2.2C Second law of thermodynamics Notes

1. The Second Law of Thermodynamics states that energy transformations are inefficient and that in every transformation, some energy is degraded into a less useful form, typically heat.
2. This law relates to the quality of energy, not its quantity.
3. Although the total energy in a system remains constant (as per the First Law), the amount of usable energy decreases after each transformation.
4. In ecosystems, the largest energy losses occur during cellular respiration, when chemical energy from food is transformed into heat.

Energy Degradation in Ecosystems

1. Energy enters ecosystems as concentrated light from the Sun (a high-quality energy form).
2. Through photosynthesis, this is converted into chemical energy in biomass.
3. As organisms use this energy (through respiration, growth, movement, etc.), much is released as heat.
4. Thus, with each transformation, energy disperses, increasing entropy (disorder) in the system.

Energy Transformations and Inefficiency in Ecosystems

1. Energy enters ecosystems in a concentrated form (solar radiation) and gradually becomes dispersed as it moves through trophic levels.
2. At each stage:
   1. Producers absorb only a small portion of incoming solar energy due to reflection, transmission, and inefficiency of photosynthesis.
   2. Consumers and decomposers lose energy through respiration, excretion, and movement.
   3. Heat is the most significant form of energy degradation.
3. In ecosystems, the largest energy losses occur during cellular respiration, where chemical energy is converted into work and heat.

Ecological Efficiency and Energy Availability

1. Ecological efficiency measures how much energy is transferred from one trophic level to the next.
2. Formula:
   $$\text{Ecological efficiency} = \frac{\text{Energy used for growth (new biomass)}}{\text{Energy supplied}} \times 100$$
3. Typically, this value ranges between 5%-20%, with an average of 10% in most ecosystems.
4. This inefficiency limits biomass production at higher trophic levels and determines ecosystem carrying capacity.

Consumers Obtain Energy from Producers or Other Organisms

1. Consumers are organisms that obtain energy and matter by feeding on other organisms.
2. They are heterotrophs, unable to produce their own food because they lack photosynthetic pigments like chlorophyll.
3. Consumers depend on carbon-containing organic compounds (e.g., carbohydrates, fats, proteins) synthesized by autotrophs.
4. They play a crucial role in transferring chemical energy and matter through food chains and webs.

Types of Consumers and Their Energy Strategies

1. Herbivores

1. Feed directly on producers (plants or algae).
2. Represent primary consumers in food chains.
3. Possess specialized teeth, digestive tracts, or symbiotic bacteria to break down cellulose.

2. Detritivores

1. Feed on dead organic matter (detritus) such as fallen leaves, feces, and carcass fragments.