SURIGAO STATE COLLEGE OF TECHNOLOGY
Surigao City

GRADUATE SCHOOL
COURSE SYLLABUS IN MA.Ed
GS 222 ENVIONMENTALSCIENCE

Reporter: HERSHIEL C. MANAIT
Topic: BIOGEOCHEMICAL CYCLES
Instructor: HAYDE D. FABROA

BIOGEOCHEMICAL CYCLES * The Earth is a closed system for matter, except for small amounts of cosmic debris that enter the Earth’s atmosphere. * The building blocks of life, continually cycle through Earth’s systems, the atmosphere, hydrosphere, biosphere, and lithosphere, on time scales that range from a few days to millions of years. These cycles are called biogeochemical cycles, because they include a variety of biological, geological, and chemical processes. * There are a few types of atoms that can be a part of a plant one day, an animal the next day, and then travel downstream as a part of a river’s water the following day. These atoms can be a part of both living things like plants and animals, as well as non-living things like water, air, and even rocks. The same atoms are recycled over and over in different parts of the Earth. This type of cycle of atoms between living and non-living things is known as a biogeochemical cycle. * Each of the chemical, biological, and geological processes varies in their rates of cycling. Some molecules may cycle very quickly depending on the pathway * Biogeochemical cycles are subject to disturbance by human activities. Humans accelerate natural biogeochemical cycles when elements are extracted from their reservoirs, or sources, and deposited back into the environment (sinks) * All chemicals, nutrients, or elements used in ecosystem by living organisms such as carbon, nitrogen, oxygen, phosphorus and hydrogen- operate on a closed system, which means that these chemicals are recycled, instead of lost, as they would be in an open system. * Components of the biogeochemical cycle are not completely lost, they can be held for long periods of time in one place. This place is called a reservoir (which for example, coal deposits that are storing carbon for a long period of time. * The most well-known and important biogeochemical cycles include the carbon cycle, the nitrogen cycle, the oxygen cycle, the phosphorus cycle and the water cycle

CARBON CYCLE * Carbon is a fundamental building block of life; life on Earth is comprised of carbon-based life forms * All cells contain carbon, because they all contain proteins, fats and carbohydrates, which themselves contain carbon * Carbon dioxide is recycled constantly through various processes that form the carbon cycle a. Photosynthesis. The first step in the biological carbon cycle is the conversion of inorganic atmospheric carbon into a biological form. This ‘fixing’ of carbon in biological form takes place within plants and other organisms – known as producers – in a process called photosynthesis
In photosynthesis, light combines with carbon dioxide and water to create carbohydrate molecules known as sucrose (C6H12O6)
The carbohydrates then become the foundation for a system of chemical energy that fuels living cells in all plants and animals. In plants, some carbon remains within glucose for short-term energy use, while some is converted to starch for longer term energy storage b. Cycling and Storage. The carbon that is absorbed from the atmosphere by plants and animals can take several paths before reentering the air as carbon dioxide. When a plant dies, it is broken down by microorganisms – called decomposers – that feed on the dead organic matter. As the microorganisms consume the plant matter, they release some of the plant’s carbon into the atmosphere in the form of CO2 c. Two Carbon Cycles and Human Alteration. Carbon converted to biological form in plants, consumed by animals, and returned to the atmosphere in respiration can travel this path over a very short period – days, weeks, or months. But carbon buried under the ocean floor might take tens of millions of years to return to the atmosphere, if it does at all. Throughout the Earth’s history, this emission of CO2 (and many other gases) from deep below the planet’s surface happens as geological events, such as volcanic eruptions.

