Energy Flow Through an Ecosystem - Essay Example

Energy Flow Through an Ecosystem An energy pyramid is indicative of the total amount of energy present at each trophic level of the food chain, trapped in terms of per unit time and unit area by the organism. It is a graphical representation of the energy available to the producers, the primary consumers (the herbivores) and the secondary consumers (the carnivores). The producers always have the maximum amount of energy available. The net energy available to the successive trophic levels dwindles to 10% for the plant eaters and is further decreased by the time it reached the meat eaters, who are right on top of the food chain.

As Lindeman (1942) stated, “Only 10% of the total chemical energy is retained at each trophic level.” This is known as the ten per cent law.The second law of thermodynamics says that at each progressive trophic level in the food chain, there is a gradual decrease in the available energy. The pyramid of energy is always upright or straight because out of the total amount of energy transferred from the lower trophic level, as much as 80-90% is lost in the form of heat. The net primary productivity (the resultant plant biomass) is the difference of the gross primary productivity (total plant biomass) and the amount used for plant respiration.

Therefore, it is only the net photosynthesis that is presented to the next trophic level of the food chain or the herbivores. The carnivores receive the gross secondary productivity from the herbivores.The food chain in a fresh water ecosystem can be accurately represented as:Phytoplanktons -- Diatoms -- Crustaceans -- Small fish -- Large fish Lakes, ponds, rivers and steams are representative of fresh water biomes. There are the shallow or eutrophic lakes and deep or olitrophic lakes.

On the basis of the penetration of light, a deep lake has three zones. The transition zone or thermocline, the basal layer or the hypolimnion and the upper layer that is warmer in summer and cooler in winter called the epilimnion.SpeciesBiotic Conditions required by speciesAbiotic Conditions required by speciesRange of tolerance for speciesA. Microscopic plants (Phytoplanktons) -Fresh water lakes and pondsHypolimnionB. Free floating surface plants (Salvinia, Azolla, etc.) These are microscopic algae and water ferns.

(Pistia, Lemna, Wolfia,etc.) These are angiosperms.-Fresh water lakes and ponds, Air, Sun light, Warmer Conditions.EpilimnionC. Suspended plants (Hydrilla, Utricularia, Ceratophyllum, etc). These are macrophytes.-Fresh water lakes and ponds, Dissolved air.ThermoclineD. Rooted plants (Typha, Nelumbo (lotus), Vallisneria, etc) -Fresh water lakes and ponds, Soil, HypolimnionE. Ciliates, Zooflagellates, Rotifers, etcFood: Symbiotic algae, Other micro organisms, etc.Fresh water lakes and pondsEpilimnionF.

Crustaceans like Cypris, Cyclops and Daphnia. Food: Smaller organic particles, Bacteria, etc.Fresh water lakes and pondsEpilimnionG. Eggs and larvae of aquatic animals like dragonfly, damsel fly and may fly, etc.Food: Eat the larvae of other insects too.Fresh water lakes and pondsEpilimnionH. Nektons (Beetles, Water bugs, Fish, Frogs, Turtles, Snakes, Tortoises, etc)Food: Eat insects and larvae.Fresh water lakes and pondsThermoclineI. Benthos (Prawns, Crabs, Mussels, Snails, Hydra, etc)Food: Eat planktons and other plants.

Fresh water lakes and pondsThermoclineIn the above table, A-D represents the autotrophs/flora and E-I represents the heterotrophs/fauna.Sources:Robert Wetzel, G. (2001). Limnology: Lake and River EcosystemsUniversity of Michigan: Academic Press