Lesson 2: Energy Nutrients Cycling

• The First Law of Thermodynamics, also known as the Law of Conservation of Energy, states that energy is neither created nor destroyed, it can only be transformed from one form to another.
• The amount of energy that comes into a system is equal to the amount of energy that comes out.
• Sulfur eventually settles back into the Earth or comes down within rainfall.
• As organisms die and decompose, some of the sulfur is again released as a sulfate and some enters the tissues of microorganisms.
• Photosynthesis converts the energy from the sun into ATP, which drives the formation of simple sugars.
• Cells metabolize the sugars to harness the energy for cellular work.
• In the food chain, energy is lost through waste heat as organisms live and die.
• The Second Law of Thermodynamics states that energy transformation is not 100% efficient, a part of high quality energy is converted to thermal energy that causes disorganized or random motion of molecules.
• The transformation of matter and energy from an organized state to a more random, disorganized state is referred to as entropy.
• A living system tends to move from a state of entropy to a state of orderliness or low entropy.
• The First Law of Thermodynamics tells us about conservation of energy among processes.
• The Second Law of Thermodynamics talks about the directionality of the processes, that is, from lower to higher entropy.
• Ecosystem obeys the First and Second law of thermodynamics.
• A nutrient cycle is the path of an element from one organism to another, and from organisms into the nonliving part of the biosphere and back.
• Nutrient cycles are sometimes referred to as biogeochemical cycles, reflecting the fact that chemicals are cycled between biological organisms, and between organisms and the geologic (physical) environment.
• Carbon, hydrogen, oxygen, nitrogen and phosphorus as elements and compounds make up 97% of the mass of our bodies and are more than 95% of the mass of all living organisms.
• These elements are passed from organism to organism by chemical conversion processes, which occur in food webs.
• They are also converted from non-living forms to living forms by photosynthesis and nitrogen fixation, and from living forms to non-living forms through cellular respiration.
• Based on the replacement period, nutrient cycles can be categorized as perfect, gaseous, or mixed.
• The nitrogen cycle is a complex biogeochemical cycle in which nitrogen is converted from its inert atmospheric molecular form (N2) into a form that is useful in biological processes.
• Nitrogen fixation can occur in any of the following ways: atmospheric fixation, which involves lightening, and industrial fixation, which involves manufacturing ammonia under high temperature and pressure conditions.
• Nitrogen is the most prevalent element in living organisms and is a constituent of amino acids, proteins, hormones, chlorophylls and many of the vitamins.
• When plants and animals die, most of their bodies are decomposed and carbon atoms are returned to the atmosphere.
• Ammonification is the process of releasing ammonia by certain microorganisms utilizing organic compounds derived from dead organic remains of plants and animals and excreta of animals.
• Assimilation is the process of absorption of the fixed nitrogen (in the soil) by the plants through their roots, with plants able to absorb ammonium from the soil via their root hairs.
• Denitrification is a process in which nitrate (NO3-) is converted back to gaseous nitrogen (N2), making its way back into the atmosphere.
• Nitrification is a process of enzymatic oxidation of ammonia to nitrate by a certain microorganism in soil and ocean, with Nitrosomonas converting ammonia to nitrites and Nitrobacter oxidizing nitrites to nitrates.
• Nitrogen fixation is the first step of the nitrogen cycle, characterized by the conversion of atmospheric N2 into ammonia (NH3), with bacteria like Azotobacter and Rhizobium having a major role in this process.
• Nitrogen is a limiting nutrient for both natural and agricultural ecosystems.
• Nitrogen fixers are organisms that perform nitrogen fixing, including non-symbiotic nitrogen-fixing bacteria or nitrogen-fixing soil bacteria, symbiotic nitrogen-fixing bacteria living in association with leguminous plants and non-leguminous root nodule plants, and some Cyanobacteria (blue-green algae), a major source of nitrogen fixation in oceans.
• When animals eat plants, some carbon is transferred and becomes part of their bodies.
• A perfect nutrient cycle is one in which nutrients are replaced as fast as they are utilized.
• Most gaseous cycles are generally considered as perfect cycles.
• Condensation: The transformation of water vapor to liquid water droplets in the air, creating clouds and fog.
• Infiltration: The flow of water from the ground surface into the ground.
• Runoff (Surface Runoff and Channel Runoff): The variety of ways by which water moves across the land.
• As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.
• Precipitation: Condensed water vapor that falls to the Earth's surface.
• Most precipitation occurs as rain, but also includes snow, hail, etc.
• Carbon is found all over the Earth.