Biogeochemical Cycles

Covers the water cycle, carbon cycle, nirtogen cycle, and phosphorus cycle.

[Water cycle] What is evaporation?

Water turns into vapor (gas), like steam from hot soup.

[Water cycle] What is condensation?

Water vapor cools and forms droplets, which make clouds.

[Water cycle] What is precipitation?

Water falls from the sky as rain, snow, or hail.

[Water cycle] What is collection in the water cycle?

Water gathers in oceans, lakes, rivers, and puddles.

[Water cycle] What is an aquifer?

An underground pool of water.

[Water cycle] What does it mean for water to percolate?

Water sinks through soil like coffee through a filter.

[Water cycle] What is the atmosphere?

The blanket of air that surrounds Earth.

[Water cycle] What is residence time?

The amount of time water stays in one place (e.g. river vs underground).

[Water cycle] What is desalination?

The process of removing salt from seawater.

[Water cycle] What are the main steps of the water cycle in order?

Evaporation → Condensation → Precipitation → Collection

[Carbon cycle] What is carbon?

A building block of life found in all living things and things that were once alive.

[Carbon cycle] What does organic mean?

Something that contains carbon — it's alive or was once alive.

[Carbon cycle] What is a carbon sink?

A place that stores carbon, like a forest or ocean.

[Carbon cycle] What is a carbon source?

A place that releases carbon into the atmosphere.

[Carbon cycle] How does carbon enter the atmosphere?

Through breathing, cars, factories, fires, and volcanoes.

[Carbon cycle] How do plants take in carbon?

Through photosynthesis — they use CO₂ from the air to make food.

[Carbon cycle] What happens when animals eat plants (carbon cycle)?

Carbon becomes part of their bodies.

[Carbon cycle] How do living things return carbon to the air?

By breathing out carbon dioxide (CO₂).

[Carbon cycle] What happens to carbon when plants and animals die?

Decomposers break them down and release carbon to the soil or air.

[Carbon cycle] How are fossil fuels formed?

Dead plants and animals are buried and trapped underground for millions of years.

[Carbon cycle] What happens when humans burn fossil fuels?

Carbon is released back into the air as CO₂.

[Nitrogen cycle] What is nitrogen gas (N₂)?

The most common gas in the air, but not usable by plants.

[Nitrogen cycle] What is nitrogen fixation?

Special bacteria (or lightning) turn nitrogen gas into ammonium (NH₄⁺).

[Nitrogen cycle] What is ammonification?

Decomposers turn nitrogen in dead things or poop into ammonium (NH₄⁺).

[Nitrogen cycle] What is ammonium (NH₄⁺)?

A form of nitrogen plants can use.

[Nitrogen cycle] What is nitrification?

Bacteria convert ammonium into nitrites (NO₂⁻) and then into nitrates (NO₃⁻).

[Nitrogen cycle] What are nitrites (NO₂⁻)?

A middle step in nitrification — not very useful for plants.

[Nitrogen cycle] What are nitrates (NO₃⁻)?

The form of nitrogen plants love to absorb.

[Nitrogen cycle] How can you remember nitrite vs nitrate?

"I took a bite, then I ate" — nitrite (bite) comes before nitrate (ate).

[Nitrogen cycle] What is assimilation (nitrogen cycle)?

Plants absorb nitrates and use the nitrogen to grow.

[Nitrogen cycle] What is denitrification?

Bacteria turn nitrates back into nitrogen gas, which returns to the air.

[Nitrogen cycle] Why can't plants use nitrogen gas?

They need it to be "fixed" into a usable form like ammonium or nitrate.

[Nitrogen cycle] What is special about legumes in the nitrogen cycle?

They have a symbiotic relationship with nitrogen-fixing bacteria and get nitrogen more easily.

[Phosphorus cycle] Where does phosphorus come from?

It’s released from rocks by rain and erosion.

[Phosphorus cycle] How do plants get phosphorus?

They absorb it from the soil.

[Phosphorus cycle] How do animals get phosphorus?

By eating plants that contain phosphorus.

[Phosphorus cycle] How is phosphorus returned to the soil?

Decomposers break down dead plants and animals.

[Phosphorus cycle] Where can phosphorus go after washing into water?

It gets buried in sediment.

[Phosphorus cycle] What is adsorption in the phosphorus cycle?

Phosphorus sticks to soil particles.

[Phosphorus cycle] What is desorption?

Phosphorus becomes unstuck from soil and moves around.

[Phosphorus cycle] What is mineralization (phosphorus cycle)?

Bacteria break down organic matter and release phosphorus.

[Phosphorus cycle] How does pH affect phosphorus?

It changes how easily phosphorus can move or be used.

[Phosphorus cycle] Does phosphorus go into the atmosphere?

No, it only moves through soil, water, and living things.