Physiological%20Ecology

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Physiological Ecology
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Outline

• Introduction to Ecology
• Evolution and Natural Selection
• Physiological Ecology
• Behavioural Ecology

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Physiological Ecology

• study of species needs and tolerances that
  determine their distribution and abundance
• species need lots of things e.g., carbon,
  nitrogen, amino acids, etc.
• we will discuss species needs and tolerances with
  regards to ENERGY

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Physiological Ecology

• Nutrient and Energy Transfer
• Endothermy and Ectothermy
• Climate
• Current Climate Change

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Physiological Ecology

• Nutrient and Energy Transfer
• Endothermy and Ectothermy
• Climate
• Current Climate Change

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Nutrient and Energy Transfer
Ch. 6.1 6.6, Bush
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Outline

• Basics of energy
• Photosynthesis
• Trophic Levels
• Efficiency of Energy Transfer

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Outline

• Basics of energy
• Photosynthesis
• Trophic Levels
• Efficiency of Energy Transfer

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Forms of Energy

• Fuel (chemical bond energy)
• nutrients, such as carbohydrates
• needed for everything a species does
• e.g., growth, movement
• Heat
• needed for all chemical reactions
• by-product of reactions
• Light
• needed by plants to create fuel

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Energy transfer
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Energy source

• The ultimate energy source for (most) life on
  earth is the sun

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Outline

• Basics of energy
• Photosynthesis
• Trophic Levels
• Efficiency of Energy Transfer

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Photosynthesis

• What is it?
• Chlorophyll, a necessary pigment
• Variations in photosynthesis
• The fate of carbohydrate

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Photosynthesis

• Synthesis of carbohydrates from CO2 and water
• Sunlight acts as energy source
• O2 is a by-product

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In Chemistry notation

• Energy from sunlight CO2 H2O ? CH2O O2

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Chlorophyll, a necessary pigment
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Pigments absorb light energy
Pigments absorb light energy between 400-700
?m -energy in this range is termed
Photosynthetically Active Radiation (PAR)
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Why are leaves green?

• Pigments cannot absorb light in the green
  wavelength region

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The Green Gap
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Why are some plants not green?

• Chlorophyll is missing from some cells, making
  the reflectance of other pigments visible

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Fall colour

• the production of chlorophyll requires sunlight
  and warm temperatures
• in many plants, chlorophyll production stops in
  fall and other pigments become visible

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Why is chlorophyll necessary?

• Other pigments pass on the energy they absorb to
  a chlorophyll molecule
• When chlorophyll is in an energized state, it is
  able to turn light energy into chemical bond
  energy
• This chemical bond energy passes through a number
  of different molecules and then rests within a
  carbohydrate (glucose) molecule

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Variations in photosynthesis

• C3 photosynthesis
• C4 photosynthesis
• CAM photosynthesis

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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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CO2 is turned into sugar with RUBISCO

• RUBISCO (short for Ribulose-1,5-bisphosphate
  carboxylase) is the most important enzyme on
  Earth
• O2 has an inhibitory effect upon photosynthesis
  because it makes RUBISCO perform PHOTORESPIRATION
  instead

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C3 photosynthesis

• CO2 enters passively so stomata have to be open
  for long periods of time
• Majority of plant species use this variation of
  photosynthesis
• C3 plants experience high rates of
• water loss in hot, arid regions
• photorespiration where O2CO2 ratio is high

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C4 photosynthesis

• Have a special enzyme that actively pumps in CO2
  and delivers it to RUBISCO enzyme so
• (1) stomata do not have to be open for long
• (2) photorespiration is reduced
• Energetically costly
• 1-4 of plant species use C4 photosynthesis.
• used by species that live in hot, sunny
  environments with low CO2
• E.g. tropical grasses

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The global distribution of C4 plants in today's
world

• C4 grasslands (orange) have evolved in the
  tropics and warm temperate regions where C3
  forests (green) are excluded by seasonal drought
  and fire.
• C3 grasses (yellow) remain dominant in cool
  temperate grasslands because C4 grasses are less
  productive at low temperatures.

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CAM photosynthesis

• open stomata at night when the air is cool and
  more humid, thereby reducing water loss
• store the CO2 in tissues to be used during the
  day
• storage space is a potential constraint, thus
  many CAM plants are succulent (e.g. cacti)

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Unrelated species with similar physiology

• -Photosynthetic pathways show CONVERGENT
  EVOLUTION
• -CAM found in at least 12 different families
• -Recent studies say C4 has independently evolved
  over 45 times in 19 families of angiosperms

Cacti (Americas)
Euphorbia (Africa)
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Why photosynthesize?

