Nitrogen & Phosphorus Cycles: Always Recycle! Part 2 - Crash Course Ecology #9

What are two essential nutrients for living organisms that are often not readily available?

Nitrogen and phosphorus.

What percentage of the human body is made up of nitrogen and phosphorus?

About 3% nitrogen and 1% phosphorus.

What do plants need to assimilate nitrogen from the atmosphere?

They need nitrogen-fixing bacteria to convert nitrogen gas into ammonia.

What special enzyme do nitrogen-fixing bacteria use to break triple bonds in nitrogen gas?

Nitrogenase.

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

To metabolize nitrogen oxides and convert them back into nitrogen gas.

In what form do plants primarily absorb nitrogen?

Nitrates, nitrites, and ammonium.

Where does phosphorus primarily come from in the phosphorus cycle?

Inorganic phosphates found in rocks.

What happens to phosphates when plants die or during decomposition?

Phosphates are released back into the soil or water.

How long can a phosphorus atom remain in a biological cycle within aquatic ecosystems?

Up to about a hundred thousand years.

What human intervention has greatly influenced the nitrogen and phosphorus cycles?

The introduction of synthetic fertilizers.

What can result from excessive use of nitrogen and phosphorus fertilizers in ecosystems?

Ecosystems can become overwhelmed, leading to environmental issues.

Who was Fritz Haber and why is he significant to the nitrogen cycle?

He developed methods for synthesizing ammonia, impacting fertilizers and chemical weapons.

Why is nitrogen considered elusive despite being abundant in the atmosphere?

It's in a form (nitrogen gas) that is not readily usable by most organisms.

What cycle involves the conversion of atmospheric nitrogen into biologically available forms?

The nitrogen cycle.

What is the lithosphere?

The Earth's crust, which contains significant amounts of phosphorus.

What is a key reason that nitrogen-fixing bacteria are crucial for plant life?

They convert atmospheric nitrogen into ammonia, making it biologically available.

What are decomposers' roles in both the nitrogen and phosphorus cycles?

They break down organic matter, returning nitrogen and phosphates to the soil.