Brooklyn College BIOL 1010 : Lab Notes

Ecological Niche

Niche

A niche isthe functional position of an organism in its environment; comprising time, space and tolerance range.

Any two (or more) variables, which can be measured (such as temp. and pH) to establish a range, defines an organism's "space" of where it can be found.

 

Principle of competitive exclusion (Gause's principle)

States that no two organisms can occupy the exact same niche within the environment.

One species will be better adapted and will out-compete and eliminate the others.

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Effects of the Environment on Growth

In our investigation, we will be using bacteria as our model organsim and determine its niche.
The variables we will use to define its "space" will be temperature and pH.

The Effect of Temperature

There are certain temperatures at which an organism can exist.
This can be defined as a temperature range. Any temperature above or below this range will severely effect an organisms life functions and may lead to its death. A range consists of the following:

• minimum temperature: growth below this point is not possible
• optimun temperature: temperature where most rapid growth occurs
• maximun temperature: is the highest temperature at which growth is possible

All these can be represented in a diagram, such as the one below:

A: minimum temp - cellular processes are so slow, that growth cannot occur
B: enzymatic reactions increasing
C: optimum temp. - enzymatic reactions at max. rate
D: maximum temp. - protein denaturization, thermal lysis

Organisms can also be classified based on their optimum temperatures.

• psychrophiles (-5 - 20ºC)
• mesophiles (20 - 40ºC)
• thermophiles ( > 50ºC)

The Effect of pH

As with temperature, pH is also important for an organism's survival.

pH Scale

pH is a measure of acidity or alkalinity of a medium

Classification based on optimal pH

• acidophiles (live at low pH)
• neutrophiles (pH6 - pH8)
• alkaliphiles (live at high pH)

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