ANSWERS FOR PRE-LAB ASSIGNMENT FOR LAB EXERCISES #2 and #3
Read the background information and complete all of the activities.
due at the beginning of Lab #2:
Microbes: Good or Bad
By the end of this pre-lab assignment, students will be able to…
Convert between nm, μm, and mm and L, ml, and μl.
Describe the size differences among microorganisms and other cells.
Compare and contrast prokaryotes, eukaryotes, and viruses.
Describe the extent to which prokaryotes dominate life on earth in terms of number of organisms.
Describe the birth of the compound light microscope and how it changed our understanding of life
Make serial dilutions and understand the math necessary to do so.
You will need a cm ruler to complete this assignment.
Metric rulers can be obtained at the Bookstore.
What are microbes?
Last week, you had a chance to make observations about a microbe called
saw how this infectious agent caused a disease in potatoes known as “soft rot.”
You determined it was the
causal agent using Koch’s Postulates.
But, were you certain at the time whether this causal agent was a
bacteria, fungus, virus, of protozoa.
It wasn’t until the invention of the microscope around 1590 that scientists
were even able to see the world of microbes.
But, once they were, then there was a need to understand more
about the similarities and differences among these microorganisms.
Using information from last week’s lab, compare the dates of the invention of the
microscope and the work of Koch.
What other progress was made in the world of science between these
What were scientists doing?
1590, two Dutch eye glass makers, Zaccharias Janssen and son Hans Janssen experimented with multiple
lenses placed in a tube. The Janssens observed that objects viewed in front of the tube appeared greatly
enlarged, creating both the forerunner of the compound microscope and the
1665 – English physicist,
looked at a sliver of cork through a microscope lens and noticed some
"pores" or "cells" in it.
Anton van Leeuwenhoek
built a simple microscope with only one lens to examine blood, yeast, insects
and many other tiny objects.
1876- A founder of the science of
, Koch devised a procedure to demonstrate that the
Bacillus anthracis causes
, a disease of animals that can also be transmitted to humans. It was the first
time that a particular bacterium was shown to be the cause of a particular disease.
It appears that there was little progress between the 1600s and the late 1800s.
You might have learned that cells and/ or microbes (remember, most microbes are cells) can be