Question

1. plants and animals (and all other living things) are part of all the natural cycles through food chains and food webs. name the four classes of carbon - containing molecules used by living things, and explain how the nitrogen and carbon cycles contribute to the usable supplies of these macromolecules.

Explanation:

The four classes of carbon - containing molecules used by living things are carbohydrates, lipids, proteins, and nucleic acids. In the carbon cycle, carbon is exchanged between the atmosphere, biosphere, hydrosphere, and geosphere. Photosynthesis by plants takes in carbon dioxide and incorporates carbon into organic molecules. Respiration by living organisms releases carbon back into the atmosphere. In the nitrogen cycle, nitrogen - fixing bacteria convert atmospheric nitrogen into ammonia, which can be used by plants to make proteins and nucleic acids. Decomposition of dead organisms also releases nitrogen back into the environment for reuse.

Answer:

The four classes of carbon - containing molecules are carbohydrates, lipids, proteins, and nucleic acids. The carbon cycle contributes to the usable supplies of these molecules through photosynthesis and respiration, and the nitrogen cycle contributes through nitrogen - fixation and decomposition.