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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Law of the minimum- ecosystems must adapt to it.

• Light in ocean floor
• Water in desert
• Heat on mountain top
• Matter is also limiting, thus have limiting
  nutrients that allow for life

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Flow of energy and nutrients

• Photosynthesis
• Metabolism

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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
• 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 Number of light energy
  (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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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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Food Web

• 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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Thermodynamics

• Total amount of energy kept constant
• Energy can be converted

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Transfer of Energy with Ecosystems

• Board notes

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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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• 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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• 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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productivity

• Refers to the production of food
• Primary production total gross primary
  production
• Activity- Compare ecosystems p. 26

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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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Cycles of matter

• Nitrogen
• Carbon

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Nutrient Cycling and Retention

• Chapter 19

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Nitrogen Cycle

• Includes major atmospheric pool - N2.
• Only nitrogen fixers can use atmospheric supply
  directly.
• Energy-demanding process.
• N2 reduced to ammonia (NH3).
• Once N is fixed it is available to organisms.
• Upon death of an organism, N can be released by
  fungi and bacteria during decomposition.

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Nitrogen fixation

• Biological Nitrogen Fixation (BNF) occurs when
  atmospheric nitrogen is converted to ammonia by a
  pair of bacterial enzymes

• N2 8H 8e- 16 ATP ? 2NH3 H2 16ADP 16
  Pi

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Nitrogen Cycle
Microbes Denitrification NO3- (nitrate) ? NO2- ?
NO ? N2O ? N2 gas
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Carbon Cycle

• Moves between organisms and atmosphere as a
  consequence of photosynthesis and respiration.
• In aquatic ecosystems, CO2 must first dissolve
  into water before being used by primary
  producers.
• Although some C cycles rapidly, some remains
  sequestered in unavailable forms for long periods
  of time.

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Carbon Cycle
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Animals and Nutrient Cycling in Terrestrial
Ecosystems

• Huntley and Inouye found pocket gophers altered N
  cycle by bringing N-poor subsoil to the surface.
• MacNaughton found a positive relationship between
  grazing intensity and rate of turnover in plant
  biomass in Serengeti Plain.
• Without grazing, nutrient cycling occurs more
  slowly through decomposition and feeding of small
  herbivores.

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Animals and Nutrient Cycling in Terrestrial
Ecosystems
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Plants and Ecosystem Nutrient Dynamics

• Fynbos is a temperate shrub/woodland known for
  high plant diversity and low soil fertility.
• Two species of Acacia used to stabilize shifting
  sand dunes.
• Witkowski compared nutrient dynamics under canopy
  of native shrub and introduced acacia.
• Amount of litter was similar, but nutrient
  content was significantly different.
• Acacia - N fixer

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Biotic communities
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Climate and weather