2.3 Flows of Energy and Matter Flashcards
Nitrogen Cycle
In which atmospheric nitrogen is transformed into a form that can be readily assimilated by plants
Nitrogen fixation
Process, involving nitrogen fixing bacteria, in which atmospheric nitrogen is transformed into ammonium ions. The bacteria are found in the nodules of leguminous plants.
Nitrogen can also be fixed by lightning (splits apart molecules where they combine with oxygen to form nitrate salts which make way into soil profile.
Haber process
In which nitrogen gas is converted into useable forms (nitrates). Used industrially in the manufacture of fertilisers.
Legume
A type (Family) of plant with pea-flowers and bean like pods (including peanuts, lupin, lentils and chickpeas), with nodules that contain bacteria that fix nitrogen.
Nitrogen fixing bacteria
Found in root nodules on legumes and involved in the fixation of nitrogen from the atmosphere into ammonium.
Nitrogen
Occurs as a diatomic gas in the atmosphere. Makes up 78% of the atmosphere.
As nitrate ion (NO3-) can be assimilated by plants for physiological processes (making of proteins and nucleic acids).
In terms of pollution, note “nitrogen” itself is not a pollutant, but “nitrates” are.
Ammonium
NH4+ Intermediate phase in nitrogen cycle between nitrogen gas and nitrites/nitrates.
Distinct from ammonia (NH3). Don’t confuse them.
Nodule
Knob like structures on the roots of leguminous plants made by nitrogen fixing bacteria
Fertilizer
Substance added to a crop to stimulate faster growth.
Can contain combinations of nitrites, nitrates, phosphates, ammonium.
Urea
Found in manure and compost (decaying organic matter). Natural source of ammonium in the nitrogen cycle. Often referred to as a “slow release” fertiliser.
Nitrification
Transformation of ammonium ions into nitrites and then nitrates (in the presence of nitrifying bacteria), to a form in which they can be assimilated by plants.
Nitrifying bacteria
Involved in the process of nitrification in which ammonium is transformed into nitrites and then nitrates for assimilation.
Denitrifying bacteria
Involved in the process of denitrification in which soil-based nitrate ions are converted back into gaseous atmospheric nitrogen
Denitrification
Process in which soil-based nitrate ions are converted back into gaseous atmospheric nitrogen (with the aide of denitrifying bacteria)
Assimilation
The taking up of nutrients by plants through their roots for use in physiological (structure building) processes.
Consumption
How animals (including humans) get the nutrients they require. Involves eating plant matter either directly or through the food chain and then digesting them before the nutrients are assimilated through the gut wall.
Nitrite
NO2 ion. Intermediate phase between ammonium and nitrate during nitrification.
Nitrate
NO3 ion. Assimilated by plants. Product of nitrification (in the presence of nitrifying bacteria).
Form water soluble salts.
Main component of some fertilizers.
Biodegrades in the environment but can be concentrated in aquatic systems following runoff events.
Photosynthesis
Occurs in plants (in the presence of chlorophyll and sunlight). Coverts light energy into stored chemical energy. Water and carbon dioxide, transforms into glucose and oxygen.
Source of energy in a food chain/food web
The Sun
Respiration
Occurs in all living cells, creates energy for organisms.
Glucose and oxygen become carbon dioxide, water (and energy)
Aerobic respiration vs anaerobic respiration
Aerobic is “in the presence of oxygen”, anaerobic is “in the absence of oxygen” and can produce toxic by products.
Chemosynthesis
certain organisms (such as deep sea bacteria) makes their own food from simple compounds and does not require sunlight
Biomass
the total mass of all living organisms in a given area or ecosystem at a given time, often measured in terms of dry weight to exclude water content
Productivity
the rate at which energy is converted by photosynthetic producers into organic substances that can be used as food by consumers.
Assimilation
process by which organisms integrate the digested nutrients from their food into their body tissues for growth, repair, and energy.
Productivity vs Assimilation
Productivity measures the rate at which organisms produce organic matter. Assimilation involves the incorporation of this produced matter into the organisms’ tissues for growth and energy.
GPP
Gross primary productivity.
The total rate at which an ecosystem’s producers, convert carbon dioxide into organic matter through photosynthesis, before any energy is used for respiration
Gross productivity vs net productivity
Gross productivity refers to the total amount of energy or biomass produced by an ecosystem, whereas net productivity is the energy or biomass remaining after accounting for the energy used in respiration.
NPP
Net primary productivity.
The difference between the energy captured through photosynthesis (gross primary productivity) and the energy expended through metabolic processes (respiration).
NPP = GPP-R
GSP
Gross secondary productivity.
The total rate at which consumers, such as animals, in an ecosystem produce biomass through the assimilation of food, before accounting for losses due to respiration and other metabolic processes.
GSP = ingestion - egestion
NSP
New secondary productivity.
The rate at which consumers in an ecosystem accumulate biomass, after subtracting the energy they expend on respiration and other metabolic activities from their gross secondary productivity.
NSP = GSP - R
Egestion
Pooping!
Expulsion of undigested material from their digestive system, essentially the removal of waste products that cannot be absorbed as nutrients
Ingestion
Food going in.
As opposed to “egestion” - food going out.
Efficiency of productivity
The percentage of energy that is transferred from one trophic level to the next.
(net productivity x 100)/gross productivity
Efficiency of assimilation
(Gross Productivity x100)/food eaten
Units for productivity
units of energy or biomass produced per unit area per unit time
(eg grams of carbon per square metre per year)
How to measure biomass
Harvesting the biological material within a sample, wash it and then dry it until it reaches a constant weight. The mass of this is called the “dry weight”. You can use this figure to extrapolate the total biomass of an ecosystem.
Modified to a measure called “above ground biomass” in which the roots are not part of the harvest.
Measuring primary productivity (terrestrial plants)
Obtain dry biomass of a sample
With two other similar samples (in situ), cover one in black plastic, so it cannot photosynthesize, and leave the other one as is.
After a period of time, harvest the two patches from above and obtain dry weight.
Measuring secondary productivity
weigh an organism, weigh how much it eats, and then weigh how much it egests. (Ingestion-egestion)
Primary productivity vs secondary productivity
Primary = plants (producers)
Secondary = animals (consumers)
Measuring primary productivity in aquatic ecosystems
Light-dark bottle method.
Two bottles of the same water. Oxygen content measured.
One bottle covered, so light cannot penetrate (no photosynthesis). After a period of time, measure oxygen content again.
