What is the fundamental difference between a habitat and an ecological niche?

A habitat is the physical location where an organism lives, whereas a niche is the specific functional role and set of interactions that the organism has within that environment.

How does niche overlap affect the abundance of the competing species?

Niche overlap increases competition for resources, which generally leads to a decrease in the abundance (population size) of both species as resources are divided or one species is suppressed.

What is the likely outcome if two species attempt to occupy the exact same niche in the same habitat?

According to the Competitive Exclusion Principle, one species will be more efficient and will out-compete the other, leading to the local extinction or migration of the less successful species.

True or False: Two species can live in the same tree and occupy different niches.

True. They can occupy different niches by feeding at different heights, at different times of day, or by consuming different parts of the tree (resource partitioning).

What is a common misconception regarding the term 'niche' in relation to location?

A common error is thinking a niche is just a physical spot or 'micro-habitat'. In reality, it includes the organism's behavior, diet, and its impact on other species, not just its location.

Why might a species' distribution change over time?

Distribution changes if the biotic or abiotic factors of a habitat shift such that the species is no longer well-adapted to its current location, forcing it to move to a more suitable area.

Define 'abundance' in an ecological context.

Abundance is the number of individuals of a particular species found within a specific habitat.

Define 'distribution' in an ecological context.

Distribution refers to the specific spatial arrangement or locations where a species is found within a habitat.

How can temporal differences allow species to share a habitat?

By being active at different times (e.g., one species hunting at dawn and another at dusk), species avoid direct competition for the same resources, effectively occupying different niches.

What happens to a species if it is not well-suited to the abiotic factors of a niche?

The species will be unable to survive or reproduce effectively in that role, meaning it will not be part of the distribution in that specific area.

Niches: Distribution & Abundance | Pearson Edexcel A-Level Biology

Niches: Distribution & Abundance

Summary

The ecological niche represents the specific functional role and position of a species within its habitat, encompassing its interactions with both biotic and abiotic factors. Understanding niches is fundamental to explaining why species are found in specific locations (distribution) and why their population sizes vary (abundance) based on competitive interactions and environmental suitability.

1. Definition & Core Concepts

Habitat vs. Niche: While a habitat is the physical location where an organism lives (its 'address'), a niche is the functional role the organism plays within that environment (its 'profession').
Components of a Niche: A niche includes what an organism eats, which species depend on it for food, its period of activity (diurnal vs. nocturnal), and the precise spatial locations where it feeds or nests.
Biotic and Abiotic Integration: A species can only occupy a niche if it is well-adapted to the abiotic factors (like temperature and pH) and can successfully navigate biotic factors (like predation and competition) present in that specific role.

A diagram showing a single tree habitat divided into three distinct vertical niches (Upper, Middle, Lower) to illustrate how different species can coexist by occupying different roles.

2. The Competitive Exclusion Principle

Unique Niche Requirement: The Competitive Exclusion Principle states that no two species can occupy the exact same niche within the same habitat for an extended period.
Direct Competition: If two species attempt to fill the same niche, they will compete directly for the same limited resources, such as food or nesting sites.
Outcome of Overlap: Eventually, the species that is slightly better adapted to the niche will out-compete the other, leading to the less successful species either migrating to a new area or facing local extinction.

3. Resource Partitioning & Subtle Differences

Niche Differentiation: Species that appear to occupy the same niche often have subtle differences that allow them to coexist, a process known as resource partitioning.
Temporal and Spatial Variation: Coexistence is possible if species feed at different times of the day (temporal) or utilize different parts of the same resource, such as different heights in a forest canopy (spatial).
Dietary Variation: Even if species live in the same area, they may avoid direct competition by specializing in different food sources or prey sizes.

4. Impact on Abundance

5. Impact on Distribution

6. Exam Strategy & Tips