Energy and Living Things

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Energy and Living Things
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Outline

• 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 Flows Through Living Systems
Heterotrophs
Plants Autotrophs
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• Autotroph self feeder - an organism that can
  gather energy (usually from light) to store in
  organic molecules
• Photosynthesis
• chemosynthesis
• Heterotroph An organism that must rely on other
  organisms to capture light energy must rely on
  breakdown of organic molecules produced by an
  autotroph as an energy source
• Classified by trophic level

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• Photosynthesis
• Capture and transfer light energy to chemical
  bonds
• Occurs in
• Plants
• Algae
• Certain Bacteria
• Not a perfect process some energy is lost -
  entropy

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• How Photosynthesis Works
• Light strikes leaf
• Energy absorbed by chemical pigments
• Absorbed energy drives chemical processes to
  convert CO2 into larger molecules
• First simple sugars 6 carbon ring structures
• Later many molecules of simple sugars joined
  together to form larger molecules or converted to
  other compounds
• Energy absorbed in building larger molecules,
  released as they are broken down

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• Only certain Wavelengths of Light are Used in
  Photosynthesis
• Light Energy Used Photosynthetically Active
  Radiation or PAR
• How Much is absorbed determined as photon flux
  density.
• Number of photons striking square meter surface
  each second.
• Chlorophyll absorbs light as photons.
• Landscapes, water, and organisms can all change
  the amount and quality of light reaching an area.
• Light not absorbed is reflected
• Some in PAR all in green and yellow wavelengths

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Wavelengths most useful in driving photosynthesis
Wavelengths not used - reflected
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Fall color

• In many plants production of chlorophyll ceases
  with cooler temperatures and decreasing light
• other pigments become visible

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• Modifications of Photosynthesis for Dry Climates
• C3 Photosynthesis
• Used by most plants and algae.
• CO2 enters leaves BUT water vapor leaves
• Poorly adapted to hot dry environments
• C4/CAM photosynthesis Modifications in
  biochemical processes
• Increased efficiency in CO2 absorption
• Fewer stomata required/stomata only open during
  night ? decreased loss of water vapor

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C3 Photosynthesis
CO2 enters passively so stomata have to be open
for long periods of time
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Why C3 Photosynthesis Doesnt always work out -
CO2 must enter though stomata

• stomata (sing., stoma) are tiny holes on the
  undersides of leaves
• CO2 enters and moisture is released
• In hot, dry climates, this moisture loss is a
  problem

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C3 grasses (yellow) dominant in cool temperate
C4 plants dont compete so well there
C4 grasslands (orange) have evolved in the
tropics and warm temperate regions
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C4 Photosynthesis
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Photosynthetic Pathways

• 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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• Producers

• Herbivores
• Animals that eat plants
• The primary consumers of ecosystems

• Green plants and algae
• Use solar energy to build energy-rich
  carbohydrates

• Carnivores

• Animals that eat herbivores
• The secondary consumers of ecosystems
• Omnivores are animals that eat both plants and
  animals
• Tertiary consumers are animals that eat other
  carnivores

• Decomposers
• Organisms that break down organic substances

• Detritivores

• Organisms that eat dead organisms

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• Efficient Breakdown of Products of Photosynthesis
  Requires Oxygen
• Complex series of reactions, oxygen serves as the
  terminal electron acceptor
• May occur in some organisms w/o oxygen (anoxic
  conditions)
• anaerobic respiration fermentation
• Inefficient
• End products vary with organism involved
• Ethanol, proprionic acid, lactic acid, etc.

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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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• Classes of Herbivores
• Grazers leafy material
• Browsers woody material
• Granivores seed
• Frugivores fruit
• Others nectar and sap feeders
• Humming birds, moths, aphids, sap suckers

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• Herbivores
• Substantial nutritional chemistry problems.
• Low nitrogen concentrations difficulty
  extracting needed protein/amino acids from
  source.
• Require 20 amino acids to make proteins 14 are
  must come from diet

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• How do plants respond to feeding pressures by
  herbivores?
• Mechanical defenses spines
• Chemical defenses
• Digestion disrupting chemicals tannins, silica,
  oxalic acid
• Toxins alkaloids
• More common in tropical species
• How do animals respond?
• Detoxify
• Excrete
• Chemical conversions use as nutrient

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• Digestion Schemes of Herbivores
• Require extensive digestive processing
• Rumnants 4 part stomach
• Rapid feeding, coarse material is re-milled
  (regurgitated bolus) after initial fermentation
• Chewing their cud

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• Coprophagy expel moist fecal material, re-ingest
• 50-80 of fecal material recycled
• acts as external rumen
• bacterial activity produces B vitamin

Cecum is site of much bacterial activity, moist
fecal pellets enclosed in protein produced
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• Carnivores
• Predators must catch and subdue prey - size
  selection.
• Usually eliminate more conspicuous members of a
  population (less adaptive).
• act as selective agents for prey species.

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• European River Otter
• Lutra lutra
• Widest ranging of otters
• Diet varies with abundance of prey

• http//itech.pjc.edu/sctag/E_OTTER/Index.htm

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Optimal Foraging Theory

• Assures if energy supplies are limited, organisms
  cannot simultaneously maximize all life
  functions.
• Must compromise between competing demands for
  resources.
• Principle of Allocation
• Fittest individuals survive based on ability to
  meet requirements principle of allocation

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Optimal Foraging Theory

• 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.
• What would a starving man do at an all you can
  eat buffet?

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Optimal Foraging in Bluegill Sunfish
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• Adaptations of Prey to being preyed upon
• Predator and prey species are engaged in a
  co-evolutionary race.
• Avoid being eaten avoid starving/becoming
  extinct
• Defenses
• Run fast
• Be toxic and make it known
• Pretend to be toxic
• Predators learn to avoid

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Carnivores

• 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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Mullerian mimicry Comimicry
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Batesian mimicry Harmless species mimic noxious
species
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Aposomatic Coloring - Warning colors
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Detritivores

• 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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Detritivores and decomposers
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Review

• 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
• Adaptations