Subscribe

9th grade · Science · Unit 7 of 14

Carbon & Nitrogen Cycles

How carbon and nitrogen move through living things, air, water and soil, and what happens when the cycles are disrupted.

What your child practices

Practices the steps of the carbon cycle (photosynthesis, respiration, decomposition, combustion) and the nitrogen cycle (fixation, nitrification, assimilation, denitrification), why they matter to ecosystem stability, and the consequences of disrupting them, such as fertilizer runoff and burning fossil fuels.

Alabama Course of Study content standard: BIO.7 · the carbon and nitrogen cycles between living and nonliving parts of ecosystems

How we explain it

Children can open this short lesson before they practice.

  1. Carbon cycle: photosynthesis takes carbon dioxide in; respiration, decomposition and combustion release it.
  2. Fossil fuels are remains of ancient organisms buried for millions of years.
  3. Nitrogen cycle: bacteria fix nitrogen, plants assimilate it, animals eat plants, denitrification returns it to the air.

Example: Which process releases carbon dioxide from living cells? Photosynthesis takes it in. Cells give it off when they release energy. Answer: cellular respiration

Carbon & Nitrogen Cycles in Alabama

In the Alabama Course of Study, this is unit 7 of 14 in 9th grade Science, after Photosynthesis & Respiration and before Genetic Crosses.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Alabama State Department of Education (ALSDE)

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Most of Earth's free nitrogen is N₂ gas in the…

    • oceans
    • atmosphere
    • living things
    • rocks

  2. Question 2

    Lightning helps the nitrogen cycle by…

    • making sugar
    • turning N₂ into compounds that rain carries to the soil
    • freezing the soil
    • removing all nitrogen

  3. Question 3

    Which process removes carbon dioxide from the air?

    • Combustion
    • Cellular respiration
    • Decomposition
    • Photosynthesis

  4. Question 4

    Cutting and burning forests disrupts the carbon cycle by…

    • fixing nitrogen
    • releasing stored carbon and reducing photosynthesis
    • cooling the planet
    • storing more carbon

  5. Question 5

    Animals get the nitrogen they need by…

    • breathing N₂
    • eating plants or other animals
    • absorbing sunlight
    • drinking seawater

  6. Question 6

    Which action helps keep the carbon cycle in balance?

    • Draining wetlands
    • Burning more coal
    • Clearing forests
    • Planting trees and burning less fossil fuel

More 9th grade