Thermodynamics Overview

Thermodynamics

• The first law of thermodynamics states: ΔE = q + w, where ΔE is the change in internal energy, q is heat flow, and w is work done on the system.
• Heat (q) and work (w) are processes that change a system's internal energy. Positive values indicate energy added to the system; negative values indicate energy leaving.
• Heat energy is molecular vibration and motion. Sunlight absorbed by land and water creates temperature differences, driving airflow (kinetic energy) which can perform work (e.g., pumping water). This work converts kinetic energy into potential energy (stored energy).
• Kinetic energy is energy of motion; potential energy is stored energy.

Entropy and the Second Law of Thermodynamics

• The second law of thermodynamics states that the entropy of an isolated system always increases. Isolated systems tend towards thermal equilibrium (maximum entropy). The universe’s entropy only increases.

Photosynthetic Bacteria

• Largely aquatic (marine and freshwater).
• Play a minor role in organic matter production; important in mineral cycling.
• Green and purple sulfur bacteria are obligate anaerobes (require no oxygen) and significant in the sulfur cycle.
• Non-sulfur photosynthetic bacteria are facultative anaerobes (can function with or without oxygen) and can be heterotrophs (obtain energy from other sources) in the absence of light.

Chemosynthetic Bacteria

• Considered "producers".
• Intermediate between autotrophic (make their own food) and heterotrophic (depend on others) organisms.
• Produce food via chemical oxidation of inorganic compounds (e.g., ammonia to nitrite, nitrite to nitrate, sulfide to nitrate, ferrous to ferric iron).

Respiration Types

• Aerobic respiration: uses oxygen as the final electron acceptor.
• Anaerobic respiration: uses an inorganic compound (other than oxygen) to accept electrons.
• Fermentation: an anaerobic process using an organic compound as the final electron acceptor.

Food Chains and Webs

• Food chain: transfer of energy from plants through a series of organisms (80-90% energy lost at each transfer).
• Grazing food chain: starts with plants, progresses to herbivores and then carnivores (can be predator or parasitic chains).
• Detritus food chain: starts with dead organic matter, decomposers, and then detritus feeders and their predators.
• Food webs are interconnected food chains.

The Nitrogen Cycle

• The conversion of nitrogen between its chemical forms through biological and physical processes.
• Key processes: fixation, ammonification, nitrification, and denitrification.
• Atmospheric nitrogen (78%) is largely unavailable for biological use.
• Human activities have significantly altered the global nitrogen cycle (fossil fuels, fertilizers, wastewater).
• Nitrogen exists in dissolved (organic and inorganic) and particulate forms in aquatic systems.

The Oxygen Cycle

• The oxygen cycle is interconnected with the carbon and hydrogen cycles.
• Primarily driven by photosynthesis (plants releasing oxygen) and respiration (animals consuming oxygen).
• The lithosphere (Earth's crust) stores oxygen in biomass, organic matter, and mineral deposits. Weathering releases trapped oxygen.
• The hydrosphere (water bodies) contains dissolved oxygen supporting aquatic life.

The Rock Cycle

• Describes the dynamic transitions between sedimentary, metamorphic, and igneous rocks.
• Driven by plate tectonics and the water cycle.
• Rocks change as they encounter different environments.
• Most elements and compounds follow a basic sedimentary cycle pattern involving erosion, sedimentation, mountain building, volcanic activity, and biological transport.

Shelford's Law of Tolerance

• An organism's presence and success depend on a complex of conditions.
• Absence or failure can be due to deficiency or excess of any single factor beyond tolerance limits.
• Species existence, abundance, and distribution are determined by whether physical/chemical factors fall within their tolerance range.
• Terms like "steno-" (narrow) and "eury-" (wide) describe tolerance levels (e.g., stenothermal vs. eurythermal for temperature).
• The zone of tolerance includes an optimum zone (best growth), a critical minimum zone (growth inhibited), and a critical maximum zone (growth ceases).

Salinity in Aquatic Ecosystems

• Salinity is a major factor in the distribution of marine, estuarine (brackish water), and freshwater species. It fundamentally shapes aquatic ecosystem structure and function.

This quiz explores key concepts in thermodynamics, including the first and second laws, energy changes, and entropy. Dive into the fundamental principles governing energy transformations and systems. Understand the role of heat and work in internal energy and learn about photosynthetic bacteria.