Chapter 45.1: The Niche

Habitat

The place where an organism lives

Ecological niche

The hypothesis that every species in an ecosystem fulfills a unique role (both the physical habitat and the ecological role)

• Unless all the dimensions of the niche are satisfied in an ecosystem of species will not be able to survive grow or reproduce

Choosing a Niche

• Dependent on both abiotic and biotic factors

1. They can tolerate the environment 

2. They can coexist with other species

• Different resources

• Active at different times

• Low population densities that competition isn’t sever

3. Benefit from interactions with other species

Types of Niches:

• Developed/shaped through evolution 

1. Fundamental Niche

2. Realized Niche

Fundamental Niche:

1. The full range of environmental conditions and resources a species could theoretically use

• “Potential range”

Realized Niche

1. The actual range it occupies, limited by competition, predation, or other interactions

• Invasive species thrive because the fundamental niche is much bigger but now competition and predation isn’t an issue

• Competition: WHen species use the same limited resource in the same place

Competitive exclusion

• Essentially when fundamental issues of two species overlap one species is expected to exclude and it becomes a competition 

  • The outcompeted species does not have a realized Niche and will be competitively excluded from the whole ecosystem

Ecological Theory

• Every species must have a realized Niche that differs from the realized niche of all other species if it is to survive in an ecosystem

  • Some species evolve to fill new niches 

Phylogenetic Niche Conservatism

• Closely related species have similar niches

Evolution of the Niche idea

1. Joseph Grinnell (1900): Habitat Based

• Defined niche as all environmental conditions needed for survival/reproduction

2. Charles Elton (1920): Role based

• Defined niche as the role or function of a species in its community

3. Evelyn Hutchinson (1950): Combination of both environment and behavior 

• niche as a multidimensional space that allows a species to “practice its way of life”