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

Question

1. The table below gives rough estimates of food chain lengths from various field studies and is taken from the Ricklefs 4e textbook. Net primaryConsumer Trophic Number of Community production transfer trophic lev ingestion 0.1 10.0 1.0 10.0 Open ocean Coastal marine Temperate grassland Tropical forest 500 8000 2000 8000 25 20 10 5.1 4.3 3.2 A(2pt) Based on Ricklefs' analysis, describe which factor appears to consistently control the length of food chains in different ecosystems? 4 pts. Explainthe ecological basis for this relationship between your chosen factor in part A and food chain length C (2 pts.) Discuss one other factor from the literature discussed in class to control food chain length in ecosystems. This factor does not necessarily have to be supported by the data in this table. (2 pts.) Normally, humans do not function as a primary consumer (herbivore) in aquatic ecosystems. No one eats phytoplankton! But we function as carnivores when we eat fish (usually higher order carnivores, sometimes apex). However, on land, we regularly function as herbivores and primary carnivores (think steak and salad) when it comes to terrestrial ecosystems. Using the data above, explain these trophic level positions of humans on land versus in the sea. (Think about the relative sizes of the organisms in each level.) (2 pts) Explain why the two aquatic systems have a higher TLTE than the two terrestrial systems. Remember the phytoplankton

Explanation / Answer

In terrestrial ecosystems, humans function as tertiary consumers as there are some people who also consume snakes. In aquatic ecosystems, humans function as 5th level consumers. Since, secondary consumers are consumers are consumed by smaller fishes, which are further consumed by large fishes example large mouth bass and the humans consume the carnivorous fishes, thus, staying on the 5th level. Trophic level transfer efficiency (TLTE) will be used for measuring the energy amount that gets transferred between different trophies levels. Number of trophic levels in food chain is also greater inn the two aquatic systems. This means that, there is less amount of energy lost during transfer of one trophic level to the other. Due to this loss in energy, the maximum number of trophic levels in terrestrial ecosystems is just 6, though, 6 trophic levels May never be reached. Hence, with lower amount of energy lost in levels, efficiency is greater.

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