Page 208 - Big Ideas Year 10 sciPAD 2025

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208 SCIPAD - BIG IDEAS - BOOK 2
LIFE OF MICROBES
Disease
Bacteria and fungi have an essential role in the decomposition of dead and rotting organic
matter, and can be found on all surfaces in our homes. Many have beneficial uses such as the
production of antibiotics, as ingredients in food and alcohol production, as well as a direct food
source (e.g. mushrooms). Our bodies are home to an estimated 100 trillion “good” bacteria, many
of which reside in our gut and assist with digestion.
However, bacteria, fungi and viruses can also be harmful. Disease causing microbes are called
pathogens. If these pathogens can spread disease from one person to another, the disease is a
classified as a communicable disease.
Direct contact
Close, physical contact with an infection or
infected person.
Mouth and nose
Major entry point for pathogens. Entry
occurs when breathing, drinking, eating
or placing contaminated fingers and
objects into the mouth or nose.
Urogenital openings
Entry point for sexually transmitted
infections.
Penetration of the skin
Entry occurs via injections, bites,
cuts, wounds, surgery, punctures
and splitting due to swelling or
drying of the skin.
Indirect contact
Pathogens are transmitted via an inanimate
object such as a drink bottle, used bandage,
money, a toilet seat, etc.
Droplet transmission
Some pathogens can be transmitted in
droplets released by coughing, sneezing or
talking.
Common vehicle transmission
Pathogens can be transmitted over a wide
area via a common vehicle such as water or air.
Vector transmission
Occurs when pathogens are transmitted to
another species who then transmits the infection.
(eg: Human to mosquito to human).
Methods of Disease Transmission Portals of Entry
The skin provides an effective barrier to most
pathogens. However, pathogens can invade
the body via:
1. Are all micro-organisms harmful? Justify your answer. 




2. What word is used to describe a disease causing microbe. 
3. Outline the method of transmission and portal of entry for pathogens in the following
situations.
(a) Sharing a drink bottle.
Method of transmission: 
Portal of entry: 
(b) Food poisoning.
Method of transmission: 
Portal of entry: 
(c) Being sneezed on.
Method of transmission: 
Portal of entry: 
(d) A dog bite.
Method of transmission: 
Portal of entry: 
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