✅13 - Energy And Ecosystems Flashcards
What are producers?
Photosynthetic organisms that manufacture organic substances using light energy, water, CO2 and mineral ions
What are consumers?
Organisms that obtain their energy by feeding on other organisms rather than using the energy of the sunlight directly
What are saprobionts?
A group of organisms that break down the complex materials in dead organisms into simple ones, releasing valuable minerals and elements that can be absorbed by plants
What is a food chain?
A feeding relationship in which the producers are eaten by primary consumers
What is a trophic level?
Each stage in the food chain
What are food webs?
The way that different food chains link together
What is biomass?
The total mass of living material in a specific area at a given time
What is biomass measured in?
Grams per square metre of dry mass
Why is most of the sun’s energy not converted into organic matter?
Over 90% of it is reflected back to space by clouds and dust
Not all wavelengths of light can be absorbed by chlorophyll
Light may not fall on a chlorophyll molecule
Other factors such as low CO2 levels may limit the rate of photosynthesis
What is gross primary production?
The total quantity of chemical energy stored in plant biomass in a given area or volume in a given time
What is net primary productivity?
Gross primary production - respiratory losses
Why is the percentage of energy transferred at each trophic level low?
Some of the organism is not consumed
Some parts are consumed but cannot be digested
Some energy is lost in excretory materials eg urine
Some energy loss occurs from heat and respiration etc
What is the net production of consumers calculated as?
I-(F+R)
I = chemical energy ingested
F = energy lost in faeces and urine
R = energy lost in respiration
Why do most food chains only have four or five trophic levels?
Because insufficient energy is available to support a large enough breeding population at trophic levels higher than these
What intensive farming practices are used to conserve energy?
Movement restricted to reduce energy used for muscle contraction
Environment kept warm to reduce energy used for heat
Feeding controlled so that maximum growth and little wastage occurs
Predators excluded
What is the general pattern that all nutrient cycles follow?
Nutrient taken up by producers
Producer converts into complex organic molecule
Producer eaten, passes into consumer
Passes along food chain where animals eaten by other consumers
Complex molecules broken down by saprobiontic microorganisms
Why do living organisms require nitrogen?
To produce organic molecules such as proteins and nucleic acids
How do plants take up nitrogen?
As nitrate, NO3-, from the soil by active transport
How is nitrate concentration of soil increased in agriculture?
Through fertilisers
What are the four main stages on the nitrogen cycle?
Ammonification, nitrification, nitrogen fixation and denitrification
What do all the main stages of the nitrogen cycle involve?
Saprobionts
What is nitrogen fixation?
Conversion of nitrogen in the atmosphere into ammonium ions or ions
