AQA · GCSE · Biology

    Course version: 8461 · Version from Sept 2018

    Malarial parasites reproduce asexually in the human host, but sexually in…

    Full specification wording

    Advantages and disadvantages of sexual and asexual reproduction (biology only): Malarial parasites reproduce asexually in the human host, but sexually in the mosquito.

    Malaria is caused by Plasmodium, a protozoan parasite spread by female Anopheles mosquitoes.

    Checked against the AQA 8461 specification (opens in a new tab) on .

    • Point 4 of 8
    • 3 key terms

    Study notes

    From the checked teaching notes for this specification point.

    The idea

    Malaria is caused by Plasmodium, a protozoan parasite spread by female Anopheles mosquitoes. The parasite has two hosts and switches reproductive mode between them. In the human host, Plasmodium reproduces asexually inside red blood cells and liver cells, multiplying rapidly to produce many identical parasites; this causes symptoms. When a mosquito bites an infected person, it takes up gametocytes. Inside the mosquito gut, these develop into gametes which fuse sexually to form a zygote, generating genetic variation. The mosquito carries infective stages to the next person. Asexual reproduction in humans amplifies numbers, while sexual reproduction in the mosquito creates variation and completes the life cycle.

    What earns the marks

    • Plasmodium is a protozoan parasite transmitted by female Anopheles mosquitoes.
    • In the human host, reproduction is asexual, producing genetically identical parasites rapidly inside red blood cells and liver cells.
    • Asexual reproduction in humans amplifies parasite numbers and causes the symptoms of malaria.
    • Gametocytes are taken up by a mosquito when it feeds on an infected person.
    • In the mosquito, gametes fuse sexually to form a zygote, generating genetic variation.
    • The sexual stage in the mosquito completes the life cycle and produces infective stages passed on at the next bite.
    • The two modes occur in different hosts, so the life cycle depends on both humans and mosquitoes.

    Common mistakes and how to put them right

    • Thinking the mosquito itself is the parasite.

      Put it right: The mosquito is the vector, while Plasmodium is the parasite.

    • Saying reproduction is sexual in humans and asexual in the mosquito.

      Put it right: The order is the reverse.

    • Believing the mosquito becomes ill from malaria.

      Put it right: The parasite's sexual stage occurs in the mosquito but the serious disease is in humans.

    • Confusing gametocytes with gametes.

      Put it right: Gametocytes are the cells taken up by the mosquito and develop into gametes there.

    Exam tips

    • Name both hosts and state clearly which reproductive mode occurs in each.
    • Use the terms asexual, sexual, gametocyte, gamete, zygote and vector accurately.
    • Link asexual reproduction to rapid increase in parasite numbers and sexual reproduction to variation.
    • When asked to explain the life cycle, sequence the stages from human to mosquito to human.

    Try the lesson

    The start of the Advantages and disadvantages of sexual and asexual reproduction (biology only): Malarial parasites reproduce asexually in the human host, but sexually in the mosquito. lesson, made from checked teaching notes for this specification point.

    Have a go first

    Where does the malarial parasite reproduce sexually?

    Listen

    Malaria is caused by Plasmodium, a protozoan parasite spread by female Anopheles mosquitoes. The parasite has two hosts and switches reproductive mode between them. In the human host, Plasmodium reproduces asexually inside red blood cells and liver cells, multiplying rapidly to produce many identical parasites; this causes symptoms. When a mosquito bites an infected person, it takes up gametocytes. Inside the mosquito gut, these develop into gametes which fuse sexually to form a zygote, generating genetic variation. The mosquito carries infective stages to the next person. Asexual reproduction in humans amplifies numbers, while sexual reproduction in the mosquito creates variation and completes the life cycle. A strong answer earns marks for these points. Plasmodium is a protozoan parasite transmitted by female Anopheles mosquitoes. In the human host, reproduction is asexual, producing genetically identical parasites rapidly inside red blood cells and liver cells. Asexual reproduction in humans amplifies parasite numbers and causes the symptoms of malaria. Gametocytes are taken up by a mosquito when it feeds on an infected person. Exam tip: Name both hosts and state clearly which reproductive mode occurs in each.

    See it

    A flowchart beginning with the Plasmodium parasite, which leads to the human host. From the human host, one path leads to asexual reproduction in red blood cells and liver cells, then to many identical parasites and the symptoms of malaria. Another path from the human host leads to gametocytes taken up by a mosquito, then to the mosquito. From the mosquito, one path leads to gametocytes developing into gametes, then to gametes fusing sexually to form a zygote, then to genetic variation. A second path from the mosquito leads to infective stages passed on at the next bite, which returns to the human host.
    It shows the malaria life cycle, with asexual reproduction in the human host and sexual reproduction in the mosquito.

    Key words

    Say what each word means before you turn the card.

    Asexual reproduction

    Try answering aloud or in your head before turning the card.

    Sexual reproduction

    Try answering aloud or in your head before turning the card.

    Vector

    Try answering aloud or in your head before turning the card.

    See every definition
    Asexual reproduction
    In the human host, Plasmodium reproduces asexually inside red blood cells and liver cells, multiplying rapidly to produce many identical parasites.
    Sexual reproduction
    In the mosquito, gametes fuse sexually to form a zygote, generating genetic variation.
    Vector
    The mosquito is the vector, while Plasmodium is the parasite.

    Label the diagram

    Some boxes have lost their names. Pick the right name for each number.

    The diagram again, with 3 boxes numbered instead of named. A flowchart beginning with the Plasmodium parasite, which leads to the human host. From the human host, one path leads to asexual reproduction in red blood cells and liver cells, then to many identical parasites and the symptoms of malaria. Another path from the human host leads to gametocytes taken up by a mosquito, then to the mosquito. From the mosquito, one path leads to gametocytes developing into gametes, then to gametes fusing sexually to form a zygote, then to genetic variation. A second path from the mosquito leads to infective stages passed on at the next bite, which returns to the human host.

    • 1Box 1

    • 2Box 2

    • 3Box 3

    0 of 3 labelled

    There is more to this lesson

    The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.

    Carry on with the full lesson

    A week of Premium from your first lesson · Then the free plan continues · No card, no charge

    Test your understanding of Advantages and disadvantages of sexual and asexual reproduction (biology only): Malarial parasites reproduce asexually in the human host, but sexually in the mosquito.

    Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.

    Take topic quiz

    A week of Premium from your first lesson · Then the free plan continues · No card, no charge

    Start free

    Cookies on MasteryMind

    Essential cookies keep you signed in.

    Analytics and advertising cookies stay off unless you accept.

    Read our Privacy Policy.