2.3 - Flows Of Energy And Matter Flashcards
What happens to some of the energy when it enters earths atmosphere
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
What is the pathway of radiation through earths atmosphere and what does it involve
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%
How does solar energy end up in producers
- 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
What are the pathways of energy through an ecosystem
- 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
What is ecological efficiency
The percentage of energy transferred from one trophies level to the next with the average being 10%
Why is energy lost from tropic level to tropic level
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
What happens to light energy as it converts to heat and chemical energy
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
What is ecological efficiency
The efficiency of energy transfer from one trophies level to the next as a percentage
How do you calculate ecological efficiency
Ecological efficiency = (energy used for new biomass / energy supplied) x 100
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.
Ecological efficiency = (energy used for new biomass ÷ energy supplied) × 100
Ecological efficiency = (4.1 ÷ 35) × 100
Ecological efficiency = 11.7 %
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.
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 %
What do primary producers do during photosynthesis
convert light energy to chemical energy stored within biological molecules
What is gross primary production
the amount of chemical energy stored in the carbohydrates within plants (during photosynthesis)
What is gross primary productivity
The rate at which plants are able to store chemical energy via photosynthesis
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.
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
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.
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
What is net primary productivity
Net primary productivity (NPP) is the GPP minus plant respiratory losses (R)
How can net primary productivity be defined
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
What is the equation for net primary productivity
NPP=GPP-R
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.
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
What is Gross secondary productivity
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
What is the equation for GSP
GSP = food eaten - faecal loss
How do you calculate NSP
NSP=GSP-R
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.
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