Module 5 - Nutrient cycles Flashcards
What are saprobionts?
They are a type of bacteria that break down dead organisms or waste material.
They are also involved in extracellular digestion.
What are the 4 key stages in the nitrogen cycle?
Nitrogen fixation, ammonification, nitrification and denitrification
Explain what nitrogen fixation is
This is when mutualistic nitrogen fixing bacteria breaks down the nitrogen gas from the atmosphere into ammonia. This then gets broken down to form ammonium ions. Some bacteria can be found in root nodules of leguminous plants
Explain what ammonification is
This is when saprobionts break down dead organisms or waste material into ammonia. These then get turned into ammonium ions.
Explain what nitrification is
This is when nitrification turns ammonium ions in the soil into nitrogen compounds that can be used by the plant. These are turned into nitrites. The, another bacteria will turn these into nitrates which can be used by the plant
Explain what denitrification is?
This is when denitrifying bacteria breaks down nitrates into nitrogen gas. This happens under anaerobic conditions
What is the phosphorus cycle?
This is the recycling of phosphate
What does assimilated mean?
Absorbed and then used to make more complex molecules
The first stage of the phosphate cycle is weathering. What is this?
This is when rocks are broken down which causes the release of phosphate ions into the soil. These are then taken up by planta through the mycorrhizae.
What are mycorrhizae
This is a form of symbiotic relationship which is when long thin filaments attach to the roots of plants - known as hyphae which increase the rate of absorption of water and ions
What is the second stage of the phosphorus cycle?
The phosphate ions are transferred through the food chain as animals eat the plants and are in turn eaten by other animals.
How can phosphate ions get lost through organisms?
They can be lost through excretion or when organisms die, saprobionts will break dowm the organisms causing the release of phosphate ions into the soil
How can aquatic producers obtain phosphate ions?
Weathering of rocks releases phosphate ions into the sea, lake and rivers. These phosphate ions can be taken up by aquatic producers and passed along the food chain
An example of a natural fertiliser and how this can be used to give phosphate back into soil and rocks.
Bird faeces is known as guano and contains a high proportion of phosphate ions back into the soil which can therefore be used as a natural fertiliser
How can harvesting remove nutrients?
When plants and animals are harvested. This prevents them from decomposing in the fields and therefore nitrogen and phosphate cannot be returned back into the soil. Furthermore, animal excretion is removed from the soil.
What is an example of a natural fertiliser
Manure and compost
What is an example of an artificial fertiliser?
Made out of chemicals containing the correct proportions of ions needed
What is leaching?
This is when water-soluble compounds in the soil are washed away into near by waterways
Why is leaching less likely to occur in natural fertiliser?
Natural fertiliser has to be decomposed by saprobionts and therefore uptake by plants is more controlled then artifical fertilisers
Which ion is more likely to be leached and why?
Nitrates because they are less soluble in water
Explain the 5 steps of eutrophication?
Minerals are leached from fertilised fields which stimulate rapid growth of algae.
Large amounts of algae block the light
The plants die because they cannot receive light for photosynthesis
Bacteria feed on dead matter and reduce oxygen conc because they respire.
Fish and other organisms die because there isnt enough oxygen
Why may too much artificial fertiliser cause a reduction in crop yield?
The water-soluble minerals inside the fertiliser will create a lower water potential in the soil around the plant. This will cause water to move out into the soil from the plant, killing it
