Virus 101                   Worksheet

2020 will be remembered as the Year of the Virus – the first year of the COVID-19 pandemic. By early 2021 the COVID virus had truly left its mark on our population, lifestyle, and biosphere, but the universe is complicated, and viruses can be good guys too.

G’day, Dr Karl here.

2020 will go down in history as the Year of the Virus. It was the first year of the COVID-19 pandemic. By early 2021, the COVID virus - SARS-CoV-2 - had well and truly left its mark on our population, lifestyle, and biosphere.

Cities got emptier, and animals came back. Canada geese waddled with their goslings along Las Vegas Boulevard, jackals occupied a city park in Tel Aviv while coyotes walked the streets of San Francisco. Animals don’t usually wander up and down modern city streets.

Even the chemistry and temperature of the atmosphere changed. Factory production and transport numbers dropped so much that air pollution plummeted. Not only did ozone levels in the lower atmosphere drop by 7%, but so did generalised air pollution. The air became clearer, so more heat from the Sun hit the ground and was re-emitted upwards. This led to a jump in air temperature of about a fifth of a degree.

In the USA, the life expectancy of Black Americans suddenly dropped by 2.7 years. While world-wide, over 2.5 million people died from COVID-19.

All this turmoil was caused by a quantity of virus so small that it would definitely fit into a milk container, and probably even a soft drink can – just several hundred grams. It makes you want to agree with the British biologist Peter Medawar and his wife, Jean, who said that a virus is, “a piece of bad news wrapped up in protein”. And the Latin root is blatant - the word “virus” means “poison”.

But you guessed it, the Universe is complicated, and viruses can be good guys as well.

For one thing, about 8% of our human DNA is made up of viruses that invaded us in the past – from the recent present way back to several hundred million years ago. Some of these virus invaders are absolutely essential for a fertilised egg to turn into a baby human some nine months later. These viruses in human DNA make human reproduction possible.

So let's dive into virus 101.

Both a bacterium and a virus have all the genetic instructions needed to make another bacterium or a virus.

But the big difference is that bacteria (and practically all other life forms) also have two extra capabilities. First, they have microscopic biological factories that can turn food into energy. And second, they have another set of mini-factories that use this energy to physically manufacture another baby from scratch.

But a virus has neither. By itself, it can’t make energy and it can’t make babies.

A virus has to get itself inside the cell of a living creature – and then take over their systems to make more viruses.

Think of a small backyard swimming pool filled with water plus all the chemicals and elements that living creatures need to live and to make babies. This water carries the basic macronutrients of fats, proteins and carbohydrates as well as all the necessary micronutrients (elements such as iron, cobalt, magnesium and the rest, along with all the vitamins). Let’s do a few mind experiments.

Experiment 1. Put a single bacterium into that pool. About 20 minutes later, there are two bacteria, and another 20 minutes later there are four, and so it repeats Within a day, the pool is jam-packed with bacteria.

Experiment 2. Start with your pool loaded with water and various chemicals and elements – and add one single virus. Nothing happens. Come back 10 years later, and still, all you have is that one single virus.

Experiment 3. Start with a fresh pool, add a few dozen bacteria and one single virus. The bacteria start doubling in number every 20 minutes - and the virus gets eaten by one of the bacteria. But the virus is not your average inert meal. No, the virus takes over the biological factories inside that bacterium, and very soon hundreds of viruses are getting squirted out into the pool, and the bacterium probably dies. As long as the virus has at least a single living cell that it can take over, it will - and then make more copies of itself.

So a virus can reproduce, but not by itself. Does that make it alive or not? That’s really complicated, and we'll talk more about that next time.


1.     What changes happened to city streets in the year of COVID?

2.     What changes happened to the atmosphere in the year of COVID?

3.     Explain the language feature “a piece of bad news wrapped up in protein”.

4.     How much of human DNA is made up of viruses?

5.     What are two things a bacterium can do?

6.     How does a virus reproduce?

7.     What is the effect of the rhetorical question Does that make it alive or not?

Note singular – bacterium      plural bacteria   ( from Latin)




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