Maarg Manthan · Topic 1.4

Habitat and Ecological Niche

Environment & Ecology › Basic Concepts of Ecology · Topic 1.4

A habitat is the physical place where an organism or a population lives, with its set of environmental conditions, and it is often called the address of the species. An ecological niche is the role and position of a species in its ecosystem, covering what it eats, where it lives, when it is active and how it interacts with others, so that the niche is called the profession of the species. The word niche was used by Joseph Grinnell in 1917 for the spatial setting and by Charles Elton in 1927 for the functional role. G E Hutchinson in 1957 defined the niche as an n-dimensional hypervolume and separated the fundamental niche, the full range a species can use without competition, from the realised niche, the smaller range it actually uses because of competition and predation. Gause's competitive exclusion principle says that two species with the same niche cannot live together for long.

5 min read · UPSC Prelims · Environment & Ecology · Basic Concepts of Ecology

At a Glance

Habitat Address of species
Niche Profession of species
Fundamental niche Potential range
Realised niche Actual range
Gause Competitive exclusion
Exam link UPSC Prelims, Environment & Ecology: Basic Concepts of Ecology

Where Does It Fit?

This topic follows the account of the ecological hierarchy. It explains where and how species live inside communities, which sets up the later topics on species interactions, succession and adaptation. Previous topic: Ecological Hierarchy. Next topic: Deep Ecology vs Shallow Ecology.

How Do Habitat and Niche Differ?

Feature	Habitat and niche
Meaning	Habitat: the place with its physical and biological conditions. Niche: the functional role, including place, food, time and interactions
Analogy	Habitat is the address; niche is the occupation or profession
Sharing	Many species can share a habitat. Two species with an identical niche cannot share it for long
Scope	Habitat is a part of the niche description. The niche has many dimensions: temperature, food size, activity time, nesting site
Example 1	A pond is the habitat of a frog. Its niche includes eating insects at night, laying eggs in water and being prey for snakes
Example 2	A forest is a habitat of many birds, but different birds feed on different parts of the trees, so they have different niches
Concept history	Grinnell (1917) saw the niche as a habitat space, Elton (1927) as a role in the food web, and Hutchinson (1957) as an n-dimensional space

Fundamental niche: the full range of conditions and resources in which a species can survive and reproduce if there are no competitors or enemies
Realised niche: the smaller part actually occupied because of competition, predation and disease
Competitive exclusion principle: proposed by G F Gause in 1934 from experiments on Paramecium species; complete competitors cannot coexist
Resource partitioning: species share a resource by using different parts or times; Robert MacArthur’s study of warblers feeding at different heights of a spruce tree is a classic example
Niche overlap: partial sharing of resources, which leads to competition
Character displacement: competing species evolve differences, such as beak size in Darwin’s finches
Niche breadth: a generalist has a wide niche; a specialist has a narrow niche
Niche construction: organisms change their own niche, as beavers do by building dams

What Else Should You Remember?

Microhabitat: a small habitat within a larger one, such as under a log
Habitat loss: the main cause of species decline, as in Causes of Biodiversity Loss
Habitat fragmentation: splitting of habitat into small patches by roads and fields
Habitat corridors: connections between patches that allow movement
Habitat specialist: a species restricted to one habitat, such as the Great Indian Bustard in grasslands
Generalist: a species like the rat or crow that lives in many habitats
Edge effect: change in conditions at the edge between habitats
Flagship species: a charismatic species used to protect a whole habitat
Umbrella species: a species whose protection also protects many others
Fundamental versus realised: the realised niche is always smaller or equal to the fundamental niche
Barnacle example: Connell’s study of barnacles Balanus and Chthamalus on Scottish rocks showed competition restricting the realised niche
Darwin’s finches: different beaks allow different foods on the Galapagos
Indian examples: the lion-tailed macaque in rainforest canopies of the Western Ghats and the snow leopard on high Himalayan slopes
Introduced species: an alien species may occupy a vacant niche and become invasive, as in Endemic Species, Keystone Species, Indicator Species, Invasive Species
Climate change: shifts habitats and niches
Conservation use: habitat suitability models predict where a species can live
Ecological equivalents: species in different regions with similar niches, like kangaroos and antelopes
Niche in exam questions: statements often swap fundamental and realised niche or claim that habitat and niche are the same
Introduced predators: an alien predator can shrink the realised niche of native species
Habitat quality: food, water, shelter and space together decide quality
Habitat types in India: forest, grassland, wetland, desert, coastal, mountain and marine habitats

