Water Cycle, Carbon Flow, Global Warming and Photosynthesis Review

The Water Cycle

• Definition: The continuous movement of water on, above, and below the surface of the Earth.
• Key stages of the water cycle:
  • Evaporation: Water from oceans, lakes, and rivers gets heated and turns into vapor.
  • Transpiration: Water vapor is released into the atmosphere from plants.
  • Condensation: Water vapor cools and forms clouds.
  • Precipitation: Water falls back to Earth as rain, snow, or fog.
  • Runoff: Water moves over the surface to streams and rivers.
  • Infiltration: Water seeps into the ground to replenish aquifers.

Properties of Water

• Hydrogen Bonds:
  • Water molecules form hydrogen bonds which influence its physical properties.
• Heat Capacity:
  • Water absorbs and releases heat effectively due to its hydrogen bonds, contributing to temperature moderation on Earth.

The Flow of Carbon

• Carbon Cycle Overview:
  • Carbon dioxide (CO2) is emitted into the atmosphere through respiration, decomposition, and the burning of fossil fuels.
  • CO2 is absorbed by oceans and plants, which convert it into organic carbon (sugars) through photosynthesis.
• Photosynthesis Reaction:
  • Equation: CO2 + H2O + light energy → C6H12O6 + O2
  • Occurs in chloroplasts of plants.

The Greenhouse Effect

• Definition: The trapping of heat in the Earth's atmosphere by greenhouse gases like CO2.
• Function: Maintains Earth's temperature but excess greenhouse gases lead to global warming.
• Global Warming Effects:
  • Global melting of glaciers.
  • Rise in sea levels.
  • Loss of habitats for temperature-sensitive species.
  • Changes in climate patterns leading to severe storms.

Human Impact on Carbon Emissions

• Deforestation:
  • Contributes 25% of CO2 emissions through the clearing of forests for agriculture and urban development.
  • Cattle farming is a major driver of deforestation and emits methane, another potent greenhouse gas.
• Major Sources of CO2 Emissions:
  • Industry, transportation, residential and commercial sectors.

Photosynthesis Process

• Location: Occurs in the chloroplasts of plants through two main stages:

  1. Light Reactions (Thylakoids): Convert light energy into chemical energy (ATP and NADPH).
  2. Calvin Cycle (Stroma): Uses ATP and NADPH to convert CO2 into sugars.

• Stomata Role:

  • Openings in leaves that regulate gas exchange.
  • Balance between CO2 uptake and water loss through transpiration affecting photosynthesis efficiency.

Global Warming Effects on Photosynthesis

• Risks to Photosynthesis:
  • Increased temperatures lead to more water loss through transpiration.
  • High temperatures may cause stomata to close, reducing CO2 absorption and hindering photosynthesis.
• Implications:
  • As temperatures rise, plant growth and agricultural yields may decline due to reduced photosynthesis.