Energy In Ecosystems Flashcards
(19 cards)
Define Producer
an organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
Define consumer
Obtains energy by feeding on other organisms
Define saprobionts
(Decomposers)
Break down complex material in dead organisms into simple ones.
This releases valuable minerals and elements in a form that can be absorbed by plants- contributed to recycling
Define food chain
Feeding relationship made up of tropic levels
Define food web
In a single habitat food chains will be linked to form food webs
Define biomass
Total mass of living material in a specific area, in a given time
Measures using dry mass per given area in a given time (gm-2) or volume (gm-3)
Explain why most food chains have no more than 4/5 tropic levels
Energy loss from one tropic level to next becomes very large after several stages
Define GPP
Gross primary production is the total quantity of the chemical energy store in plant biomass
Includes organic material used in respiration and stored as new plant tissue
Equation with NPP GPP R
NPP= GPP-R
Net primary productivity = gross primary productivity - respiratory losses
What is NPP
Net primary productivity is the energy available for plant growth and reproduction
NPP values are used to compare the productivity of different ecosystems
In a food chain the low % of energy transfer is due to:
Some of the organism isn’t consumed
Some parts can’t be digested so when consumed=faeces
Loss due to excretory materials eg urine
Loss due to heat loss from respiration
Most of the suns energy is not converted to organic matter by photosynthesis because:
Most of suns energy is reflected back into space
Not all wavelength of light can be absorbed
Light might not fall on a chlorophyll molecule
Low CO2 may limit rate of photosynthesis
Net production of consumers equation
N = I - (F+R)
Net production= chemical energy store of ingested food - (energy lost respiring +energy lost in faeces and urine)
Percentage efficiency equation
Energy available after transfer/energy available before transfer x 100
Keeping animals in confined spaces increases energy conversion rate because:
Movement is restricted so less energy used in muscle contraction
Environment kept warm so reduced heat loss
Feeding controlled so animals receive optimum amount and type of food for max growth and no wastage
Predators excluded so no loss to other organisms in food web
The inefficiency of energy transfer between trophic levels means that:
Most food chains only have 4/5 trophic levels
The total mass of organisms in a particular place is less at higher trophic levels
Total amount of energy available decreases moving up the food chain
Why would keeping animals in the dark for longer periods improve the energy conversion rate
More time spent resting, less energy is expended and more energy is converted into body mass
Pest control aim
Balance cost of pest control with the benefits it brings
Simplify the food web and so limit effect of pests on productivity to a commercially acceptable level
Pesticides are used to increase productivity. Suggest how their use might sometimes reduce productivity
Pesticide might kill beneficial organism (eg ones that prey on organisms that are harmful to the farmed organism)
If the pesticide kills most of the pests then the population of organisms (predators) feeding on it will fall. With no predators controlling it, pest pop increases possibly to higher level
The crop will be even more affected by pest so decreases productivity
