Quiz 47: Ecosystems


An ecosystem consists of a group of organisms together with their physical and chemical environment. In an ecosystem, there is a one-way flow of energy. Every ecosystem shows inputs and outputs of energy and nutrients. Hence, the option (a) energy inputs and outputs is correct. Food chain shows a sequence of trophic levels. Energy trapped by sun is transferred from first trophic to subsequent trophic levels. Hence, the option (b) one trophic level is incorrect. In biogeochemical cycles, nutrients are recycled whereas in ecosystem there is one-way flow of energy and nutrients. Hence, the option (c) no nutrient outputs, all nutrients are cycled is incorrect. Option (d) a and b is incorrect.

Primary productivity refers to the rate at which producers or green plants apprehend and store energy in their tissues during a specified interval of time. Typically the factors that will influence primary productivity in Maine and Spain depends on- a. Number of producers present in that particular area in a specified interval of time. b. Balance between photosynthesis and aerobic respiration.

Producers or green plants occupy the lowest trophic level. They directly utilize solar energy for the process of photosynthesis. Producers are also called as autotrophs. Hence, the option (a) at the first step away from the original energy input is incorrect. Autotrophs are organisms that can make their own food in the presence of sunlight by the process of photosynthesis. Green plants are producers. Hence, the option (b) autotroph is incorrect. Heterotrophs are organisms that depend on producers for energy needs. They derive nutrition from green plants. Hence, the option (c) heterotroph is incorrect. Organisms at the lowest trophic levels in a tall grass prairie are autotrophs and just one step away from the ultimate source of energy. Hence, the option (d) both a and b is correct. Plants are autotrophs and not heterotrophs. Hence, the option (e) both a and c is incorrect.

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