Nutrient Cycles: Phosphorous Cycle

Question 1

Why is phosphorous an important biological element?

Answer 1

component of ATP, phospholipids, and nucleic acids = life depends on it being recycled

Question 2

In phosphorous cycle, unlike nitrogen and carbon cycles, the main reservoir is in ______ form rather than in the atmosphere in fact, phosphorous cycle lacks a gaseous phase all together

Answer 2

Mineral

Question 3

Summarise main elements of phosphorous cycle

Answer 3

• Phosphorous mostly exists as phosphate ions in the form of sedimentary rock deposits that have their origin in the seas but brought to surface by geological uplifting of rocks
• weathering and erosion of these rocks helps phosphate ions to become dissolved and so available for absorption by plants which incorporate them into their biomass
• phosphate ions pass into animals that feed on them
• excess phosphate ions excreted by animals and may accumulate in waste material

Question 4

On the death of plants and animals, decomposers such as bacteria and fungi break them down releasing phosphate ions into water or soil- what next?

Answer 4

• some phosphate ions remain in parts of animals such as bones or shells that are very slow to breakdown
• phosphate ions releases by excreta, decomposition and dissolved out of rocks are transported by streams and rivers into lakes and oceans where they form sedimentary rocks thus completing the cycle

Question 5

what is the role of mycorrhizae in nutrient cycles?

Answer 5

• mycorrhizae are associations between certain types of fungi and the roots of the vast majority of plants
• fungi act as extensions of the plant’s root system and vastly increase S.A. for the absorption of water and minerals
• the mychorriza act like a sponge holding water and minerals in the neighbourhood of the roots
• enabling plant to better resit drought and to take up inorganic ions more readily
• the mychorriza plays a part in the nutrient cycles by improving the uptake of relatively scarce ions such as phosphate ions

Question 6

explain how the relationship between fungi and plants is a mutualistic one

Answer 6

• plant benefits from improve inorganic ion and water uptake

- while the fungus receives organic compounds such as sugars and amino acids from the plant