4 public questions tagged with this topic.
The parasympathetic nervous system is responsible for "rest and digest" functions, promoting digestion and energy conservation.
Ref: NCERT Class 11 Biology Chapter 18: Neural Control and Coordination Peripheral and Autonomic Nervous System - Cranial and Spinal Nerves
The first law of thermodynamics expresses conservation of energy: energy changes form but is neither created nor destroyed. In ecosystems, radiant or chemical energy becomes organic chemical energy, work, and ultimately dispersed heat. Energy-budget equations must therefore balance inputs, storage changes, exports, and respiratory losses. The second law adds directionality by stating that transformations increase entropy and reduce the fraction capable of doing work; together, the laws explain why energy is conserved quantitatively yet flows one way through ecosystems. Food-web structure also reflects population persistence: upper levels need enough total production and sufficiently stable prey populations to avoid demographic extinction. Detrital and grazing channels continually exchange material, because waste and mortality feed decomposers while microbial and detritivore biomass supports predators. Quantitative interpretation requires explicit system boundaries and time scales; otherwise export, migration, storage, or seasonal turnover can appear to violate energy balance. Thermodynamic constraints set broad patterns, but species traits, defenses, body size, habitat structure, and disturbance determine the efficiencies observed in a particular ecosystem.
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3
“1-2%” for production efficiency of endotherms is generally. This relationship follows from the ecological mechanism represented by the terms in the item, not merely from an association between their names. Rates depend on temperature, moisture, substrate quality, consumer physiology, and the elemental balance between organisms and their food. These controls explain why the same process can differ among terrestrial, freshwater, and marine systems without changing its definition. The remaining alternatives—“20-50%”, “0.1”, “0.005”—refer to different states, processes, or scales and therefore do not express the same causal relationship. Ecosystem processes are constrained by energy conservation and by the cycling of matter. Energy enters mainly through primary production, is lost as metabolic heat at every transfer, and therefore cannot be recycled in the way that carbon, nitrogen, phosphorus, or water can. The cited framing is therefore most useful when treated as a conditional biological claim, with assumptions about scale and environmental context kept explicit.
Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3
The total energy of a system remains constant is the scientifically accurate answer to this question. Within the study of Thermodynamics, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of The total energy of a system remains constant directly address what is being asked. Among the other options, Energy is always destroyed, Entropy always increases, and Energy flows from cold to hot spontaneously do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.
Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 1
