Nutrient Cycles and the Carbon Cycle Flashcards

Definition of Nutrients: Nutrients are specific chemical elements and compounds that are required by organisms for growth, reproduction, and all other essential life processes.
Primary Nutrients for Life: There are five key chemical elements required for life:
- Carbon
- Hydrogen
- Oxygen
- Nitrogen
- Phosphorus (cycles primarily from sedimentary rock, unlike the others which cycle between living things and the atmosphere)
Nutrient Flow and Storage:
- Sources: Areas or processes that release nutrients.
- Stores: Locations where nutrients are accumulated and held for various periods of time.
- Sinks: Locations that absorb and store nutrients for long periods, effectively removing them from active cycling.
The Dynamics of Nutrient Cycles: Nutrients move continuously in and out of stores through biological and geological processes.
Natural Balance: Under natural conditions without external interference, the amount of nutrients flowing into a store generally equals the amount flowing out, maintaining a balanced state.

Biological Importance of Carbon: Carbon atoms serve as the fundamental structural unit in the cells of all living organisms.
Short-Term Carbon Storage:
- Found within aquatic and terrestrial organisms.
- Exists as $CO_2$ in the atmosphere.
- Located in the top layers of the ocean.
Long-Term Carbon Storage:
- Found in the middle and lower layers of the ocean.
- Located in coal, oil, and gas deposits within land and ocean sediments.
- Formation of Fossil Fuels: Carbon stored in the decomposing remains of organisms that are buried deep in the ground eventually transforms into carbon-rich fossil fuels over geologic time.
Carbon Movement through Earth's Spheres: Carbon is constantly exchanged among the biosphere (living things), the atmosphere (air), and the geosphere (land/rocks).
- Atmosphere to Biosphere: Carbon dioxide ( $CO_2$ ) moves from the atmosphere into living things through the process of photosynthesis and cellular respiration.
- Biosphere to Atmosphere: $CO_2$ is released back to the atmosphere when organisms die and undergo decomposition.
- Biosphere to Geosphere: Carbon enters the geosphere specifically when the remains of organisms are trapped under layers of sediment.

Upsetting Natural Balance: Human activities can disrupt the equilibrium of nutrient cycles by increasing nutrient levels more rapidly than natural stores can absorb them.
Contributing Human Activities:
- Land clearing
- Agriculture
- Urban expansion
- Mining and industry
- Motorized transportation
- Burning of fossil fuels
Mechanism of Carbon Imbalance: Human activity upsets the carbon cycle in two primary ways:
1. Reintroduction: Burning fossil fuels reintroduces carbon into the atmosphere that had been locked in long-term stores.
2. Reduction of Sinks: Clearing land reduces the number of plants available to absorb and convert $CO_2$ through photosynthesis.

Greenhouse Gases: Carbon dioxide is a greenhouse gas, meaning it has the capacity to absorb solar energy within the Earth's atmosphere.
The Greenhouse Effect: Excess $CO_2$ in the air traps heat, leading to significant environmental shifts.
Definitions of Key Terms:
- Global Warming: A specific increase in the average temperature of the Earth's surface.
- Global Climate Change: A long-term shift or change in the Earth's overall climate patterns.
Causes of Climate Change:
- Natural Factors: Natural variations in greenhouse gas levels, changes in ocean and atmospheric circulation, and fluctuations in the Earth's orbit.
- Human Activity: Significant increases in greenhouse gases specifically caused by the burning of fossil fuels.

Melting Sea and Land Ice:
- Leads to the destruction of habitats for polar organisms.
- Causes increased local flooding.
- Results in the release of methane gas (a potent greenhouse gas) from melting permafrost.
- Case Study: Bear Glacier (Northern British Columbia): Photographic evidence shows the rapid retreat of this glacier. Photo (A) taken in 2002 compared to Photo (B) taken in 2007 reveals that in just five years, the glacier retreated by several kilometers and decreased significantly in height.
Rising Sea Levels:
- Submergence of some islands.
- Saltwater intrusion into drinking water supplies.
- Coastal flooding and the destruction of vital wetlands.
Changing Ocean Chemistry:
- The ocean becomes more acidic as it absorbs higher concentrations of $CO_2$ from the atmosphere.
- Impact on Marine Life: An acidic and warming ocean can destroy coral reefs. The acidity physically dissolves the shells of corals and other marine organisms.

Water Vapour:
- Source: Evaporation from bodies of water.
- Details: The most abundant greenhouse gas.
Carbon Dioxide ( $CO_2$ ):
- Sources: Given off by plants, animals, and other organisms; released by volcanoes, forest fires, and decaying organisms; released from oceans.
- Details: The second most abundant greenhouse gas; produced during cellular respiration and specific plant processes.
Methane ( $CH_4$ ):
- Sources: Certain micro-organisms in bogs, wetlands, and melting permafrost; bacteria in the guts of animals like cows and termites; vents/openings in the Earth's crust (land and ocean floor).
- Details: A by-product of cellular processes used by anaerobic micro-organisms to extract energy from food in the absence of oxygen.
Nitrous Oxide ( $N_2O$ ):
- Sources: Bacteria living in oceans and wet, warm soils (e.g., the tropics).
- Details: Produced when specific bacteria break down nitrogen-rich compounds for food.

Carbon Dioxide: Primarily released when fossil fuels such as oil, natural gas, and coal are burned for energy.
Nitrous Oxide: Enters the atmosphere largely through the application of nitrogen-based fertilizers to agricultural crops.
Methane: Released in massive quantities by industrial herds of cattle.