Biomass transfer 23.2 Flashcards
What is the main source of energy in all ecosystems and why?
The sun is the main source of energy as it is converted into chemical energy in plants during photosynthesis. The plants are then eaten by animals and that chemical energy is transferred as food.
What is biomass?
The mass of living material present in a particular organism or place.
What do food chains and webs show?
The transfer of biomass and energy through organisms
What is a trophic level?
A trophic level is a stage in a food chain
What is the first trophic level in a food chain?
Producers are the first trophic level which are organisms that convert light energy from the sun into chemical energy (usually plants)
What is the second trophic level in a food chain?
Primary consumers are the second trophic level and these are organisms that consume producers and obtain energy from them.
Why do food chains not have many trophic levels?
Biomass will decrease further and further up the trophic levels so eventually there isn’t enough energy left to support any other organisms.
What are decomposers?
Decomposers are organisms that break down dead organisms to release nutrients back into the soil.
How do you draw a pyramid of biomass?
You multiply the biomass present with the number of organisms in the trophic level. You then draw a rectangle to represent it. The producers always go at the bottom and will have the biggest biomass
How do you measure biomass?
You have to measure the dry mass of an organism which means it has to have no water in it. The organism has to be killed and placed in an oven at 80 degrees until all of the water has evaporated. There then need to be two identical measurements taken to prove all the water is gone.
Why do you need dry mass for the biomass measurement?
There are varying amounts of water in different organisms and when measuring the biomass, you want the living material only that is going to be used as energy. To measure this, you must eliminate the water from the organisms or it will be unreliable.
What do scientists do to minimise destruction when measuring biomass, how can this affect results?
They take small samples of organisms to dry out and this may not be representative of the entire population.
Why does biomass decrease through each successive trophic level?
Biomass consists of all cells and tissues in a living organism. Carbon compounds are the store of energy in an animal (organism) and they convert only a small fraction of what they have eaten into new tissues. When a consumer eats that animal, the new tissues convert are all that the consumer has to eat, this is why biomass decreases.
What is productivity?
The rate at which an organism converts energy
What is primary productivity?
The rate at which a producer converts light energy into chemical energy
How do you measure primary productivity?
- Harvest method where you measure the biomass and divide it by the area and unit of time - CO2 assimilation where you measure the CO2 taken up by photosynthesis and released by respiration - O2 production where you measure the amount of CO2 taken up and released
What is ecological efficiency?
This is the efficiency with which biomass is transferred between trophic levels.
How efficient are producers at converting sunlight to chemical energy?
Producers only convert 1-3% of sunlight energy. This is because: - a lot of light is reflected off the plant - factors like temperature and water availability can affect photosynthesis - some energy is used for photosynthesis to occur
What is the gross primary productivity (GPP)?
The total energy that an organism has received e.g. total energy a plant converted from sunlight to chemical
How efficient are primary consumers?
Primary consumers only convert 20-50% of the gross production energy from plants into biomass. The rest is used for the primary consumer to respire.
What is the net primary productivity and how do you calculate it?
NPP = GPP - respiratory losses Net primary productivity is the amount of energy the consumer will convert into biomass
How do you increase the NPP?
- Irrigation for good water availabilty - Fertilisers to increase growth - Herbicides to kill weeds that compete - Plant crops close together to maximise light hitting plants
What is the biomass production of consumers like and why?
Consumers only convert 10% of the energy they eat to biomass because: - they may not eat all the biomass like the bones of an animal - the energy is transferred to metabolic reactions like respiration - some parts aren’t digested and excreted - some energy is also lost in excretion
What is the formula for ecological efficiency?
ecological efficiency = energy available after transfer / x100 energy available before transfer
What is agriculture?
Agriculture is manipulating the environment to favour plant species that we can eat (crops).
How can human activities manipulate the transfer of biomass?
We are in the 3rd of 4th trophic level in a natural ecosystem, and we know that this means a lot of energy is lost. In agriculture, they make sure there are only 2 trophic levels so the crops are the producers and we are the consumers. We provide optimum temperature, light intensity as water availability as well as eliminating competition and predators.
