topic 5 (nutrient cycles) Flashcards
what is a natural ecosystem?
ecosystem that hasn’t been changed by human activity
what is a saprobiont?
type of decomposer
how do saprobionts digest organisms?
secrete enzymes and digest their food externally, and absorb the nutrients they need (extra cellular digestion)
what is a symbiotic relationship?
close relationship between members of two different species
what are fungi made of?
long thin strands called hyphae, which connect to the plant’s roots
what are the benefits of hyphae?
increase the surface area of the plant’s root system, helping to absorb scarce ions
increase water uptake
hold water and minerals around the roots
what do fungi obtain from a plant?
organic compounds like glucose
what are mycorrhizae?
fungal associations between plant roots and beneficial fungi
what is phosphorus used for in organisms?
DNA
RNA
ATP
Phospholipid Bilayer
what form is phosphorus found in?
mineral form in sedimentary rocks
what are the stages of the phosphorus cycle?
1) phosphate ions in the rocks are released into the soil by weathering
2) phosphate ions are taken into plants via the roots, where mycorrhizae increase the rate phosphorus can be assimilated
3) phosphate ions are transferred by the food chain
4) phosphate ions lost from animals in waste products
5) saprobionts release phosphate ions
6) weathering of rocks releases phosphate ions into seas/lakes/rivers
7) taken up by aquatic producers
8) waste produced by sea birds= guano
9) returns phosphate to the soil
what percentage of the air is made of nitrogen?
78%
how can plants/animals obtain nitrogen?
microorganisms convert nitrogen gas to nitrogen containing substances which can be absorbed
what biological molecules is nitrogen found in?
proteins, ATP, nucleic acids
what are the 4 stages of the nitrogen cycle?
nitrogen fixation
ammonification
nitrification
dentrification
what happens in nitrogen fixation?
nitrogen gas in the atmosphere is converted into nitrogen containing compounds
turn nitrogen into ammonium
what happens in ammonification?
nitrogen compounds from dead organisms/animal waste are turned into ammonia by saprobionts, goes onto form ammonium ions
what happens in nitrification?
ammonium ions in the soil are changed into nitrogen compounds which can be used by plants
ammonium ions into nitrites into nitrates
what is dentrification?
nitrates in the soil are converted into nitrogen gas by dentrifying bacteria
use nitrates in the soil to carry out respiration and produce nitrogen gas
happens in anaerobic conditions
how do microorganisms produce nitrates?
nitrogen containing compounds converted into ammonia by saprobionts ammonia converted into nitrite nitrite converted into nitrate by nitrifying bacteria nitrogen converted to ammonia by nitrogen fixing bacteria
when are nutrients lost?
when crops are harvested or animals are removed from the land
what are the two types of fertilisers?
artificial and natural
what are artificial fertilisers?
inorganic- contain pure chemicals
what are natural fertilisers?
organic, eg manure, composted vegetables
what is leaching?
when water soluble compounds in soil are washed away
when does applying fertilisers lead to leaching?
when more fertiliser is applied than a plant can need/use
especially before heavy rainfall
when is leaching more likely?
when using chemical fertilisers
contain inorganic ions that are fairly soluble, so excess minerals not immediately used are more likely to leach
when is leaching less likely?
when using natural fertilisers
nitrogen/phosphorus contained in organic molecules that need to be decomposed before they can be absorbed
release into soil more controlled so leaching less likely
are phosphates or nitrates more likely to leach?
nitrates, as phosphates are less soluble in water
what happens in the process of eurotrophication?
mineral ions leached from fertilised fields stimulate the rapid growth of algae in ponds/rivers
large amounts of algae block light from reaching the plants below
eventually plants die as they cannot photosynthesise enough
bacteria feed on dead plant matter- more bacteria reduce the oxygen concentration by carrying out aerobic respiration
fish and other aquatic organisms die due to a lack of dissolved oxygen
