What is the principal source of energy for life on Earth?
Show answer & explanation
Correct answer: B
Explanation
Solution: The correct answer is Sunlight.
Explanation:
☛ Sunlight is the ultimate and principal source of energy for virtually all forms of life on Earth.
☛ Green plants, algae, and cyanobacteria capture solar energy using the green pigment chlorophyll through the process of photosynthesis.
☛ During photosynthesis, light energy is converted into chemical energy, producing glucose and oxygen from carbon dioxide and water.
☛ This stored chemical energy serves as the nutritional and metabolic foundation for herbivores, carnivores, and decomposers across terrestrial and aquatic food chains.
☛ In addition, sunlight drives the Earth's water cycle, atmospheric circulation, and ocean currents, maintaining a climate suitable for life.
Extra Exam-Relevant Facts:
☛ Photosynthetically Active Radiation (PAR): Only the 400–700 nm wavelength range of solar radiation is absorbed by plants for photosynthesis, representing roughly 50% of total incident solar radiation.
☛ Plants capture only about 2% to 10% of the PAR (or 1% to 2% of total incident sunlight) to sustain the entire living world.
☛ Water, Soil, and Wind: These are vital abiotic components of ecosystems that support plant growth and distribute nutrients, but they do not serve as primary biological energy sources.
☛ Deep-sea hydrothermal vent communities are rare ecosystems independent of sunlight, deriving their primary energy from chemosynthesis powered by hydrogen sulfide.
Important One-Liners for Upcoming Exams:
☛ What wavelength range of sunlight is designated as Photosynthetically Active Radiation (PAR)? → 400 nm to 700 nm
☛ Who formulated the famous 10% law of energy transfer across trophic levels in an ecosystem? → Raymond Lindeman (1942)
☛ Which cellular organelle in green plants contains chlorophyll to trap solar energy? → Chloroplast
☛ Which molecule acts as the primary source of oxygen released during photosynthesis? → Water (H₂O)
☛ What term is used for organisms that synthesize organic compounds directly from sunlight? → Photoautotrophs