IB Biology Topic B4.2.1: Ecological Niche as the Role of a Species in an Ecosystem Notes

Ecological Niche: A Species' Unique Role in Its Ecosystem

1. Every species occupies a unique role in its ecosystem, called its ecological niche.
2. The niche combines both biotic (living) and abiotic (non-living) factors that determine how a species survives, grows, and reproduces.

What Defines a Niche: Where a Species Lives, What It Eats, Who It Interacts With

1. Zones of tolerance for abiotic variables
   1. A species' habitat is set by its zones of tolerance for factors like temperature, light, and moisture.
   2. These abiotic conditions define where a species can survive.
2. Mode of nutrition
   1. How a species obtains energy, whether by photosynthesis or by consuming other organisms, is one dimension of its niche.
   2. The specific modes of nutrition (holozoic, mixotrophic, saprotrophic, and others) are covered in B4.2.4 to B4.2.7.
3. Interactions with other species
   1. Many species depend on others for key services.
   2. Pollination of flowers.
   3. Seed dispersal by animals.
   4. Nutrient recycling by decomposers breaking down organic material.

The Niche Is Multidimensional and Unique to Each Species

1. A species' niche is multidimensional, combining every factor it needs to survive.
   1. Abiotic factors such as light, temperature, and pH.
   2. Biotic interactions such as competition, predation, and symbiosis.
2. Because it combines so many dimensions, each species' niche is effectively unique.
3. Where niches overlap, competition can push species apart, a process developed in B4.2.13 (competitive exclusion).