3.5.3.1 - Energy and Ecosystems (GPP and NPP)

Question 1

Define ecosystem

Answer 1

All the organisms living in a particular area and all the abiotic conditions.

Question 2

What are producers?

Answer 2

Organisms that make their own food - usually by photosynthesis.

Question 3

What is biomass?

Answer 3

The chemical energy stored in the plant

Question 4

Define dry mass

Answer 4

The mass of the organism with the water removed

Question 5

What unit are typically used to measure biomass?

Answer 5

dry mass of tissue per unit area per time.

Question 6

How do you measure dry mass?

Answer 6

The sample is dried in a over (low temperature). The sample is then reweighed at intervals until a constant mass is reached.

Question 7

How can you estimate the chemical energy stored in biomass?

Answer 7

Burn it in a calorimeter. The amount of heat given off tells you how much energy is in it.

Question 8

What is the unit of energy?

Answer 8

Joules or kilojoules

Question 9

What does GPP stand for?

Answer 9

Gross primary production

Question 10

Define GPP

Answer 10

The total amount of chemical energy converted from light energy by plants, in a given area, in a given time.

Question 11

How much GPP is lost to the environment as heat when the plants respire?

Answer 11

approximately 50%

Question 12

Define respiratory loss?

Answer 12

The amount of GPP that is lost to the environment as heat when the plants respire.

Question 13

How can you calculate NPP?

Answer 13

NPP = GPP - R

Question 14

What does NPP stand for?

Answer 14

Net primary production

Question 15

Define net primary production

Answer 15

The energy available to the plant for growth and reproduction. The energy is stored in the plants biomass.

Question 16

Why does only 90% of the chemical stored in the consumers food transferred to the next trophic level?

Answer 16

Not all the food is eaten.
Some parts are indigestible.
Some is egested as faeces.
Some is lost through respiration or excretion of urine.

Question 17

How can Net production of consumers (N)be calculated?

Answer 17

N = I - (F+R)
N Net production 
I Chemical energy in ingested food
F Chemical energy lost in faeces and urine
R Energy lost through respiration