5-3 Ecological Niches and Adaptation

What Is an Ecological Niche? How Species Coexist

A niche is a species’ way of life or functional role in a community or ecosystem and involves everything that affects its survival and reproduction. A species’ ecological niche includes the adaptations or adaptive traits its members have acquired through evolution. It also includes that species’ range of tolerance for various physical and chemical conditions, such as temperature and water availability.

The ecological niche of a species is different from its habitat, the physical location where it lives. Ecologists often say that a niche is like a species’ occupation, whereas habitat is like its address

A species’ fundamental niche is the full potential range of physical, chemical, and biological conditions and resources it could theoretically use if there were no direct competition from other species.

What Are Generalist and Specialist Species? Broad and Narrow Niches

Scientists use the niches of species to broadly classify them as generalists or specialists.

Generalist species have broad niches. They can live in many different places, eat a variety of foods and tolerate a wide range of environmental conditions. Specialist species have narrow niches. They may be able to live in only one type of habitat, use only one or a few types of food, or tolerate only a narrow range of climatic and other environmental conditions.

Divergent evolution occurs when there is an increase in specialized species when the niches of species compete intensely for scarce resources. Over time one species may evolve into a variety of species with different adaptations that reduce competition and allow them to share limited resources.

In contrast, convergent evolution occurs when two distantly related groups of organisms develop similarities because they are adapting to similar environmental constraints or opportunities.

What Limits Adaptation? Life Is a Genetic Dice Game

Humans will not evolve to live in harsher environmental conditions because of two limits to adaptations in nature:

  1. A change in environmental conditions can lead to adaptation only for genetic traits already present in the gene pool of a population. You must have dice to play the genetic dice game.

  2. Even if a beneficial heritable trait is present in a population, the population’s ability to adapt may be limited by its reproductive capacity.

What Are Two Commonly Misunderstood Aspects of Evolution?

There are two common misconceptions about evolution:

  1. Organisms evolve in response to the use and disuse of different structures/resources.

  2. “Survival of the fittest” means “survival of the strongest.” To biologists, fitness is a measure of reproductive success, not strength. Thus the fittest individuals are those that leave the most descendants.