Biogeochemical Cycles: Matter, Water, Carbon, Nitrogen, Phosphorus, and Sulfur

All flashcards

What is a biogeochemical cycle?

The movement and recycling of inorganic matter between living organisms and the physical environment through biological, geological, and chemical processes.

How does energy flow differ from matter cycling?

Energy flows through ecosystems and ultimately leaves as heat; matter is conserved and can be reused in organisms and environmental reservoirs.

What is a reservoir in a biogeochemical cycle?

A place where an element or compound is stored, such as the ocean, atmosphere, soil, or rock.

Which six elements are especially common in organic molecules?

Carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur.

How can water link different nutrient cycles?

Water can dissolve and transport nutrients such as nitrogen and phosphate from land into rivers, lakes, and oceans.

Quiz questions

1. Why can most plants not use atmospheric nitrogen gas, $N_2$, directly?Answer: Its two nitrogen atoms are joined by a strong triple covalent bond.
2. What do autotrophs generally do with carbon dioxide in the biological carbon cycle?Answer: They use it to build organic compounds such as glucose.
3. Why can nutrient enrichment lead to low dissolved oxygen in aquatic ecosystems?Answer: Decomposition of excess microbial or algal growth consumes oxygen.
4. Why are fossil fuels considered nonrenewable on human timescales?Answer: They form over millions of years, far more slowly than they are used.
5. Which human activity increases sulfur emissions, especially through sulfur dioxide release?Answer: Burning fossil fuels, particularly coal.