z z Describe the defining features of bacteria and viruses.
Consider the important role that bacteria play as producers and decomposers.
Discuss the role of bacteria and viruses as disease-causing organisms. Microorganisms
Microorganisms are very small living things. They cannot be seen by the human eye alone and must be viewed using microscopes. Bacteria and viruses are microorganisms.
Kingdom Monera
Kingdom Bacteria is also referred to as Kingdom Monera, as the prefix ‘mono’ means ‘one’ and all members of this kingdom are composed of a single cell. The prefix ‘uni’ also means ‘one’.
Bacteria Bacteria are the most common organisms on Earth.
They can survive in environments that are too harsh for other organisms to live in. For example, bacteria can be found living in geysers, salty rock pools and the human body.
All bacteria are made up of only one cell (unicellular). They do not have a nucleus.
Binary Fission
Bacteria reproduce by a process called binary fission. This means that one bacteria cell divides in two and the number of bacteria doubles with each generation.
Parent cell
Learn more about fission in Earth and Space 24.2
Binary fission
Some bacteria can reproduce every 20 minutes. This means that a lot of bacteria are produced in a very short period of time.
8 daughter cells z
Fig. 5.2.1 Binary fission
We can model the number of bacteria present after a certain number of generations using the function y = 2n, where y is the number of bacteria and n is the number of the generation (n = 0, 1, 2, etc.). For example, when n = 2, then y = 22 = 4.
1. Why do we start with 20? 2. How many bacteria are there after 10 generations? 3. What assumptions are made in this model? 4. What are some of the limitations of this model?
