Cycles of matter
Atoms circulate among living things, water, soil and the atmosphere. Photosynthesis, respiration and decomposition contribute to the carbon cycle; microorganisms transform nitrogen. Matter can be reused while some energy disperses as heat. This is why an ecosystem needs continuing energy inputs.
Where this sits
- Comes after
- Food webs
Exercises from this rung
Generated by the app, from easiest to hardest
Which process incorporates carbon from atmospheric CO₂ into organic molecules in a plant?
- Carbon fixation during photosynthesis
- Light absorption without any chemical reactions
- Water evaporation alone
Why Carbon fixation incorporates carbon from CO₂ into organic compounds during photosynthesis. These atoms can pass to other organisms through feeding and return as CO₂ through respiration or decomposition. Light energy does not supply the carbon atoms.
easierMany plants cannot directly use N₂ from the air. What do nitrogen-fixing microorganisms do?
- Convert it into compounds such as ammonia or ammonium
- Remove the need for nitrogen in proteins
- Turn nitrogen into light
Why Biological fixation converts N₂ into reduced forms that can enter living systems. Some fixing microorganisms associate with roots; others live freely. Nitrogen is needed for molecules such as proteins and nucleic acids.
in betweenBurning coal moves carbon from one place to another. From where to where?
- From underground to the atmosphere
- From the ocean to the rocks
- From the air to the soil
Why Coal is organic matter from ancient forests that dropped out of the cycle. Burning it returns that carbon to the air as CO₂ within decades, far faster than any natural process removes it, which is why its share of the atmosphere rises.
harder