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Fundamental Niche vs. Realized Niche: What's the Difference?

Edited by Janet White || By Harlon Moss || Published on November 13, 2023
A fundamental niche represents all conditions under which an organism can survive, while a realized niche defines where it actually exists due to competition and other factors.

Key Differences

Both the fundamental niche and the realized niche are concepts in ecology that relate to the roles and spaces an organism occupies in an ecosystem. However, the fundamental niche considers all possible conditions where an organism can thrive without competition or predators, whereas the realized niche is its actual space given the presence of competitors and other environmental factors.
The fundamental niche represents an idealized sphere of existence, encompassing all conditions—be it temperature, food sources, or humidity—where a species could potentially live. On the other hand, the realized niche, being narrower, signifies where that species is found after accounting for real-world challenges like predation, competition, and other interactions.
For instance, a certain fish's fundamental niche might encompass a wide range of water temperatures, but the presence of a more dominant fish species might limit its actual habitat, thus defining its realized niche. This limitation is due to the natural checks and balances in an ecosystem.
When studying ecosystems, understanding the difference between the fundamental niche and the realized niche is crucial. It aids in recognizing not just the potential range and behaviors of a species but also the actual constraints placed upon it by the environment and other species.
To summarize, while both concepts describe the "space" a species can occupy, the fundamental niche is about potential without interference, and the realized niche reflects the practical, often limited, existence due to various environmental factors.

Comparison Chart


The full range of environmental conditions suitable for an organism
The actual conditions under which an organism exists in nature


Broad and idealized
Narrower due to competition and other factors

Influencing Factors

Absence of competition and predators
Presence of competition, predators, and other real-world factors

Conceptual Nature

Theoretical or potential habitat
Actual or practical habitat


Where a species could potentially live
Where a species actually lives

Fundamental Niche and Realized Niche Definitions

Fundamental Niche

Fundamental niche represents a species' possible role in an ecosystem without competition.
Given its dietary flexibility, the bird's fundamental niche is vast.

Realized Niche

Realized niche indicates the practical extent of an organism's existence in an ecosystem.
The beetle's realized niche is concentrated in drier parts of the forest.

Fundamental Niche

Fundamental niche refers to the full range of conditions under which a species can thrive.
Without competitors, the bear's fundamental niche extends across various terrains.

Realized Niche

Realized niche is where an organism is found considering competition, predation, and other factors.
The tree's realized niche is in shaded areas due to faster-growing neighbors.

Fundamental Niche

Fundamental niche is an organism's theoretical environmental range.
The butterfly's fundamental niche spans multiple temperature ranges.

Realized Niche

Realized niche pertains to the actual environmental conditions where an organism lives due to ecological constraints.
Due to predators, the rabbit's realized niche is limited to certain areas.

Fundamental Niche

Fundamental niche encapsulates all conditions suitable for an organism's existence.
In theory, the fundamental niche of this amphibian includes both freshwater and slightly brackish environments.

Realized Niche

Realized niche describes the practical habitat of a species given real-world interactions.
The fish's realized niche is confined to cooler waters due to competitors.

Fundamental Niche

Fundamental niche describes the potential habitat of an organism without interference.
The fundamental niche of the plant covers various altitudes.

Realized Niche

Realized niche represents the actual role a species occupies in its ecosystem.
With specific pollinators, the flower's realized niche is very specialized.


Why might an organism's realized niche be limited?

Due to factors like competition, predators, and other interactions.

Are the two concepts similar?

Both pertain to an organism's role and space in an ecosystem, but they differ in scope.

What does "fundamental niche" mean?

It represents all conditions where an organism can potentially thrive.

Which niche is broader in scope?

The fundamental niche.

Which niche considers all possible conditions for survival?

The fundamental niche.

Which niche is determined by real-world ecological interactions?

The realized niche.

What does the realized niche reflect?

The actual conditions where an organism is found in nature.

Can an organism's realized niche change over time?

Yes, due to environmental changes and species interactions.

Which niche represents an organism's idealized existence?

The fundamental niche.

How is "realized niche" defined?

It's the actual conditions where an organism exists due to ecological constraints.

Is the fundamental niche about potential or reality?

It's about potential.

How do competitors affect an organism's niche?

They can limit the range of the realized niche.

What's a simple way to distinguish the two concepts?

Fundamental niche is about potential; realized niche is about reality.

Does the realized niche consider ecological constraints?

Yes, it accounts for factors like competition and predation.

Do human activities impact these niches?

Yes, changes in the environment can affect both niches.

Is the fundamental niche affected by predators?

No, it represents conditions without interference like predation.

Can an organism's fundamental and realized niches be the same?

In the absence of competition and other constraints, they can be identical.

How do ecologists use these concepts?

To study potential versus actual roles and spaces of species in ecosystems.

How does the realized niche affect biodiversity?

It reflects species interactions, which can shape community structures.

Can these concepts be applied to any organism?

Yes, they're applicable to any species in an ecosystem.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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