3.5.3 Energy and Ecosystems Flashcards
What are biotic factors?
all the living components
What are abiotic factors?
all the non living components
Examples of primary producers and what they are?
An organism that synthesises organic molecules from simple inorganic ones. (plants and algae through photosynthesis)
(bacteria through chemosynthesis). usually form first trophiv level in a food chain
Why are primary producers important?
They transfer light energy into chemical energy stored in biological molecules.
They use Carbon dioxide, water and sunlight to synthesise organic compounds.
What are the first and second trophic levels?
1st are producers
2nd are primary consumers
What are biological compounds that make up biomass?
Starch, cellulose, lipids and proteins,.
What is Biomass?
Chemical energy stored from biological molecules.
How can Biomass be measured?
Dry biomass (mass after all the water is removed)
Mass of Carbon (0.5 the dry mass)
sample dried in an oven (avoid combustion)
sample weighed and reheated at regular intervals
untill mass remains constant (all water evaporated)
how does a calorimeter work?
A calorimeter burns the dried sample and uses the energy released to heat a known volume of water.
Measure the change in temperature of the water.
This temperature change can be used to estimate the chemical energy stored within the sample.
This energy is measured in joules (J) or kilojoules (kJ).
Limitations of Calorimeter?
Can take a long time to fully dehydrate a sample as low temperature should be used so sample doesnt burn
Precise equipment to measure small changes in mass and temperature might not be available
Bomb calorimeter is needed for accurate measurements as no energy lost to environment.
What is Gross Primary Production?
Gross primary production ( GPP) is the chemical energy store in plant biomass, in a given area or volume, in a given time
What is Net Primary Production?
Net primary production (NPP) is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account,
NPP =GPP–R
Why is not all light energy used for photosynthesis?
99% of the light either passes through the leaf without hitting chloroplasts, is reflected off of the leaf or by greenhouse gasses, or is transferred to heat energy.
there is another limiting factor effecting photosynthesis
What units does GPP use?
Jm^-2
gm^-2
kg/km ^-3 (equatic plants)
Gross primary productivity
The rate at which plants are able to store chemical energy via photosynthesis.
expressed using units of energy/mass per unit area per unit time
For example
Mj m–2 y-1 (megajoules per square metre per year)
kg km-2y-1 (kilograms per square kilometre per year)
What do decomposers do
- Secrete digestive enzymes onto the surface of dead organisms
2.breaks down dead mater into small soluble food molecules - absorbed by decomposers
How is biomass formed in plants
during photosynthesis, plants make organic compounds from atmospheric or aquatic co2
most sugars synthesised are used by the plant as respiratory substrates
rest are used to make biological molecules to form biomass
explain how features of a calorimeter enable valid measurements of heat energy released
-stirrer evenly distributes heat energy in water
- insulation reduces heat loss or gain from surroundings
-water has a high specific heat capacity
explain the importance of NPP in ecosystems
available for plant growth and reproduction
available in other trophic levels such as herbivores and decomposers
state the formula for net production of consumers
N=I-(F+R)
I- chemical energy in ingested food
F- chemical energy lost through faeces and urine
explain why energy transfer between trophic levels is inefficient
-heat energy is lost via respiration
-energy lost via parts of organism that arent eaten
-energy lost as faeces
-energy lost as excretion
explain how crop farming practices increase energy transfer efficiency
- simplifying food webs to reduce biomass losses to non human food chains
-herbicides kills weeds, less competion to light, more energy to create biomass
-pesticides kill insects -reduce loss of biomass from crops
-fungicides reduce fungal infections - more enrgy to create biomass
explain how livestock farming practicies increase energy transfer efficiency
-reducing respiratory losses within a human food chain
-restrict movement and keep warm - reduce energy loss from respiration and heat
-slaughter while young, when most of energy is used for growth
-treat with antibiotics to prevent energy loss due to pathogens
-selective breeding to produce breeds with higher growth rates.
