Question

This is regarding microbiology. Identify, describe, and give examples of 3 different uses of controls and 2 different controlled variables used in microbiology experiments. I have done these procedures so far:

Fluid Thioglycollate,
Anaerobic Jar,
Effect of Temperature on Microbial Growth,
Effect of pH on Microbial Growth,
Effect of Osmotic Pressure on Microbial Growth,
Effect of Ultraviolet Radiation on Microbial Growth

Answer 1

Uses of controls are:-

(1)It is important in scientific experiments to test the validity of results.

(2)If control changes it can effect the results.

(3)It helps in establishing correlation between dependent and independent variables.

Following procedures can be done to study two more controlled variables.

(1)Aim:-To study the effect of humidity on growth of microorganisms.

Hypothesis:-Microorganisms grow rapidly in moist conditions.

Variables:- Manipulated variable:-presence of water

Responding variable:-The growth of microorganisms.

Constant variable:-same type of bread.

Apparatus required:-2 pieces of bread,Water,Clear plastic bag.

Procedure:-

(1)A piece of bread is sprinkeled with water and placed in a clear plastic bag and labelled it as A.

(2)Another piece of bread was kept dry and placed in another plastic bag and labelled as B.

(3)Both bags were kept in dark for 2 days.

(4)Observe the results.

Result:-

presence of moisture	The growth of microorganism(Mucor)
Bread with moisture	A lot of microorganism growth.
Dry bread	A few microorganisms grew.

Discussions:-

Microorganisms need moisture for their growth.

There was no growth on dry piece of bread.

Hence,hypothesis is proved.

(2)Another procedure can be done to observe the effect of time on the growth of Eschercia coli bacteria by simply growing it in laboratory and observing its growth as the doubling time of this bacteria is 20 mins it needs atleast 20 mins to grow.