Question

part iii – the phosphorus cycle

1. pick one step in the phosphorus cycle and briefly research it. what step did you choose? give a real - world example of this step and explain what happens to the phosphorus atoms as they move.
2. how are human activities disrupting the natural phosphorus cycle? why is this a problem?

part iv – the hydrologic (water) cycle

1. pick one step in the water cycle and briefly research it. what step did you choose? give a real - world example of this step and explain what happens to the water molecules as they move.
2. in \water’s incredible journey\, what was your journey like? did you make it to all nine locations, or did you get stuck somewhere? do you think this simulation was realistic, or were there locations that were missing? explain.

Explanation:

Question 5 (Phosphorus Cycle Step)

Let's choose the "Weathering of Rocks" step in the phosphorus cycle. Real - world example: In a mountainous area with granite rocks containing phosphorus - bearing minerals (like apatite). When rain falls on these rocks, the water, along with carbonic acid (formed from atmospheric $CO_2$ dissolving in water), chemically weathers the rocks. The phosphorus atoms in the mineral structure are released into the soil as dissolved phosphate ions ($PO_4^{3 - }$, $HPO_4^{2 - }$, etc.). These phosphate ions then become available for plant uptake.

Human activities like excessive use of phosphate - based fertilizers in agriculture disrupt the cycle. When these fertilizers are applied in large amounts, more phosphate enters water bodies (via runoff) than natural processes can handle. Also, sewage discharge (containing phosphorus from human waste) and industrial waste with phosphorus contribute. This is a problem because it causes eutrophication in water bodies. Eutrophication leads to rapid growth of algae (algal blooms). When the algae die, decomposers use up large amounts of oxygen in the water, creating dead zones where aquatic life can't survive. Also, it disrupts the natural balance of nutrient cycling in ecosystems.

Let's choose "Evaporation". Real - world example: A lake on a sunny day. Water molecules in the lake gain kinetic energy from the sun's heat. Some molecules at the surface gain enough energy to break free from the liquid - water intermolecular forces and enter the atmosphere as water vapor (gaseous state). These water vapor molecules then move with air currents, and can later condense to form clouds.

Answer:

Step chosen: Weathering of Rocks. Real - world example: In a mountainous granite - rich region, rainwater with dissolved $CO_2$ (forming carbonic acid) weathers phosphorus - containing minerals in rocks. Phosphorus atoms are released as phosphate ions into the soil, available for plants.

Question 6 (Human Disruption of Phosphorus Cycle)