2.2A First law of thermodynamics Notes

What Makes Ecosystems Open Systems?

1. Ecosystems are open systems, meaning they exchange energy and matter with their surroundings.
2. This exchange drives the processes that sustain life and maintain the functionality of ecosystems.
3. The continuous movement of energy and matter through ecosystems is essential for the biodiversity, growth, and reproduction of organisms.

Energy Flow in Ecosystems

1. Energy enters ecosystems primarily from the Sun.
2. Producers (autotrophs) capture solar energy and convert it into chemical energy through photosynthesis.
3. This energy is stored as biomass, which moves through trophic levels as organisms feed on one another.
4. The transfer of energy follows the pathway:
   Sun → Producers → Primary consumers → Secondary consumers → Tertiary consumers → Decomposers
5. At each transfer, a portion of energy is lost as heat through metabolic processes such as respiration.
6. Because of these losses, energy flow is unidirectional.i
7. It cannot be recycled like matter.

Matter Cycling in Ecosystems

1. While energy moves in one direction, matter cycles continuously through biotic (living) and abiotic (non-living) components.
2. Nutrients such as carbon, nitrogen, phosphorus, and water move through the biosphere via biogeochemical cycles.
3. Producers absorb inorganic nutrients, consumers obtain them through feeding, and decomposers recycle nutrients back to the environment.
4. This closed-loop process maintains nutrient balance and prevents depletion.

Interrelationship Between Energy and Matter

1. Energy drives the processes that allow matter to be cycled (e.g., photosynthesis converts solar energy into chemical energy stored in matter).
2. The cycling of matter supports the growth and reproduction of organisms, which in turn supports energy transfer across trophic levels.

The First Law of Thermodynamics in Ecosystems

What is the First Law of Thermodynamics?

1. The First Law of Thermodynamics, also known as the Law of Conservation of Energy, states that energy cannot be created or destroyed, only transformed from one form to another.
2. Within ecosystems, energy enters as sunlight, is converted to chemical energy, and is eventually released as heat.
3. The total quantity of energy remains constant, even though its form and availability change.

Forms and Transformations of Energy in Ecosystems

1. Light energy: absorbed by producers during photosynthesis.
2. Chemical energy: stored in glucose and biomass, transferred through food webs.
3. Kinetic energy: used for movement and physiological functions.
4. Heat energy: released during respiration, metabolism, and decay.

Energy Transformations in Ecosystems

1. Producers transform solar energy into chemical energy via photosynthesis.
2. Consumers eat producers or other consumers, converting chemical energy into movement, heat, and new biomass.
3. Decomposers release remaining stored energy from dead matter as heat.
4. Energy transformations are never 100% efficient.
5. Some energy always escapes as heat, which cannot be reused by organisms.

Energy Efficiency and Availability

1. Energy transfers between trophic levels are inefficient.
2. On average, only 10% of energy moves to the next level.
3. The remaining 90% is lost as heat, waste, or used for metabolic activities.
4. This inefficiency shapes energy pyramids.
5. They always narrow toward higher trophic levels.
6. Total system energy stays constant, but usable energy decreases with each transformation.

Limitations and Clarifications

1. The First Law does not address energy quality or degradation (this is covered by the Second Law of Thermodynamics).
2. It assumes closed energy accounting, even though ecosystems are open systems.
3. Energy transformations are never 100% efficient; heat loss reduces the usable portion available for biological work.