Ecosystems and Energy Flow

Ecosystems as Open Systems

• Ecosystems are open systems where both energy and matter can enter and exit.
• Ecosystems are a collection of all the living organisms (biotic) and non-living components (abiotic) in an area.

Sunlight as the Principal Energy Source

• Sunlight is the primary source of energy for most ecosystems.
• Producers convert solar energy into chemical energy through photosynthesis.
• Producers include cyanobacteria, plants, and eukaryotic algae.
• Light intensity and absorption by producers vary depending on global positions or depths in aquatic environments.
• In some environments, like closed caves, chemosynthetic bacteria use energy from chemical reactions.

Flow of Energy Through Food Chains

• Food chains represent feeding relationships in an ecosystem, starting with producers.
• Arrows in a food chain symbolize the flow of energy.
• The last organism in a food chain has no predators.

Food Webs

• Food webs illustrate all possible food chains within a community.
• Organisms are categorized into trophic levels: primary producers, primary consumers, secondary consumers, and tertiary consumers.

Decomposers and Energy Supply

• Decomposers obtain energy from dead organisms, waste products, and feces.
• They play a crucial role in nutrient recycling.
• Saprotrophs - Decomposers that digest externally.
• Detritivores - Decomposers that digest internally.

Autotrophs

• Autotrophs synthesize all necessary carbon compounds from inorganic substances.
• Examples include plants, algae, and cyanobacteria.

Energy Sources for Autotrophs

• Autotrophs require energy to convert inorganic substances into organic compounds.
• Photoautotrophs utilize sunlight as their energy source.
• Chemoautotrophs use energy from oxidation reactions.
• Oxidation reactions release energy, like when iron is oxidized in the presence of air.
• Chemoautotrophs harness energy from oxidation reactions, similar to ATP production during cellular respiration.

Heterotrophs

• Heterotrophs obtain carbon compounds (and energy) by consuming other organisms.
• They use digestion to break down molecules for absorption and synthesis of new compounds.
• Digestion can be internal (consuming, digesting, absorbing, and synthesizing) or external (releasing enzymes, digesting, absorbing, and synthesizing).

Energy Release in Autotrophs and Heterotrophs

• All organisms require ATP.
• ATP is produced during cellular respiration.
• Cellular respiration involves oxidizing carbon compounds to release energy and produce ATP.
• Autotrophs create and oxidize their own carbon compounds.
• Heterotrophs oxidize carbon compounds obtained from their food.

Trophic Levels

• Trophic levels are based on an organism's position in a food chain.

Energy Pyramids

• Energy pyramids represent the amount of energy gained per year per unit of area at each trophic level.
• The 10% Rule states that only approximately 10% of energy is transferred to the next trophic level.
• Energy pyramids are proportionally stepped, not triangular.

Energy Loss Between Trophic Levels

• About 90% of energy is lost between trophic levels due to:
  • Cellular respiration (heat loss from oxidizing carbon compounds)
  • Incomplete consumption (not all parts of an organism are eaten)
  • Incomplete digestion (not all parts are digestible)

Heat Loss During Respiration

• Cellular respiration produces heat as a byproduct of energy conversion.
• Heat is lost to the environment and cannot be converted back into chemical energy.

Trophic Level Limitations

• Energy loss limits the number of trophic levels in an ecosystem.
• Longer food chains have more energy loss and limited biomass at higher levels.

Primary Production

• Primary production represents the accumulation of carbon compounds in biomass by producers.
• Gross Primary Production (GPP) is the total biomass produced during photosynthesis.
• Net Primary Production (NPP) is the available biomass to consumers after accounting for plant respiration.
• Different biomes have varying production capacities.

Secondary Production

• Secondary production refers to the accumulation of carbon compounds in biomass by heterotrophs.
• Secondary production decreases with each trophic level due to reduced oxidizable carbon compounds.
• Increasing plant-based diets can enhance productivity.

Carbon Cycling

• Pools are reserves or storage places for certain elements.
• Fluxes are the transfers of elements from one pool to another.
• Ecosystems are open, meaning they can gain and lose matter and energy.
• Photosynthesis and respiration are the main fluxes in the carbon cycle.
• Carbon sinks are ecosystems that have a net uptake of carbon, where photosynthesis exceeds respiration.
• Carbon sources are ecosystems that have a net release of carbon, where respiration exceeds photosynthesis.
• Factors that can influence the carbon sink/source status of an ecosystem include decomposition rates, biosequestration, fires, etc.

Release of Carbon Dioxide

• Burning biomass, peat, coal, oil, and natural gas releases carbon dioxide into the atmosphere.
• Fossilization creates a carbon sink in the form of peat, coal, and natural gas.
• Combustion of these fossil fuels releases carbon back into the atmosphere.
• For atmospheric carbon dioxide levels to remain constant, uptake in sinks needs to be equal to release from sources.
• Currently, the release of carbon from sources is outpacing the uptake by sinks.

Explore the dynamics of ecosystems as open systems, focusing on the roles of sunlight and food chains. This quiz will test your understanding of how energy flows through ecosystems, how producers function, and the interconnectedness of food webs. Get ready to dive into the world of biotic and abiotic interactions!