APES 1.8 Primary Productivity

Primary Productivity

• Energy can be converted from one form to another

• Solar energy is integral to the movement of energy and sustaining organisms

• Primary productivity is the rate at which solar energy is converted into organic compounds

• Gross primary productivity is the total rate of photosynthesis in an area

• Net primary productivity is the rate of energy storage after subtracting lost energy

• Productivity measures in energy per area per time (kcal/m^2/yr)

• Most red light is absorbed in the first 1m of water, and blue light penetrates, at most, 100m. This greatly affects ecosystems in aquatic areas. Photosynthesizers have adaptations for this.

• Producers in areas with no/little light have used chemosynthesis as an alternative.

• Nearly all energy that powers ecosystems comes from the sun.

• Producers (autotrophs) use the sun’s energy to create useable forms of energy

• Through photosynthesis, producers use solar energy to convert carbon dioxide and water into glucose (sugar) and oxygen

• Photosynthesis: Solar energy + 6 H₂O + 6 CO₂ → C₆H₁₂O₆ + 6 O₂

• Respiration: C₆H₁₂O₆ + 6 O₂ → energy + 6 H₂O + 6 CO₂

• Gross primary productivity: The total amount of solar energy that producers in an ecosystem capture over a given amount of time - or the rate at which this occurs. Some fraction of energy used for cellular respiration and homeostasis.

• Net primary productivity: Energy captured by producers minus the energy used (respired.) Refers to the remaining stored energy. Rate at which all plants "net" useful chemical energy - some goes towards growth and reproduction, some utilized by herbivores.

• Producers usually only capture about 1% of available solar energy

• It is not a very efficient process and most solar energy returns as heat to the atmosphere

• Some lost energy is wavelengths producers can’t absorb