Why are there fewer organisms at the top of the food chain compared to lower trophic levels?

• A. Because organisms at the top of the food chain are less likely to be affected by natural selection.
• B. Because energy is lost at each trophic level, resulting in less available energy for top predators.
• C. Because top predators reproduce much faster than organisms at lower trophic levels.
• D. Because top predators have more access to sunlight for photosynthesis.

Answer: (B)

Verified step by step guidance

1. Understand the concept of energy transfer in ecosystems: Energy flows through an ecosystem via trophic levels, starting with primary producers (plants and algae) that convert sunlight into chemical energy through photosynthesis.
2. Recognize that energy is lost at each trophic level: Only a small fraction of energy (approximately 10%) is transferred from one trophic level to the next. The rest is lost as heat, through metabolic processes, or as waste.
3. Identify the implications of energy loss: Because energy diminishes as it moves up the food chain, there is less energy available to support organisms at higher trophic levels, such as top predators.
4. Connect energy availability to population size: Fewer organisms can be supported at higher trophic levels due to the limited energy available, resulting in smaller populations of top predators compared to organisms at lower trophic levels.
5. Clarify misconceptions: Top predators do not rely on sunlight for photosynthesis, nor do they reproduce faster than organisms at lower trophic levels. Natural selection affects all organisms, but energy availability is the key factor in determining population sizes at different trophic levels.