Ecology and Ecosystem Basics

5 min

Understanding Energy Flow, Trophic Levels, and Nutrient Cycles

The Golden Rule of Energy

Energy flow in an ecosystem is unidirectional. Only 10% energy is transferred to the next trophic level, while nutrient cycling maintains the biological balance.

Why Study This?

High weightage in SSC CGL, CHSL, and Railway Biology sections.
Direct questions on 10% Law and Biogeochemical cycles are frequent.
Essential for scoring in Environment and Ecology topics.

Memory Hooks

L for Lindeman: 10% Law was given by Raymond Lindeman.
Flow is UP: Energy flow is always Unidirectional and Upward.
Web is Messy: Food Web is a complex network of many Food Chains.

Trophic Levels and Examples

Trophic Level	Category	Example
T1	Producers	Grass, Trees
T2	Primary Consumers	Rabbit, Deer
T3	Secondary Consumers	Frog, Fox
T4	Tertiary Consumers	Snake, Eagle

Ecosystem Components

PRODUCERS

(Autotrophs)

Autotrophs

Plants make food via photosynthesis.

CONSUMERS

(Heterotrophs)

Heterotrophs

Animals depend on plants for food.

DECOMPOSERS

(Saprotrophs)

Saprotrophs

Fungi break down dead matter.

BIODIVERSITY

(Life Variety)

Life Variety

Variety of species in a habitat.

Common Exam Traps

Energy flow is cyclicEnergy flow is unidirectional

Nutrients cycle, but energy is lost as heat and never returns.

Top level has most energyTop level has least energy

According to 10% law, the top predator gets the minimum energy.

Food chain is more stableFood web is more stable

A web provides multiple food options, making the ecosystem stable.

Quick Practice

Q1.Which law states that only 10% of energy is transferred to the next trophic level?

Q2.In a food chain, the flow of energy is always:

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