Post Assignment #3: Duaa Khan

During the past week, our miniature broccolis are growing healthy as three seedlings have begun to sprout. They have a short light green stem with heart-shaped leaves. On each plant, there are two leaves on them as they are continuing to be much more healthy. 

Plants contribute greatly to the water cycle because of the processes they use to absorb and release energy. Unlike animals, which get their energy from food, plants convert sunlight into usable energy through photosynthesis. Plants also absorb nutrients and water through their roots. When a plant absorbs water, it travels throughout its stems and its leaves. Needed for photosynthesis, plants cannot get the energy they need from the sun without water. During photosynthesis, some excess water evaporates from the surface of the leaves, becoming water vapor. The water vapor in the process of transpiration travels into the atmosphere and becomes part of the water cycle.

The processes of photosynthesis and respiration are the basis of the carbon cycle. In photosynthesis, plants use energy from the sun and carbon dioxide (CO2) gas from the atmosphere to create carbohydrates (sugars) and oxygen (O2). Carbohydrates are then stored in their biomass (living parts, such as leaves, stems, and roots) as plants live and grow. Stored carbohydrates can be used as energy. To use the energy, carbohydrates need to be broken down in respiration and CO2 is released back into the atmosphere. Also, plants that die and are buried may turn into fossil fuels made of carbon like coal and oil over millions of years. When humans burn fossil fuels, most carbon enters the atmosphere as carbon dioxide.

In the nitrogen cycle, plants receive the components of the "fixed" nitrogen using nitrates in the soil to provide the nutrients they need. Plants absorb ammonium and nitrate during the assimilation process, after which they are converted into nitrogen-containing organic molecules, such as amino acids and DNA. When nitrogen nutrients have served their purpose in plants and animals, specialized decomposing bacteria will start a process called ammonification, to convert them back into ammonia and water-soluble ammonium salts. After the nutrients are converted back into ammonia, anaerobic bacteria will convert them back into nitrogen gas, during a process called denitrification. Finally, nitrogen is released into the atmosphere again. The whole process starts over after release.