OXYGEN CYCLE * Oxygen is an important element to life on Earth. It is the most common element of the human body. It makes up about 65% of the mass of the human body. Most of this is in the form of water (H2O). Oxygen also makes up about 30% of the Earth and 20% of the atmosphere * Oxygen is constantly being used and created by different processes on planet Earth. All of these processes together make up the oxygen cycle. The oxygen cycle is interconnected with the carbon cycle

Processes That Use Oxygen * Breathing - The scientific name for breathing is respiration. All animals and plants use up oxygen when they breathe. They breathe in oxygen and breathe out carbon dioxide. * Decomposing - When plants and animals die, they decompose. This process uses up oxygen and releases carbon dioxide. * Rusting - This is also called oxidation. When things rust they use up oxygen. * Combustion - There are three things needed for fire: oxygen, fuel, and heat. Without oxygen you can't have a fire. When things burn, they use up oxygen and replace it with carbon dioxide.

Processes That Produce Oxygen * Plants - Plants create the majority of the oxygen we breathe through a process called photosynthesis. In this process plants use carbon dioxide, sunlight, and water to create energy. In the process they also create oxygen which they release into the air. * Sunlight - Some oxygen is produced when sunlight reacts with water vapor in the atmosphere
NITROGEN CYCLE * Nitrogen is an element. It is found in living things like plants and animals. Atoms of nitrogen don't just stay in one place. They move slowly between living things, dead things, the air, soil and water. These movements are called the nitrogen cycle * All plants and animals need nitrogen to make amino acids, proteins and DNA, but the nitrogen in the atmosphere is not in a form that they can use * The molecules of nitrogen in the atmosphere can become usable for living things when they are broken apart during lightning strikes or fires, by certain types of bacteria * Most plants get the nitrogen they need to grow from the soils or water in which they live * Animals get the nitrogen they need by eating plants or other animals that contain nitrogen. When organisms die, their bodies decompose bringing the nitrogen into soil on land or into ocean water. Bacteria alter the nitrogen into a form that plants are able to use. Other types of bacteria are able to change nitrogen dissolved in waterways into a form that allows it to return to the atmosphere. * Certain actions of humans are causing changes to the nitrogen cycle and the amount of nitrogen that is stored in the land, water, air, and organisms (ex. use of nitrogen-rich fertilizers can add too much nitrogen in nearby waterways as the fertilizer washes into streams and ponds)

PHOSPHORUS CYCLE * Phosphorus is an essential nutrient for animals and plants. It plays a critical role in cell development and is a key component of molecules that store energy, such as ATP (adenosine triphosphate), DNA and lipids (fats and oils) * Phosphorus moves in a cycle through rocks, water, soil and sediments and organisms
Here are the key steps of the phosphorus cycle: * Over time, rain and weathering cause rocks to release phosphate ions and other minerals. This inorganic phosphate is then distributed in soils and water. * Plants take up inorganic phosphate from the soil. The plants may then be consumed by animals. Once in the plant or animal, the phosphate is incorporated into organic molecules such as DNA. When the plant or animal dies, it decays, and the organic phosphate is returned to the soil. * Within the soil, organic forms of phosphate can be made available to plants by bacteria that break down organic matter to inorganic forms of phosphorus. This process is known as mineralization. * Phosphorus in soil can end up in waterways and eventually oceans. Once there, it can be incorporated into sediments over time.
SULFUR CYCLE * Sulfur cycle, circulation of sulfur in various forms through nature. Sulfur occurs in all living matter as a component of certain amino acids. It is abundant in the soil in proteins and, through a series of microbial transformations, ends up as sulfates usable by plants. * Sulfur-containing proteins are degraded into their constituent amino acids by the action of a variety of soil organisms. The sulfur of the amino acids is converted to hydrogen sulfide (H2S) by another series of soil microbes. In the presence of oxygen, H2S is converted to sulfur and then to sulfate by sulfur bacteria. Eventually the sulfate becomes H2S. * Hydrogen sulfide rapidly oxidizes to gases that dissolve in water to form sulfurous and sulfuric acids. These compounds contribute in large part to the “acid rain” that can kill sensitive aquatic organisms and damage marble monuments and stone buildings.