Week 3: Energy and Nutrient Cycling

Define primary productivity

the rate at which primary producers capture and store energy

What are some ways to measure primary productivity?

CO2 uptake, O2 production, biomass production

What is the purpose for the Light-Dark Bottle Experiment?

This experiment is used to study productivity and respiration. Allows scientist to estimate net primary productivity.

What occurs in the light-bottle experiment and what is measured?

-the leaf is receiving light; therefore, photosynthesis and respiration occurs

-measures the CO2 and O2 produced

What occurs in the dark-bottle experiment and what is measure?

-the leaf is receiving no light; therefore photosynthesis stops but respiration continues

-measure the CO2 released

In photosynthesis, which gas is used and which gas produced?

-uses CO2

-produces O2

In respiration, which gas is used and which gas produced?

-uses O2

produces CO2

Why is it difficult to measure the primary productivity of aquatic organisms?

Measuring CO₂ in water can be complicated because CO₂ interacts with water and can form carbonic acid. Therefore, in aquatic experiments it can be easier to measure oxygen.

Productivity can be estimated by measuring biomass, what is biomass?

the amount of living biological material in an area

What is Gross Primary Productivity (GPP)?

GPP = total energy captured through photosynthesis

Which term best describes the following statement: the rate at which primary producers produce biomass within an ecosystem, i.e. the rate at which solar energy is concerted to organic matter

Gross Primary Production

What is Net Primary Productivity (NPP)?

NPP is the energy remaining after the plant uses some energy for its own cellular respiration

What is the equation for NPP?

NPP = GPP - respiration

What limits NPP?

phosphorous and nitrogen

Why is NPP always lower than GPP?

Because respiration is always occurring; NPP is approximately half of GPP

What is Evapotranspiration?

the amount of water returned to the atmosphere by the combined processes of evaporation and transpiration in plants

Where are the most productive biomes located and why?

Tend to be near the equator because there is lots of sunlight, lots of rainfall, warm temperatures, and long growing seasons.

What is transpiration?

Plants losing water vapor thru their stomata in their leaves

What happens to primary productivity when nutrients are abundant?

It can cause ecological issues such as dead zones

What is eutrophication?

the process where a body of water, such as a lake or pond, becomes overloaded with nutrients, especially nitrogen and phosphorus

Describe what happens in the body of water when eutrophication occurs

The excessive nutrients cause algae to grow rapidly, forming an algal bloom. When the algae die, bacteria decompose them and use up dissolved oxygen in the water. This can lead to low oxygen levels, causing fish and other aquatic organisms to die.

List decomposers that were discussed in class

Fungi

Bacteria

Worms

Vultures; tear apart carcasses

Dermestid Beetles; consume animal tissue

Dung Beetles; use animal feces as food/resources

Which biome has the highest decomposition rate and which biomes has the lowest decomposition rate?

-tropical rain forest

-boreal forest/tundra

In which biomes are leaf litter accumulation the highest and lowest?

-Boreal forest because of low decomposition rate

-Tropical rain forest because of high decomposition rate

What makes plant material difficult to decompose?

-Lignin and cellulose

Which factors does the decomposition rate depend on?

temperature, presence of decomposers, and the chemical composition of leaves

Warm + moist + lots of decomposers + easily digestible material = ?

faster decomposition

Cold + dry + fewer decomposers + high lignin/cellulose =?

slower decomposition

What allows for vertical mixing of nutrients in oceans and ponds/lakes?

-upwelling in oceans

-turnover in ponds/lakes

What are detritivores and what do they feed on>

Detritivores(worm/fungus) feed on the waste products and decayed remnants of dead organisms rather than on larger recently dead organisms

How do invertebrates enhance the rate of decomposition of leaf litter?

they increase the surface area by consuming pieces of the leaves

Stratification of lake waters is due to differences in?

temperature

Which organisms are primarily responsible for terrestrial decomposition?

bacteria and fungi

In the equation NPP = GPP – respiration, the term "GPP" is best defined by total ____?

carbon fixed by primary producers

Tropical terrestrial ecosystems, such as rainforests, have very high NPP. NPP declines as you move northward through temperate deciduous forests and then boreal forests. In the open ocean, NPP shows much less variation with location. These differences reflect varying land and ocean patterns based on?

Latitude