Energy Flow in the Biosphere

Introduction to Energy Flow Through the Biosphere

• Living things require energy for survival.
• Organisms use cellular respiration to obtain energy from chemical compounds.
• Producers create these chemical compounds.

What are Autotrophs/Producers?

• Autotrophs are organisms that create their own food through processes like photosynthesis.
• They are crucial at the base of food chains.
• Examples include plants, algae, and some bacteria

Photosynthesis

• Photosynthesis, a process used by plants, converts light energy into chemical energy.
• The overall process can be summarised as: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
• This process occurs in the chloroplasts of plant cells.
• Chlorophyll is the key pigment involved in absorbing sunlight.

Energy Transfer

• The sun provides the initial energy source for most ecosystems.
• Only a small portion—roughly 1–2%—of solar energy is captured for photosynthesis.
• Significant amounts of energy are reflected or absorbed by the atmosphere and clouds.

Chemosynthesis

• Chemosynthesis is an alternative process to photosynthesis, found in environments without sunlight.
• Specialized bacteria utilize chemical energy from inorganic molecules, such as hydrogen sulfide.
• These chemoautotrophs serve as primary producers in deep-sea ecosystems and other extreme environments.

Consumers

• Consumers are organisms that depend on other organisms for their food.
• They cannot produce their own food and obtain it from producers or other consumers.
• Consumers can be classified into primary, secondary, and tertiary consumers, based on their position in the food chain.

Levels of Consumers

• Primary Consumers (herbivores) eat producers like plants.
• Secondary consumers (carnivores) eat primary consumers.
• Tertiary Consumers are animals that eat secondary consumers

Decomposers

• Decomposers break down dead organisms and organic waste, releasing nutrients back into the ecosystem.
• They play a vital role in nutrient cycling.

Energy in the Biosphere

• Earth is a closed system regarding matter.
• Energy doesn't cycle, as it is lost as heat through trophic levels.

Laws of Thermodynamics

• First Law: Energy cannot be created or destroyed, only transformed.
• Second Law: Entropy always increases in a closed system.
• The transfer of energy between levels in a food chain can be characterized by the loss of energy.

Trophic Levels

• A trophic level represents an organism's position in a food chain.
• Energy availability decreases at higher trophic levels.
• Ecological pyramids illustrate the decreasing energy transfer efficiency with each trophic level.

Food Chains and Food Webs

• Food chains depict a linear, one-way transfer of energy through organisms.
• Food webs illustrate the interconnected nature of energy flow through multiple food chains— showing the complex interactions among species.

Ecological Pyramids

• Ecological pyramids depict the relative abundance of biomass, numbers, or energy at various trophic levels within an ecosystem.
• Three types exist: Pyramid of Numbers, Pyramid of Biomass, Pyramid of Energy.
• The Pyramid of Energy is always upright, while others can be inverted in certain situations—such as the inverted pyramid of biomass in marine ecosystems with abundant phytoplankton producers at the base.

Advantages and Disadvantages of Ecological Pyramids (especially Pyramids of Numbers)

• Advantages of the pyramid of numbers include its simplicity for general overview and usefulness in comparing ecosystems at different times.
• Disadvantages include inaccuracy regarding total numbers to accurately measure, as it doesn't distinguish between juvenile or immature forms.

Summary of Concepts

• Energy flow through ecosystems follows specific patterns.
• Producers, consumers, and decomposers play critical roles in these patterns.