EN: Nutrient Cycles Flashcards
Natural ecosystem
An ecosystem that hasn’t been changed by human activity and whose nutrients are recycled through the food webs.
Extracellular digestion
When saprobionts secrete enzymes and digest their food externally, then absorb the nutrients they need.
Saprobiotic nutrition
Obtaining nutrients from dead organic matter using extracellular digestion.
An ecosystem that hasn’t been changed by human activity and whose nutrients are recycled through the food webs.
Natural ecosystem
When saprobionts secrete enzymes and digest their food externally, then absorb the nutrients they need.
Extracellular digestion
Obtaining nutrients from dead organic matter using extracellular digestion.
Saprobiotic nutrition
Mycorrhizae
When some fungi form symbiotic relationships with roots of plants.
What are fungi made of?
How does this help them connect to plant roots?
Long, thin strands called hyphae - connect to plant roots.
How are fungi beneficial to plants?
The hyphae connect to the plant’s roots.
This greatly increases the surface area of the root system - helps it to absorb ions from the soil that are usually scarce.
Also increases the uptake of water by the plant.
Why are plants beneficial to fungi?
They obtain organic compounds from the plant, eg glucose.
Why do plants and animals need nitrogen?
To make proteins and nucleic acids.
Can plants and animals use nitrogen in gaseous form?
No - they need bacteria to convert it into nitrogen-containing compounds first.
What are the 4 stages of the nitrogen cycle?
- Nitrogen fixation
- Ammonification
- Nitrification
- Denitrification
What do all stages of the nitrogen cycle have in common?
They all involve saprobiontic microorganisms.
What is converted in nitrogen fixation?
Nitrogen gas is converted into the nitrogen-containing compounds.
Ammonia –> ammonium ions.
How can nitrogen fixation be carried out?
Industrially or naturally when lightning passes through the atmosphere.
What are the two main types of microorganisms that carry out nitrogen fixation?
- Free-living nitrogen-fixing bacteria
- Mutualistic nitrogen-fixing bacteria
Describe the role of free-living bacteria in nitrogen-fixation:
- Reduce gaseous nitrogen to ammonia.
- This is used to manufacture amino acids.
- Nitrogen-rich compounds are released from them when they die and decay
Describe the role of mutualistic bacteria in nitrogen-fixation:
- Live in nodules on the roots of plants like peas and beans.
- Obtain carbohydrates from the plant and the plant acquires amino acids from the bacteria.
Briefly describe ammonification:
Nitrogen compounds in dead organisms are turned into ammonia by saprobionts, which goes on to form ammonium ions.
Nitrogen returns to the non-living part of the ecosystem.
What is nitrification performed by?
What is needed for these to perform this?
Nitrifying bacteria called Nitrosomonas and Nitrobacter
Requires oxygen to carry out these conversions and so they require a soil that has many air spaces.
What are the two stages of nitrification?
- Oxidation of ammonium ions to nitrite ions (NO2-)
- Oxidation of nitrite ions to nitrate ions (NO3-)
What is denitrification?
When nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrogen in the soil to carry out respiration and produce nitrogen gas.
