2.3 - Flows Of Energy And Matter

Question 1

What happens to some of the energy when it enters earths atmosphere

Answer 1

When solar radiation (insolation) enters the Earth’s atmosphere, some of the energy becomes unavailable for ecosystems due to being:
- Absorbed by inorganic matter
- Reflected back into the atmosphere

Question 2

What is the pathway of radiation through earths atmosphere and what does it involve

Answer 2

The pathway of radiation through the atmosphere involves a loss of radiation through reflection and absorption, with the following (approximate) percentage losses:
- Reflection from clouds ~ 19%
- Absorption of energy by clouds ~ 3%
- Reflection by scatter from aerosols and atmospheric particles ~ 3%
- Absorption by molecules and dust in the atmosphere ~ 17%
Reflection from the surface of the Earth ~ 9%

Question 3

How does solar energy end up in producers

Answer 3

• Most incoming solar radiation fails to enter chloroplasts in leaves because it is reflected, transmitted (passes straight through the leaf), or is the wrong wavelength to be absorbed
• Of the radiation captured by leaves, only a small percentage ends up as biomass in growth compounds because the conversion of light to chemical energy is inefficient
• In total, only around 0.06% of all solar radiation falling on Earth is captured by plants

Question 4

What are the pathways of energy through an ecosystem

Answer 4

• Conversion of light energy to chemical energy
• Transfer of chemical energy from one trophic level to another with varying efficiencies
• Overall conversion of ultraviolet and visible light to heat energy by an ecosystem
• Re-radiation of heat energy to the atmosphere

Question 5

What is ecological efficiency

Answer 5

The percentage of energy transferred from one trophies level to the next with the average being 10%

Question 6

Why is energy lost from tropic level to tropic level

Answer 6

Energy losses occur due to various reasons, such as movement, inedible parts (e.g. bone, teeth, fur), waste products (e.g. faeces), and the inefficient energy conversions that occur during the process of respiration
- Ultimately, energy is lost as heat due to the second law of thermodynamics

Question 7

What happens to light energy as it converts to heat and chemical energy

Answer 7

Energy is converted from one form to another but cannot be created or destroyed due to the first law of thermodynamics
The inputs of the system as a whole, and of any individual trophic level, are equal to the outputs

Question 8

What is ecological efficiency

Answer 8

The efficiency of energy transfer from one trophies level to the next as a percentage

Question 9

How do you calculate ecological efficiency

Answer 9

Ecological efficiency = (energy used for new biomass / energy supplied) x 100

Question 10

Answer this question:
A butterfly lays an egg on a blackberry bush. In its first day, the caterpillar that hatches consumes blackberries containing a total of 35 J of energy. 4.1 J of this energy are used to form new caterpillar biomass. Calculate the ecological efficiency of this step of the food chain.

Answer 10

Ecological efficiency = (energy used for new biomass ÷ energy supplied) × 100

Ecological efficiency = (4.1 ÷ 35) × 100

Ecological efficiency = 11.7 %

Question 11

Answer this question:

A wheat farmer decides to use biological control against insect pests that are eating her wheat crop. The farmer introduces a species of toad. By eating the insect pests the toads ingest 10 000 kJ m-2 yr-1 of energy. The toads lose 7 000 kJ m-2 yr-1 of this energy as heat from respiration and 2 000 kJ m-2 yr-1 of energy in faeces and urine. Calculate the ecological efficiency of energy transfer from the insects to the toads.

Answer 11

Step 1: Calculate the energy used for toad growth (new biomass)

Toad energy received = 10 000 kJ m-2 yr-1
Toad energy losses = 7 000 + 2 000 = 9 000 kJ m-2 yr-1
Energy for growth = 10 000 - 9 000 = 1 000 kJ m-2 yr-1

Step 2: Substitute the values into the equation

Ecological efficiency = (energy used for new biomass ÷ energy supplied) × 100
Ecological efficiency = (1 000 ÷ 10 000) × 100
Ecological efficiency = 10 %

Question 12

What do primary producers do during photosynthesis

Answer 12

convert light energy to chemical energy stored within biological molecules

Question 13

What is gross primary production

Answer 13

the amount of chemical energy stored in the carbohydrates within plants (during photosynthesis)

Question 14

What is gross primary productivity

Answer 14

The rate at which plants are able to store chemical energy via photosynthesis

Question 15

Solve this question:

The total chemical energy contained within the grass that grows in a 200 m2 field over the course of one year is found to be 1 000 kJ. Calculate the gross primary productivity of the grass field. Give appropriate units.

Answer 15

Step 1: Calculate the total chemical energy contained within the grass in 1 m2 of the field over the course of one year

1 000 ÷ 200 = 5 (kJ)

Step 2: Give the appropriate units

5 kJ m-2 yr-1

Question 16

Answer this question :
On average, a patch of arctic tundra covering an area of 1 km2 is estimated to produce a total biomass of 1,500 kg per year. Calculate the gross primary productivity of this patch. Give your answer in g m-2.

