Energy and Ecosystems / Nutrient Cycles Flashcards
What is the ultimate source of energy? + Why is it needed?
Sunlight, in order to make organic compounds from CO2/Water
What are producers?
photosynthetic organisms that manufacture organic substances using light, water, CO2 and mineral ions
What are consumers?
organisms that obtain energy by feeding on other organisms. Those that directly eat producers are called primary consumers and those animals eating primary consumers are called secondary consumers etc.
What are saprobionts?
(decomposers) break down complex materials in dead organisms to simpler ones, mainly fungi and bacteria.
What is a food chain?
Food chain: stages in a food chain are called trophic levels, arrows show direction of energy flow.
What is a food web?
many food chains joined together but they are complex
What is biomass?
total mass of living material in a specific area at a given time. Unreliable due to the varying amounts of water, dry biomass involves organisms being killed so sample sizes are small thus it is not representative. Measured in grams per square metre (g m-2)
How much of the suns energy is converted into organic matter?
1-3%
Why is most of the suns energy not converted to organic matter in photosynthesis?
- rate of photosynthesis may be limited
- not all wavelengths of light can be absorbed
- 90% of energy is reflected back to space by clouds.
What is gross primary production (GPP)?
is the total quantity of chemical energy in plant biomass in a given area/volume, in a given time. However 20-50% is used in respiration.
What is net primary production (NPP)?
chemical energy left when losses from respiration have been taken into account
How is net primary production calculated?
Net primary production (NPP)= gross primary production - respiratory losses
Why is a low percentage of energy transferred between each trophic level?
- some organism not consumed
- some parts cannot be digested so lost in faeces
- lost in urine (excretory materials)
- lost as heat in respiration, this is high in mammals/birds because of their high body temperatures (lots of energy is required to maintain this)
What is the equation for net production of consumer?
chemical energy store in ingested food - (energy lost in faeces/urine + energy lost in respiration)
N= I - (F + R)
What does the inefficiency of energy transfer between trophic levels explain?
- most food chains have only 4-5 trophic levels as there is not enough energy to support a bigger population
- biomass is lower in higher trophic levels
- total amount of energy available at each level is less going up the chain
What is a flow chart of energy transfer efficiency?
Sun → 1-3% Primary Producers → 5-10% Primary Consumers → 15-20% Secondary Consumers → 15-20% Primary Consumers
What is the equation for energy efficiency?
Percentage efficiency = energy available after / energy available before x 100
What percentage of the atmosphere is nitrogen?
78%
What are the 4 stages of the nitrogen cycle?
Ammonification, Nitrification, Nitrogen Fixation, Denitrification
What occurs in Ammonification?
production of ammonia from organic nitrogen-containing compounds e.g urea, proteins, nucleic acids, vitamins. Saprobionts feed on faeces/dead organisms which releases ammonia and forms ammonium ions.
What occurs in Nitrification?
Conversion of ammonium ions to nitrate ions which is an oxidation reaction and releases energy. Carried out by nitrifying bacteria, that require oxygen for these conversions air spaces in, in 2 stages:
- oxidation of ammonium ions to nitrite ions (NO2-)
- oxidation of nitrite ions to nitrate ions (NO3-)
What occurs in Nitrogen Fixation? (2 types of bacteria)
Nitrogen gas is converted into nitrogen containing compounds by microorganisms:
-free-living nitrogen-fixing bacteria: gaseous nitrogen is reduced to ammonia to produce amino acids
-mutualistic nitrogen-fixing bacteria: live in roots of plants and obtain carbohydrates from them, give amino acids to the plant
What occurs in Denitrification?
Soils become waterlogged thus have a low oxygen concentration and therefore there is fewer aerobic nitrifying/nitrogen fixing bacteria found but there is an increase anaerobic denitrifying bacteria, which convert soil nitrates into nitrogen gas. The availability of nitrogen-containing compounds for plants then reduces. For productivity to be high in land, soil needs to be kept aerated in order to prevent the growth of denitrifying bacteria.
Why is phosphorus important?
Phosphorus is a key part of ATP, phospholipids and nucleic acids thus phosphorus needs to be constantly recycled
What is Mycorrhizae?
Fungi which allow extensions of a plants root system in order to increase surface area for the absorption of water and minerals
Why is Mycorrhizae useful?
plants can resist drought and take up inorganic ions more easily (that may be scarce like phosphate ions).
What type of relationship does Mycorrhizae have with plants? + WHY
mutualistic relationship with plants as it receives organic compounds like sugars from the plant whilst the plant receives inorganic ions.
What is the purpose of fertilisers?
Increase the efficiency of energy transfer and thus improve productivity
Fertilisers are added to the soil in order to prevent the loss of mineral ions
What are organic (natural) fertilisers?
made of dead remains of plants, animals and animal wastes such as manure and bone meal
What are inorganic (artificial) fertilisers?
mined from rocks and converted into different forms by being blended together with other minerals to create a balance for crops e.g nitrogen, phosphorus and potassium.
What is the best fertiliser for farmers to use?
A combination of natural and artificial fertilisers give the greatest long term increase of productivity
Why do fertilisers increase productivity?
they allow minerals to be readily available so that plants cam develop earlier, grow taller, have greater area on their leaves thus this increases rate of photosynthesis and hence productivity.
What are detrimental effects of using nitrogen-containing fertilisers?
- reduced species diversity: due to competition between grass, nettles etc which out-compete other species and causes them to die
- leaching: leading to pollution of water sources
- eutrophication: as a result of leaching
What is leaching?
process of nutrients being removed from the soil, rainwater dissolves soluble nutrients like nitrate ions and these will be transported to water sources like rivers. This can be harmful to humans if a source of drinking water and can lead to eutrophication
What is the process of eutrophication?
Eutrophication - nutrient concentrations increase in water
- Algae blooms block light
- No photosynthesis so plants die
- Saprobiotic decomposition occurs
- Microorganisms respire aerobically and thus use up all oxygen
- Not enough oxygen for fish for respiration so they die
- Microorganisms release harmful toxins/hydrogen sulphide etc
- Water is polluted
Refer to flow charts of nitrogen and phosphorus cycles
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