15. Nutrient Cycles Flashcards
What is the nutrient cycle
nutrients cycle between the biotic and abiotic components of ecosystems and they exist as organic and inorganic compounds.
Organic compounds tend to be found inside organisms and are large, complex molecules that all contain the element carbon.
Inorganic compounds consist of simple, small molecules and tend to be found in the abiotic phase.
What are features of nutrient cycles
· The nutrients in a simple, inorganic form are taken up by producers
· The producers use the nutrients to synthesise more complex organic molecules
· They are then passed along food chains as producers and animals are eaten by other consumers.
· When producers and consumers die, they are decomposed by saprobionts and nutrients are eventually returned to their original inorganic form to complete the cycle.
What molecules is N present in
DNA and RNA
proteins and their monomers - Amino acids
ATP / ADP
Why cant organisms use gaseous N
Nitrogen gas is inert/unreactive
Why will lack of nitrogen lead to stunted growth?
Organism is unable to make proteins which are needed for growth
What are the stages of the N cycle
-Nitrogen fixation
-Nitrification
-Nitogen flow through food webs
-Decomposition and ammonification
-Denitrification
What is nitogen fixation
· carried out by nitrogen fixing bacteria.
·convert the nitrogen gas into ammonia/ammonium ions
· Some bacteria live in special swellings on the roots ( root nodules) of plants called legumes.
·bacterium receives water and sugars from the plant and in return supplies the plant with ammonia.
· The ammonia can be used to make proteins and other nitrogen containing organic compounds.
· Some ammonia produced by the bacteria in root nodules may also end up in the soil.
· also free living nitrogen fixing bacteria in the soil. The ammonia that they produce dissolves in water in the soil to form ammonium ions.
· Plants take up nitrogen from the soil in the form of nitrates through their roots by active transport. This is how most of the nitrogen returns to the biotic phase.
What is nitrification
by nitrifying bacteria. These bacteria convert ammonium ions into nitrates
· There are two stages of nitrification, each carried out by different types of nitrifying bacteria.
1. The oxidation of ammonium ions to nitrite ions by nitrifying bacteria.
2. The oxidation of nitrites to nitrates by nitrifying bacteria.
· Plants take up the nitrates through their roots by active transport returning the nitrogen returns to the biotic phase.
How does N flow through food webs
· The inorganic nitrogen taken up by plants from the soil, is largely in the form of nitrates
· This is then used to synthesise molecules such as proteins or DNA.
· These move into other organisms when they eat the plants, and digest and absorb the organic compounds.
What is decomposition and ammonification
· When organisms die, excrete urea or egest faeces, saprobiotic microorganisms convert the organic nitrogen in compounds into ammonia/ammonium ions
· This returns the nitrogen to the abiotic phase.
· The saprobiotic microorganisms secrete enzymes on to the detritus so the nitrogen-containing compounds are digested externally.
· This is extracellular digestion .
· The products of digestion are absorbed by the saprobionts, but some ions/molecules are released into the environment.
What is denitrification
the loss of nitrates from the soil under anaerobic conditions (often in water-logged soil).
Nitrates are converted to nitrogen gas .
Aerating the soil will reduce this process.
What molecules contain P
Phospholipids, Nucleic Acids (DNA and RNA), ATP, ADP, NADPH
What is the phosphorous cycle
· Saprobionts decompose dead organisms or waste materials using extracellular digestion.
· Saprobionts absorb the products of digestion and release phosphate ions into soils, lakes, rivers and oceans where they dissolve.
· Some phosphate ions are absorbed by plants and algae and used to form organic biological molecules used in growth
· phosphate ions are passed to the animals that feed on the plants and algae. The phosphate-containing organic compounds are digested then absorbed
· Some dissolved phosphates in oceans can, by sedimentation, form rocks.
· The phosphates in sedimentary rocks are only returned to the cycle if geological upheavel and erosion occurs.
What is mycorrhizae
fungi that grow in association with plant roots and improve the plant’s uptake of water and inorganic ions.
An example of a mutualistic relationship
What do Mycorrhizae do
· fungus colonizes host plant’s roots.
They grow in and around the roots producing a large system of threads or hyphae.
· This provides the fungus with carbohydrates from the plant, such as glucose and sucrose.
· In return, plant gains the benefits of the fungal hyphae’s greater ability to absorb water and minerals due to the large surface area of the thread like hyphae.
