Skip to content
New summer mock series is live Attempt timed papers for SSC, banking, and engineering entrances with updated syllabi for this season. View exams
Login Register

#phosphorus

10 public questions tagged with this topic.

Modern Periodic Law and Present Form - Long Form Periodic Table

Which element in group 15 forms a pentoxide with the highest thermal stability?

Thermal stability of group 15 pentoxides (X₂O₅) decreases down the group due to weaker X-O bonds. N₂O₅ is the most stable thermally, decomposing at a higher temperature than P₂O₅, As₂O₅, or Sb₂O₅.

Ref: NCERT Class 11 Chemistry > Chapter 3: Classification of Elements and Periodicity in Properties > Topic: Modern Periodic Law and Present Form - Long Form Periodic Table

View Details
ECOSYSTEM TYPES

What nutrient often limits productivity in aquatic systems?

Phosphorus frequently limits primary productivity in freshwater because photosynthetic organisms require phosphate for ATP, nucleic acids, phospholipids, and many metabolic reactions, yet biologically available phosphate is often scarce. Unlike carbon and nitrogen, phosphorus has no large gaseous reservoir that rapidly replenishes most ecosystems. It enters lakes mainly through rock weathering, soil erosion, sewage, detergents, and fertilizer runoff, and it can become adsorbed to sediments or precipitated with minerals. When the supply of phosphate is below biological demand, adding more light or another nutrient produces little growth, whereas adding phosphorus can stimulate phytoplankton and aquatic plants. Excess input may therefore initiate eutrophication, algal blooms, decomposition, and oxygen depletion. The wording “aquatic systems” is broad: nitrogen often limits marine production, and nitrogen-phosphorus co-limitation is common. Nevertheless, among the substances listed, phosphorus is the standard limiting nutrient emphasized for many lakes and other fresh waters; potassium and sulfur are rarely the principal controls, while inorganic carbon is usually replenished through dissolved carbon and atmospheric exchange.

Ref: Ecology: Concepts and Applications, Molles, 9th Ed., Ch. 2-3

View Details
Ecosystem Pyramid

Which nutrient often becomes limiting once nitrogen is sufficient?

Phosphorus often becomes limiting after nitrogen limitation is relieved because organisms require both elements for growth, and supplying one shifts demand toward the other. Phosphorus is needed for nucleic acids, ATP, and phospholipids, but its geological cycle lacks a large atmospheric reservoir and replenishment can be slow. In freshwater systems and old, highly weathered soils, phosphate availability is especially low because it binds to minerals or is occluded. The sequence is context-dependent: light, micronutrients, or other macronutrients may instead become limiting. Energy and matter should not be conflated: nutrients can cycle among levels, but respiratory heat cannot be recycled into chemically useful energy by the community. Pyramid shape is an accounting result with biological causes, including body-size distributions, tissue longevity, consumption, assimilation, respiration, and population turnover. A snapshot may differ seasonally, especially in plankton or annual vegetation, whereas integrated production better represents ecosystem functioning across time. The ten-percent heuristic is useful for prediction but not exact; empirical transfer efficiencies vary with food quality, ectothermy, producer defenses, and detrital routing.

Ref: Fundamentals of Ecology, Odum & Barrett, 5th Ed., Ch. 3

View Details