Unit 1.8: Primary Productivity

Primary Productivity - The rate that solar energy is converted into organic compounds via photosynthesis over a unit of time (the rate of photosynthesis [the amount of plant growth] in an area over a given period of time)

  • UNITS - kcal/m2/yr.

  • Energy/Area/Time

High Primary Productivity - High plant growth equals lots of food and shelters for animals leading to more diversity

Photosynthesis -

Reactants: CO2 + H2O ——> Products: O2 + C6H12O6 (Glucose)

Cellular Respiration - When plants need energy for themselves, they break down Glucose in the presence of oxygen and release energy in a different form, not solar energy, in the form of H2O and CO2

O2 + C6H12O6 ——> H2O + CO2

  • Producers photosynthesize more than they respire

Surplus - Used by heterotrophs (Herbivores)

  • The process of which cells unlock the energy of chemical compounds

  • Organisms then convert glucose and oxygen into CO2 and H2O which release the energy they need to live, grow and reproduce (aerobic vs anaerobic respiration)

Calculating Primary Productivity - GPP - R = NPP

Gross Primary Productivity (GPP) - photosynthesis from producers

Cellular Respiration of Producers (R) - plants use some of GPP to combust the energy into a different form

Net Primary Productivity (NPP) - the energy captured by the producers in an ecosystem minus the energy producers respire

  • Difference between GPP and NPP equals the surplus product removed from the plant when it does not photosynthesize

  • Compares productivity between different ecosystems

Primary Versus Secondary Productivity -

Primary Productivity - Photosynthesis (plants, algae, bacteria)

  • Producers, autotrophs, photo synthesizers

Secondary Productivity - Eats surplus from primary productivity

  • Cellular Respiration (all life, including plants)

  • Primary consumer, heterotroph (cannot make its own food), herbivore

  • Process of reversing and taking the glucose and oxidizing it, to make its own energy

Trends in Productivity - The more productive a biome is, the wider the diversity of animal life it can support (high biodiversity)

  • Water availability, high temperatures, and nutrient availability are all factors that lead to high NPP

  • Shortage of these equals a decrease in NPP

Tundra (Least) and Tropical Rainforest (Highest)

Primary Productivity and Wavelength - Sunlight is composed of many different wavelengths of sunlight - red, blue, green

    Fundamental Property of Water - Absorbs long wavelengths of light more than it absorbs short wavelengths of light - Different photosynthetic pigments absorb light at specific wavelengths - Example: chlorophyll, a common pigment, absorbs strongly in the blue and red parts

Human Impact -

    Agricultural Land - Land in which humans have converted from the native natural to a monoculture (rice paddy fields, soybean fields, corn fields, palm oil plantations, wheat fields)

  • Clearcutting a forest and converting it into a monoculture lowers the NPP