Ecological Niches

HSC Biology | Free Study Notes

In this lesson

• what a habitat is

• what an ecological niche is

• how a niche includes a species’ role in the ecosystem

• how competition relates to niches

• what niche overlap means

What is a habitat?

A habitat is the place where an organism lives.

A habitat provides the environmental conditions an organism needs, such as:

• shelter

• food or energy sources

• water

• suitable temperature

• space for reproduction

Important point

A habitat is mainly about where an organism lives.

What is an ecological niche?

An ecological niche is more than just the place where an organism lives.

A niche includes:

• the habitat of the organism

• its role in the ecosystem

• how it obtains resources

• how it interacts with other species

• the conditions it needs to survive and reproduce

A syllabus glossary definition describes a niche as a position or function in a habitat that provides all the requirements for life of a species. 

Simple comparison

• Habitat = where an organism lives

• Niche = where it lives and what it does there

Role in the ecosystem

A species’ niche includes its role in the ecosystem.

What this can include

Its role may involve:

• what it eats

• what eats it

• when it is active

• where it feeds

• how it reproduces

• how it affects other organisms

Example idea

A frog’s niche might include:

• living near water

• feeding on insects

• being prey for snakes and birds

• breeding in ponds

This shows that a niche is about the whole way a species fits into the ecosystem.

Competition

Competition happens when organisms need the same limited resources.

These resources may include:

• food

• water

• light

• shelter

• mates

• nesting sites

Module 4 specifically includes competition as a key biotic factor affecting ecosystems. 

Why competition matters for niches

If two species need exactly the same resources in the same place and at the same time, they are likely to compete strongly.

This means niche relationships help explain why competition happens.

Niche overlap

Niche overlap happens when two species use similar resources or have similar roles in an

ecosystem.

What this means

If two species:

• live in similar places

• eat similar food

• are active at similar times

then their niches overlap.

Why niche overlap matters

Greater niche overlap usually means greater competition, because both species are trying to use the same limited resources.

Important point

Species can often live in the same habitat without having identical niches.

For example:

• two birds may live in the same forest

• one may feed high in the canopy

• the other may feed on the ground

Their habitats overlap, but their niches are different, so competition is reduced.

Habitat and niche are not the same

This is one of the most common points of confusion.

Same habitat, different niche

Different species can share the same habitat but have different niches.

Same role, different habitat

In some cases, similar niches can be found in different habitats if organisms play similar ecological roles.

Key idea

A niche includes the species’ position, function and requirements, not just its location.

Why niches matter in ecosystems

Ecological niches help explain:

• how species coexist

• why some species compete more than others

• how changes in one species can affect others

• why biodiversity can increase when species use resources in different ways

This is why niches are a key part of ecosystem dynamics in Module 4. The syllabus specifically lists investigation of ecological niches alongside competition, predation and disease. 

Example 1: same habitat, different niche

In a woodland:

• one bird species may feed on insects in tree bark

• another may feed on seeds on the ground

Both live in the same habitat, but they occupy different niches.

Example 2: niche overlap and competition

Two grass species in the same area may both need:

• sunlight

• soil nutrients

• water

If these resources are limited, niche overlap may lead to competition.

Worked example

Exam-style question

Explain the difference between a habitat and an ecological niche.

Worked answer

A habitat is the place where an organism lives. An ecological niche includes not only where the organism lives, but also its role in the ecosystem, how it uses resources, and the conditions it needs to survive and reproduce.

Why this works

This answer:

• defines both terms clearly

• shows that a niche is broader than a habitat

• uses the idea of role and requirements

Common mistakes

• Saying habitat and niche mean the same thing.

• Defining a niche only as a place.

• Forgetting that a niche includes interactions with other species.

• Describing competition without linking it to resource overlap.

• Assuming two species in the same habitat must have the same niche.

Quick quiz

1. What is a habitat?

2. What is an ecological niche?

3. How is a niche different from a habitat?

4. What is niche overlap?

5. Why can niche overlap increase competition?