4. The table below gives rough estimates of food chain lengths from various fiel

Question

4. The table below gives rough estimates of food chain lengths from various field studies and is taken from the Ricklefs textbook. Consumer ingestion (kcal/m 2/year) Number of trophic levels in Net primary Trophic level transfer efficiency (%) 25 20 Community production (kcal/m2/year) | food chain Open ocean 500 Coastal marine Temperate2000 grassland Tropical forest 8000 10.0 10 4.3 8000 10.0 3.2 a) Based on Ricklefs' analysis, what factor appears to consistently control the length of food chains in different ecosystems? b) Explain the ecological basis for this relationship? c) Describe one other factor that has been argued to control food chain length in some ecosystems. This factor does not necessarily have to be supported by the data in this table

Explanation / Answer

A) trophic level transfer efficiency controls the length of food chain.

B) amount of energy that flows through the trophic levels is further dependent on NPP and conversion efficiencies of animals eating the plants. A trophic level transfer energy only about 5-20%. Organisms digest only a portion of the food they eat and rest is passed as faecal matter. Some energy is utilised in various activities like respiration, digestion etc.

3. Ecosystem size also controls food chain length. Food chain length shortens with reduced ecosystem size. Larger ecosystems are more diverse and have longer food chains

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