BIOL-208 Lecture Notes - Lecture 20: Nitrogen Fixation, Nitrogen Cycle, Nutrient Cycle
17 Dec 2016
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Nutrient Cycling and Retention
- Introduction
- Common elements are used over and over before eventually leaving the
ecosystem
- Elements such as Carbon, Phosphorous, Nitrogen, Potassium, and Iron
- Switch back and forth between organic and inorganic forms
- Nutrients: elements organisms require for development, maintenance,
reproduction
- Nutrient cycling: used, transformed, moves, reused
- Essential nutrient: subset of elements in ecosystem required by living organisms
- Macronutrients: required in large concentrations
- Carbon and Nitrogen ratio; more Carbon than Nitrogen
- Micronutrients: required in small concentrations
- Copper, Aluminum, etc; toxic if in large concentrations
- Nutrient Cycling
- Though energy makes a one-way passage through ecosystems, essential
nutrients, such as phosphorous, may be recycled
- In some cases, such as a person catching a fish, some nutrients will be removed
from an ecosystem
- Phosphorous Cycle
- Essential: energetics, genetics, and structure
- Not abundant on a global scale
- Source: mineral deposits and marine sediments
- Weathering of rocks: slow release
- Global scale doesn’t include atmospheric pool
- Not really in air and being breathed in; really only comes from
sediments
- Nitrogen Cycle
- Important to structure and functioning of organisms
- Limit rates of primary production in terrestrial and marine systems
- 2 critical aspects of the nitrogen cycle
- Mineralization: organic into mineral forms
- Immobilization: mineral into organic forms
- Limitation to plants, and microbes play a key role
- Organic → decomp → inorganic
- Major atmospheric pool of nitrogen gas (N2)
- Only nitrogen fixers can use atmospheric supply
- Some cyanobacteria
- Free living soil bacteria
- Rhizobia and Frankia bacteria
- Nitrogen fixation is an energy demanding process
- Nitrogen gas (N2) is reduced to ammonia (NH2)
- Death: fungi and bacteria
- Decomposition
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Document Summary
Common elements are used over and over before eventually leaving the ecosystem. Elements such as carbon, phosphorous, nitrogen, potassium, and iron. Switch back and forth between organic and inorganic forms. Nutrients: elements organisms require for development, maintenance, reproduction. Essential nutrient: subset of elements in ecosystem required by living organisms. Carbon and nitrogen ratio; more carbon than nitrogen. Copper, aluminum, etc; toxic if in large concentrations. Though energy makes a one-way passage through ecosystems, essential nutrients, such as phosphorous, may be recycled. In some cases, such as a person catching a fish, some nutrients will be removed from an ecosystem. Not really in air and being breathed in; really only comes from. Limit rates of primary production in terrestrial and marine systems. 2 critical aspects of the nitrogen cycle. Limitation to plants, and microbes play a key role. Major atmospheric pool of nitrogen gas (n2) Only nitrogen fixers can use atmospheric supply. Nitrogen fixation is an energy demanding process.