• sugars created from photosynthesis are necessary
  for
• chemical reactions
• plant functions
• e.g., conduction of water and nutrients up the
  stem
• growth (biomass)

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Outline

• Basics of energy
• Photosynthesis
• Trophic Levels
• Efficiency of Energy Transfer

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Energy transfer
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Two types of organisms

• Autotrophs (producers)
• organisms which can manufacture their own food
• e.g., plants
• Heterotrophs (consumers)
• other feeders organisms which must consume
  other organisms to obtain their carbon and energy
• e.g., animals, fungi, most protists, most bacteria

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Trophic Levels

• Tropic level refers to how organisms fit in based
  on their main source of nutrition
• Primary producers
• autotrophs (plants, algae, many bacteria,
  phytoplankton)
• Primary consumers
• heterotrophs that feed on autotrophs
  (herbivores,zooplankton)
• Secondary, tertiary, quaternary consumers
• heterotrophs that feed on consumers in trophic
  level below them (carnivores)
• Detritivores
• bacteria, fungi, and animals that feed on
  decaying organic matter

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Trophic levels examples
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How many trophic levels?
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Exceptions to the rule?

• Carnivorous plants capture and digest animal prey
• They are able to grow without animal prey, albeit
  more slowly
• 600 spp. of carnivorous plants have been
  described

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Food chains versus food webs

• Food chain the pathway along which food is
  transferred from trophic level to trophic level
  in an ecosystem
• Food web the feeding relationships in an
  ecosystem many consumers are opportunistic
  feeders

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Food chains versus food webs
Food chains
Food web
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Outline

• Basics of energy
• Photosynthesis
• Trophic Levels
• Efficiency of Energy Transfer

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The energy budget

• The extent of photosynthetic activity sets the
  energy budget for the entire ecosystem
• Of the visible light that reaches photosynthetic
  land plants, 1 to 2 is converted to chemical
  energy by photosynthesis
• Aquatic or marine primary producers (algae)
  convert 3-4.5 - this difference accounts for why
  aquatic and marine food chains tend to be longer

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Efficiency of Producers
One difference among ecosystems is their
reflectance. Broadleaf forests reflect up to 20
of visible radiation. Conifer forests reflect
only about 5.
Ecosystems with low leaf area (e.g. deserts)
absorb very little light. Conifer forests with
very high leaf area index can absorb almost 95
or more of the incident light
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Coniferous versus deciduous forest
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Efficiency of photosynthesis

• Of the energy that is actually absorbed by
  chloroplasts, at best about 20 is converted into
  sugars

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Plant biomass a fraction of total energy

• Of the solar energy that is converted into
  organic molecules in photosynthesis, about 40-50
  is lost in the processes of respiration

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Primary productivity

• Gross Primary Productivity (GPP)
• total amount of photosynthetic energy captured in
  a given period of time.
• Net Primary Productivity (NPP)
• the amount of plant biomass (energy) after cell
  respiration has occurred in plant tissues.
• NPP GPP
  Plant respiration
• plant growth/ total photosynthesis/
  
• unit area/ unit area/unit time
• unit time

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Secondary Productivity

• Secondary productivity the rate at which
  consumers convert the chemical energy of the food
  they eat into their own new biomass

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Pyramid of productivity

• Energy content of each trophic level
• Pyramid has large base and gets significantly
  smaller at each level
• Organisms use energy for respiration so less
  energy is available to each successive trophic
  level

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Productivity pyramid
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Calculating Ecological Efficiency

• Lindeman Efficiency
• -can be seen as the ratio of assimilation between
  trophic levels
• energy (growth respiration) of predator
• energy (growth respiration) of food species

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Simplifying Ecological Efficiency

• Production Efficiency
• -can be seen as the ratio of biomass production
  between trophic levels
• energy (growth respiration) of predator
• energy (growth respiration) of food species

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Calculating efficiencies
e.g., grasshopper Efficiency 1,000 J /
10,000 J 10 efficient
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Efficiencies

• Herbivores are generally more efficient than
  carnivores (7 versus 1)
• Ectotherms are more efficient than endotherms (up
  to 15 versus 7)

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The Lost energy

• First Law of Thermodynamics
• energy cannot be created or destroyed it can only
  change form
• Second Law of Thermodynamics
• as energy changes form it becomes more
  disorganized. I.e., ENTROPY increases
• Energy quality index
• lightgtchemical bondgtmovement,heat

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What happens to the rest of the energy?

• used to do work (cell processes, activity,
  reproduction)
• Lost as heat (entropy)
• not consumed or not assimilated
• decomposers eventually get this!

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Detritivores and decomposers
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Summary

• Virtually all energy comes from the sun this
  energy is never destroyed, it just changes form
• Photosynthesis converts light energy into
  chemical energy
• All other trophic levels depend on photosynthesis
  for life
• Organisms vary in their ability to extract energy
  from the trophic level below them but most
  efficiencies are below 15, leaving much for
  detritivores

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