BioInteractive Outputs and Ecological Roles of Photosynthesis

Question 1

What are the overall reactants and products of the photosynthesis equation?

Accepted Answer

Reactants: CO2 + H2O + light; Products: glucose + O2

Answer

Reactants: O2 + glucose; Products: CO2 + H2O

Answer

Reactants: CO2 + O2; Products: glucose + H2O

Answer

Reactants: glucose + light; Products: CO2 + H2O

Question 2

How does photosynthesis contribute to the oxygen content of Earth's atmosphere?

Accepted Answer

Photosynthetic organisms have released O2 as a byproduct for billions of years, creating the modern atmosphere

Answer

Photosynthesis consumes O2 from the atmosphere

Answer

O2 is produced only by deep-sea photosynthesis

Answer

Photosynthesis converts N2 to O2

Question 3

What is gross primary productivity (GPP) in an ecosystem?

Accepted Answer

The total rate of carbon fixation by photosynthesis before subtracting respiration losses

Answer

The carbon remaining after plant respiration

Answer

The amount of carbon consumed by herbivores

Answer

The net gain of biomass by the entire food web

Question 4

What is net primary productivity (NPP)?

Accepted Answer

GPP minus the carbon lost to plant respiration, representing energy available to consumers

Answer

Total carbon fixed by photosynthesis

Answer

Carbon stored in soil organic matter

Answer

Energy used by animals for growth

Question 5

How does photosynthesis influence the global carbon cycle?

Accepted Answer

It removes CO2 from the atmosphere and stores carbon in organic molecules, partially offsetting emissions

Answer

It releases CO2 into the atmosphere

Answer

It has no significant effect on atmospheric CO2 on human timescales

Answer

It converts methane to CO2

Question 6

Why is photosynthesis considered the foundation of most food webs on Earth?

Accepted Answer

It converts light energy into chemical energy stored in organic molecules that all other organisms depend on

Answer

It produces O2 that animals use for cellular respiration only

Answer

It directly feeds all organisms in a food web

Answer

It is the only way plants can survive