Recycling of All Chemical Elements Required by Living Organisms in Ecosystems
- Life on Earth depends on the continuous recycling of essential chemical elements.
- These elements such as carbon, hydrogen, oxygen, nitrogen, and phosphorus are required to build the macromolecules that make up living organisms.
- Carbon, hydrogen, and oxygen form carbohydrates, lipids, and proteins, which are the foundation of life.
- Nitrogen and phosphorus are critical for proteins, nucleic acids, and other molecules.
- Approximately 15 other elements—used in trace amounts—are also essential, including potassium, sodium, and calcium.
- Without recycling, these finite resources would quickly be exhausted, disrupting the balance of ecosystems.
The Role of Decomposers in Nutrient Cycling
- Decomposers such as bacteria and fungi are the backbone of nutrient cycling.
- These organisms:
- Break down organic matter, such as dead organisms, releasing nutrients back into the environment.
- Convert complex compounds (e.g., proteins) into inorganic forms (e.g., ammonia in the nitrogen cycle).
- Ensure nutrients like nitrogen and phosphorus are available for reuse by plants.
Fungi breaking down fallen leaves return nitrogen to the soil, making it accessible to nearby plants.
Key Nutrient Cycles
1. The Carbon Cycle
- Photosynthesis: Plants absorb carbon dioxide from the air, storing it as glucose.
- Respiration: Animals and plants release carbon dioxide back into the atmosphere.
- Decomposition: Dead organisms and waste products release carbon dioxide via decomposers.
- Don’t confuse the carbon cycle with the energy flow.
- While energy is lost as heat, carbon is continuously recycled.
2. The Nitrogen Cycle
- Nitrogen Fixation: Certain bacteria convert atmospheric nitrogen into ammonia, a form plants can use.
- Nitrification: Other bacteria convert ammonia into nitrates and nitrites, which plants absorb.
- Decomposition: Decomposers break down proteins in dead organisms, returning nitrogen to the soil as ammonia.
Remember that plants can only use nitrogen in its inorganic forms, such as nitrates.
Exam techniqueWhile you don’t need to memorize every step of the nitrogen cycle, remember that decomposers play a critical role in converting organic nitrogen into inorganic forms.
3. The Phosphorus Cycle
- Weathering: Phosphorus is released from rocks into the soil through weathering.
- Absorption: Plants absorb phosphorus, which then moves through the food chain.
- Decomposition: Decomposers return phosphorus to the soil when organisms die.
- Think of nutrient cycles like a recycling system in a city.
- Waste is collected, processed, and transformed into new materials that can be used again.
- Similarly, ecosystems recycle nutrients to sustain life.
Human Impact on Nutrient Cycles
- Humans have significantly altered natural nutrient cycles, often with negative consequences:
- Fossil Fuel Combustion: Releases large amounts of carbon dioxide, contributing to climate change.
- Agricultural Runoff: Excess fertilizers add nitrogen and phosphorus to water bodies, leading to algal blooms and dead zones.
- Deforestation: Reduces the number of plants available to absorb carbon dioxide and disrupts local nutrient cycles.
How can we balance human needs with the health of natural ecosystems?
Self review- Can you identify the key steps of the carbon, nitrogen, and phosphorus cycles?
- Why are decomposers critical for recycling nutrients in ecosystems?
- How do human activities disrupt nutrient cycles, and what can be done to minimize this impact?
