BIOL 3309 Study Guide - Midterm Guide: Sexy Son Hypothesis, Photosynthetically Active Radiation, Photosynthetic Efficiency

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Chapter 7
Trophic Biology
Trophic: pertaining to nutrition
Autotrophs: self-nutrition
Inorganic sources of carbon and energy
Photosynthetic autotrophs: use CO2 as carbon source, sunlight as energy
Chemosynthetic autotrophs: use CO2 as carbon source, inorganic
chemicals (ex. H2S) as energy
Heterotrophs: get nutrition from others
Organic molecules as source of both carbon and energy
Examples: Osedax worms. Eat whale bones. SO they are heterotrophic
Venus flytraps: Eats flies. therefore heterotrophic
Photosynthetic sea slugs
Eat photosynthetic algae and then can photosynthesize
Heterotroph at first then become autotroph
Specifically a photosynthetic autotroph
Dual nature of light
Light propagates through space as a wave
Described as wavelength and frequency
Light interacts with matter as a particle
Longer wavelengths carry less energy
Photosynthetically active radiation (PAR)
400-700 nm
Goldilocks principle
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Enough energy to power photosynthesis, but not so much that molecules
are damaged
Photosynthetic pigments absorb different wavelengths
Plants absorb all of the colors except green
PAR is the number of photons striking m^2 per second, expressed in umol
Factors affecting photon flux density
Latitude
Season
Weather
Time of day
Landscape
Water
Organisms
Photosynthetic pathways
C3 Photosynthesis
Most common pathway
Need high concentrations of CO2 or rubisco catalyzes photorespiration
reduces photosynthetic efficiency
C02 + RuBP -----(rubisco)----→ PGA(6 carbons)
Used when water balance is not an issue
C4 Photosynthesis
Does the reaction in two parts of the cell
Mesophyll and Bundle sheath cells
Lower CO2 concentration to reduce water loss
Ex. Grasses
CAM photosynthesis
Reaction occurs at different times
Highest water efficiency
Ex. succulents, epiphytes
Chemosynthetic autotrophs- synthesize organic molecules using CO2 as a carbon source
and inorganic molecules as an energy source
Ex. Hydrothermal vent communities are chemosynthetic autotrophs
Heterotrophs- use organic molecules both as a source of carbon and as an energy source
Herbivores: feed on plants
Usually have plenty of plants to feed on
Ex. Wildebeest migrating from a land with grass because they want
BETTER grass
Quantity vs Quality
Plants have very low amounts of key nutrients
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Herbivores must consume large amounts of plant material (excess
carbon) to acquire essential nutrients
ex. nitrogen and phosphorus
Ecological Stoichiometry: the balance of chemical elements in ecological
interactions
Plant physical defenses
Physical defenses
Thorns, silica
Non digestible material
Cellulose, lignin
Plant Chemical defenses
Digestion reducing compounds
Phenolic compounds that bind to plant proteins, inhibit enzymatic
breakdown, reduce nitrogen availability
Toxins
Kill, impair, repel herbivores
Ex. Alkaloids
Why not more toxins?
Principle of allocation!!! Limited energy must be allocated
between growth, reproduction, and maintenance/defense
Detritivores: feed on dead plant material, so many of same challenges as herbivores
(Even greater in some cases) This is because the plant nutrient contents is low when
compared to animals
Carnivores: feed on animal flesh
Predator and prey have similar stoichiometry
Should be easy for carnivores to meet nutritional requirements (get the essential
nutrients)
Prey have ways to avoid predators. Ex. Shells, spitting, playing dead, flight,
refuge
Aposematism- Warning colors (Oppose the enemy; way i remember)
Advertise noxiousness to predator
Mimicry
Mullerian mimicry: co-mimicry among several noxious organisms (Are
actually noxious)
Batesian mimicry (think of bait, so trick)
Try to look like other noxious organisms. Not actually noxious
Camouflage
Ex. peppermoth
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