Question 1

In an ecosystem, plants are eaten by herbivores, which are then eaten by carnivores. What percentage of energy from plants is typically available to the carnivores in this food chain?

Accepted Answer

This question tests understanding of the 10% Law (or Law of Energy Transfer) in ecosystems, a core NCERT Class 10 concept. According to this principle, only approximately 10% of energy is transferred from one trophic level to the next; the remaining 90% is lost through respiration, heat, and other metabolic processes. Therefore, if plants (producers) contain 100% energy, herbivores (primary consumers) receive ~10%, and carnivores (secondary consumers) receive ~10% of that 10%, which equals ~1%. The correct answer is B (1%).

Question 2

In an ecosystem, the primary consumers are herbivores that feed on plants. If the primary consumers have a total biomass of 5000 kg, approximately how much biomass would be expected in the secondary consumers (carnivores) that feed on these herbivores, following the 10% law of energy transfer?

Accepted Answer

The 10% law of energy transfer (also called the Lindeman efficiency rule) states that only approximately 10% of the energy available at one trophic level is transferred to the next trophic level. The remaining 90% is lost through respiration, heat, and other metabolic processes. Since secondary consumers obtain their energy from primary consumers, the biomass of secondary consumers is approximately 10% of the primary consumer biomass. Therefore: Secondary consumer biomass = 10% of 5000 kg = 0.10 × 5000 kg = 500 kg. This principle is fundamental to understanding energy flow in ecosystems as taught in NCERT Class 10 Biology Chapter on Ecosystems.

Question 3

In a forest ecosystem, the primary productivity is measured at 10,000 kcal/m²/year. If the efficiency of energy transfer between trophic levels is 10%, what is the total energy available to secondary consumers (herbivores that feed on plants)?

Accepted Answer

This question tests understanding of energy flow in ecosystems and the 10% law of energy transfer. The primary productivity (10,000 kcal/m²/year) represents the total energy fixed by producers (plants) through photosynthesis. Primary consumers (herbivores) receive 10% of this energy: 10,000 × 0.10 = 1,000 kcal/m²/year. Secondary consumers receive 10% of the primary consumer energy: 1,000 × 0.10 = 100 kcal/m²/year. Therefore, the answer is C (100 kcal/m²/year). The 10% law, established by Lindeman and confirmed in NCERT Class 10 Biology Chapter 15 (Our Environment), states that only approximately 10% of energy is transferred from one trophic level to the next; the remaining 90% is lost through respiration, heat, and incomplete consumption.

NDA Ecosystems & Environment

Ecosystems & Environment— Rules & Concept

Key Points to Remember

Exam-Specific Tips

Ecosystems & Environment — Practice Questions

60-Second Revision — Ecosystems & Environment