IPA - Daur Biogeokimia (Ekosistem) | GIA Academy

Scientific concepts & nature phenomena presented

Acid rain (phenomenon + effects)

• Definition: Rain with pH < 5.6 (more acidic than normal rain).
• Impacts:
  • Lowers soil and surface-water pH, harming fish, plants, frogs, plankton, and humans.
  • Damages plant leaves and inhibits growth.
  • Disrupts ecosystem function, contributing to imbalance in the water cycle/ecosystem.
• Cause/mechanism: Chemical reactions in the atmosphere:
  • SO₂ (sulfur dioxide) → forms sulfuric acid
  • NOx (nitrogen oxides) → forms nitric acid
• Sources named: burning coal, motor vehicles, and chemical factories.

Biogeochemical cycle (core concept)

• Definition: Cycling of chemical elements through biotic (living things) and abiotic environments (air, soil, water).
• Purpose: Elements don’t disappear; they return to nature, maintaining ecosystem survival and balance.
• Elements mentioned: carbon, nitrogen, hydrogen, oxygen, sulfur, phosphorus.
• Cycles discussed: water (hydrological) cycle, carbon cycle, oxygen cycle, nitrogen cycle, sulfur cycle, phosphorus cycle.

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Methodology / process lists (cycle stages)

1) Water (Hydrological) cycle

Stages:

• Evaporation: Solar heat evaporates water from oceans/rivers/lakes; also evaporation from plant and soil surfaces (liquid → gas).
• Condensation: Water vapor changes to liquid droplets due to temperature/pressure changes, forming clouds.
• Precipitation: When clouds are saturated, water falls as rain/snow/hail/frost; replenishes rivers, lakes, oceans.
• Infiltration: Some surface water seeps into the ground, becoming groundwater or flowing into rivers.
• Surface runoff: Water not infiltrating flows over land into rivers/lakes/reservoirs.
• Transpiration: Plants absorb water via roots and release water vapor from leaves via stomata.

Cycle types:

• Short cycle: Sea evaporation → condensation → precipitation → back to the sea.
• Medium cycle: Sea evaporation carried by wind to land → precipitation → infiltration/surface flow → back to the sea.
• Long cycle: Sea evaporation/condensation → wind carries clouds to high/cold regions → formation of snow/ice → glaciers melt → runoff returns to sea.

Human impacts mentioned:

• Greenhouse effect → climate warming:
  • Gases: CO₂, CH₄, water vapor
  • Effects: faster evaporation, increased atmospheric water vapor, altered rainfall patterns (droughts and flooding).
• Acid rain: damaging water/soil and ecosystems.
• Water pollution:
  • Industrial/domestic waste introduces toxic chemicals, heavy metals, excess nutrients (N, P) → reduced water quality and disrupted natural cycling.

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2) Carbon cycle

Core idea: Exchange of carbon compounds between the atmosphere and Earth’s surface.

Main pathways described:

• Photosynthesis (autotrophs): Plants/algae/phytoplankton use solar energy, water, CO₂ → carbohydrates.
• Food chain transfer: Carbon compounds move from autotrophs → heterotrophs.
• Respiration (cellular respiration): Organisms use oxygen → release CO₂ back to the atmosphere.
• Decomposition: Dead organisms/waste decompose → carbon released to soil/air.
• Fossil fuel burning: Petroleum/coal/natural gas release CO₂ and greenhouse gases → global warming potential.

Notable comparisons/source:

• Tropical rainforests absorb carbon far more than deserts (ratio stated as 100 times).

Benefits mentioned:

• Environmental: carbon helps “insulate” by trapping solar energy (greenhouse concept).
• Biological: carbon is building blocks of life and forms stable bonds in biomolecules.

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3) Oxygen cycle

Link to carbon cycle: Oxygen is involved in forming organic compounds and exchanging gases.

Processes described:

• Photosynthesis: plants release O₂ to the atmosphere.
• Respiration (aerobic organisms): organisms inhale O₂, exhale CO₂.
• Decomposition: dead matter returns nutrients including C, O, water to soil/air.
• Burning fossil fuels: releases CO₂ into the atmosphere.
• Rusting: metals react with moisture and oxygen → oxide formation.

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4) Nitrogen cycle

Core idea: Nitrogen converted among forms across atmosphere → soil → organisms → atmosphere.

Stages:

• Nitrogen fixation: N₂ → NH₃ (ammonia) using nitrogenase enzymes from Azotobacter and Rhizobium.
• Nitrification: NH₃ → NO₃⁻ (nitrate) via Nitrobacter (ammonia is toxic to plants).
• Assimilation: plants absorb nitrite (NO₂⁻), nitrate (NO₃⁻), ammonium (NH₄⁺) → used to build proteins.
• Ammonification: decomposers convert organic nitrogen back to ammonium/ammonia (bacteria + fungi).
• Denitrification: NO₃⁻ → N₂ gas returning to the atmosphere via Clostridium and Pseudomonas (described as using nitrate to obtain oxygen and releasing nitrogen gas).

Benefits mentioned:

• Enables plants to form chlorophyll.
• Converts inert N₂ into plant-usable forms.
• Supports decomposition and soil nutrient enrichment (nitrates/nitrites).
• Nitrogen as a component of cells and biomolecules.

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5) Sulfur cycle

Core idea: Sulfur moves between air/soil and living organisms.

Key stages described:

• SO₂ sources: volcanism, burning fossil fuels, rock weathering, and rainfall (acid rain linkage mentioned).
• SO₂ → sulfuric acid via reaction with oxygen and water.
• Acid deposition forms sulfate (SO₄²⁻).
• Plants absorb sulfate → used to form proteins.
• Food transfer: sulfur moves from plants → animals/humans.
• Decomposition: produces H₂S (hydrogen sulfide) in air/soil.
• H₂S re-oxidation → sulfur oxides → sulfate formation via bacteria → reabsorbed by plants.

Benefits mentioned:

• Promotes formation of greener leaves.
• Increases protein and vitamin content.
• Supports plant production of sugar substances.

Adverse impact mentioned:

• Air pollution from sulfur compounds damaging the atmosphere.

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6) Phosphorus cycle

Core idea: Phosphorus is vital but limited; large source is rocks and sediments.

Stages:

• Weathering/erosion: rocks release phosphate salts.
• Soil/water dissolution: phosphates dissolve and move in water.
• Plant uptake: plants absorb phosphates.
• Trophic transfer: animals/humans get phosphorus by eating plants.
• Return to soil: dead organisms/excretion (urine, feces) add organic phosphate.
• Bacterial breakdown: organic phosphate → inorganic phosphate, then returned to the ecosystem.

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Researchers / sources featured (as named in subtitles)

• Azotobacter
• Rhizobium
• Nitrobacter
• Clostridium
• Pseudomonas