Why Does It Matter for the Exam?

Analogy: address versus profession
Hutchinson: fundamental and realised niche
Gause: competitive exclusion
Current affairs link: habitat loss and reintroduction
Common errors: saying two species can share the same niche or that realised niche is larger

As an analytical point, habitat protection alone does not guarantee survival, because the niche includes food, partners and interactions. Conservation therefore needs to protect the ecological roles as well as the places.

Why Is This Topic Important?

Meaning Place and role
Types Fundamental, realised
Rule Gause

What Came Next?

The next topic covers deep ecology and shallow ecology. Next topic: Deep Ecology vs Shallow Ecology.

Key People and Terms

Habitat Place where species lives
Niche Functional role
Fundamental niche Potential niche
Realised niche Actual niche
Resource partitioning Sharing resources
Generalist Wide niche species

Exam Corner

Points to Remember

Habitat = address; niche = profession.
Realised niche is smaller than fundamental.
Gause: 1934, Paramecium.
Hutchinson: 1957.
Resource partitioning: MacArthur’s warblers.

Do Not Confuse With

Habitat and niche Place versus role
Fundamental and realised niche Potential versus actual
Generalist and specialist Wide versus narrow niche

Memory Hook

Address is habitat, job is niche; fundamental free, realised squeezed; Gause says no two the same.

Mains Angle

Questions ask for definitions and principles. These points help.

Concepts Habitat and niche
Competition Gause
Use Conservation

A Question You May Face

An original practice question, not a past paper question.

“Distinguish between habitat and ecological niche and explain how competition shapes the realised niche of a species.”

How to Answer

Define Both terms.
Types Fundamental, realised.
Principle Gause.
Use Conservation.

GS Relevance

Prelims: habitat versus niche, fundamental and realised niche, Gause's principle, examples. GS Paper 3: ecology.

Frequently Asked Questions

What is the difference between habitat and niche?

A habitat is the physical place where a species lives, its address, while an ecological niche is the full role of the species in its ecosystem, including what it eats, when it is active, where it breeds and how it interacts with others, its profession. Many species can share a habitat, but each has its own niche.

What are fundamental and realised niches?

The fundamental niche is the complete range of conditions and resources in which a species could live and reproduce in the absence of competitors and predators. The realised niche is the smaller range that the species actually occupies because of competition, predation and other interactions. The idea comes from G E Hutchinson.

What is the competitive exclusion principle?

The competitive exclusion principle, or Gause's principle, states that two species that compete for exactly the same limited resources cannot coexist for long, as one will eventually outcompete the other. Gause showed this in 1934 by growing two Paramecium species together in the laboratory.

What is resource partitioning?

Resource partitioning is the division of a shared resource among species by using different parts of it, or using it at different times, which reduces competition and allows coexistence. Robert MacArthur showed that different warbler species feed in different parts of a spruce tree.

What is the difference between generalist and specialist species?

A generalist species has a broad niche and can use many habitats and foods, like the crow or the rat, so it adapts well to change. A specialist species has a narrow niche and depends on a particular habitat or food, like the koala on eucalyptus, so it is more at risk of extinction.

PYQ Practice — Statement Analysis

1 A habitat is often described as the address of an organism.

True

The niche is the profession.

2 The realised niche is larger than the fundamental niche.

False

It is smaller or equal.

3 Gause's principle is based on experiments with Paramecium.