GoalSay what microbes are, name their main groups and explain that some help us and some harm us.
New words
microbe · a living thing too small to see without a microscopebacteria · tiny prokaryotes with simple cellsprotozoa · single-celled eukaryotes such as the amoebafungi · eukaryotes such as yeast and mould
Explanation
Microbes are living things that are too small to see without a microscope. They live everywhere: in air, water, soil and food, on our skin and even inside our bodies. The main groups are bacteria, protozoa and fungi. Bacteria are prokaryotes, and protozoa and fungi are eukaryotes. Viruses are even smaller. They are not made of cells and do not fit in these groups, so they are a good topic for your research. Many microbes are harmless, some are very helpful and a few can make us ill. So it is wrong to say that all microbes are harmful. We cannot draw microbes realistically, so in this book we use simple shapes: circles, rods and spirals, and labelled boxes.
Group
Cell type
Example
bacteria
prokaryote
lactic acid bacteria
protozoa
eukaryote
amoeba
fungi
eukaryote
yeast
viruses
not made of cells
research them
Worked examples
Where
Example
soil
decomposers
food
yoghurt bacteria
inside the body
bacteria in the gut
Microbes are found in many places: soil, water, air, food, on skin and inside the body. Most of them cannot be seen without a microscope, but we can see signs of them, such as bread dough rising or milk turning into yoghurt.
Shape of the microbe
Draw it as
round
a circle
rod-shaped
a short thick line
spiral
a wavy line
Draw microbes as simple shapes: a circle for round bacteria, a rod for rod-shaped bacteria and a spiral for spiral-shaped bacteria. Label each box with its name. A drawing like this is only a symbol, not a real picture.
Is a virus a bacterium? No. A virus is not made of cells, so it does not belong to bacteria, protozoa or fungi. Finding out more about viruses is your research task.
Class activity
Microbe map. Draw a big picture of your home and mark the places where microbes may live. Draw a simple symbol for each group: a circle, a rod and a spiral for bacteria, a blob for protozoa and a branching line for fungi. Then ask an adult to help you look up what a virus is. Never grow mould or collect microbes yourself.
Practice
1
What is a microbe?
A living thing too small to see without a microscope.
2
Which groups of microbes are prokaryotes, and which are eukaryotes?
Bacteria are prokaryotes. Protozoa and fungi are eukaryotes.
