Question
In a stable natural ecosystem, how is the supply of nutrients and energy maintained?
▶️Answer/Explanation
Energy, on the other hand, flows through the ecosystem. It enters primarily through solar radiation, is converted into chemical energy by producers (plants), and flows through the food chain as organisms consume each other. Energy is not recycled but is lost as heat at each trophic level (according to the second law of thermodynamics).
Option Breakdown:
A. Incorrect – Energy is not cycled, it flows through the ecosystem and is ultimately lost as heat.
B. Incorrect – While nutrients are cycled, energy is not cycled but flows through the system.
C. Correct – This statement accurately describes how nutrients are cycled, and energy flows through the ecosystem.
D. Incorrect – Energy is not cycled through photosynthesis and respiration, but rather flows, and while food chains do help with nutrient flow, this option doesn’t fully capture the roles of energy and nutrients.
Question
Which processes occur in an ecosystem?
I. Biomass increases in each successive trophic level.
II. Inorganic nutrients are recycled.
III. Chemical energy is stored in carbon compounds.
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
▶️Answer/Explanation
Answer: C. II and III only
Explanation:
I. Biomass increases in each successive trophic level – This statement is incorrect. Typically, biomass decreases as you move up trophic levels due to energy loss at each step in the food chain (about 90% of energy is lost at each trophic level as heat, and only about 10% is transferred to the next level).
II. Inorganic nutrients are recycled – This statement is correct. Nutrients like nitrogen and phosphorus are recycled through the ecosystem via the biogeochemical cycles.
III. Chemical energy is stored in carbon compounds – This statement is correct. Producers (like plants) store chemical energy in carbon compounds (such as glucose) during photosynthesis, and this energy is passed through the food chain.
Question
The global carbon cycle involves sinks where carbon is stored, and fluxes where carbon is transferred. What are the largest sink and flux?
▶️Answer/Explanation
Answer: C.
Explanation:
In the global carbon cycle:
Largest carbon sink: Oceans — they store more carbon than the atmosphere or terrestrial biosphere.
Largest carbon flux: Photosynthesis — it’s the primary process moving carbon from the atmosphere into living organisms.
So, the correct answer is: C. oceans – photosynthesis