Ecosystem Energy Flow and Biogeochemical Cycles

Trophic Levels in Ecosystems

Producers

Producers are organisms that use photosynthesis to capture energy from sunlight, water, and carbon dioxide to create organic matter (carbohydrates). They also synthesize complex biomolecules such as proteins and lipids. They perform autotrophic nutrition.

Consumers

Consumers are organisms incapable of producing their own basic molecules, requiring them to consume other organisms for nutrition. They perform heterotrophic nutrition and are categorized as follows:

• Primary: Herbivores that consume producers.
• Secondary: Carnivores that consume herbivores.
• Tertiary: Carnivores that consume other carnivores.

Decomposers

Decomposers consume dead plant and animal material, converting it into energy and nutrients for producers. They perform heterotrophic nutrition.

Biological Adaptation

Adaptation refers to the adjustments species make over millions of years of evolution to thrive in their environments. These include:

• Morphological: Physical structural changes.
• Physiological: Changes in internal body functions.
• Behavioral: Changes in actions or habits.

The Nitrogen Cycle

Nitrogen Cycle: Part 1

Nitrogen is introduced into the soil via precipitation, such as rain and lightning. Nitrates are also obtained through the conversion of ammonia—commonly found in fertilizers—by nitrifying bacteria in the soil. Additionally, some root nodules convert soil nitrogen into nitrates.

Nitrogen Cycle: Part 2

Plants build proteins using nitrates absorbed from the soil. When animals consume these plants, they use the nitrogen to build animal protein. When these animals excrete waste or die, decomposers break down the urea or carcass, re-introducing nitrogen into the soil as ammonia. Under specific conditions, denitrifying bacteria can break down soil nitrates and release nitrogen gas into the air, which may reduce soil fertility.

The Carbon Cycle

Carbon moves through the atmosphere and biosphere via several key processes:

• Combustion: Human activities, such as heating homes and driving vehicles, release carbon into the atmosphere.
• Respiration: Animals release carbon dioxide into the atmosphere as a byproduct of respiration.
• Photosynthesis: Green plants (producers) absorb atmospheric carbon dioxide to create food.
• Consumption: Carbon compounds are passed through the food chain as animals feed on plants and other animals.
• Decomposition: When plants and animals die, decomposers (bacteria and fungi) break down the organic matter, releasing stored carbon compounds.
• Fossil Fuels: Energy trapped in dead organic material can eventually become fossil fuels, which are later used in combustion.