The Ecological Niche
Definition
Ecological niche
An ecological niche is the unique set of abiotic and biotic conditions and resources that a species requires to survive, grow, and reproduce.
- Every species in an ecosystem has a unique ecological niche, its role and position within that system.
- The niche describes the set of abiotic and biotic conditions that determine where and how a species lives, survives, and reproduces.
- It includes all environmental requirements and interactions necessary for an organism’s growth, survival, and reproduction, such as food sources, temperature tolerance, and behavioral adaptations.
Components of a Niche
- Habitat: The physical environment where the species lives (e.g., forest floor, coral reef, tundra).
- Feeding habits: Type of food consumed and method of obtaining it (e.g., carnivore, herbivore, detritivore).
- Temporal activity: When the species is active (diurnal, nocturnal, seasonal).
- Interactions: Symbiotic relationships, competition, and mutualistic partnerships.
- Physiological range: Tolerance limits for temperature, salinity, pH, and humidity.
- Reproductive strategy: Mating behavior, breeding season, and parental investment.
A habitat is the species’ address, while its niche is its occupation, what it does and how it fits into the ecosystem.
Exam techniqueWhen explaining a niche in exams, always include both biotic (feeding, competition, predation) and abiotic (temperature, humidity, soil, light) components.
ExampleThe Ecological Niche of the Bengal Tiger (Panthera tigris)
- Habitat: Tropical and subtropical forests, mangroves, and grasslands in India, Bangladesh, Nepal, and Bhutan.
- Diet (Food Source): Carnivorous; preys on deer, wild boar, and smaller mammals.
- Hunting Strategy: Ambush predator; hunts alone at night.
- Competitors: Other large carnivores like leopards and dholes (wild dogs).
- Abiotic Factors: Requires dense vegetation for cover, water sources for drinking and cooling, and a temperature range between 20–40°C.
- Predator-prey dynamics: Controls herbivore populations, maintaining ecosystem balance.
- Territorial behavior: Competes with other tigers for territory and mates.
Types of Niches
- Fundamental niche: The full range of environmental conditions under which a species could survive and reproduce.
- Realized niche: The portion of the fundamental niche that a species actually occupies, considering competition and other limiting factors.
Barnacle species on rocky shores illustrate this distinction:
- The species Chthamalus can tolerate a wide range of tidal levels (fundamental niche),
- But due to competition from Balanus, it is confined to higher tidal zones (realized niche).
Competitive Exclusion Principle
- Proposed by G.F. Gause (1934), this principle states that no two species can occupy the exact same niche indefinitely in a stable ecosystem.
- If two species compete for identical resources, the superior competitor will eventually exclude the other.
- Some species avoid this by resource partitioning, i.e., dividing resources spatially or temporally.
- Three North American warbler species feed in the same conifer trees but at different heights.
- This resource partitioning reduces direct competition and allows coexistence.
Population Interactions
- Populations interact in various ways within ecosystems, shaping ecological balance, population sizes, and evolutionary adaptations.
- These interactions drive natural selection, influencing species behavior and survival.
- These interactions create complex food webs and energy flows within ecosystems.
- The major interaction types include herbivory, predation, parasitism, mutualism, disease, and competition.
1. Herbivory
Definition
Herbivory
Herbivory is an interaction in which an animal (the herbivore) feeds on a plant or algal species (producer) for energy and nutrients.
- Herbivory occurs when an animal feeds directly on plant material.
- It influences both the plant population (by reducing biomass) and the herbivore population (through food availability).
- Effect on Population Dynamics:
- Overgrazing reduces plant availability, limiting herbivore populations.
- Plants develop chemical defenses, reducing herbivore feeding success.
- The hippopotamus spends nights feeding on grasses and days submerged in rivers.
- It's feeding maintains open grasslands and influences the distribution of aquatic vegetation.
- Ecological impact: Shapes plant community composition.
- Behavioural adaptation: Grazing at night avoids heat stress.
- Evolutionary effect: Selection for digestive systems capable of processing fibrous plants.
Plants evolve defensive adaptations such as thorns, toxins, or thick bark, while herbivores evolve resistance or specialized feeding behaviors.
2. Predation (Predators vs. Prey)
Definition
Predation
Predation is an interaction in which one organism (the predator) kills and consumes another organism (the prey) for food.
- Predation is an interaction in which one organism (predator) kills and eats another (prey).
- Predator-prey relationships regulate population sizes through negative feedback loops, maintaining ecological balance.
- Effect on Population Dynamics:
