Oxygen Cycle
What process produces most of Earth's oxygen?
Photosynthesis
What form of energy drives the carbon cycle?
Energy from sunlight
What is the largest reservoir of nitrogen on Earth?
The atmosphere (N2 gas)
What is a reservoir in a biogeochemical cycle?
A place where an element is stored for a period of time.
How does burning fossil fuels affect the carbon cycle?
Releases stored carbon as CO2 into the atmosphere.
What process uses oxygen and releases carbon dioxide?
Cellular respiration
What process returns carbon to the atmosphere from animals?
Respiration
What process turns nitrogen gas into a form plants can use?
Nitrogen fixation
Give one example of a carbon reservoir and the form it is stored in.
Oceans
Stored as dissolved carbonates
What human process changes the nitrogen cycle by creating fertilizers?
The Haber-Bosch process
Name two places where oxygen is stored naturally.
Atmosphere and oceans
Name tree carbon reservoirs.
Atmosphere, oceans, fossil fuels/rocks, living organisms
Which organisms carry out nitrogen fixation?
Bacteria (Rhizobium, cyanobacteria)
In what form is nitrogen stored in the soil?
As nitrates and ammonium.
How can fertilizer runoff affect aquatic oxygen levels?
Causes algal blooms -> oxygen depletion -> dead zones
Explain why the oxygen cycle is essential for life.
It provides oxygen for respiration and maintains balance with CO2 for photosynthesis.
How do oceans help regulate carbon dioxide levels?
They absorb and store CO2 as dissolved carbonates and bicarbonates.
What process converts ammonia into nitrates?
Nitrification
What form of oxygen is found in the atmosphere that protects us from UV rays?
Ozone
How does deforestation affect both the carbon and oxygen cycles?
Reduces photosynthesis -> less CO2 absorbed, less O2 produced
Describe the path of oxygen from a tree to an animal and back.
Plants produce O2 -> animals inhale O2 -> respiration releases CO2 -> plants use CO2 -> repeat
Describe the full carbon cycle in short.
CO2 absorbed by plants -> photosynthesis -> animals eat plants -> respiration/decomposition releases CO2 -> carbon stored in oceans/fossil fuels
Explain how the nitrogen cycle supports life.
It provides usable nitrogen for making proteins and DNA in living things.
Match each element to a form found in living things: (O, C, N) -> ?
O: water & sugars; C: carbohydrates, fats; N: proteins, DNA
Name one way humans can help restore balance to Earth's cycles.
Plant trees, reduce fossil fuel use, manage fertilizer responsibly.