Answer 16

Step 1: Calculate the average yearly biomass of 1 m2 of the arctic tundra patch (1 km2 = 1 000 000 m2)

1 500 ÷ 1 000 000 = 0.0015 (kg yr-1)

Step 2: Convert this into grams

0.0015 × 1,000 = 1.5 g m-2 yr-1

Question 17

What is net primary productivity

Answer 17

Net primary productivity (NPP) is the GPP minus plant respiratory losses (R)

Question 18

How can net primary productivity be defined

Answer 18

NPP can therefore be defined as the rate at which energy is stored in plant biomass, allowing for respiratory losses
NPP is important because it represents the energy that is available to organisms at higher trophic levels in the ecosystem, such as primary consumers and decomposers

Question 19

What is the equation for net primary productivity

Answer 19

NPP=GPP-R

Question 20

Answer this question:
The grass in a meadow habitat converts light energy into carbohydrates at a rate of 17 500 kJ m-2 yr-1. The grass releases 14 000 kJ m-2 yr-1 of that energy during respiration. Calculate the net primary productivity of the grass in the meadow habitat.

Answer 20

Step 1: Work out which numbers correspond to which parts of the equation

The meadow grass converts 17 500 kJ m-2 yr-1 into carbohydrates; this is GPP

The meadow grass releases 14 000 kJ m-2 yr-1 of that energy in respiration; this is R

Step 2: Substitute numbers into the equation

NPP = GPP - R

NPP = 17 500 - 14 000

Step 3: Complete calculation

17 500 - 14 000 = 3 500

NPP = 3 500 kJ m-2 yr-1

Question 21

What is Gross secondary productivity

Answer 21

Gross secondary productivity (GSP) is the total energy/biomass assimilated by consumers and is calculated by subtracting the mass of faecal loss from the mass of food eaten

Question 22

What is the equation for GSP

Answer 22

GSP = food eaten - faecal loss

Question 23

How do you calculate NSP

Answer 23

NSP=GSP-R

Question 24

Solve this question:
In a patch of woodland, caterpillars ingest 2 000 kJ m-2 yr-1 of chemical energy from the biomass of oak leaves. The caterpillars lose 1 200 kJ m-2 yr-1 of this energy in faeces. They lose a further 600 kJ m-2 yr-1 of this energy through respiration. Calculate the net secondary productivity of the caterpillars.

Answer 24

Step 1: Calculate GSP

GSP = food eaten - faecal loss
GSP = 2 000 - 1 200
GSP = 800 kJ m-2 yr-1

Step 2: Calculate NSP

NSP = GSP - R
NSP = 800 - 600
NSP = 200 kJ m-2 yr-1

Question 25

What is annual yield

Answer 25

The annual yield for a natural resource (such as a forest) is the annual gain in biomass or energy, through growth

Question 26

What is the maximum sustainable yield

Answer 26

The maximum sustainable yield is the maximum amount of a renewable natural resource that can be harvested annually without compromising the long-term productivity of the resource (i.e. without a reduction in natural capital)

Question 27

What resources does max sustainable yield apply to

Answer 27

Crops

Question 28

Define max sustainable yield

Answer 28

The amount of renewable natural resource that can be harvested annually without compromising the long term productivity of the reosurse

Question 29

What productivity is max sustainable yield in relation to

Answer 29

In this way, maximum sustainable yield is equivalent to the net primary productivity (NPP) or net secondary productivity (NSP) of a system (as these values represent the amount of energy stored and new plant or animal biomass per year)

Question 30

What are the 7 stores in a carbon cycle

Answer 30

1. The atmosphere (as CO2)
2. Sedimentary rocks
3. Fossil fuels like coal, oil, and gas; coal is largely carbon
4. Soil and other organic matter
5. Vegetation (e.g. as cellulose)
6. Animals
7. Dissolved in the oceans (as CO2)

Question 31

What are the 6 flows in a carbon cycle

Answer 31

1. Consumption (feeding)
2. Death and decomposition
3. Photosynthesis
4. Respiration
5. Dissolving
6. Fossilisation

Question 32

How is photosynthesis a store

Answer 32

• Autotrophs use the energy of sunlight to ‘fix’ carbon dioxide, turning its carbon into sugars and other organic molecules
• This removes carbon from the atmosphere
• Terrestrial plants use gaseous CO2 directly from the air
• Aquatic organisms use CO2 dissolved in water
• As much CO2 is fixed from ocean microorganisms, as from terrestrial plants

