Problem 9 - Biology Today and Tomorrow with Physiology

Question

Match each substance with its largest environmental reservoir. One reservoir choice will be used more than once. a. seawater b. rocks and sediments c. the atmosphere carbon _____ water _____ phosphorus _____ nitrogen _____

Step-by-Step Solution

Answer

Carbon: b. rocks and sediments; Water: a. seawater; Phosphorus: b. rocks and sediments; Nitrogen: c. the atmosphere.

Step 1: Identify the Main Reservoir for Carbon

Carbon is stored in various forms globally, but the largest reservoir is typically in rocks and sediments, where it is found as carbonate minerals and fossil fuels.

Step 2: Determine the Largest Reservoir for Water

Water is mostly found in seawater; oceans cover about 71% of the Earth's surface, making them the largest reservoir of water.

Step 3: Locate the Main Reservoir for Phosphorus

Phosphorus is mainly stored in rocks and sediments. It is not found in a gaseous form and is primarily cycled through soil and rock.

Step 4: Identify the Largest Reservoir for Nitrogen

The atmosphere holds the largest portion of nitrogen on Earth, in the form of nitrogen gas (N2), comprising roughly 78% of the Earth's atmosphere.

Key Concepts

The Carbon Cycle

The carbon cycle is a natural process by which carbon is exchanged among the atmosphere, oceans, soil, and living organisms on Earth. Carbon is an essential building block of life and is present in all living things. However, its largest reservoir is found in rocks and sediments, where it is stored as carbonate minerals and fossil fuels such as coal and petroleum.

The carbon cycle involves several key processes:

• Photosynthesis: Plants absorb carbon dioxide (CO2) from the atmosphere and convert it into organic matter, like glucose, using sunlight.
• Respiration: Animals and plants release carbon back into the atmosphere as CO2 when they breathe.
• Decomposition: When organisms die, decomposers break down the organic material, releasing carbon into the soil or atmosphere.
• Combustion: Burning fossil fuels releases stored carbon back into the atmosphere, increasing the level of CO2.

These processes ensure that carbon is continually cycled, maintaining balance in the environment.

The Water Cycle

The water cycle describes how water moves through our environment, playing a crucial role in weather and climate. It is the process by which water is recycled from the Earth's surface to the atmosphere and back again.

The largest reservoir of water is the oceans, covering about 71% of the Earth's surface. The water cycle consists of several stages:

• Evaporation: Water from oceans, rivers, and lakes turns into vapor and rises into the atmosphere.
• Condensation: Water vapor cools and changes back into liquid, forming clouds.
• Precipitation: Water falls from clouds as rain, snow, or other forms of precipitation.
• Collection: Precipitated water gathers in bodies of water like rivers, lakes, and oceans, restarting the cycle.

This cycle is driven by solar energy and gravity, essential for sustaining life by providing fresh water and influencing weather patterns.

The Phosphorus Cycle

The phosphorus cycle is an essential biogeochemical cycle that involves the movement of phosphorus through rocks, water, soil, and living organisms. Unlike other cycles, phosphorus does not include a gaseous phase and is not found in the atmosphere in significant amounts. Instead, its largest reservoir is in rocks and sediments.

In this cycle:

• Weathering: Over time, weathering of rocks releases phosphate ions into the soil and water.
• Absorption by Plants: Plants take up phosphorus from the soil to use in cellular processes and energy transfer.
• Consumption: Animals obtain phosphorus by eating plants or plant-eating organisms.
• Decomposition: When plants and animals die, phosphorus returns to the soil through decomposition.

The phosphorus cycle is crucial for DNA and RNA production and helps in plant growth. Because it lacks a significant atmospheric component, it cycles less freely but is vital to ecosystem productivity.

The Nitrogen Cycle

The nitrogen cycle is the biogeochemical cycle that describes how nitrogen is converted between its various chemical forms. This transformation is crucial for living organisms, as nitrogen is a key component of amino acids and proteins. The largest reservoir of nitrogen is the atmosphere, constituting about 78% of it in the form of nitrogen gas (N2).

The cycle includes several processes:

• Nitrogen Fixation: Specialized bacteria in the soil or root nodules of legumes convert nitrogen gas from the atmosphere into ammonia, a form that plants can use.
• Nitrification: Other bacteria in the soil convert ammonia into nitrites and then nitrates, which plants can absorb.
• Assimilation: Plants incorporate nitrates and ammonia into organic compounds like amino acids.
• Denitrification: Some bacteria convert nitrates back into nitrogen gas, releasing it into the atmosphere and completing the cycle.

The nitrogen cycle is essential for building proteins in all living organisms and maintaining ecosystem productivity.