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2020 PSLE Science malaria-mosquito question: Simplest answer

2020 PSLE Science malaria-mosquito question: Simplest answer

Certain PSLE science questions have gained notoriety for their high level of difficulty, often leaving students puzzled. In the past, we successfully tackled challenging questions like the turkey and the mosquito questions from 2022. In this article, our focus will be on unravelling the 2020 question about malaria-carrying mosquitoes.

The 2020 Malaria-carrying mosquito question

Malaria is a disease spread by mosquito A. Children infected with malaria are found to be bitten more often by mosquito A.

Joel wanted to find out if children infected with malaria are more attractive to mosquito A due to a certain smell that they produce. He used the set-up shown in the above image with 20 of mosquito A in box P.

Joel counted the number of times mosquitoes landed on the shirt for three minutes. He repeated the experiment using another shirt worn by an uninfected child in box Q.

(i) State a hypothesis on how the smell on a shirt affects its attractiveness to mosquito A.

(ii) Joel used a white shirt instead of a black shirt for the experiment. Suggest why using a white shirt allows him to obtain more accurate results.

(iii) Joel recorded his results in the table.

  Number of times mosquitos landed
Shirt in box P 300
Shirt in box Q 120
Scientists are able to store the smell produced by infected people in a container. Suggest how Joel could use this smell and his results to reduce the number of bites on people. 


(i) To answer this question, let's first understand what the examiner is asking for. We need to "State a hypothesis." So, what does "hypothesis" mean? Well, it's like making an educated guess or prediction. It's an idea or statement you create before doing a scientific experiment or research. A hypothesis guides your investigation to see if it's true based on what you observe and the data you collect. It's a way for scientists to test their ideas and learn more about the world.

Now, take another look at Joel's question. Is there something he's trying to find out?

Let's help you with that. Consider this statement: "Joel wanted to find out if children infected with malaria are more attractive to mosquito A due to a certain smell they produce."

Did you figure it out?

If you said, "The hypothesis here is that mosquito A will be attracted to a shirt if it smells like children who have malaria," you're absolutely correct!

Model answer: Most mosquito A will be attracted to a shirt if it has the smell released by malaria-infected children.

(ii) Why did Joel choose a white shirt instead of a black one? 

Picture two shirts, one white and one black, side by side. Now, imagine a mosquito sitting on each of them. What do you see? You can easily spot the mosquito on the white shirt, even from a distance. But on the black shirt, it's hard to see the mosquito. That's the answer. Joel picked the white shirt because he wanted a clear view of the mosquitoes to get accurate results for his experiment.

Model answer: A white shirt will allow Joel to be able to see the mosquitos clearly and count them accurately. Using a black shirt decreases the visibility of the mosquitoes being camouflaged by the black colour of the shirt.

(iii) For the third question, we need to think about how Joel can use the scent and his results to prevent mosquito bites on people. Let's break it down step by step, considering two key factors: the scent and Joel's findings.

First, regarding the scent, we know that scientists can capture the scent produced by infected people.

Now, let's look at Joel's results. Mosquitoes were more attracted to the shirt in box P, which had the smell of malaria-infected children. This suggests that the scent stored by scientists is the same scent that attracts mosquitoes, as shown in Joel's experiment.

So, how can we reduce mosquito bites on people? Is there something we can do to make mosquitoes go away?

Here's a clue from the question: It's related to a scent that can be collected.

Indeed! If we take the malaria-infused scent and place it in an area where fewer people are present, mosquitoes will be drawn to that place and leave people alone. Once the mosquitoes are gathered in a different area, we can eliminate them, ensuring fewer mosquito bites! That's the solution.

Model answer: Joel's results show that mosquitos are attracted to the smell produced by infected people. The container which stores the smell produced by infected people can be used to attract and trap mosquitos which will then lead to fewer bites on people. 

Questions like this are added to the PSLE paper as they test a student's higher-order thinking skills.

What are higher-order thinking skills?

Higher-order thinking skills, often referred to as HOTS, are a set of cognitive abilities that go beyond basic memorisation and understanding of information. These skills, like the ones mentioned below, involve more complex mental processes and are crucial for critical thinking and problem-solving. 

  • Analysing: This skill involves breaking down information into its component parts to understand its structure and relationships. It helps in identifying patterns and trends within data or concepts.
  • Evaluating: Evaluating means making judgments about the quality, credibility, or validity of information. It involves weighing evidence and making informed decisions or assessments.
  • Synthesising: Synthesising is the process of combining different elements or ideas to form a coherent whole. It's about seeing connections between seemingly unrelated concepts.
  • Creating: Creating involves synthesising information or ideas to generate something new. It can be a new solution to a problem, a piece of artwork, or even a written composition. This skill is about creativity and innovation.
  • Applying: Applying is about using what you've learned in new situations or contexts. It's the ability to transfer knowledge and skills from one area to another.

These skills enable individuals to think critically, solve complex problems, and adapt to new challenges effectively. MOE expects the top 20% of the students to answer such questions correctly. At Geniebook, our teachers help students learn effective strategies that will help them answer such questions that require them to apply high-order thinking skills and ace their PSLE Science exam. Fill the form on the side to sign up for a free Geniebook demo ->

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