Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Autotrophs convert atmospheric carbon dioxide into carbohydrates and other carbon compounds through the process of carbon fixation during photosynthesis ().
In aquatic ecosystems, carbon is present as dissolved and hydrogen carbonate ions (). The dissolves in water to form carbonic acid (), which dissociates to lower the pH.
Carbon dioxide diffuses from the atmosphere or water into autotrophs, moving down a concentration gradient created as autotrophs use for photosynthesis.
Carbon dioxide is produced by the respiration of all organisms (producers, consumers, and decomposers) and diffuses out of cells into the atmosphere or water.
Methane () is produced from organic matter in anaerobic conditions by methanogenic archaeans; it typically diffuses into the atmosphere or accumulates in the ground.
Methane is oxidized to carbon dioxide and water in the stratosphere (), which explains why atmospheric concentrations remain relatively low despite constant production.
Peat forms when organic matter is not fully decomposed because of acidic and/or anaerobic conditions in waterlogged soils, trapping carbon for long periods.
Partially decomposed organic matter from past geological eras was converted into oil and gas in porous rocks or into coal; combustion of this fossilized organic matter releases .
Reef-building corals and mollusks have hard parts composed of calcium carbonate () that can become fossilized in limestone rock, acting as a major carbon sink.
📐Formulae
💡Examples
Problem 1:
Explain how the formation of limestone from the shells of marine organisms acts as a carbon sink and how ocean acidification affects this process.
Solution:
Marine organisms like corals use and to build shells. When they die, these shells settle on the ocean floor and are compressed into limestone. However, increased atmospheric dissolves in the ocean to form , which reacts with carbonate: .
Explanation:
The reduction in available ions due to increased acidity makes it difficult for organisms to synthesize , potentially dissolving existing coral reefs and slowing the sequestration of carbon into limestone.
Problem 2:
Given that a specific forest has a gross primary productivity () of and the autotrophic respiration () is , calculate the Net Primary Productivity ().
Solution:
Explanation:
represents the actual amount of carbon stored as biomass in the producers after accounting for the carbon lost through their own cellular respiration.