C4.2 — Transfers of Energy and Matter Revision Checklist (May 2026)

Open Systems (Ecosystems)

Systems where both energy and matter enter and exit

Principal Energy Source

Sunlight, which provides the energy required for most ecosystems to function

Flow of Chemical Energy

The movement of energy through an ecosystem via food chains as organisms are consumed

Food Chain

A linear sequence showing the transfer of energy from one organism to the next

Food Web

A complex diagram representing all the interconnected food chains in an ecosystem

Trophic Level

The specific position or level an organism occupies in a food chain or food web

Producers

Organisms (like plants) that capture light energy to produce their own chemical energy

Primary Consumers

Organisms that feed directly on producers

Secondary Consumers

Organisms that feed on primary consumers

Tertiary Consumers

Organisms that feed on secondary consumers

Apex Predators

Organisms at the top of the food chain with no natural predators

Pyramid of Energy

A graphical representation showing the total energy available at each trophic level

Energy Decrease Between Levels

The phenomenon where available energy significantly drops as you move up trophic levels

Energy Loss (Respiration)

Energy lost to the environment as heat during cellular respiration

Energy Loss (Movement)

Energy consumed for physical activity that is not passed to the next level

Energy Loss (Waste)

Energy lost through excreted waste products

Energy Loss (Undigested Material)

Energy that remains in material that cannot be digested by the consumer

10% Energy Transfer Rule

The general principle that only approximately 10% of energy is successfully transferred from one trophic level to the next

Limited Trophic Levels

Food chains are usually short because energy loss at each level eventually leaves insufficient energy to support more levels

Primary Production

The amount of energy or biomass produced by autotrophs (producers)

Secondary Production

The generation of biomass by heterotrophs (consumers)

Primary vs. Secondary Productivity

Primary refers to energy fixed by plants; secondary refers to energy stored by animals after consumption

Energy Transfer Efficiency

A calculation determining the percentage of energy successfully passed between two specific levels

Pyramid of Biomass

A diagram showing the total mass of living organisms at each trophic level

Describe (Command Term)

Give a detailed account or provide a word picture of a process

Explain (Command Term)

Provide reasons or causes for a specific biological trend or phenomenon

Compare (Command Term)

Identify similarities and differences between two items

Construct (Command Term)

Create a diagram, such as a food web or energy pyramid, from provided data

Outline (Command Term)

Give a brief summary of the main points of a process