Topic 1.8 Primary Productivity Notes

Primary Productivity (Topic 1.8)

Objective

  • Explain how solar energy is acquired and transformed by living organisms.

Skill

  • Describe an environmental concept or process in FRQs.

Basics of Primary Productivity

  • Definition: The rate at which solar energy (light) is transformed into organic compounds (e.g., glucose, cellulose) through photosynthesis over a period of time.
  • Units of Measurement: Kilocalories per meter squared per year (kilocaloriesm2⋅year\frac{kilocalories}{m^2 \cdot year}).
    • Must be expressed as energy per area per time.
  • Analogy: Rate of photosynthesis of all producers in an area over time.
    • Plants are like workers in a factory producing gadgets.
  • Primary productivity is essentially the rate of plant growth.
  • Higher primary productivity $\implies$ higher plant growth $\implies$ more food and shelter for animals $\implies$ higher biodiversity.
  • Ecosystems with high primary productivity have a higher diversity of species and are considered more biodiverse.

Calculating Primary Productivity

  • Plants use some harnessed energy for cellular respiration (fueling movement, internal transportation).
    • Respiration loss: Energy plants use to keep themselves running (like taxes).
  • Gross Primary Productivity (GPP): Total amount of sunlight plants capture and convert into energy (total photosynthetic rate).
    • The total paycheck amount the plant earns.
  • Net Primary Productivity (NPP): Amount of energy plant stores as biomass (plant growth).
    • Energy left for consumers after plants use energy for respiration.
    • The take-home pay after taxes.
  • Equation: NPP=GPP−Respiration LossNPP = GPP - Respiration\, Loss
  • Diagram Explanation:
    • Total sunlight converted into energy = GPP.
    • Respiration loss = Energy used by the plant for basic processes.
    • NPP = Energy left after respiration, stored as sugars in fruit or biomass (bark, leaves).

Ecological Efficiency

  • Definition: Portion of incoming sunlight captured by plants and converted into biomass (NPP).
  • Only about 1% of sunlight is captured by plants for GPP.
    • 99% is reflected or passes through.
  • About 40% of the 1% (0.4% of total) is converted into biomass (NPP).

Trends in Productivity

  • More productive ecosystem $\implies$ higher biodiversity.
  • Factors Contributing to High NPP:
    • More water available.
    • Higher temperature.
    • More nutrient availability.
  • Examples:
    • Highly productive:
      • Swamps and marshes: High water, warm temperatures, high nutrient availability (organic matter).
      • Tropical rainforest: High water, warm temperatures and high nutrient availability.
      • Coral reef: Warm, abundant water, nutrients from organic matter.
    • Low productivity:
      • Desert: Deficiency of water and nutrients (sandy soil).
      • Tundra: Extremely cold, low access to liquid water (frozen water).
      • Open ocean: Warm, abundant water, but deficiency of nutrients (not a lot of organic matter).

Practice FRQ

  • Describe the process of net primary productivity.
  • Describe the relationship between primary productivity and biodiversity.