Nutrient Cycling In Nature - SS2 Biology Past Questions and Answers - page 2

Denitrification

Transpiration

Nitrogen fixation

The carbon cycle is a complex process that involves the exchange of carbon between various reservoirs. Carbon dioxide in the atmosphere is taken up by plants through photosynthesis, converting it into organic compounds. This carbon is then passed through the food chain as organisms consume plants or other animals. Carbon is eventually released back into the atmosphere through respiration and decomposition. Additionally, carbon is stored in the Earth's crust as fossil fuels, which can be released through combustion. The cycle continues as carbon is continuously exchanged between these reservoirs.

The oxygen cycle involves the production and consumption of oxygen in the environment. Oxygen is primarily produced through photosynthesis by plants, algae, and cyanobacteria. During photosynthesis, these organisms convert carbon dioxide and sunlight into oxygen and glucose. Oxygen is then consumed by organisms through respiration, where it is used in the breakdown of organic molecules to release energy. The cycle is maintained by a balance between oxygen production and consumption by various organisms.

The nitrogen cycle involves the conversion of nitrogen into different forms that can be utilized by living organisms. Nitrogen gas in the atmosphere is converted into ammonia through a process called nitrogen fixation. This can be done by nitrogen-fixing bacteria or through human activities like industrial processes or the use of fertilizers. Ammonia is then further converted into nitrites and nitrates through nitrification, which can be taken up by plants. Animals obtain nitrogen by consuming plants or other animals. Nitrogen is returned to the atmosphere through denitrification, where certain bacteria convert nitrates back into nitrogen gas.

The water cycle, also known as the hydrological cycle, describes the continuous movement of water on, above, and below the Earth's surface. Water evaporates from bodies of water, plants, and soil, and rises into the atmosphere as water vapor. In the atmosphere, water vapor condenses to form clouds, and precipitation occurs when water droplets or ice crystals fall to the Earth's surface as rain, snow, sleet, or hail. Precipitation can infiltrate the soil and become groundwater or flow into streams, rivers, and eventually the oceans, completing the cycle. Transpiration, the process by which plants release water vapor through their leaves, also plays a significant role in the water cycle.

The carbon-oxygen balance refers to the equilibrium between carbon dioxide (CO₂) and oxygen (O₂) in the atmosphere. It is essential to maintain appropriate levels of these gases for the survival of living organisms. During photosynthesis, plants utilize carbon dioxide and release oxygen, which is essential for respiration in animals. In turn, animals produce carbon dioxide during respiration and depend on oxygen for their metabolic processes. Maintaining a proper balance ensures a sustainable environment for both plants and animals, supporting the overall health and balance of ecosystems.

Decomposition is the process by which organic matter, such as dead plants and animals, is broken down into simpler substances by microorganisms, primarily bacteria and fungi. These decomposers secrete enzymes that break down complex organic molecules into smaller, more accessible compounds. During decomposition, nutrients locked in organic matter are released