Question 33

How is sedimentation a store

Answer 33

• Plants that die are not fully decomposed by saprobionts; their bodies form layers of sediment that can accumulate over millions of years, locking carbon into the ground
• This sediment is a store of energy and can form fossil fuels like peat and coal
• Aquatic organisms that die also form sediments on the sea bed; these can go on to form other fossil fuels like oil and gas
• Shells and other calcium-containing body parts can form sedimentary rocks such as limestone
• The existence of life forms over billions of years has shaped the biosphere, in that their remains are still being recycled

Question 34

How is respiration a flow

Answer 34

• All life forms respire, including autotrophs
• Heterotrophs rely on respiration for all their energy needs
• Respiration puts CO2 into the atmosphere, in the opposite direction to photosynthesis
• Anaerobic respiration also releases CO2 into the atmosphere, via fermentation by yeast, moulds and bacteria

Question 35

How is carbon moved through feeding

Answer 35

• Carbon is passed from autotroph to heterotroph during feeding
• Carbon is also passed from primary consumer to secondary consumer
• Biomass transfer always includes the transfer of carbon, the main element in biomass

Question 36

How is decay and decomposition a flow

Answer 36

• Dead plants and animals are fed upon by detritivores and decayed by saprophytes
• Releasing carbon into the surroundings
• Supplying carbon to the detritivores
• Supplying carbon to the saprophytes
• Waste matter such as faeces and urine is used by decaying saprobionts
• Such processes can release CO2 back into the air

Question 37

How does human impact affect the carbon cycle

Answer 37

Human activities such as burning fossil fuels, burning, deforestation, urbanisation and agriculture impact the balance of storages and flow within the carbon cycle

Question 38

Answer this question:
Discuss human impacts on the carbon cycle

Answer 38

Humans have a significant impact on the carbon cycle, mainly through the combustion of fossil fuels and deforestation. Fossil fuels such as coal, oil, and natural gas contain carbon that has been stored underground for millions of years. When these fuels are burned, carbon is released into the atmosphere as carbon dioxide (CO2), contributing to the greenhouse effect and climate change.

Deforestation, especially in tropical regions, also affects the carbon cycle. Trees and other plants absorb CO2 from the atmosphere during photosynthesis, storing carbon in their biomass. When trees are cut down and burned or left to decay, the stored carbon is released back into the atmosphere as CO2.

Other human activities that contribute to carbon emissions include agriculture, transportation, and industry. For example, livestock farming produces methane, a potent greenhouse gas, through enteric fermentation in cows, sheep, and other ruminants. Transportation, especially cars and trucks, burns fossil fuels and releases CO2 into the atmosphere. Industry and manufacturing processes also contribute to carbon emissions through the burning of fossil fuels and other energy-intensive processes.

Question 39

What are the stores in the nitrogen cycle

Answer 39

• Organisms (organic)
• Soils ( inorganic)
• Fossil fuels (organic)
• Atmosphere (inorganic)
• Water bodies (inorganic)

Question 40

What are the flows in the nitrogen cycle

Answer 40

• Nitrogen fixation by bacteria and lightning
• Absorption
• Assimilation
• Consumption (feeding)
• Excretion
• Death and decomposition
• Denitrification by bacteria in water logged soils

Question 41

What are the human impacts on the nitrogen cycle

Answer 41

• increased use of fertilisers
• burning of fossil fuels
• industrial nitrogen fixation
• land use changes
• livestock farming
• wastewater treatment

Question 42

How does increased use of fertilisers impact the nitrogen cycle

Answer 42

• Fertilisers, especially nitrogen fertilisers, are widely used in agriculture to increase crop yield
  However, excess nitrogen can leach into waterways, leading to eutrophication and harmful algal blooms

Question 43

How does burning of fossil fuels impact the nitrogen cycle

Answer 43

Burning fossil fuels releases nitrogen oxides into the atmosphere, which can lead to the formation of acid rain
Acid rain can increase soil acidity, which can affect the ability of plants to take up nitrogen

Question 44

How does industrial nitrogen fixation impact the nitrogen cycle

Answer 44

Humans have developed methods to fix nitrogen industrially, for example, in the production of fertilisers and explosives
This has greatly increased the amount of fixed nitrogen available for use in human activities

Question 45

How has land use change impacted the nitrogen cycle

Answer 45

Conversion of natural landscapes, such as forests and wetlands, into agricultural or urban areas can lead to changes in nitrogen cycling
For example, wetlands are important nitrogen sinks, and their loss can result in nitrogen being released into waterways and the atmosphere

Question 46

How does livestock farming impact the nitrogen cycle

Answer 46

Livestock farming produces large amounts of manure and urine, which can contribute to increased nitrogen inputs to ecosystems
This can lead to eutrophication and other environmental problems if not managed properly

Question 47

How does waste water treatment impact the nitrogen cycle

Answer 47

Wastewater treatment plants can be a source of nitrogen pollution if they do not effectively remove nitrogen from treated water before releasing it into the environment