PRE-LAB ASSIGNMENT FOR LAB EXERCISES #2 and #3
Read the background information and complete all of the activities. This entire
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,
m, and mm and L, ml, and
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.
Question: 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
two dates? What were scientists doing? (Sadava, 4-5)
You might have learned that cells and/ or microbes (remember, most microbes are cells) can be
prokaryotic or eukaryotic cells. The three domains include
Question: Briefly, what is the difference between
What is a virus?
range in size from 20 - 300 nm. Viruses can replicate themselves only by infecting a host cell.
They therefore cannot reproduce on their own. At the most basic level, viruses consist of genetic material
contained within a protective protein coat. They infect a wide variety of organisms: both eukaryotes (animals,
plants, protists, and fungi) and prokaryotes (
). A virus that infects bacteria is known as a
, often shortened to
For convenience, we will refer to a virus as a microbe in this exercise.
It has been argued extensively whether viruses are living organisms. Most virologists
consider them non-living, as they do not meet all the criteria of the generally accepted definition of life.
Would you classify them as living or non-living or does it matter at all? (Sadava, 283)