The malarial protist has a life cycle that includes the mosquito.

The idea

This statement explains that the malarial protist completes part of its life cycle inside a mosquito, making the mosquito a vector. When a mosquito feeds on an infected person, it takes up the protist along with blood. Inside the mosquito, the protist develops and multiplies, then moves to the mosquito's salivary glands. When that mosquito bites a healthy person, saliva containing the protist enters the blood, so the infection is passed on. The mosquito is therefore essential for transmission between humans; malaria is not spread directly from person to person. This explains why controlling mosquito numbers, using nets and repellents, and taking preventive drugs reduce malaria. The human is the host where the protist multiplies in red blood cells and causes symptoms.

What earns the marks

• The mosquito is a vector that transmits the malarial protist between humans.
• The protist is taken up by a mosquito when it feeds on an infected person.
• The protist develops and multiplies inside the mosquito before reaching its salivary glands.
• A later bite injects the protist into a healthy person's blood, continuing the life cycle.
• Malaria is not spread directly from person to person, so mosquito control reduces transmission.

Common mistakes and how to put them right

• Saying the mosquito is the pathogen.

  Put it right: The mosquito is the vector, and the protist is the pathogen.

• Thinking malaria spreads by direct human contact.

  Put it right: The mosquito is required to transmit the protist between people.

• Believing the protist multiplies only in humans.

  Put it right: Part of its life cycle and multiplication occurs in the mosquito.

Exam tips

• Use the term 'vector' and explain its role in the life cycle.
• Sequence the stages: mosquito feeds on infected person, protist develops in mosquito, mosquito bites healthy person.
• Link the life cycle to a control method, such as mosquito nets, to show applied understanding.