Nitrogen Cycle Flashcards
what is the nitrogen cycle?
the movement of atoms and molecules containing the element nitrogen between sources and sinks
how long do reservoirs in which nitrogen compounds occur hold these compounds?
most of the reservoirs in which nitrogen compounds occur in the nitrogen cycle hold these compounds for relatively short periods of time (compared to the carbon cycle)
what is nitrogen fixation?
nitrogen fixation is the process in which atmospheric nitrogen is converted into a form of nitrogen (primarily ammonia) that is available for uptake by plants and that can be synthesized into plant tissue
what do nitrogen sources do?
sources release nitrogen into the atmosphere
what is the major reservoir of nitrogen?
the atmosphere is the major reservoir of nitrogen
what do nitrogen sinks do?
sinks take nitrogen out of the atmosphere in increasing amounts
what are some examples of short term nitrogen reservoirs?
plants (only hold nitrogen as long as they’re alive, then it’s returned to the soil), soil (nitrogen removed from soil by plants for growth), the atmosphere
what is nitrogen critical for?
nitrogen is a critical plant and animal nutrient
what things need nitrogen and for what?
all living things need nitrogen for DNA and amino acids to create proteins
what is the key difference between the carbon cycle and the nitrogen cycle?
nitrogen reservoirs hold nitrogen for shorter periods of time than carbon reservoirs; sedimentary rocks can hold carbon for millions of years
what is the primary form of atmospheric nitrogen?
nitrogen in the atmosphere exists mostly as N2 gas, not useable by plants or animals
what is nitrogen fixation?
the process of nitrogen gas being converted into biologically available (useable by plants) ammonia (NH3) or nitrate (NO3-)
how do living things take in nitrogen if most exists as unusable nitrogen gas?
nitrogen fixation
what is synthetic fixation?
humans combust fossil fuels to convert nitrogen gas into nitrate
what is bacterial fixation?
certain bacteria that live in the soil, or in symbiotic relationship with plant root nodules convert N2 into ammonia
what is an example of bacterial fixation?
rhizobacteria live in root nodules of legumes (peas/beans) and fix nitrogen for them in return for amino acids from the plant
what is an example of synthetic fixation?
nitrates are added to synthetic fertilizers like miracle grow and used in agriculture
what is the first step in the nitrogen cycle?
nitrogen fixation
how can nitrogen fixation occur naturally?
through lightning storms (converts nitrogen to ammonia in the atmosphere) or bacteria
what are the two types of bacteria in bacteria fixation?
bacteria in the soil and symbiotic bacteria
what are the nitrogen cycle steps?
Nitrogen Fixation
Nitrification
Assimilation
Ammonification
Denitrification
what is assimilation?
the process of plants and animals taking in nitrogen and incorporating it into their body (a similar back and forth like the process of photosynthesis and respiration with carbon)
what is ammonification?
soil bacteria, microbes, and decomposers converting waste and dead biomass back into ammonia and returning it to soil
what is nitrification?
conversion of ammonia into nitrite and then nitrate by soil bacteria
how do animals assimilate nitrogen (absorbs and incorporate it?)
animals assimilate nitrogen by eating plants or other animals that have eaten plants (all starts with plants)
what is critical to almost every step of the nitrogen cycle?
bacteria
what is denitrification?
conversion of soil nitrogen (NO3) into nitrous oxide gas (N2O) which returns to the atmosphere, this nitrougs oxide gas can break down into nitrogen gas
how do plants assimilate nitrogen (absorbs and incorporate it?)
plant roots take in ammonia or nitrates from soil
how have humans had an impact on the nitrogen cycle?
through climate change by growing food (nitrous oxide), ammonia volatilization, leaching, and eutrophication
how has the climate affected the nitrogen cycle?
nitrous oxide is a greenhouse gas that warms earth’s climate
what is ammonia volatilization?
excess fertilizer use leading to ammonia gas entering the atmosphere
what is leaching?
synthetic fertilizer use leads to nitrates leaching, or being carried out of soil by water because there are more nitrates in the soil than it can hold
how is nitrous oxide produced?
it’s produced by agricultural soils when humans clear land and til the soil for crops; the bacteria in the soil, through the denitrification of nitrate in agricultural soils especially when waterlogged or over watered, will turn the nitrates in the soil into nitrous oxide
what are the effects of ammonia volatilization?
ammonia gas in the atmosphere can lead to acid precipitation and respiratory irritation in humans and animals by combining with other pollutants
it also leads to lost profits while growing crops because less nitrogen stays in the soil for crops to use for growth
what is eutrophication?
eutrophication occurs when bodies of water are enriched with nutrients, increasing the amount of plant and algae growth, leading to harmful algal blooms, dead zones, and fish kills
agricultural runoff (leaching) moves into local bodies of water, causing aggressive algae growth which covers the surface of the body of water, blocking light from aquatic plants, killing them
