Energy and ecosystems Flashcards
What is a producer?
Photosynthetic organisms that manufacture organic substances using light energy, water, carbon dioxide and mineral ions
What is a consumer?
Organisms that obtain their energy by feeding on other organisms
What are saprobionts?
Decomposers are a group of organisms that break down the complex materials in dead organisms into simple ones releasing minerals and elements (fungi and bacteria)
What is a trophic level?
Each stage in a food chain
What do the arrows on food chain diagrams show?
The direction of energy flow
What is biomass?
Total mass of living material in a specific area at a given time
How is chemical energy in dry mass estimated?
Calorimetry
What is gross primary production (GPP)?
The total quantity of the chemical energy store in a plant in a given are/volume at a given time
How much of their chemical energy to plants use in respiration?
20-50%
What is net primary production?
GPP- respiration losses
What is NPP used for?
Plant growth and reproduction
How much energy do primary consumers use for growth from NPP of producers?
<10%
Why is such a low percentage of energy transferred at each stage?
Some of the organism not consumed, some cannot be digested (faeces), some lost in excretory materials (urine) and some energy losses occur as heat from respiration and lost to the environment
How is net production of consumers calculated?
N = I - (F+R)
net production = chemical energy stored - (respiration + faeces and urine loss)
Why do most food chains have only 4 or 5 trophic levels?
The inefficiency of energy transfer between trophic levels
What are the four main stages in the nitrogen cycle?
Ammonification, nitrogen fixation, nitrification and denitrification
What is denitrification?
Nitrates within the soil are converted to gaseous nitrogen by anaerobic bacteria
What is ammonification?
Release of ammonium ions from DOM
What is nitrification?
Aerobic oxidation of ammonium ions to nitrite then nitrate ions by bacteria
What is nitrogen fixation?
Converting nitrogen gas into compounds (by lightning, free-living bacteria or symbiotic bacteria)
How does phosphate mostly exist?
Mostly as phosphate ions PO4 3-
How does phosphate move through the cycle?
Geological uplifting bring it out of the sea and into land, then weathering and erosion makes them available for uptake or guano from seabirds
What are mycorrhizae and what do they do?
Fungi networks between plant roots, help to resist drought and take up inorganic ions
What does mycorrhizae receive from the plant?
Sugars and amino acids
What are the environmental effects of nitrogen fertilisers?
Reduced species diversity, leaching and eutrophication
How do nitrogen fertilisers reduce species diversity?
Nitrogen rich soils favour the growth of nettles, grasses and other rapidly-growing species which may out-compete other species
Why is eutrophication bad?
Lead to algal blooms the stop light entering the water body, this means photosynthetic organisms under the water will die and decompose under anaerobic conditions, oxygen content of the water will drop and consumers with suffocate.
What happens to phosphate ions not absorbed by the plants?
Washed away by rain and end up in lakes, rivers and seas
