Energy Flow Through Ecosystems

Ecosystem Definition

• Ecosystem: The sum of all organisms in a given area plus the abiotic factors they interact with.
• Biotic factors: Living or once-living aspects (e.g., animals, plants, decomposed organisms like wood).
• Abiotic factors: Non-living components (e.g., sunlight, air, soil, water).

Importance of Ecosystem Components

• Together, biotic and abiotic factors create an ecosystem through their interactions.
• Exercise: Identify three biotic and three abiotic factors observed in your surroundings.

Laws of Thermodynamics

1. First Law: Energy cannot be created or destroyed; it can only be transferred or transformed.
2. Second Law: Energy exchanges increase the entropy (disorder) of the universe.

• Example: Energy from food converts to heat when organisms like squirrels digest food.

Energy Dynamics in Ecosystems

• Net Gain: Results in storage or growth of an organism.
• Net Loss: Leads to loss of mass and potentially death.
• Metabolic Rate: Total energy used by an organism in a set time; measured in calories through Heat loss or oxygen consumption.
• Relationship to body mass: Smaller organisms typically have higher metabolic rates due to higher surface area to volume ratio.

Temperature Regulation Strategies

• Endotherms: Organisms that maintain body temperature through metabolic processes (e.g., mammals).
• Ectotherms: Organisms that utilize external sources of heat (e.g., reptiles).

Trophic Levels and Energy Transfer

• Trophic Levels: Groups of species based on nutrition and energy sources.

1. Primary Producers (Autotrophs): Convert light energy to organic compounds (e.g., plants, algae).
2. Primary Consumers: Herbivores that eat plants.
3. Secondary Consumers: Carnivores that eat herbivores.
4. Tertiary Consumers: Carnivores that eat other carnivores.
5. Decomposers: Break down non-living organic material (e.g., fungi, bacteria).

• Energy Transfer: Arrows in food chains represent energy transfer, not predator-prey relationships.

Food Chains vs. Food Webs

• Food Chain: A linear sequence of energy transfer between specific organisms.
• Food Web: Interconnected food chains reflecting complex feeding relationships.

Effects of Energy Availability on Ecosystems

• Changes in energy availability impact the number and size of trophic levels.
• Decrease in primary producers can drastically affect all consumers above them.

Primary Production

• Primary Production: Light energy converted to chemical energy by producers.
• Gross Primary Production (GPP): Total primary production.
• Net Primary Production (NPP): GPP minus energy used in respiration by primary producers.

Variability in Net Primary Production (NPP)

• Areas with lush plant life (like tropical rainforests) typically have higher NPP due to effective solar energy capture.

Secondary Production and Energy Efficiency

• Secondary Production: Chemical energy in food converted to new biomass at a 10% efficiency rate in trophic transfers (over 90% energy loss at each level).
• Remember: This is also known as the 10% Rule.

Matter Cycling in Ecosystems

• Unlike energy, matter can cycle through ecosystems (e.g., water, carbon, nitrogen, phosphorus).
• Biogeochemical Cycles: Nutrient cycles involving both biotic and abiotic factors.

Biological Importance of Key Cycles

1. Water Cycle: Essential for life; influences ecosystem processes.
2. Carbon Cycle: Crucial for forming organic compounds.
3. Nitrogen Cycle: Important for amino acids and proteins.
4. Phosphorus Cycle: Vital for nucleic acids and ATP.

Summary of Biological Importance

• Remembering the role of these elements in life processes: Water for hydration, Carbon for structure and energy, Nitrogen for building blocks of life, and Phosphorus for metabolic energy and genetic material.