Ecology Extras. Growth of photosynthetic organisms because used CO 2 in photosynthesis to make food.
Section 3. Review primary source of energy for photosynthetic organisms is the sun/light. Food web...
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Transcript of Section 3. Review primary source of energy for photosynthetic organisms is the sun/light. Food web...
Energetics of Marine Ecosystems Part II
Section 3
Reviewprimary source of
energy for photosynthetic organisms is the sun/light.
Food webFood chainBiomass
Gross Primary Production (GPP)calculate the % of incident light energy which
appears as energy of newly synthesised organic substances
The total energy captured by primary producers = GPPrespiration (R)Net primary production (NPP) - Remaining organic
substances Transferred to higher trophic levels
NPP = GPP – R~10% energy available at one trophic level is
transferred to the next trophic level
Energy Losses Along Food Chains
3 reasons:Respiration/heatWaste/feces
Excretion (feces) or egestion (from cells)
Some parts of organism not eaten
Of total energy from Sun, only a small percentage is captured and used for synthesis (NOT ALL ENERGY BECOMES AVAILABLE AS NET PRODUCTION)Reflected back from
surfacesPass straight through a
producer – not absorbedInefficiencies of
photosynthesisNPP = GPP – R
Energy Flow in a Food Chain
BIG reason why RARELY have more than 5 levels
Energy losses between trophic levels
“loss of heat energy”
Insufficient energy available to transfer to more than 5 trophic levels
Efficiency of Energy transfer between trophic levels
Net productivity of plants in a food chain is 36,000 kJ/m2 per year
Net production of herbivores is 1,700 kJ/m2 per year
Efficiency of transfer of energy from the producers to herbivores
(1,700 / 36,000) x 100 = 4.72%Energy losses: heat from respiration, losses in
urine, undigested plant material (fecal matter)Energy of production of herbivores represent
total energy available to carnivores (next trophic level)
Example
3.5%Show work! [1 point]
Productivity can be measured as mass of carbon incorporated into biological molecules per unit area per unit time
The primary productivity of the phytoplankton in this food web is 90 g of carbon per m2 per year.
The efficiency of transfer between phytoplankton and herbivores is approximately 10%.
Assuming that zooplankton and bottom-feeding herbivores eat equal quantities of phytoplankton, calculate the amount of carbon incorporated into zooplankton per m2 per year. Show your working.
....................................................... g C m–2 year–1 [2]
Answer: 90/10% = 9/2 = 4.5
Ecological PyramidsGraphical representation of food chainProducers at base
Horizontal bars represents successive trophic levels
Width of bar proportional to numbers, biomass or energyImpossible to have more energy in higher
trophic levels
Ecological Pyramid
ExampleDraw a pyramid of biomass for the following food
chain:Phytoplankon krill fish penguins killer
whales [2]
Answer:pyramid with 5 levels;each level named; (trophic)
1st trophic level
2nd2nd, 3rd
3rd, 4th, 5th 3rd, 4th , 5th
4th, 5th, 6th
4th, 5th, 6th, 7th
4th, 5th, 6th
3rd, 4th, 5th
4th, 5th, 6th
3rd, 4th
1st trophic level
2nd
2nd3rd, 4th
3rd
3rd3rd, 4th
3rd, 4th, 5th4th, 5th