APES 3.1 - Energy in Ecosystems

Lesson 3.1

Energy in Ecosystems (Part 1)

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

What is Primary Productivity?

Primary productivity is the rate at which the Sun's energy is converted into organic material by photosynthetic organisms (called producers).

Primary Productivity in Biomes

How to Measure Productivity

Primary Productivity Creates Trophic Levels

Net Primary Productivity

Because producers need to use some of the glucose they make to do their own cellular respiration, only a fraction of what they make is available to consumers. That "leftover" amount is called net primary productivity. You will be expected to be able to calculate this!

CO2 + H2O + energy

C6H12O6 + O2

Cellular Respiration

ALL organisms (producers and consumers/heterotrophs) use cellular respiration to obtain energy. Producers use the glucose that they make for this. Consumers get that glucose by eating the consumers.

CO2 + H2O

O2 + C6H12O6

Photosynthesis

Photosynthesis uses the sun's energy to convert inorganic carbon from the atmosphere into organic material. This organic material can be used by the producer for energy or to add biomass.

Some of the organic material gets transferred to other organisms when they eat the producers. They are called consumers (or heterotrophs).

Highest terrestrial primary productivity due to:

• high density of plants

• year-round consistent sunlight

• rich soil

Highest aquatic primary productivity due to:

• high high levels of nutrients in water

The ocean has very high productivity, but only at the surface where light is available!

What human-caused factors could cause this productivity to change?

Since we know the inputs and outputs of photosynthesis, we can use them to measure the rate of primary productivity in an ecosystem. The independent variables are things that can impact the amount of primary productivity in ecosystems, as well as in the lab!

Trophic levels help us visualize how energy is transferred from primary producers up through the organisms that consume them, and then the organisms that consume those organisms, and so on. Pay attention to the amount of energy at each level. What happens to it? Where does the excess energy go?

For your notes, research some different species that exist at each trophic level in both aquatic and terrestrial ecosystems!