Food webs and Energy flow
Food Webs — Detailed Understanding
A food web is a complex system of overlapping food chains that shows how organisms are linked by feeding relationships.
Why food webs are important
Increase ecosystem stability: if one food source disappears, organisms may switch to another.
Show real-life feeding behavior (animals don’t eat just one thing).
Help scientists predict the impact of changes like pollution, deforestation, or species extinction.
Types of consumers in food webs
Herbivores – eat plants (cow, deer)
Carnivores – eat animals (lion, snake)
Omnivores – eat plants and animals (human, bear)
Scavengers – feed on dead animals (vulture, hyena)
Energy Flow — In Depth
Energy flow explains how usable energy decreases as it moves upward.
Energy transfer steps
Solar energy captured by producers
Stored as chemical energy (glucose)
Passed to consumers through feeding
Lost at every step as:
Heat (respiration)
Movement
Growth and repair
Energy Pyramid
Base: Producers (maximum energy)
Middle: Herbivores
Top: Carnivores (least energy)
⚠️ This is why an energy pyramid is always upright.
More on Food Webs
A food web helps maintain balance in an ecosystem. If one organism disappears, many others are affected.
Example (Grassland ecosystem):
Grass 🌱 → Deer 🦌 → Lion 🦁
Grass 🌱 → Grasshopper 🦗 → Frog 🐸 → Snake 🐍All these chains connect to form one food web.
👉 If grass decreases:
Herbivores starve
Carnivores lose prey
Whole ecosystem becomes unstable
So food webs show interdependence among organisms.
More on Energy Flow
Energy flow follows trophic levels:
Sun ☀️ – main source of energy
Producers – trap solar energy
Primary consumers
Secondary consumers
Tertiary consumers
10% Law of Energy
If plants have 1000 units of energy
Herbivores get 100 units
Carnivores get 10 units
That’s why:
Food chains are short
Top predators are few
Energy flow is:
Unidirectional (never cycles back)
Different from nutrients (nutrients recycle, energy doesn’t)
Importance of Food Webs & Energy Flow
Help understand ecosystem stability
Explain population control
Important for environmental conservation
Asked often in school exams
Nutrient Cycling vs Energy Flow
Energy: flows one-way and is lost as heat
Nutrients: recycled through soil, air, and water