3. What are the main sources of
phosphorus in the phosphorus cycle?
Rocks, water, soil, and sediments constitute the primary
nonliving sources of phosphorus, whereas plants and
animals form the major living sources.
4. Role of phosphorus:
• Central role in cell metabolism, contained in energy-transferring
molecules:
❑Adenosine monophosphate (AMP)
❑Adenosine diphosphate (ADP)
❑Adenosine triphosphate (ATP)
• Cell reproduction, as key component of the molecules that
contain and transfer the genetic code:
❑Deoxyribonucleic acid (DNA)
❑Ribonucleic acid (RNA)
7. 1) Weathering
phosphates found in the sedimentary rocks as
PO4
3-
, are leached out of the disintegrated rocks
from its various environmental sources in the
form of inorganic phosphate ions.
2) Mineralization
by plants
Plants absorb organic phosphorus present in
soil and underground water and convert them
to inorganic forms for utilization.
The aquatic plants absorb inorganic
phosphorus from lower layers of water bodies
due to their low solubility in water.
3) Assimilation
by animals
Herbivorous and carnivorous animals, including
humans, absorb phosphorus when they
consume these plants for their food,
8. 4) Decomposition
by microorganisms
Microorganisms such as bacteria and fungi
decompose organic phosphates back into
the inorganic form, which is then returned
to the soil and water bodies.
Phosphorus-containing compounds may
also be carried in the surface runoff to
rivers, lakes, and oceans to form sediments.
5) Geological
uplift by tectonic
movements
a process where in sedimentary rocks
containing phosphorus may be moved from the
ocean to the land. The phosphorus thus
deposited as sediments are ultimately released
back into the environment through the process
of weathering, thus completing the cycle.
9. Why is the phosphorus cycle
important?
1) Acts as an essential component of nucleotides and nucleic acids
such as DNA and RNA
2) Forms an essential component of our bone and the enamel of
mammalian teeth
3) Constitutes an essential component of the phospholipids
present in the biological membranes such as cell membrane
4) Forms the exoskeleton structure of insects
5) Functions as a buffering agent to maintain a steady
physiochemical condition of the body
10. How do humans affect the
phosphorus cycle?
•Using of phosphate-containing fertilizers
•Cutting down of tropical rainforests
•Spilling of phosphate during transportation
•Leaching of phosphorus from households and
industries into water bodies (from water
softeners and detergents)
11. How does the use of fertilizer
affect the phosphorus cycle?
Excessive use of phosphate fertilizers to enrich the soil also
potentially increases the phosphorus content of the water
bodies through surface runoff. This phenomenon leads to
excessive growth of algae, thus lowering the dissolved
oxygen level in the water bodies, resulting in severe loss of
aquatic lives. (EUTROPHICATION)
12. How does deforestation affect the
phosphorus cycle?
Cutting down of trees increases soil erosion and thus decrease the
phosphorus content of the soil. Since phosphorus acts as a limiting
nutrient for plant growth, deforestation affects the phosphorus
cycle.
13. SUMMARY:
• Phosphorus is essential for plant and animal growth, as well as the
production of DNA, RNA, cell membranes, and ATP.
• The phosphorus cycle involves five key steps: weathering, absorption and
mineralization by plants and animals, returning to the environment by
decomposition, and geological uplift as sediments.
• Human activities, such as adding phosphorus-rich fertilizers to the soil, can
impact the phosphorus cycle. Overabundance of phosphorus can lead to
excessive algae growth, which can be toxic to plants and animals in the
ecosystem.
• Phosphorus cycle is a slow process and does not include any gaseous phase,
understanding it can help promote a healthier environment.
16. Different Steps of the Sulfur Cycle
1) Formation of Inorganic Sulfur
It occurs through two different processes:
Biological – By decomposers present in the soil
Geological – Through weathering of rocks formed from
geological uplift
17. Different Steps of the Sulfur Cycle
2) Oxidation of Inorganic Sulfur to Sulfate (SO42−)
It involves two steps:
1.Hydrogen sulfide is oxidized to produce elemental sulfur
by certain photosynthetic bacteria such
as Chlorobiaceae and Chromatiaceae species
2.Elemental sulfur is then converted to sulfate by
chemolithotrophic bacteria
18. Different Steps of the Sulfur Cycle
3) Assimilative Reduction of Sulfate to Sulfide (S2−)
Also known as sulfur reduction, it is performed by plants,
fungi and various microorganisms such as Desulfovibrio and
Desulfobulbus species in two steps:
➢ Sulfates are converted to sulfites
➢ Reduction of sulfites to hydrogen sulfides
19. Different Steps of the Sulfur Cycle
4) Incorporation of Sulfide into Organic Compounds
The sulfide assimilated is converted into an organic form
which the animals consume and fix through the foods they
eat. Once these plants and animals die, decomposers
release the fixed organic sulfur back into its free form as
elemental sulfur.
20. Why is the sulfur cycle important?
1) Forming an essential component of all kinds of proteins and some vitamins
and hormones in living organisms
2) Producing fossil fuels such as coal, petroleum and natural gas
3) Contributing to a majority of metal deposits because of its ability to act as an
oxidizing as well as reducing agent
4) Serving as the source of energy to the sulfur-reducing bacteria present in the
hydrothermal vents
5) Reducing global warming caused by the greenhouse gases by absorbing the
ultraviolet radiation of the sun
6) Helping in the growth of plants, the primary producers of the ecosystem
21. How do humans affect the Sulfur
Cycle?
1) Releasing sulfur from oil and coal-based power
plants
2) Processing of sulfur-containing metals
3) Using sulfur-containing fertilizers
22. What are the effects of Sulfur
dioxide?
When you inhale or contact sulfur dioxide, you can encounter
issues such as:
1. Difficulty breathing
2. Respiratory system issues
3. Asthma
4. Sneezing and coughing
5. Changes in lungs function
6. Irritation of the eyes
23. HOW TO PREVENT SULFUR
DIOXIDE POLLUTION?
1. Use fuel-efficient vehicles
2. Consider renewable sources of energy
3. Dispose of sulfur dioxide waste properly
