What is a Niche A niche describes the
What is a Niche? A niche describes the way of life of a species. In other words it is the ‘profession’ an organism has in its community. This encompasses/ includes: • Where it lives • What it eats • What time of the day or night it is active • What level of a food chain it occupies etc.
Example: Common green Gecko (Naultinus elegans) • Where it lives- In tea tree and small bushes • What it eats- Flying insects and flightless invertebrate • When it is active- Diurnal (during day) • Level of food chain- Secondary consumer (carnivore)
Ecological Niche: is the term used to describe the place of an organism within an ecosystem. It describes how an organism interacts with its habitat (abiotic factors) and with its local community (biotic factors).
Ecological Niche
Fundamental Niche: is the term used to describe the maximum environmental range of an organism as defined by its tolerance range to abiotic factors and by the availability to a food supply.
Fundamental Niche
Realised Niche: is the term used to describe the range of an organism which has been narrowed due to limiting factors. Yeah, realised and ecological niche are the same thing…
Realised Niche
Question: What would happen if two species with similar niches occupied the same habitat? • Inter-specific competition between species for food/ space. • The best competitor (or species with the best adaptations for that particular environment) will outcompete the second species. • Second species may die out or may have to move (if they can survive the environmental pressures outside of their niche environment).
Competition: The Competitive Exclusion Principle Biologists A. J. Lotka and V. Volterra theorized that no two species with similar requirements for resources (food, shelter, etc. ) could coexist in the same niche without competition driving one to local extinction.
Gause’s principle of competitive exclusion A Russian scientist, G. F. Gause, tested the Lotka–Volterra theory. • He grew two different species of Paramecium alone, under identical conditions. • Their populations grew to their carrying capacity and levelled off— showing a logistic growth pattern. • He grew them together and discovered that one species died out (it couldn't compete).
Gause’s principle of competitive exclusion Conclusion: • Two species competing for limited resources cannot co-exist in the same place at the same time. • This concept was named the competitive exclusion principle (or Gause's Principle).
Joseph Connell's Famous Experiments Two species of barnacles live in a stratified distribution in the intertidal region along the Scottish coast. Observations: • Balanus is most concentrated in the lower intertidal area. • Chthamalus is most concentrated in the upper intertidal area. • The free-swimming larvae of each species can settle anywhere on the rocky shoreline, and presumably be able to grow to be an adult. Question: Why don't we see Balanus and Chthamalus growing together?
Experiment 1: • Connell removed Chthamalus from the upper area, and no Balanus replaced it. • Inference: Balanus could not survive in an area that experienced so much desiccation (due to low tides). • Conclusion: Balanus's realised niche was the same as its fundamental niche.
Experiment 2: • Connell removed Balanus from the lower area and Chthamalus replaced it. • Inference: Balanus was a more successful competitor in the lower intertidal zone. • Conclusion: The fundamental niche and realised niche for Chthamalus were not the same—its realized niche was smaller due to interspecific competition.
Conclusion: Competition occurs in nature and can explain the distinction between a fundamental niche and a realised niche. Also, two species competing for limited resources cannot co-exist in the same place at the same time.
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