Nitrogen cycle Flashcards
(12 cards)
What is the nitrogen cycle, and why is it important?
The nitrogen cycle shows how nitrogen is recycled in ecosystems. Plants and animals require nitrogen to produce proteins and nucleic acids (DNA and RNA), but they cannot use atmospheric nitrogen gas directly.
What are the four key processes in the nitrogen cycle carried out by bacteria?
The four key processes are nitrogen fixation, ammonification, nitrification, and denitrification. Each process is carried out by specific types of bacteria that help convert nitrogen into usable forms or return it to the atmosphere.
What percentage of the atmosphere is nitrogen gas, and can plants and animals access it in this form?
About 78% of the atmosphere is nitrogen gas, but plants and animals cannot access it in this gaseous form. They rely on bacteria to convert nitrogen gas into nitrogen-containing compounds that plants can take up.
What happens during nitrogen fixation?
Atmospheric nitrogen gas is converted into nitrogen-containing compounds by nitrogen-fixing bacteria. These bacteria convert nitrogen into ammonia, which forms ammonium ions that plants can use.
Where are nitrogen-fixing bacteria typically found, and what is their relationship with plants?
Nitrogen-fixing bacteria are often found in root nodules of leguminous plants like peas, beans, and clover. They have a symbiotic relationship with these plants, providing nitrogen compounds to the plants, while the plants provide organic compounds like carbohydrates to the bacteria.
What is ammonification, and which organisms carry it out?
Ammonification is the process where nitrogen compounds in waste products (e.g., urine, feces) and dead organisms are converted into ammonia by saprobionts, which include fungi and bacteria. This ammonia then forms ammonium ions in the soil.
What role do nitrifying bacteria play in the nitrogen cycle?
Nitrifying bacteria convert ammonium ions in the soil into nitrogen compounds that plants can use, known as nitrates. The process occurs in two stages: Nitrosomonas convert ammonium ions into nitrites, and Nitrobacter convert nitrites into nitrates.
What is nitrification, and what are the two types of nitrifying bacteria involved?
Nitrification is the process where ammonium ions are converted into nitrates, which plants can use. Nitrosomonas convert ammonium ions into nitrites, and Nitrobacter convert nitrites into nitrates.
What is denitrification, and when does it occur?
Denitrification is the process where denitrifying bacteria use nitrates in the soil during respiration, producing nitrogen gas that returns to the atmosphere. This process occurs in anaerobic conditions, such as waterlogged soil, where little or no oxygen is available.
How does denitrification affect the nitrogen cycle and the environment?
Denitrification reduces the amount of nitrates in the soil, returning nitrogen to the atmosphere as nitrogen gas. It occurs in anaerobic conditions and can affect the availability of nitrogen for plants, especially in waterlogged or poorly aerated soils.
What is the role of nitrogen-fixing bacteria in the nitrogen cycle?
Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia, which is essential for plant growth. They play a critical role in supplying nitrogen compounds to plants that cannot directly access nitrogen gas.
Why is ammonification important in the nitrogen cycle?
Ammonification is crucial because it recycles nitrogen from organic waste and dead organisms back into the ecosystem, converting it into ammonia that can be further processed into ammonium ions and later into nitrates.
