The Biosphere and Ecosystems

Definition of Ecosystem:
- An ecosystem is defined as the combination of all organisms (biotic components) and the surroundings environment (abiotic components) within a designated area.

Energy Flow
- Energy flows through an ecosystem starting from the sunlight, which is utilized by producers to create energy:
$ ext{Sunlight} ightarrow ext{Producers} ightarrow ext{Consumers} ightarrow ext{Decomposers} $
Nutrient Cycling
- Essential nutrients involved in ecosystem cycles include:
- Carbon
- Nitrogen
- Water

A food web illustrates the interconnections between organisms across various trophic levels.
Arrows in food webs indicate direction of energy transfer, pointing from consumed organisms to those that consume them.
All producers and consumers serve as nourishment for decomposers such as fungi, mold, earthworms, and bacteria found in the soil.

Visual representation of the relative energy content across different trophic levels:
- Primary Producers: 100%
- Primary Consumers: 10%
- Secondary Consumers: 1%
- Tertiary Consumers: 0.1%
- Apex Predators: 0.01%
Energy is lost as heat at each trophic level but is originally sourced from the sun's energy.

Examples of organisms at each trophic level include:
- Producers: Diatoms, water lettuce, arrowhead, eel grass
- Primary Consumers: Red-bellied turtle, Florida apple snail, flathead mullet, midge larvae
- Secondary Consumers: Killifish, bluegill sunfish, whirligig beetle, water strider
- Tertiary Consumers: Bass, gar, water snake
Energy content measured in $ext{kcal/m}^2/ ext{yr}$ displays values ranging from 5,000 to 20,000 kcal/m²/yr.

Water Cycle Mechanism:
- Water evaporates or sublimates from land and ocean surfaces into the atmosphere, condensing into clouds and eventually precipitating as rain or snow.
- Precipitated water can flow into freshwater bodies or infiltrate soil, returning to oceans to complete the cycle.

Carbon Cycle Dynamics:
- Carbon dioxide (CO2) exists in the atmosphere and dissolved in water.
- Photosynthesis converts CO2 to organic carbon while respiration re-introduces CO2 into the atmosphere.
- Long-term carbon storage occurs when organic matter is buried deep and fossilized.
- Carbon is cycled back into the atmosphere through volcanic activity or human emissions.

Nitrogen Cycle Overview:
- Nitrogen is fixed from the atmosphere by nitrogen-fixing bacteria, entering the living world and is returned to the atmosphere as gaseous nitrogen by soil bacteria, crucial for terrestrial food webs.

Phosphorus Cycle Details:
- Exists primarily as phosphate ions (PO₄³⁻) found in soil and marine environments released by weathering rocks and volcanic activity.
- Phosphate enters food webs through various flows including surface runoff and groundwater.
- Organisms utilize dissolved phosphate, which may settle to the ocean floor and form sediment.

Sulfur Cycle:
- Sulfur dioxide becomes available to ecosystems as it dissolves in precipitation forming weak sulfuric acid, and through direct fallout.
- Weathering of rocks releases sulfates, and decomposition returns sulfates to terrestrial and marine ecosystems.

Small Ecosystem: A tidal pool ecosystem located in Matinicus Island, Maine.
Large Ecosystem: The Amazon rainforest in Brazil demonstrates extensive biodiversity and ecological dynamics.

Desert variability illustrated through:
- Saguaro National Park, Arizona, showcasing abundant plant life.
- The rocky desert of Boa Vista Island, Cape Verde, Africa, highlighting aridity and a lack of flora.

Definition of Biosphere:
- Biosphere is the sum of all ecosystems on Earth.
- Discusses various biomes such as forests, deserts, tundra, and oceans emphasizing climatic factors (temperature, precipitation) shaping ecosystems.
- Questions raised about impacts of biome disruptions on overall biospheric health.

Divisions in ocean ecosystems based on water depth, distance from shore, and light availability are significant to ecological organization.

Coral reefs are biologically created through calcium carbonate skeletons from coral organisms, identified as marine invertebrates within the phylum Cnidaria.

Issues such as uncontrolled algae growth leading to algal blooms in waterways.
Examples of biodiversity within ecosystems like deciduous trees dominating temperate forests, boreal forests characterized by coniferous trees, and the tundra known for low-growing plants and vegetation.