Maarg Manthan · Topic 2.1

Definition, Functions and Properties of an Ecosystem

Environment & Ecology › Ecosystem Structure and Function · Topic 2.1

An ecosystem is a functional unit of nature in which living organisms interact with one another and with the non-living physical environment, connected by a flow of energy and a cycling of nutrients. The term was coined by A G Tansley in 1935. An ecosystem has no fixed size; it may be as small as a pond or as large as the biosphere. It is an open system because it exchanges energy and matter with its surroundings. Its main functions are energy flow, nutrient cycling, productivity, decomposition and regulation of populations. Its properties include structure, boundaries, self-regulation through feedback, diversity, productivity and stability, and the ability to resist and recover from change, called resistance and resilience. Ecosystems are grouped as natural or artificial, and terrestrial or aquatic.

5 min read · UPSC Prelims · Environment & Ecology · Ecosystem Structure and Function

At a Glance

Coined by Tansley, 1935
System type Open system
Key functions Energy flow, nutrient cycling
Self-control Feedback and homeostasis
Stability traits Resistance, resilience
Exam link UPSC Prelims, Environment & Ecology: Ecosystem Structure and Function

Where Does It Fit?

This is the first topic of the macro on ecosystem structure and function. It defines the unit of study for the next topics on components, energy flow, food chains, productivity and biomagnification. Previous topic: Distinction Between Ecology, Environment and Ecosystem. Next topic: Structure/Components of an Ecosystem: Abiotic and Biotic Components.

What Is an Ecosystem and What Are Its Functions?

Aspect	Details
Definition	A community of living organisms interacting with each other and with the non-living environment as a single functional unit
Coined by	A G Tansley, 1935. Raymond Lindeman (1942) studied its energy dynamics, and Eugene Odum made it central to ecology
Size	Any scale: a drop of water, a pond, a forest, an ocean or the biosphere
Open system	Receives energy from the Sun and exchanges matter and energy with neighbouring ecosystems
Energy flow	Energy enters through photosynthesis, moves along food chains in one direction and is lost as heat. It is not recycled
Nutrient cycling	Materials like carbon, nitrogen and phosphorus move between living and non-living parts in cycles
Productivity	The rate at which organic matter is produced

What Are the Properties and Types of Ecosystems?

Structure: physical environment, producers, consumers and decomposers arranged in food chains
Boundaries: often fuzzy and chosen for study
Self-regulation: negative feedback keeps populations and conditions stable; for example, if prey increase, predators increase and reduce prey
Homeostasis: the ability to maintain a steady state
Resistance: ability to stay unchanged under stress
Resilience: ability to recover after disturbance
Natural ecosystems: forest, grassland, desert, lake, river, ocean
Artificial ecosystems: cropland, aquarium, reservoir, urban areas

What Else Should You Remember?

Decomposition: breakdown of dead matter by bacteria and fungi, releasing nutrients
Regulation: control of populations and climate by ecosystem processes
Ecosystem services: provisioning (food, water), regulating (climate, floods), supporting (soil formation) and cultural services
Millennium Ecosystem Assessment: 2005 study that classed and assessed services
TEEB: The Economics of Ecosystems and Biodiversity study that values nature
Terrestrial ecosystems: forests, grasslands, deserts, tundra
Aquatic ecosystems: freshwater and marine
Ecosystem boundaries: a watershed is often used as a unit
Productivity gradient: tropical forests and estuaries are among the most productive
Low productivity systems: deserts and open oceans
Biomass: total mass of living matter
Stability: diverse ecosystems tend to be more stable
Keystone effects: loss of certain species can change the system
Tipping point: a threshold beyond which an ecosystem shifts to a different state
Ecosystem health: capacity to keep functions and recover
Carrying capacity: maximum population an ecosystem can support
Human impact: pollution, land use change and overuse reduce resilience
Restoration: UN Decade on Ecosystem Restoration is 2021 to 2030
Man and Biosphere: UNESCO programme with biosphere reserves
Concept in law: the ecosystem approach is promoted by the Convention on Biological Diversity
Pond example: sunlight, water and minerals, plants and algae, insects and fish, and bacteria form a pond ecosystem
Link: components are explained in Structure/Components of an Ecosystem: Abiotic and Biotic Components
Examples in India: the Sundarbans mangrove, Chilika lagoon, Western Ghats rainforest and the Thar desert are well known ecosystems
Negative feedback: a process that reduces change and keeps stability, such as predators controlling prey numbers
Positive feedback: a process that increases change, such as melting ice reducing reflection and increasing warming
Ecosystem collapse: coral reefs and lakes can shift suddenly to a degraded state when stressed beyond limits
Assessing health: indicators include species richness, productivity, water quality and nutrient levels
Scale of study: ecologists choose the boundary according to the question, often a watershed or forest block
Ecotone and boundary: ecosystems grade into each other through transition zones
Why it matters: all later topics on energy, cycles and biodiversity use the ecosystem as the basic unit

