Energy Flow in the Biosphere

Energy Flow Through the Biosphere

• The biosphere encompasses all life-supporting areas on Earth, including the atmosphere, lithosphere, and hydrosphere.
• The atmosphere is Earth's gaseous envelope, primarily composed of nitrogen, oxygen, and argon, extending many kilometers above the surface.
• The lithosphere comprises Earth's solid, rocky portion.
• The hydrosphere encompasses all water, both liquid and solid, found on Earth.
• Systems can be categorized as open, closed, or isolated.
  • Open systems exchange energy and matter with their surroundings.
  • Closed systems exchange energy but not matter.
  • Isolated systems exchange neither energy nor matter.
• The biosphere is an open system, exchanging energy and matter with its surroundings.
• Energy transfer in biosphere occurs via radiation, conduction, and convection.
  • Radiation transmits energy as electromagnetic waves.
  • Conduction involves thermal energy transfer through direct particle contact.
  • Convection involves thermal energy transfer through the movement of particles.
• The primary energy source for Earth is the Sun. Some solar radiation is reflected, some absorbed and radiated as heat and a tiny amount is used in photosynthesis.
• The one-way flow of energy through the biosphere adheres to the laws of thermodynamics.
• The first law states that energy is conserved, not created or destroyed; only transformed.
• The second law dictates that entropy (disorder) always increases in an isolated system, meaning that some energy is lost as heat with each transfer.

Energy Flow in Ecosystems

• Energy flows from producers to consumers, through the living components in the biosphere.
• The flow is a series of energy transfers, with some energy lost as heat in each transfer. Heat eventually radiates into space.
• Photosynthesis uses solar energy to create chemical energy in producers (autotrophs).
• Chemosynthesis uses chemical energy to create chemical energy in some organisms (e.g., deep-sea vent organisms).
  • Chemoautotrophs are essential in environments lacking sunlight.
• Cellular respiration releases energy stored in glucose.
• Cellular respiration is crucial for organisms and decomposing/recycling organic matter.

Food Chains and Food Webs

• Producers are organisms able to create their own food (e.g., plants and phytoplankton and some bacteria).
• Consumers are organisms consuming producers or other consumers (e.g., herbivores, carnivores, omnivores).
• Decomposers consume dead organic matter and waste, recycling nutrients.
• Trophic levels represent feeding positions in an ecosystem.
  • Producers constitute the first trophic level.
  • Consumers form higher trophic levels based on their diets. Tertiary and quaternary levels exist depending on diet.
• Food chains represent a linear transfer of energy through trophic levels.
• Food webs represent the complex network of energy transfers in an ecosystem.
• A larger more complicated food web correlates to a stable ecosystem.
• Transfer of energy through the levels of a food chain or web is never 100%. Energy lost at each phase.

Ecological Pyramids

• Ecological pyramids depict the relationship of energy flow through trophic levels.
• Pyramids of numbers illustrate the number of organisms at each trophic level.
• Pyramids of biomass represent the biomass at each level. Biomass being the mass of living matter.
• Pyramids of energy graphically represent the energy available in the organisms at each trophic level.
• Ecological pyramids are always upright because energy decreases as trophic levels increase.