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Energy and Living Things. 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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Presentation Transcript
  • 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

Energy Flows Through Living Systems


Plants= Autotrophs

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

Capture and transfer light energy to chemical bonds

Occurs in:



Certain Bacteria

Not a perfect process – some energy is lost - entropy

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
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

Wavelengths most useful in driving photosynthesis

Absorption spectra of chlorophylls and carotenoids

Wavelengths not used - reflected

fall color
Fall color
  • In many plants production of chlorophyll ceases with cooler temperatures and decreasing light
  • other pigments become visible
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
c 3 photosynthesis
C3 Photosynthesis

CO2 enters passively so stomata have to be open for long periods of time

why c3 photosynthesis doesn t always work out co 2 must enter though stomata
Why C3 Photosynthesis Doesn’t 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

C3 grasses (yellow) dominant in cool temperate – C4 plants don’t compete so well there

C4 grasslands (orange) have evolved in the tropics and warm temperate regions

photosynthetic pathways
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.
  • 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
  • Detritivores
  • Decomposers
    • Organisms that break down organic substances
  • Organisms that eat dead organisms
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.
Three Feeding Methods of Heterotrophs:
    • Herbivores: Feed on plants.
    • Carnivores: Feed on animal flesh.
    • Detritivores: Feed on non-living organic matter.
Classes of Herbivores
  • Grazers – leafy material
  • Browsers – woody material
  • Granivores – seed
  • Frugivores – fruit
  • Others – nectar and sap feeders
    • Humming birds, moths, aphids, sap suckers …
  • 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
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
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’
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

  • 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.
European River Otter:

Lutra lutra

Widest ranging of otters

Diet varies with abundance of prey

optimal foraging theory
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
optimal foraging theory1
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?
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
  • 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.
  • 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.
  • 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