Why Does It Matter for the Exam?

Definition: functional unit
Functions: energy flow, cycling
Properties: homeostasis, resilience
Current affairs link: restoration decade
Common errors: calling an ecosystem a closed system or saying energy cycles

As an analytical point, ecosystems provide services worth far more than their market value, and the loss of resilience can lead to sudden collapse. Management should protect functions and not only species.

Why Is This Topic Important?

Unit Functional
Functions Energy, nutrients
Properties Resilience

What Came Next?

The next topic covers the structure and components of an ecosystem. Next topic: Structure/Components of an Ecosystem: Abiotic and Biotic Components.

Key People and Terms

Ecosystem Functional ecological unit
Open system Exchanges energy and matter
Homeostasis Steady state
Resilience Recovery ability
Resistance Ability to withstand
Ecosystem service Benefit from nature

Exam Corner

Points to Remember

Term by Tansley, 1935.
Energy flows one way; nutrients cycle.
Ecosystem is an open system.
Restoration decade: 2021 to 2030.
Four service types: provisioning, regulating, supporting, cultural.

Do Not Confuse With

Resistance and resilience Staying unchanged versus bouncing back
Natural and artificial ecosystem Self-sustaining versus human-managed
Energy flow and nutrient cycling One-way versus cyclic

Memory Hook

Tansley named, energy flows once, nutrients go round, feedback keeps steady.

Mains Angle

Questions ask for definitions, functions and properties. These points help.

Concept System
Functions Flow, cycles
Services Value

A Question You May Face

An original practice question, not a past paper question.

“Define an ecosystem and discuss its functions, properties and the services it provides to people.”

How to Answer

Define Ecosystem.
Functions Energy, nutrients.
Properties Feedback.
Services Four types.

GS Relevance

Prelims: definition, functions, properties, types of ecosystem. GS Paper 3: ecology.

Frequently Asked Questions

What is an ecosystem?

An ecosystem is a functional unit of nature made up of a community of living organisms and their non-living physical environment, which interact with each other through flows of energy and cycles of nutrients. A pond, a forest and an ocean are all examples, and A G Tansley introduced the term in 1935.

What are the main functions of an ecosystem?

The main functions of an ecosystem are the flow of energy from the Sun through producers and consumers, the cycling of nutrients such as carbon, nitrogen and phosphorus, the production of organic matter, the decomposition of dead matter, and the regulation of populations and conditions through feedback.

Why is an ecosystem called an open system?

An ecosystem is called an open system because it constantly exchanges energy and matter with its surroundings. It receives solar energy and loses heat, and materials flow in and out through air, water and the movement of organisms. A completely closed ecosystem does not exist except in small experiments.

What is the difference between resistance and resilience of an ecosystem?

Resistance is the ability of an ecosystem to remain unchanged when it is disturbed, while resilience is the ability to return to its original state after being disturbed. A tropical rainforest has high resistance but takes long to recover, while a grassland has low resistance but recovers quickly after fire.

What are ecosystem services?

Ecosystem services are the benefits that people obtain from ecosystems. They are classed as provisioning services such as food and water, regulating services such as climate and flood control, supporting services such as soil formation and nutrient cycling, and cultural services such as recreation and spiritual values.

PYQ Practice — Statement Analysis

1 The term ecosystem was coined by Tansley.

True

In 1935.

2 Energy flows in cycles within an ecosystem.

False

Energy flows in one direction.

3 An ecosystem is an open system.