Energy and Ecosystems Flashcards
(14 cards)
How are organic compounds synthesised?
In any ecosystem, plants synthesise organic compounds from atmospheric or aquatic CO2.
What are the sugars synthesised by plants used for?
Most sugars synthesised by plants are used as respiratory substrates and the rest are used to make biological molecules which form the biomass of the plant.
What is biomass?
Biomass is the mass of carbon or dry mass of tissue per given area.
What is the name of the process used to measure biomass?
Biomass can be measured by calorimetry.
What is the process of calorimetry?
1) Dry the sample and then burn it.
2) Use this to heat a known volume of water.
3) Measure the temperature change and use this to calculate the chemical energy that was stored in the dry biomass.
What is the gross primary production (GPP)?
The GPP is the chemical energy store in plant biomass in a given area or volume.
What is the net primary production (NPP)?
The NPP is the chemical energy store in plant biomass after respiratory losses to the environment have been taken into account.
How can NPP be calculated?
Using the formula NPP=GPP-R where R is respiratory losses.
How can the new production of consumers (N) be calculated?
Using the formula N=I-(F+R) where I is the chemical energy store in indigested food, F is the energy lost to the environment in faeces and urine, and R is respiratory losses to the environment.
Why is so much energy lost at each trophic level?
In plants, some light energy is reflected or transmitted through leaves or not of the right wavelength resulting in a low efficiency of photosynthesis.
Some energy is lost to the surroundings as heat from respiration.
Some energy is lost in faeces and urine.
Also, some parts of the organism are not eaten, so some energy is not transferred to the next throphic level.
Why are food chains often limited to 4-5 trophic levels?
Energy is lost at each trophic level so the efficiency of energy transfer is very low. Total biomass is therefore less at higher trophic levels meaning that at more than 4-5 trophic levels, there is insufficient energy available to support a large enough breeding population.
How are farming practices designed to increase the efficiency of energy transfer?
Simplify food webs by reducing energy losses to non-human food chains to increase the NPP, this can be done by using pesticides so energy isn’t lost when pests feed on crops.
Reduce respiratory losses within a human food chain by controlling the conditions livestock are kept in by restricting their movement so less energy is lost as heat from respiration, or keep them warm so less energy is used to generate body heat from respiration.
Overall, this results in more biomass meaning there’s a higher chemical energy store so greater NP and efficiency of energy transfer.
What is meant by primary and secondary productivity?
Primary and secondary productivity refer to the rate of primary and secondary production, respectively.
How is primary and secondary productivity measured?
Primary and secondary productivity are measured as biomass in a given area in a given time.
Example units: KJha^-1year^-1
