Lesson 1.5 Viruses

This is a free lesson. We trust you enjoy it!

Introduction to the lesson

There is one 'organism' that does not fit into any of the five kingdoms you explored in the last lesson. In fact, viruses are not even considered to be living things! In this lesson, you will explore what a virus is and how it relates to the five kingdoms of living organisms.

Review of past lessons

Before you begin the lesson, review

  1. the seven characteristics of living things (you will need to apply these in this lesson).
  2. the classification stages from kingdom to species.
  3. the general characteristics of the five kingdoms of living organisms (animals, plants, fungi, protoctists and prokaryotes)

Preparing for the lesson

  1. What do you think a virus is?
  2. Why are some viruses so dangerous for people's health?
  3. What diseases do you know of that are caused by viruses?
  4. Do you know any names of particular viruses?
  5. Why are diseases caused by viruses difficult to treat?
  6. Why do antibiotics not work on viruses?


Read section 1.4 'Viruses' on p.9 of the Coursebook.

Learning Activity 1

Think through the following questions:

  1. Why are viruses not considered to be living organisms? (Hint: think of the seven characteristics of living organisms). List all the characteristics that viruses do display and then list the characteristics they do not display.
  2. If viruses are not considered to be living organisms, why do you think they are included in this study of biology?

Answer the following questions in your exercise book:

  1. Make a table with two columns - one for characteristics of living organisms that viruses do display and the other column for characteristics of living organisms that viruses do not display. Complete the table.
  2. List the characteristics of viruses.
  3. Study Figure 1.9 on p.9.
    1. Copy the diagram into your exercise book.
    2. Label your drawing.
    3. Compare the diagram of the virus, with the bacteria and the paramecium. Write a short paragraph describing the similarities and differences between these three cells.

Learning Activity 2

In your exercise book, answer Questions 1.4-1.6 in the Coursebook

In your biology reference book, add the following terms and definitions: (These terms come from section 1.3 'The kingdoms of living organisms' and section 1.4 'Viruses')


multicellular - (of an organism or part) having or consisting of many cells.

unicellular - consisting of a single cell.

chloroplast - an organelle found in some plant cells, which contains chlorophyll and where photosynthesis takes place.

organic - a term used to describe substances that have been made by living organisms, or whose molecules contain: carbon, hydrogen and oxygen.

chlorophyll - a green, light absorbing pigment found inside chloroplasts in plant cells.

photosynthesis - the process by which plants manufacture carbohydrates from raw materials using the energy from light.

antibiotics - a drug that kills bacteria in the human body without damaging human cells.

parasite - an organism that lives in or on another organism (its host) and benefits by deriving nutrients at the host's expense.

saprophyte - a plant, fungus, or microorganism that lives on dead or decaying organic matter.

hyphae - each of the branching filaments that make up the mycelium of a fungus

mycelium - the vegetative part of a fungus, consisting of a network of fine white filaments (hyphae).

sporangium - (in ferns and lower plants) a receptacle in which asexual spores are formed

RNA - ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information.

Learning Activity 3

In your exercise book, copy and complete the following table comparing the cells of the different kingdoms and viruses:

 Cell wall            
 Cell membrane            

Common misunderstandings and misconceptions

Students often think of viruses as living organisms. Make sure you understand why they are not considered to be living organisms and why they do NOT belong to any of the five kingdoms.

Closing the lesson

  •  What new things did you learn in this lesson?
  • What did you already know?
  • Are you unsure of anything? Ask your parent or teacher to help you.