3.5.3.1 - Energy and Biomass/GPP and NPP (Unit 5 Energy Transfers)

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 mass of living material in a given area (g per m2)

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 heated (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

Define respiratory loss?

Answer 11

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

Question 12

How can you calculate NPP?

Answer 12

NPP = GPP - R

Question 13

What does NPP stand for?

Answer 13

Net primary production

Question 14

Define net primary production

Answer 14

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

Question 15

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

Answer 15

Some parts aren’t eaten (bones) and some parts are eaten and are not absorbed (faeces)
Some parts are eaten, absorbed but excreted (urine)
Some biomass us broken down and lost as heat in respiration (temp regulation/movement)

Question 16

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

Answer 16

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

Question 17

Why is not all of the energy from the sun converted into GPP?

Answer 17

Some light is the wrong wavelength (e.g. green)
Some doesn’t hit a chlorophyll molecule/transmitted
Most light is reflected by other molecules in the atmosphere
Other limiting factors may be involved

Question 18

How do farmers increase productivity

Answer 18

Food chains/webs are simplified (pests are removed)
Respiration of livestock is reduced (movement limited, temperature regulated)

Question 19

Describe two ways that farming practises can increase the amount of energy available for human consumption.

Answer 19

1. Reduce the energy lost to other organisms e.g pest control.
   Reduce the energy lost through respiration e.g restrict movement, control temp.

Question 20

What are insecticides used for?

Answer 20

To kill insect pests that eat and damage crops.

Question 21

What are herbicides used for?

Answer 21

To kill weeds to remove direct competition for sunlight.

Question 22

How do biological agents increase crop yield?

Answer 22

They reduce the number of pests, so crops lose less energy and biomass.

Question 23

What type of biological agents can be used?

Answer 23

Parasites to either kill the insect or reduce it’s ability to function or
Pathogenic bacteria and viruses

Question 24

What is an integrated system ?

Answer 24

A system of using both chemical and biological methods to reduce pests.

Question 25

What ethical issues might arise from keeping animals in pens?

Answer 25

It may cause animals pain, distress and restrict their natural behaviours.

Question 26

Why are intensively reared animals kept indoors?

Answer 26

To control the environmental temperature so less energy is wasted by generating body heat.

Question 27

Keeping cattle indoors, in barns, leads to a higher efficiency of energy transfer.

Explain why.

Answer 27

Less energy lost as heat / in maintaining body

temperature / in movement

Question 28

Explain 3 advantages for a farmer of removing hedgerows.

Answer 28

1. source of pests / animals, this effect on crop;
2. source of weeds / no longer taking nutrients, hence competition / reduced yield;
3. creation of larger fields / leaving room, hence more efficient use of machinery / grow more crops;

Question 29

Apart from providing a habitat for predators of crop pests, give 3 biological benefits of replanting hedgerows.

Answer 29

1. increases biodiversity;
2. source of food for animals;
3. habitat / nest for animals;

Question 30

Give one reason why not all the light energy falling on the producers is used in photosynthesis.

Answer 30

transmission / reflected / misses chlorophyll / chloroplasts / wrong wavelength;

Question 31

What is meant by the term ecological niche?

Answer 31

An organism’s role / in the ecosystem / community;