APES 1.8 Primary Productivity

Primary Productivity

The rate at which solar energy (sunlight) is converted into organic compounds via photosynthesis over a unit of time

Gross Primary Productivity (GPP)

The total rate of photosynthesis in a given area

Net Primary Productivity (NPP)

The rate of energy storage by photosynthesizers in a given area, after subtracting the energy lost to respiration.

Productivity is measured in:

units of energy per unit area per unit time (eg. kcal/m²/yr)

Most red light is absorbed in the upper

1m of water

Blue light only penetrates deeper than

100m in the clearest water

Red and blue light affect _____________ in aquatic ecosystems

Photosynthesis

Photosynthesizers in aquatic ecosystems:

Have adapted mechanisms to address the lack of visible light

Primary Productivity is AKA

Rate of photosynthesis in all producers in a given area over a given period of time

Since photosynthesis leads to growth, you can also think of PP as the

Amount of plant growth in an area over a given period of time

Ecosystems with high PP are usually more:

Biodiverse (more diversity of species) than ecosystems with low PP

High PP =

High plant growth = lots of food & shelter for animals

Formula to calculate PP

NPP = GPP - RL

NPP

The amount of energy (biomass) leftover for consumers after plants have used some for respiration

Respiration Loss (R/RL)

Plants use up some of the energy they generate via photosynthesis by doing cell respiration (movement, internal transportation, etc.)

You can think of RL as:

Taxes plants need to pay

GPP

The total amount of sun energy (light) that plants capture and convert to energy (glucose) through photosynthesis

You can think of GPP as the:

Total paycheck amount the plant earns

You can think of NPP as the:

Actual amount of the plant’s paycheck it keeps after taxes

Energy used by respiration is lost as:

Heat

The total energy captured

GPP

Energy left after respiration

NPP

Ecological Efficiency

The portion of consumed (or captured) energy that can be passed from one trophic level to the next

Generally, only _______ of all incoming sunlight is captured and converted into GPP via photosynthesis

1%

About _______ of solar energy comes in wavelengths plants can’t use for photosynthesis & is reflected by or passes through them

99%

Of that 1% of sunlight captured, an average of ____________ is converted into biomass/plant growth (NPP)

40% (or 0.4% of total incoming solar energy)

Energy transfer is roughly _________ efficient from trophic level to trophic level (10% rule)

10%

Some ecosystems are more efficient than others

True; they have a higher NPP

About how much of GPP is lost to respiration?

60%

How much GPP is left over to support the growth and reproduction of producers (NPP)

40%

The more productive a biome is the:

Wider the diversity of animal life it can support (high biodiversity)

What are factors that lead to high NPP

Water availability, higher temperature, and nutrient availability

What is the 1st factor that leads to high NPP

Water availability

What is the 2nd factor that leads to high NPP

Higher temperature

What is the 3rd factor that leads to high NPP

Nutrient availability

Shortage of any of the 3 factors that lead to high NPP will result in:

Decreased NPP

What kind of biomes might decreased NPP lead to?

Desert (low H₂O & nutrients) Tundra (low temp & liquid H₂O) Open Ocean (low nutrients, photosynthesis limited to photic zone)