The Nitrogen Cycle - GCSE Biology | kayscience.com

Summary

The nitrogen cycle is a vital process that moves nitrogen through the atmosphere, soil, and living organisms. Nitrogen in the atmosphere is converted into nitrates by lightning and nitrogen-fixing bacteria, which plants absorb to create proteins and DNA. Animals obtain nitrogen by eating plants and excrete waste containing nitrogen, which decomposers break down into ammonia. Nitrifying bacteria then convert ammonia into nitrites and nitrates, which plants use again. Denitrifying bacteria return nitrogen to the atmosphere, completing the cycle. This process ensures nitrogen availability for all living organisms.

Takeaways

• 😀 Nitrogen makes up 78% of Earth's atmosphere and can be converted into nitrates by lightning strikes.
• 😀 Nitrogen fixing bacteria in the roots of legumes convert atmospheric nitrogen into ammonia (NH3).
• 😀 Ammonia is further converted into nitrites and then nitrates by nitrifying bacteria.
• 😀 Nitrates are absorbed by plants through their roots, where they are used to create proteins and DNA.
• 😀 Animals like sheep consume plants for nitrogen-based proteins and DNA, and excrete urea as nitrogen waste.
• 😀 Decomposers (bacteria) break down dead animals, converting proteins and urea into ammonia.
• 😀 Nitrifying bacteria in the soil convert ammonia into nitrites and then nitrates, replenishing plant nutrients.
• 😀 Denitrifying bacteria in waterlogged soil convert nitrates back into atmospheric nitrogen, reducing soil nitrate levels.
• 😀 The nitrogen cycle consists of atmospheric nitrogen, nitrogen fixation, nitrification, assimilation by plants, consumption by animals, decomposition, and denitrification.
• 😀 The cycle of nitrogen ensures that essential nutrients are continuously recycled between the atmosphere, soil, plants, and animals.

Q & A

What role does lightning play in the nitrogen cycle?

Lightning fixes atmospheric nitrogen by converting it into nitrates (NO3−), which can then be absorbed by plants.

Why do plants need nitrates from the soil?

Plants need nitrates to make essential molecules like proteins and DNA, which are crucial for their growth and survival.

What are legumes, and how do they contribute to the nitrogen cycle?

Legumes are plants that have nitrogen-fixing bacteria in the nodules on their roots, which convert atmospheric nitrogen into ammonia (NH3), enriching the soil with usable nitrogen.

What is the function of nitrogen-fixing bacteria?

Nitrogen-fixing bacteria convert atmospheric nitrogen into ammonia (NH3), which is then further processed by other bacteria to create usable nitrogen compounds for plants.

How do nitrifying bacteria contribute to the nitrogen cycle?

Nitrifying bacteria convert ammonia (NH3) into nitrites (NO2−) and then into nitrates (NO3−), which are essential for plant growth.

What happens to nitrogen when animals die?

When animals die, decomposers break down their bodies, including proteins and urea, releasing ammonia (NH3) back into the soil, where it can be processed into nitrates.

How does nitrogen from animal urine affect the nitrogen cycle?

Animal urine contains nitrogen-based waste in the form of urea, which is returned to the soil and decomposed into ammonia by bacteria, contributing to the nitrogen content in the soil.

What is the role of denitrifying bacteria in the nitrogen cycle?

Denitrifying bacteria convert nitrates (NO3−) back into nitrogen gas (N2), reducing the nitrate concentration in the soil and completing the cycle.

Why are nitrates important for plant growth?

Nitrates are crucial for plants as they are used to synthesize proteins and DNA, both of which are essential for the plant's development and survival.

How do human activities, such as agriculture, impact the nitrogen cycle?

Human activities like agriculture can disrupt the nitrogen cycle by introducing excess fertilizers containing nitrates, leading to soil and water pollution, and potentially disrupting the balance of nitrogen compounds in ecosystems.