Niches and competitive exclusion

Niches and competitive exclusion Learning objectives:

To define the terms ecology, habitat, population and niche

Use a model to describe the principle of competitive exclusion

Definitions Ecosystem: “All of the biotic and abiotic factors in a self-

supporting system”

Habitat: “The geographical area occupied by an ecosystem”

Community: “All of the living things in a defined habitat”

Population: “The number of individuals of a defined species in a defined habitat at a particular time”

Niche The role of a species within an ecosystem. (The complex

interrelationship between this species and other organisms in the habitat, its effect on the ecosystem and its “place” within it)

You could think of an organism’s (or a species’) habitat as its address, and its niche as its occupation. But this is far too simplistic.

Competitive Exclusion What happens when two living things have

the same or overlapping niches?

Brother Gregory Investigates:Niches

Being the fictionalized story ofGregor Mendel, the discover of Genetics,ace detective and much more!

Herr Gustav Druer, the Brno wine grower and merchant has a problem and Brother Gregory has been asked to help.

You are to become his research assistants and help him carry out a research investigation into the properties of microbes.

Bacteria, single celled eukaryotes and other microbes, can only live and reproduce within a certain range of environmental conditions. Factors that can influence if or how microbes can grow are temperature, pH, dissolved gases, osmotic pressure and water availability.

Microbes, such as bacteria are more tolerant of environmental conditions than other organisms. However, each species has its own characteristic and particular range of values in which it grows and reproduces best. This determines its NICHE.

Background

Brother Gregory has collected a variety of microbes from around Brno. He has taken these back to the monastery for you (the research monks and nuns) to investigate their growth and find out the conditions under which they grow best.

One species of microbe appears to have contaminated all of Herr Druer’s stocks of yeast, and is competitively excluding it, preventing fermentation of the wine.

But which species is responsible?

Get to your scriptoriums!(This seemed funny at the time)

Collecting data Data can be collected on temperature

ranges here: http://www.brooklyn.cuny.edu/bc/ahp/CellBio/Growt

h/MGecol.html

Scroll to the bottom of the page for the links

Yeast The Saccharomyces cerevisiae strain used

by Herr Druer survives within a temperature range of 15 - 20oC and a pH range of 4 - 4.5.

Which species of microbe has contaminated the yeast – explain your answer

Data collectedSpecies of microbe Temperature range

(oC)pH range

S. englensis 5 – 40 6.5 – 8.0

F. rebrantus 35 – 70 1.0 – 6.0

R. uglitus 30 – 45 6.5 – 10.1

P. retii -10 – 15 4.5 – 7.0

E. coli 20 – 40 4.5 – 9.0

S. litia 55 – 80 1.0 – 6.0

L. bololus 10 – 25 7.5 – 9.5

N. atol 10 – 30 3.0 – 6.0

Niches

Any two variables, such as temperature and pH, which can be measured, and a range established, will define a "space" (or set of values) within which a species can be found; i.e. its ecological niche.

Move outside this "space" and you will no longer find that species. You may find another species, but its niche will be different.

Niches Niches may overlap slightly. In these cases,

organisms come into competition for resources.

However, A fundamental principle of ecology is that no two species can occupy exactly the same niche within the environment. This is called Gause's Principle, or the principle of competitive exclusion.