Nutrient Cycles: Nitrogen Cycle Flashcards
Why is it important that elements such as carbon, nitrogen and phosphorous are recycled?
- energy enters an ecosystem as sunlight and is lost as heat= cannot be recycled
- flow of energy through an ecosystem is therefore in 1 direction, that is linear
- provided the sun continues to supply energy to the Earth, this is not a problem
- nutrients by contrast do not have an extraterrestrial source
- there is limited availability of nutrient ions in a useable form
- so it’s important that elements such as carbon, nitrogen and phosphorous are recycled = flow of nutrients within an ecosystem is not linear, but more cyclic
ALL nutrient cycles have one simple sequence at their heart:
- nutrient is taken up by producers (plants) as simple inorganic molecules
- when the producer is eaten, the nutrient passes into consumers (animals)
- it then passes along the food chain when these animals are eaten by other consumers
- when the producers and consumers die, their complex molecules are broken down by saprobiontic microorganisms that release the
nutrient in its original simple form - cycle then complete
What is the role of saprobiontics?
- they are in many ways the driving forces that ensure nutrients are released for reuse
- without them, nutrients would remain locked up as part of complex molecules that cannot be taken up and used again by plants
Why do we need nitrogen?
Manufacture proteins, nucleic acids and other nitrogen-containing compounds obtained from diet (eating and digesting plants)
Although a large % of the atmosphere being nitrogen, there are very few organisms that can use nitrogen gas directly- plants take up most of the nitrogen they require in form on
Nitrate ions from the soil
What is formula for nitrate ion?
How do plants obtain nitrate ions?
Absorbed using active transport by the roots = where nitrogen enters the loving component of the ecosystem
Nitrate ions are very soluble and easily _____ (wash) through the soil beyond the reach of plant roots
Leach
In natural ecosystems, the nitrate concentratioms are restored largely by the recycling of nitrogen-containing compounds. In agricultural ecosystems, the concentration of soil nitrate can be
Further increased by the addition of fertilisers
When plants and animals die, the process of decomposition begins in a series of steps which micro-organisms replenish the nitrate concentration in the soil- the release of nitrate ions by decomposers is very important because
In natural ecosystems, there are very few nitrate ions available from other sources
What are the 4 main stages of the nitrogen cycle?
1- nitrogen fixation
2- ammonification
3- nitrification
4- denitrification
What is equation for nitrogen fixation?
Camera roll
Explain nitrogen fixation
- done by free-living nitrogen-fixing bacteria which reduce gaseous nitrogen to ammonia (used to manufacture amino acids)
- done by mutualistic nitrogen-fixing bacteria that live in nodules on the roots of plants such as peas and beans- they obtain carbohydrates from the plant and the plant acquires amino acids from the bacteria
Explain ammonification
- production of ammonia from organic nitrogen-containing compounds e.g. urea (from breakdown of excess amino acids), nucleic acids and vitamins (found in faeces and dead organisms)
- saprobiontic microorganisms, mainly fungi and bacteria, feed on faeces and dead organisms materials, releasing ammonia which then forms ammonium ions in the soil
What is the formula for ammonium ions?
