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Difficulty: MediumNutrient and Biogeochemical Cycles

Arrange the following ecological events of the phosphorus cycle in the correct chronological order, starting from the initial abiotic release of phosphorus to its recycling back into soil sediments by decomposers.

  1. 1Weathering and erosion of phosphate-containing rocks release inorganic phosphate ions (PO43−PO_4^{3-}) into soil solution.
  2. 2Plant roots absorb dissolved inorganic phosphate ions and assimilate them into cellular components such as ATP and nucleic acids.
  3. 3Herbivorous consumers ingest producer biomass and incorporate phosphorus into animal tissues and structural skeletal elements.
  4. 4Decomposing soil microorganisms break down organic excreta and dead animal remains, releasing phosphate back into soil sediments.

Answer

The correct chronological order is: (1) Weathering and erosion of phosphate-containing rocks release inorganic phosphate ions into soil solution, (2) Plant roots absorb dissolved inorganic phosphate ions and assimilate them into cellular components, (3) Herbivorous consumers ingest producer biomass and incorporate phosphorus into animal tissues, and (4) Decomposing soil microorganisms break down organic excreta and dead animal remains, releasing phosphate back into soil sediments.
The phosphorus cycle is a classic sedimentary biogeochemical cycle. It begins with the abiotic release of inorganic phosphate ions (PO43−PO_4^{3-}) from rock minerals via weathering. These ions are absorbed by plant roots and assimilated into organic macromolecules (ATP, nucleic acids). Primary consumers ingest plants, incorporating the nutrient into animal tissues. Finally, saprophytic decomposers mineralize organic detritus, returning inorganic phosphate to soil sediments.

Step-by-Step Solution

1
Identify the abiotic reservoir origin of phosphorus.
Phosphorus is sedimentary and originates in rocks; weathering releases PO43−PO_4^{3-} into soil.
Unlike carbon or nitrogen, phosphorus lacks a significant gaseous atmospheric phase.
2
Trace phosphorus uptake by autotrophs (producers).
Plants absorb inorganic soil phosphate and assimilate it into organic compounds like ATP, DNA, and RNA.
Producers must convert abiotic inorganic ions into organic forms for food webs.
3
Trace phosphorus transfer through trophic levels.
Herbivores ingest plant materials, assimilating organic phosphorus into animal tissues, bones, and cell membranes.
Consumers obtain phosphorus by consuming producer biomass.
4
Identify the final recycling mechanism.
Decomposers hydrolyze organic waste and detritus, returning inorganic phosphate ions back to the soil.
Mineralization by phosphatases and decomposers completes the biogeochemical loop.

Key Concept

Sedimentary Phosphorus Cycle Dynamics
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Topics

Nutrient and Biogeochemical Cycles

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