The following illustration depicts a general model of a nutrient cycle.



Why are some of the arrows thicker than other arrows?

The following illustration depicts a general model of a nutrient cycle.



What does the large question mark, and related arrows, on the illustration represent?

“This nutrient is cycled through ecosystems by the chemical and physical weathering of rocks. Stores of this nutrient are often buried deeply in the ground as sedimentary rock for thousands of years. Like other nutrients, it is absorbed through plant roots and becomes available to animals when they consumer these plants. Human activities that change the natural cycling of this nutrient include the use of fertilizers and detergents, which greatly increase the amounts of this nutrient in ecosystems.”

Which nutrient does the above paragraph refer to?

“This nutrient cycles through ecosystems by photosynthesis, cellular respiration and decomposition. As well, ocean mixing and volcanic eruptions can cycle this nutrient. Human activities that change the natural cycling of this nutrient include the burning of fossil fuels.”

Which nutrient does the above paragraph refer to?

“This nutrient is the most prevalent gas in Earth’s atmosphere. It cycles through ecosystems via plants. Unusable in its normal form, once it is converted by lightning in the atmosphere or special bacteria in the soil or water it is absorbed by plants and enters food webs. Human activities, such as the burning of fossil fuels, and the use of fertilizer in agriculture, have more than doubled the amount of the nutrient in the biosphere in the past 50 years.”

Which nutrient does the above paragraph refer to?

Which of the following is not a short-term carbon store?

Which of the following is not a long-term carbon store?

“The process where nitrogen gas, N₂, is converted into compounds that contain nitrates (NO₃^–) or ammonium (NH₄⁺). This conversion can occur via lightning or bacteria like Rhizobium that live on the roots of legumes.”

What is being described in the paragraph above?

An excess of fertilizer use can allow for the run-off or leaching of this nutrient from agricultural land. When this nutrient enters waterways, it eventually gathers in lakes and oceans and can cause eutrophication. The algal bloom shown in the photograph below illustrates how this can occur in an ocean, cutting off sunlight to lower depths and using up all of the oxygen in the water, often killing many animals as a result.



Which nutrient is involved in the process described above?

Which of the following is a biotic component of the carbon cycle?