Lec 9- autotrophs Flashcards
trophic/trophy/troph
having to do with food nourishment
autotrophy
own complex carbs for nourishment from inorganic C-sources
- photosynthesis (light)
- chemosynthesis (oxidation)
heterotrophy
organic sources of C synthesized by others to derive energy
How diverse are trophics in organismal groups?
- strategies evolved independently
Prokaryotes- most diverse
Fungi/animals- heterotrophs only
Plants- mostly photosynthesizers
Chemosynthesizers- only prokaryotes
photosynthesis
converts co2 to complex sugars
derives energy from light -triggers rxns
chemosynthesis
converts co2 (or CH4) to complex sugars
derives energy from oxidation
- has rxn similar to photosynthesis
What is light?
electromagnetic radiation
what is wave-particle duality?
radiation behaves as a wave and particle (photon)
how can electromagnetic radiation be described as?
wavelength and photon energy
infrared and radio waves
too little energy for photosynthesis
UV, x-ray, gamma
too much energy for photosynthesis
- harmful to cellular structure
Photosynthetically Active Radiation (PAR)
- quantity and quality of light influences photosynthesis rates
- how much PAR plants receive is is visible
- influenced by many factors: latitude, clouds, landscape, position of plant w/in terrestrial vegetation, aquatic
Light Partitioning in Forests
many: adapted to high and low PAR
one: adapted to moderate PAR availability
shrubs: adapted to low PAR availability
how does water depth affect amount of light?
PAR modified in quantity and quality as light passes through water column of aquatic sys
- PAR decreases and changes in spectrum representation
red light
absorbed by autotrophs near surface
- green emitted by organisms
- no red light reaches the deep layers
blue light
reaches deep layers
- autotrophs adapted to use PAR in blue range
absorbed by autotrophs at great depths
- red light emitted
deep water algae
deep water algae appear red b/c chlorophyll absorbs blue and green light
reflects red
sunlight (euphotic) zone
sunlight penetrates beyond this zone
twilight (dysphotic) zone
sunlight decreases rapidly with depth
photosynthesis is not possible here
- chemosynthesis
midnight (aphotic) zone
sunlight does not penetrate
- bathed in darkness
PAR in aquatic systems
- penetrate only 100-200m
changes in quality and quantity with depth
photosynthetic response curves
energy limitation in plants
- as photon flux density increases then NPR increases but to a point
Lsat - irradiance at saturation
Pmax- max net photosynthesis
LCP- light compensation point, light intensity at which photosynthesis = respiration
- if more light is available, plant produces more sugars than it uses
seedlings growth in open
higher Pmax and Lsat
seedlings growth in shade
lower Pmax and Lsat
Sun plants- adaptations
achieve higher Pmax
inefficient in using PPFD
Shade plants- adaptations
achieve small Pmax
more efficient at using low PPFD
low Lsat = damaged by sunny sites
Photosynthesis eqn
6 co2 + 6 h2o = c6h12o6 + 6 o2
carbon- photosynthesis
enters through stomata in leaves through diffusion
water- photosynthesis
enters through water transportation
glucose- photosynthesis
carbs used to gain energy via resp
- respiration
oxygen- photosynthesis
byproduct is essential for other organisms
C3 photosynthesis
- no anatomic/time separation of processes
- initial C fixation: mesophyll (day)
- Calvin cycle: mesophyll (day)
C4 photosynthesis
anatomic separation of processes
- initial C fixation: mesophyll (day)
- Calvin cycle: bundle sheath cells (day)
CAM photosythesis
time separation of processes
- initial C fixation: mesophyll (night)
- Calvin cycle: mesophyll (day)
C3 photosynthesis process
- light rxn photon
- mesophyll rich in chloroplasts
- creates ATP and NADPH - Calvin cycle
RuBP+ RUBISCO + CO2 = C3 acid (PGA) and NADPH and ATP to sugars and starch
Problems in hot climates with C3 (3)
rubisco = inefficient at high temps
open stomata = wastes water
closed stomata - o2 increases, photosynthesis suppressed
adaptations for C4 photosynthesis during hot climates
o2 accumulates in mesophyll
calvin cycle in bundle sheath - keep stomata closed
water efficient
adaptations for CAM photosynthesis during hot climates
- separates timing of process
night- open stomata and fix
C to C4 - day: close stomata and complete C-fixation
C4 photosynthesis process
2 step
- light rxn: o2 production
co2 fixation to C4 acid
PEP + CO2 = C4
C4 to CO2 and rubisco to PGA to sugars and starch to RuBP
C4 strategy
most prominent: Corn
wild-growing C4 in AB esp in prairies
3% of vascular plants
Why are there so few native C4 plants in Edmonton?
C4 pathway: more water efficient but water is not such a limiting factor as in hot climates further south
C3 pathway: more energy efficient than C4 pathway - evolutionary advantage
CAM photosynthesis process
crassulacean acid metabolism
- 2 steps
- day: light rxn and Calvin cycle
Convergent evolution
distantly related organism independently evolve similar traits to adapt
C4 and CAM photosynthesis evolved convergently
chemosynthesis
do not depend on light
energy from oxidizing chemicals
- hydrothermal vent fissure in seafloor that releases H2S and heat
occupy region on planet that light does not reach- deep ocean floors and caves
bacteria support a rich life- primary producers of ecosystem
symbionts of a giant tube worms
Chemosynthesis eqn
2H2S + O2 = 2S + 2H2O + energy (from oxidation)
- hydrogen sulfide bonds rich in energy
- elemental sulfur
- used to bind C and produce carbs
chemolithoautotrophs
derive energy from oxidizing compounds of inorganic origin
- H2S, Fe2+, NH3, NH4+
- bacteria and archaea
chemoorganoautotrophs
derive energy from oxidizing compounds of organic origin
- CH4
- bacteria and archaea
