate of feeding
will increase and then levels off.
Holling described (3) basic functional responses:
 1. Feeding rate increases linearly as food
density increases - levels off at maximum.
 Consumers require little or no search and
handling time.
 2. Feeding rate rises in proportion to food
density.
 Feeding rate partially limited by
search/handling time.
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Food Density and Animal Functional Response
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3. Feeding rate
increases most
rapidly at
intermediate
densities
 (S-shaped).
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Fig. 6.22
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Fig. 6.23
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Optimal Foraging Theory
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Optimal forging theory: Natural selections
will favor individuals within population that
are more effective at acquiring energy.
Assures if energy supplies are limited,
organisms cannot simultaneously maximize
all life functions.
 Must compromise between competing
demands for resources.
 Principle of Allocation
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Optimal Foraging Theory
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All other things being equal,more abundant
prey yields larger energy return. Must
consider energy expended during:
 Search for prey
 Handling time
Tend to maximize rate of energy intake.
Optimization: The animal will adjust its diet
(preys) until the rate of energy intake
reaches a maximum.
Need to know the formula and application
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Model for Prey Choice
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Optimal Foraging in Bluegill Sunfish
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Optimal Foraging By Plants
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Limited supplies of energy for allocation to
leaves, stems and roots.
Bloom suggested plants adjust allocation in
such a manner that all resources are equally
limited.
 Appear to allocate growth in a manner that
increases rate of acquisition of resources
in shortest supply.
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Fig. 6.25
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Fig. 6.26
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Application and Tools
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Bioremediation-using the tropic diversity of
bacteria to solve
environmental problems.
Sewage treatment-using bacteria for
degrading organic matters
at different temperatures .
Cyanide and Nitrates in mine spoil-using soil
bacteria in breaking down
CN, and Nitrates.
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Fig. 6.27
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Fig. 6.28
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