Productivity in ecosystems

Question 1

What do plants do in an ecosystem?

Answer 1

Synthesise organic compounds from atmospheric or aquatic carbon dioxide.

• Most of the sugars synthesised by plants are used by the plants in respiration
• The rest are used to make other groups of biological molecules. These form the biomass of the plants

Question 2

Which processs are not 100% efficient

Answer 2

• photosynthesis and respiration are not 100% efficient
• transfer of biomass and its stored chemical energy is also not 100% efficient

Question 3

What is gross primary production (GPP)?

Answer 3

The chemical energy store in plant biomass in a given area or volume

Question 4

What is net primary production (NPP)

Answer 4

The chemical energy store in plant biomass in after respiratory losses to the environment have been taken into account

Question 5

What is the equation for net primary production (NPP)?

Answer 5

NPP = GPP + R

R= energy used in respiration

Question 6

Why is gross primary production so low?

Answer 6

Only 1% of the light falling on a plant is used in photosynthesis to produce glucose

99% of the light either passes through the leaf without hitting chloroplasts, is reflected off of the leaf, or is transferred to heat energy

Question 7

What is a community?

Answer 7

all living organisms of all species

Question 8

What is an ecosystem?

Answer 8

living and non living organisms and components

Question 9

What are the units for NPP and GPP

Answer 9

kJ m-2 yr-1

Question 10

What is the equation for net production of consumers (N)

Answer 10

N = I - (F+R)

Question 11

What does R represent in the equation, N = I - (F+R)

Answer 11

respiratory losses to the environment as heat

Question 12

How is biomass measured

Answer 12

in terms of mass of carbon or dry mass of tissue per given area per given time

Question 13

What are the units for biomass

Answer 13

kgm^-2 yr^-1 / gm^-2 yr^-1

Question 14

What does N represent in the equation, N = I - (F+R)

Answer 14

net production of consumers (kJ m^-2 yr^-1)

Question 15

What does I represent in the equation, N = I - (F+R)

Answer 15

chemical energy stored in ingested food

Question 16

What does F represent in the equation, N = I - (F+R)

Answer 16

chemical energy lost to the environment in faeces and urine

Question 17

Define trophic

Answer 17

feeding

Question 18

What is a food chain

Answer 18

a straightforward feeding (trophic) relationship from producers through consumers

Question 19

Why are trophic levels in food chains limited to below 5

Answer 19

energy is lost at every trophic level

Question 20

What is the first trophic level

Answer 20

producer (plant)

Question 21

What is the 2nd trophic level

Answer 21

primary consumers

Question 22

What is the 3rd trophic level

Answer 22

secondary consumers

Question 23

What is the 4th trophic level

Answer 23

tertiary comsumers

Question 24

What units is energy flow through an ecosystem measured

Answer 24

in units of energy per area per unit of time

kJ m^-2 yr^-1

Question 25

What is the ultimate energy source in an ecosystem

Answer 25

sunlight

Question 26

Why is the utilisation and conversion of sunlight into chemical energy not efficient

Answer 26

- light may miss chloroplasts - some light may be reflected - some light is the wrong wavelength

Question 27

How efficient is energy transfers between trophic levels

Answer 27

5-10% efficient this is why food chains tend to only have 4/5 trophic levels

Question 28

Why are energy transfers between trophic levels not 100% efficient

Answer 28

- most energy is transferred to the environment as heat, which is lost during respiration - some parts of an organism are not consumed or digested - loss occurs via excretory products

Question 29

Outline the methos of measuring biomass of plant material

Answer 29

1. Heat plant material at 100C for 15 minsand then weigh and record mass. - A lower temperature for a longer time-period can be used. Higher temperatures can cause organic compounds to burn. 2. Reheat at same temperature for the same period and reweigh. 3. Repeat until a constant mass is obtained - this indicates all the water has been removed. 4. **Divide the dry mass by the area from which the plant material was removed.**

Question 30

What is the purpose of cAlorimetry

Answer 30

estimates the chemical energy store in biomass

Question 31

What is the basic procedure of calorimetry

Answer 31

1. Known mass biomass is completely burnt so all the energy released is used to heat a known volume of water. 2. The increase in the temperature of the water is then used to calculate the chemical energy of the biomass.

Question 32

How much energy is required to raise the temperature of 1cm^3 of water

Answer 32

4.2 joules of energy is required to raise the temperature of 1cm^3 of water 1°C.

Question 33

What is the function of the stirrer in a calorimeter

Answer 33

so water temperature is even throughout

Question 34

What is the function of the ignition wires in a calorimeter

Answer 34

they make the sample hot

Question 35

What is the function of the insulation in a calorimeter

Answer 35

so heat energy isnt transferred to surroundings

Question 36

What is the function of the reaction chameber in a calorimeter

Answer 36

made of metal so heat is easier to be conducted into the water

Question 37

What is the function of the oxygen atmosphere in the reaction chamber of a calorimeter

Answer 37

allows complete combustion to occur

Question 38

What is the equation for the efficiency of energy transfer between two trophic levels

Answer 38

(energy available after transfer ÷ energy available before transfer) x 100

Question 39

Why is growing crops more efficient than cattle farming?

Answer 39

Growing crops involves only one trophic level whereas cattle farming uses two with a larger % of energy trapped in photosynthesis being lost as heat energy from respiration

Question 40

What is the purpose of intensive rearing?

Answer 40

designed to maximise yield from animals by reducing energy loss - attempt to convert the smallest amount of food into maximum yield of meat/animal products

Question 41

Why does keeping animals confined increase the efficiency of energy conversion

Answer 41

* Movement restriction means less energy use in muscle contraction * Environment is warmer so animals lose less heat and therefore respire less in order to maintain body temperature * Food is highly controlled so optimum nutrition is provided with little wastage. Food has a high energy content and high digestibility so more of the food is used to increase biomass.

Question 42

What are other ways of improving yield in domestic livestock

Answer 42

selective breeding - to produce high-yield varieties growth hormones - to increase growth rates and biomass

Question 43

What is a factory farming environment like?

Answer 43

- control feeding - restrict movement - warm environment - exclude preadarotes

Question 44

What is selective breeding?

Answer 44

- more efficient at converting food to body mass - high yield - hormones to increase growth rate and produce more milk - unethical

Question 45

What ethical issues are involved with factory farming and selective breeding

Answer 45

- increased stress injury and aggressiveness - rapid spread of disease - increased use of drugs (antibiotics) - reduced genetic diversity