An ecological niche is the role and position of a species in its ecosystem, including where it lives, what it eats, when it is active, and how it interacts with other organisms. Niches matter because they help explain why species are found in some places but not others. They also show how biodiversity can be maintained when different species use resources in different ways.
Studying niches helps ecologists predict how communities may change after competition, climate shifts, or habitat disturbance.
A species has a fundamental niche, which is the full range of conditions and resources it could use if there were no limiting interactions. Its realized niche is usually smaller because competition, predation, disease, and barriers restrict where it can survive and reproduce. When two species need the same limited resource in the same place and time, competitive exclusion can cause one species to decline or disappear locally.
Resource partitioning reduces direct competition by dividing resources across space, food type, activity time, or environmental conditions.
Key Facts
- Ecological niche = the role, habitat, resource use, and interactions of a species in an ecosystem.
- Fundamental niche = all conditions and resources a species can potentially use.
- Realized niche = the part of the fundamental niche actually used after biotic limits are included.
- Realized niche is often smaller than fundamental niche because of competition, predation, and disease.
- Competitive exclusion principle: two species cannot stably occupy the exact same niche when a limiting resource is shared.
- Resource partitioning reduces competition by separating resource use by space, food, time, or environmental tolerance.
Vocabulary
- Ecological niche
- The ecological niche is the full role and position of a species in an ecosystem, including habitat, food, timing, conditions, and interactions.
- Fundamental niche
- The fundamental niche is the complete range of environmental conditions and resources a species could use without limiting biotic interactions.
- Realized niche
- The realized niche is the actual range of conditions and resources a species uses in nature after competition and other limits.
- Competitive exclusion
- Competitive exclusion is the principle that two species cannot coexist indefinitely if they require the same limiting resource in the same way.
- Resource partitioning
- Resource partitioning is the division of resources among species so they compete less directly.
Common Mistakes to Avoid
- Treating a niche as only a habitat is wrong because a niche also includes food, activity time, environmental tolerances, and species interactions.
- Assuming the fundamental niche and realized niche are the same is wrong because real ecosystems include competitors, predators, parasites, and other limits.
- Thinking competitive exclusion always causes global extinction is wrong because it often means one species is excluded only from a local habitat or resource zone.
- Ignoring time as a niche dimension is wrong because two species can use the same space and food but avoid competition by being active at different times.
Practice Questions
- 1 A lizard can survive from 18°C to 38°C in a lab, but in the wild it is found only from 24°C to 34°C because a competitor dominates cooler and warmer areas. What is the temperature range of its fundamental niche, and what is the temperature range of its realized niche?
- 2 Two bird species eat insects on the same tree. Species A forages from 0 m to 4 m above the ground, while Species B forages from 3 m to 8 m. What height range overlaps, and how many meters of foraging space does each species use without overlap?
- 3 Explain how two species that eat the same type of seed in the same grassland could avoid competitive exclusion through resource partitioning.