A1 - How Energy Enters The Biosphere

How Energy Enters the Biosphere

• The biosphere is the narrow zone around Earth that supports life. It has three main structural zones: lithosphere (land), hydrosphere (water), and atmosphere (air).
• The laws of thermodynamics govern energy flow.
• The first law states that energy cannot be created or destroyed, only converted from one form to another. Radiant energy is converted to chemical energy in carbohydrate molecules.
• The second law states that energy conversion isn't 100% efficient - there's an energy loss with each conversion and less usable energy with each step in the chain.
• All organisms need energy to survive. This energy comes from the sun and is captured and converted through photosynthesis and chemosynthesis.
• Living things obtain energy through photosynthetic/chemosynthetic and cellular respiration processes.

Energy Flow

• All organisms need energy.
• Energy cannot be created or destroyed (First Law of Thermodynamics)
• Plants and some bacteria capture energy from the sun through photosynthesis.
• Chemical energy (glucose) is stored then used in cellular respiration which releases energy in the form of ATP (adenosine triphosphate) to fuel organismal function.

Albedo

• 100% of Earth's energy comes from the Sun.
• Not all of the Sun's energy reaches Earth's surface - some is reflected (Albedo).
• ~30% of the incoming solar radiation is reflected.
• 51% is absorbed at Earth's surface.

Photosynthesis

• Photosynthesis is how producers (plants, algae, bacteria) convert light energy to chemical energy stored in the bonds of glucose (sugar).
• The equation for photosynthesis is: 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2

Cellular Respiration

• Cellular respiration is how consumers (and some producers) convert chemical energy from glucose into the usable energy molecule ATP.
• The equation for cellular respiration is: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy.
• ATP is used to power organismal activities like movement and metabolic processes.

Fermentation

• Fermentation is an anaerobic process that occurs in the absence of oxygen.
• It converts glucose into other byproducts like ethanol (alcohol) and lactic acid, and releases energy in the form of ATP, but is less efficient than aerobic respiration.
• Different organisms and situations (e.g. muscle cells) result in different fermentation outcomes.

Chemosynthesis

• Chemosynthesis is a process used by some organisms that don't use sunlight.
• Instead, they use chemical energy from inorganic substances like hydrogen sulfide to build organic molecules.
• It's a crucial process in environments like deep-sea vents where sunlight is absent.

Producers and Consumers

• Producers: (autotrophs) create their own food through photosynthesis/chemosynthesis.
• Consumers: (heterotrophs) obtain energy from consuming other organisms (producers or other consumers).

Trophic Levels

• Trophic levels categorize living things by how they obtain energy.
• The first trophic level consists of producers which create energy using sunlight or inorganic compounds.
• Subsequent trophic levels consist of consumers that obtain their energy from other organisms.
• Decomposers break down dead organisms for nutrient recycling.

Decomposers

• Decomposers are organisms that break down dead organisms and wastes, returning essential nutrients to the ecosystem.
• They play a vital role in nutrient cycling.

Energy Transfer

• Energy transfer along the trophic levels is less than 100% efficient.
• There are losses as heat, unusable energy.
• Organisms in higher trophic levels require more consumed energy to equal energy gains.

Food Webs

• Food webs represent energy transfer and feeding relationships within an ecosystem.
• They depict organisms feeding at multiple trophic levels.
• Arrows demonstrate the direction of energy flow.

Rule of 10

• Approximately 90% of energy is lost at each trophic level.
• Less than 10% of energy is transferred to the next trophic level.
• This limits the number of trophic levels in food chains/webs.

Pre-Assessment Questions

• What is the biosphere? (The narrow zone on Earth that supports life.)
• How does matter/energy cycle through the biosphere? (Through processes like photosynthesis, cellular respiration, and decomposition.)
• What impacts might humans have on the biosphere? (Many.)