Energy and ecosystems

Question 1

Definition of an ecosystem

Answer 1

It is formed from a community and the non-living components of its environments.

Question 2

Biomass is a measurment of…(2 points)

Answer 2

1. The mass of carbon per unit area.
2. The dry mass of tissue produced per unit area.

Question 3

What does dry mass tell scientists?

Answer 3

The measure of productivity of an ecosystem.

Question 4

Describe the relationship between productivity and biomass.

Answer 4

The higher the productivity, the higher the biomas- directly proportional.

Question 5

Describe how to measure dry mass (5 points).

Answer 5

1. The sample of organism is dried in an oven.
2. The sample is weighed after a certain amount of time, for example: 24 hours.
3. The sample is dried again in the oven and re-weighed over and over until the mass remians constant, which means all the water has been removed.
4. If taking a sample of a whole ecosystem, scale up (multiply).
5. Units: Kgm^-2Yr^-1 / Kgha^-1Yr^-1

Question 6

What are the units for dry mass?

Answer 6

Kgm^-2Yr^-1 / Kgha^-1Yr^-1

Question 7

Describe calorimetry (5 points)

Answer 7

1. This is used to measure the chemical energy stored in organic material (biomass).
2. Dry matter burnt in oxygen in a combustion chamber- closed system.
3. Energy given off is used to heat a known volume of water.
4. Increase in temeperature of water indicated energy contained in material.
5. Units: Joules / kiloJoules.

Question 8

What are the units of colorimetry?

Answer 8

Joules / kiloJoules

Question 9

Definition of gross primary production (GPP)

Answer 9

The chemical energy store in plant biomass from photosynthesis in a given area.

Question 10

Definition of net primary production (NPP)

Answer 10

The chemical energy store in plant biomass after repsiratory losses (R) have been subtracted.

Question 11

Equation for net primary production…

Answer 11

NPP = GPP - R

Question 12

Units for NPP

Answer 12

kJm^-2 (energy per area)

Question 13

Explain why the majority of the light that falls on the producer is not used in photsynthesis (4 points).

Answer 13

1. Light is reflected.
2. Light misses the chloroplast (passes straight through the leaf).
3. Light is the wrong wavelength (chlorplasts don’t absorb green light).
4. CO2 concentration / temperature is a limiting factor. Light energy is unable to be trapped = more energy lost.

Question 14

What is a food chain?

Answer 14

Shows the flow of energy between organisms.

Question 15

What is NPP energy availiable to? (3 points)

Answer 15

1. Producers for growth and reproduction.
2. Primary consumers when they eat the producers.
3. Decomposers when they eat the producers.

Question 16

Why is 90% of the NPP lost and 10% only transferred to the consumer? (3 points)

Answer 16

1. Some of the organism is indigestible and the energy is egested as faeces.
2. Some of the energy is exctreted in urine.
3. Some of the biological molecules taken in are respired and not incorporated into consumer biomass, this respired energy is lost as heat.

Question 17

Definition of net production (N) in a consumer.

Answer 17

The energy available to the next trophic level. The N reduces as the trophic levels progress due to energy loss at each level.

Question 18

The equation for net production…

Answer 18

N = I - (F + R)

Question 19

What is the equation for calculating the % efficiency of energy transfer?

Answer 19

% efficiency of energy transfer = (net production of trophic level) / (net prodcution of previous trophic level) x 100.

Question 20

Explain the effect of simplifying food webs involved with humans.

Answer 20

This involves getting rid of food chains

Question 21

How can removing organisms from food webs be done?

Answer 21

1. Using chemical control: using an insesticide or herbicide.
2. Using biological control.

Question 22

Describe 4 reasons for the low efficiency of energy transfers from producer to primary consumers (4 points).

Answer 22

1. The primary consumers, herbivores / cattle, do not eat all the grass.
2. They do not digest all the grass consumed (produces lots of faeces).
3. Most of the energy they do absorb is used in respiration.
4. A lot of energy is used to keep themselves warm by moving around.

Question 23

Describe reasons for the low efficiency of energy transfer between consumers (4 points).

Answer 23

1. Secondary consumers don’t eat all the organism.
2. They can’t digest everything they eat (produces faeces).
3. There are losses in excretory materials- urine.
4. Some is lost as heat from respiration to the environment- the higher the body temperature, the higher the energy needed to maintain it.

Question 24

Describe reasons for low efficiency of energy transfer through ecosystems (6 points).

Answer 24

1. Some light is refelcted / not of the appropriate wavelength.
2. Some light misses the leaves / doesn’t strike chloroplasts.
3. There is heat loss / energy is used to maintain temperature in the body.
4. There is energy loss via excretion.
5. There is energy loss in faeces / undigested food / some parts of organism are not eaten.
6. There is loss via excretion / urine.

Question 25

Why does adding fertilisers to soil improve productivity? (2 points).

Answer 25

1. Nitrates for protein synthesis.
2. Phosphate for ATP and DNA synthesis.

Question 26

Why does adding weed killers, herbicides and pesticides improve productivity? (1 point).

Answer 26

Removes competition.

Question 27

Why does ploughing / aeration improve productivity? (2 points)

Answer 27

1. Aerating soil improves drainage.
2. Allows nitrification and decreases denitrification.

Question 28

Why does crop rotation improve productivity?

Answer 28

Improves soil nutrients.

Question 29

How does livestock being slaughtered when still growing improve productivity?

Answer 29

More energy is transferred into biomass.

Question 30

How does livestock being fed on concetrate / a controlled diet improve productivity?

Answer 30

A higher rporportion of food is digested, absorbed and used for biomass / less is lost in faeces.

Question 31

How is CO2 concetration levels managed in greenhouses/polytunnnels? (1 point).

Answer 31

Increased by burning propane in a generator.

Question 32

How is light controlled in a greenhouse/polytunnel?

Answer 32

Light through glass.
Lights in the dark.

Question 33

How is temperature controlled in greenhouses/polytunnels?

Answer 33

Glass traps lights’ heat.
Heating and cooling systems include circulating systems.