Feeding Relationships
Food chains, webs, and energy flow through ecosystems
Energy Flow in Ecosystems
From producers to top consumers - how energy moves through nature
A food chain shows the sequence of organisms where each eats the previous one. Energy flows from producers through various consumers: grass → rabbit → fox.
Trophic Levels
- Producers (1st level): Plants that make food via photosynthesis
- Primary consumers (2nd level): Herbivores that eat plants
- Secondary consumers (3rd level): Carnivores/omnivores that eat herbivores
- Tertiary consumers (4th level): Top predators that eat other carnivores
A food web shows interconnected food chains in an ecosystem. Real ecosystems are complex - most organisms eat multiple things and are eaten by multiple predators. Food webs show this complexity more accurately than simple chains.
Only about 10% of energy is transferred from one trophic level to the next. The rest is lost as heat from respiration, movement, and waste products (feces and urine).
Why Energy Is Lost
- Respiration: Energy used for life processes and released as heat
- Movement and heat loss: Maintaining body temperature in warm-blooded animals
- Waste: Not all parts eaten (bones, fur), not all food absorbed
- Result: Only 10% available for the next trophic level
Ecological pyramids represent the structure of ecosystems at each trophic level.
Pyramid of Numbers
Count of organisms at each level. Can be inverted when parasites involved (many parasites on few hosts).
Pyramid of Biomass
Dry mass of organisms at each level. Usually decreases up the chain (more plant mass than herbivore mass).
Pyramid of Energy
Energy content at each level. Always decreases up the chain due to energy losses (never inverted).
Step 1: Select Organisms
Select Pyramid Type
Pyramid of Energy
Energy pyramids are always pyramid-shaped (never inverted)
Given organisms: Algae, Water fleas, Small fish, Pike, Bacteria
Step 1: Create Food Web
Algae → Water fleas → Small fish → Pike
Dead matter → Bacteria (decomposers break down all levels)
Step 2: Draw Biomass Pyramid
From bottom to top: Algae (largest - producers), Water fleas (medium), Small fish (smaller), Pike (smallest - top predator)
Food Chain
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