FREESCIENCELESSONS- BIOLOGY PAPER 1- MALARIA, SPECIFIC AND NON SPECIFIC DEFENCE SYSTEMS.

What is 'Malaria'?

Malaria is a very common disease in certain parts of the world and causes 400,000 deaths every year.

Malaria is a communicable disease. It is spread by a pathogen.

The malaria pathogen is an example of a:

PROTIST. This cannot pass directly from one person to another.

Why is malaria a very serious disease?

People with malaria experience repeated bouts of fever.

Malaria can be fatal.

How is malaria spread?

The infected individual is bitten by a mosquito. The malaria pathogen passes into this mosquito.

The mosquito then bites a different person and passes the malaria pathogen to them.

What do scientists call the mosquito and why?

They call it a vector because it carries the pathogen from one person to another.

How do we prevent the spread of malaria?

Firstly, we need to stop the vector from breeding.

Mosquitos breed in water. To stop mosquitos from breeding, we need to find areas of still water and drain them.

We could also spray areas of still water with insecticide which kills mosquitoes.

What is the problem with this method?

It is impossible to kill ALL mosquitoes.

What else can we do to reduce the spread of malaria?

We can prevent the mosquitoes from biting humans.

One of the best ways to do this is to sleep under a mosquito net.

The mosquitoes cannot get through the net so they cannot bite anyone sleeping in the bed.

If we spray the mosquito net with insecticide, any mosquitoes that land on the net are also killed.

So to summarise, if we prevent mosquitoes from breeding or biting humans, we reduce the spread of MALARIA!!

Explain the job of a non-specific defence system.

The job of a non-specific defence system is to prevent pathogens from entering the human body.

Explain the first part of a non specific defence system.

The skin.

The skin forms a protective layer, covering the body.

The outer layer of the skin consists of dead cells. This is difficult for pathogens to penetrate.


The skin also produces an oily substance called sebum, which can kill bacteria.

Sometimes the skin is damaged. What could this allow?

This could allow pathogens to enter the body.

How do we stop this?

The skin scabs over.

There are some parts of the body that are not covered by the skin. Give some examples of these.

The nostrils and the mouth.

What do these present?

Openings where pathogens can enter the body.

How does the 'nose' protect us from pathogens?

The nose contains hair and mucus. These can TRAP pathogens before they enter the breathing system.


However, sometimes pathogens pass through the nose and then make their way down towards our lungs.

How is this stopped?

The trachea and the bronchi are covered with tiny hairs called cilia.

What are cilia covered in?

Mucus which can trap pathogens.

The cilia now waft the mucus upwards towards the throat, where it is swallowed into the stomach.

How does the stomach defend us against pathogens?

The stomach contains hydrochloric acid.

This kills pathogens before they can make their way further down into the digestive system.

Even with all of these non specific defence systems, pathogens can still get into the human body and cause serious disease.