Protist diseases — AQA GCSE Biology
Test yourself on Protist diseases with AQA GCSE practice questions.
7 days Premium · Then free forever · No card, no charge
Protist diseases explained
This statement identifies the type of pathogen responsible for malaria.
Read the full explanation
Malaria is caused by single-celled eukaryotic organisms called protists, specifically species of Plasmodium. A protist is not a bacterium, virus or fungus; it is a eukaryotic microorganism, so it has a nucleus and other membrane-bound organelles. The malarial protist enters the human blood when an infected mosquito bites and feeds. Inside the human body it invades red blood cells, multiplies and causes the recurring fever and other symptoms of malaria. Because the pathogen is a protist, antibiotics that target bacteria are not effective against it. Recognising the pathogen type helps explain transmission, symptoms and why control focuses on mosquitoes and protective drugs.
The malarial protist has a life cycle that includes the mosquito.
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.
Malaria causes recurrent episodes of fever and can be fatal.
Malaria is a disease caused by a protist pathogen, Plasmodium, which is transmitted between humans by mosquito vectors. The protist enters the blood when an infected female mosquito takes a blood meal, then travels to the liver and later invades red blood cells, where it multiplies in cycles. When these cells burst, toxins are released that trigger recurrent episodes of fever, often with chills, sweating and headache. Because the cycle repeats, the fever comes back again and again rather than staying constant. In severe cases, malaria can damage organs such as the brain and kidneys, and it can be fatal, especially in young children, pregnant women and people with weakened immunity. Understanding this helps explain why controlling mosquito numbers and avoiding bites are so important.
The spread of malaria is controlled by preventing the vectors, mosquitos, from breeding and by using mosquito nets to avoid being bitten.
Malaria spreads when a female mosquito bites an infected person, picks up the Plasmodium protist, and later bites someone else. To reduce transmission, people target the vector rather than the pathogen directly. Preventing mosquitoes from breeding means removing or treating standing water where they lay eggs, for example draining ponds, covering water containers and clearing blocked drains. Using mosquito nets, especially nets treated with insecticide, creates a physical barrier that stops mosquitoes biting people while they sleep. Other measures include insect repellents, window screens and spraying insecticides. These methods work best together because they reduce both the number of mosquitoes and the chance of being bitten, lowering the spread of malaria in a community.
Your focus
- State that malaria is caused by a protist.
- Distinguish the malarial pathogen from its mosquito vector.
- Explain why antibiotics do not treat malaria.
Show all 12 objectives
- Describe the role of the mosquito in the malarial protist life cycle.
- Explain how the protist passes from an infected person to a healthy person.
- Relate the life cycle to methods that reduce malaria transmission.
- State that malaria is caused by a protist pathogen transmitted by mosquitoes.
- Describe how the pathogen causes recurrent fever by infecting and bursting red blood cells.
- Explain why malaria can be fatal, referring to severe effects on the body.
- Describe how preventing mosquito breeding reduces malaria transmission.
- Explain how mosquito nets reduce the chance of being bitten by vectors.
- Evaluate why combining several control methods is more effective than using one alone.
Protist diseases exam tips
Marking Points
- Malaria is caused by a protist pathogen, for example Plasmodium.
- Protists are eukaryotic, single-celled organisms with a nucleus.
- The malarial protist is transmitted to humans by mosquitoes and infects red blood cells.
- Because the pathogen is a protist, antibacterial antibiotics are not an effective treatment.
- Identifying the pathogen type helps explain the disease symptoms and the methods used to control it.
- 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.
- Malaria is caused by a protist pathogen, specifically Plasmodium species.
- The pathogen is transmitted to humans by the bite of an infected mosquito, which acts as a vector.
- The protist multiplies inside red blood cells, causing them to burst and release toxins.
- The release of toxins produces recurrent episodes of fever rather than a single continuous fever.
- Malaria can be fatal, particularly in vulnerable groups such as young children and pregnant women.
- The recurring nature of the fever is linked to the repeated cycle of infection and bursting of red blood cells.
- Mosquitoes are the vectors that transmit the malaria protist between humans.
- Preventing breeding involves removing or treating standing water where mosquitoes lay eggs.
- Mosquito nets act as a physical barrier that reduces the chance of being bitten.
- Insecticide-treated nets can also kill or repel mosquitoes, giving extra protection.
- Combining methods such as draining water, nets and repellents reduces malaria transmission more effectively than one method alone.
- Control measures aim to break the transmission cycle between mosquito and human.
Examiner Tips
- 💡Write 'protist' clearly and, if asked for an example, name Plasmodium.
- 💡Distinguish the pathogen from the vector by using the terms correctly in the same answer.
- 💡Link the pathogen type to treatment, noting that antibiotics are ineffective against protists.
- 💡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.
- 💡Name the pathogen group (protist) and the genus Plasmodium to show precise knowledge.
- 💡Link the recurrent fever to the life cycle of the pathogen inside red blood cells, not just to the bite.
- 💡Use the word vector correctly: the mosquito transmits the pathogen but is not the pathogen itself.
- 💡Always link each control method to how it breaks the transmission cycle.
- 💡Use the term vector correctly when referring to mosquitoes.
- 💡Give specific examples of standing water, such as water butts, drains or discarded containers.
Common Mistakes
- Naming a virus or bacterium as the cause of malaria; correction: the pathogen is a protist.
- Thinking that the mosquito is the pathogen; correction: the mosquito is the vector that transmits the protist.
- Assuming antibiotics cure malaria; correction: antibiotics act on bacteria, so they do not kill the malarial protist.
- Saying the mosquito is the pathogen; correction: the mosquito is the vector, and the protist is the pathogen.
- Thinking malaria spreads by direct human contact; correction: the mosquito is required to transmit the protist between people.
- Believing the protist multiplies only in humans; correction: part of its life cycle and multiplication occurs in the mosquito.
- Saying that malaria is caused by a virus or bacterium; the correction is that it is caused by a protist, Plasmodium.
- Saying that mosquitoes cause malaria directly; the correction is that mosquitoes are vectors that transmit the protist pathogen.
- Describing the fever as constant rather than recurrent; the correction is that fever episodes repeat as red blood cells burst in cycles.
- Saying that mosquito nets kill the malaria pathogen; the correction is that nets prevent bites by blocking mosquitoes.
- Confusing prevention of breeding with killing adult mosquitoes; the correction is that removing standing water stops eggs and larvae developing.
- Thinking one control method is enough; the correction is that combining methods is more effective at reducing spread.