Unit 2.3 - Energy flows and matter

Question 1

Define productivity

Answer 1

The exchange of energy into biomass

Question 2

Define gross primary productivity

Answer 2

All the biomass of a photosynthetic organism created prior to losses

Question 3

Define net primary productivity

Answer 3

All the biomass of a photosynthetic organism created minus the losses (from respiration)

Question 4

Define gross secondary productivity

Answer 4

The amount of biomass consumed minus the fecal matter excreted

Question 5

Define net secondary productivity

Answer 5

The amount of biomass consumed minus the fecal matter excreted minus energy lost from respiration

Question 6

What happens to the incoming energy from the sun?

Answer 6

A lot is reflected off of the clouds, the ground, and the atmosphere via albedo effect. Also, a lot is absorbed by the clouds and atmosphere. Only around 50% reaches the ground, where it is absorbed by plants and other things.

Question 7

How do nitrates form naturally?

Answer 7

Electricity has enough energy to form nitrates in the soil from the atmospheric nitrogen. However, nitrogen is also formed by microorganisms like bacteria and cyanobacteria (that can be fixed onto the root nodules) which undergo nitrification to turn ammonia into nitrates. Ammonia is naturally created through the decomposition of living organisms, like plants and animals, in decomposing organisms . Plants then use the nitrates in the soil to synthesise amino acids.

Question 8

How are nitrates turned back into nitrogen

Answer 8

Denitrifying bacteria, commonly found in the wetlands, returns nitrates back into nitrogen gas and returned into the atmosphere