AP Biology Unit 8: Ecosystem Energetics

Energy Flow

The linear passage of energy through an ecosystem, entering as sunlight and exiting as heat.

First Law of Thermodynamics

Energy cannot be created or destroyed, only transformed.

Second Law of Thermodynamics

Every energy transfer increases the entropy (disorder) of the universe.

Autotrophs

Organisms that capture energy from physical or chemical sources, such as plants.

Photosynthetic Autotrophs

Organisms that use solar energy to convert carbon dioxide and water into glucose.

Chemosynthetic Autotrophs

Organisms that capture energy from inorganic molecules in the absence of light.

Heterotrophs

Organisms that obtain energy by consuming carbon compounds produced by others.

Trophic Levels

Categories of organisms in a food chain defined by their primary source of food.

Primary Producers

Autotrophs that support all other trophic levels in an ecosystem.

Primary Consumers

Herbivores that directly consume primary producers.

Secondary Consumers

Carnivores or omnivores that eat primary consumers.

Tertiary Consumers

Carnivores that consume secondary consumers.

Decomposers

Organisms that break down non-living organic matter, recycling nutrients.

Food Chain

A linear pathway illustrating energy transfer from one organism to another.

Food Web

A complex network of interconnected food chains.

Gross Primary Productivity (GPP)

The total amount of energy captured by producers via photosynthesis.

Net Primary Productivity (NPP)

The energy remaining after producers use some for their own respiration.

Ecological Efficiency

The percentage of energy transferred from one trophic level to the next.

Pyramid of Energy

Illustrates the amount of energy available at each trophic level.

Pyramid of Biomass

Shows the dry weight of organic material at each trophic level.

Pyramid of Numbers

Depicts the count of individual organisms at each trophic level.

Energy Cycling Mistake

The erroneous belief that energy recycles within an ecosystem.

Direction of Arrows Mistake

Incorrectly indicating the energy flow direction from predator to prey.

GPP vs NPP Confusion

Mistaking Gross Primary Productivity for the energy available to consumers.

Endotherms vs Ectotherms

The distinction between warm-blooded and cold-blooded organisms based on energy efficiency.