🌞 Productivity in Ecosystems

Every ecosystem runs on a steady supply of sunlight. Plants use this light to build biomass (organic matter). We call the amount made in a given space and time primary production 📈. Scientists usually measure it as weight (g m–2) or energy (kcal m–2):contentReference[oaicite:0]{index=0}.

🚀 Key Productivity Terms

  • Gross Primary Productivity (GPP) – the total rate at which plants make new organic matter during photosynthesis:contentReference[oaicite:1]{index=1}.
  • Respiration Losses (R) – the energy plants use up for their own life processes.
  • Net Primary Productivity (NPP) – what remains after plants subtract their respiration. In symbols:
    \( \text{GPP} – R = \text{NPP} \)✨:contentReference[oaicite:2]{index=2}
  • Secondary Productivity – the rate at which consumers (herbivores, decomposers, etc.) build their own new organic matter:contentReference[oaicite:3]{index=3}.

🌱 Why NPP Matters

NPP represents the food energy available to all heterotrophs—think grazing deer, buzzing bees, and soil microbes 🤗:contentReference[oaicite:4]{index=4}.

⚙️ Units & Comparisons

  • Productivity rate: g m–2 yr–1 or kcal m–2 yr–1 (lets us compare grasslands, forests, oceans, etc.):contentReference[oaicite:5]{index=5}.

🌍 Global Snapshot

Earth’s living world manufactures about 170 billion tons (dry weight) of new organic matter each year! Of this, oceans—though they blanket ~70 % of the planet—contribute just 55 billion tons:contentReference[oaicite:6]{index=6}.

🔧 What Controls Primary Productivity?

  • Plant species present in the area.
  • Local environmental factors (light, temperature, moisture).
  • Nutrient availability in soil or water.
  • Photosynthetic capacity of the resident plants:contentReference[oaicite:7]{index=7}.

🎯 Important Concepts for NEET

  1. The equation \( \text{GPP} – R = \text{NPP} \) and what each term means.
  2. NPP supplies energy to all consumers in a food web.
  3. Standard units for expressing productivity (weight or energy per area per year).
  4. Main factors that raise or lower primary productivity.
  5. Global distribution: land vs. ocean contribution to total NPP.