NCERT Class 5 The World Around Us / EVS • Classic CBSE Track

Chapter 8: A Treat for Mosquitoes

Malaria, Anopheles Mosquito, Anaemia & Iron, Ronald Ross Discovery & Vector Control | CBSE Session 2026–27

Core Pedagogical Competencies & Concepts
  • Malaria is caused by a tiny single-celled protozoan parasite (Plasmodium) transmitted through the bite of a female Anopheles mosquito.
  • Malaria causes shivering, chills, high recurring fever, sweating, and severe headache; it is confirmed through a microscopic blood smear test.
  • Anaemia is a condition where haemoglobin or iron levels in the blood fall below the normal range (12 to 16 g/dL in children), causing weakness, poor physical growth, and difficulty concentrating.
  • Iron-rich foods: Amla (Indian gooseberry), Jaggery (gur), green leafy vegetables (spinach, methi), and beans.
  • Ronald Ross discovered in Secunderabad that mosquitoes spread malaria, winning the Nobel Prize in Medicine in 1902.
  • Mosquito control: Pour kerosene/oil on standing water to choke larvae, introduce Gambusia fish in ponds, and keep water coolers dry.
Mosquito Life Cycle & Transmission Prevention 🥚 1. Eggs 🐛 2. Larvae 🫧 3. Pupa 🦟 4. Mosquito Oil on water creates a thin surface film that blocks the breathing tubes of larvae, terminating reproduction.

All Textbook Exercises & In-Text Tasks (22 Questions)

100% Complete Ingestion
Q1 Textbook Exercise
What causes malaria, which mosquito transmits it, and what symptoms appear in a patient suffering from malaria?
[3 Marks]
✅ Step-by-Step Solution & Working
Malaria is caused by a microscopic protozoan parasite called Plasmodium, transmitted from one person to another through the bite of an infected female Anopheles mosquito (identifiable by its spotted wings and tilted posture while resting).
Symptoms: Shivering with chills, recurring high fever every alternative day, severe headache, muscle pains, nausea, and profuse sweating when fever drops.
CBSE Step-by-Step Marking Scheme
Causative agent (Plasmodium parasite) 1 Mark
Vector identification (female Anopheles mosquito) 1 Mark
Key symptoms (chills, recurring fever, sweating) 1 Mark
Q2 Textbook Exercise
What is anaemia? What is the normal haemoglobin level for growing school children, and what dietary changes cure anaemia?
[4 Marks]
✅ Step-by-Step Solution & Working
Anaemia is a blood condition that occurs when the amount of haemoglobin or red blood cells in the body drops below the healthy threshold.
  • Normal Haemoglobin Range: 12 to 16 grams per decilitre (g/dL) for children.
  • Effects: Weakness, dizziness, stunted physical growth, and reduced stamina and concentration during studies.
  • Dietary Cure: Foods rich in iron and Vitamin C—such as Amla (Indian gooseberry), Jaggery (gur), green leafy vegetables (spinach, fenugreek), beetroot, and pulses, along with iron folic acid tablets distributed in schools.
CBSE Step-by-Step Marking Scheme
Definition of anaemia as haemoglobin deficiency 1 Mark
Normal range 12-16 g/dL & cognitive/physical impacts 1.5 Marks
Dietary sources (amla, jaggery, spinach, iron tablets) 1.5 Marks
Q3 Textbook Exercise
Describe the historic discovery made by Ronald Ross regarding malaria in Secunderabad.
[3 Marks]
✅ Step-by-Step Solution & Working
In the late 19th century, people believed malaria was caused by bad air from swampy marshes (mala-aria = bad air). British doctor Ronald Ross spent years in Secunderabad inspecting blood slides under microscopes. He let mosquitoes bite malaria patients, dissected the mosquitoes' stomachs, and discovered the exact same Plasmodium parasites inside the mosquito gut. This proved conclusively that mosquitoes transmit malaria, earning him the Nobel Prize in Medicine in 1902.
CBSE Step-by-Step Marking Scheme
Disproving the 'bad air' myth through dissection 1.5 Marks
Verification of parasites in mosquito stomach & 1902 Nobel Prize 1.5 Marks
Q4 Textbook Exercise
Name three diseases transmitted by mosquitoes. How can we differentiate between a normal mosquito and an Anopheles mosquito?
[3 Marks]
✅ Step-by-Step Solution & Working
Three mosquito-borne diseases:
  1. Malaria (transmitted by female Anopheles mosquito).
  2. Dengue (transmitted by Aedes mosquito).
  3. Chikungunya (transmitted by Aedes mosquito).
Distinguishing features of Anopheles: Anopheles mosquitoes are brownish with spotted wings. When resting on a wall or skin, they tilt their bodies upward at a distinct 45-degree angle, unlike common house mosquitoes (Culex) that sit flat and parallel to the surface.
CBSE Step-by-Step Marking Scheme
Naming Malaria, Dengue, and Chikungunya with vectors 1.5 Marks
Physical posture difference (45-degree tilt and spotted wings) 1.5 Marks
Q5 Textbook Exercise
Why do doctors advise hanging mosquito nets and applying wire mesh to windows rather than solely spraying chemical insect repellents?
[3 Marks]
✅ Step-by-Step Solution & Working
Physical barriers like bed nets and window wire mesh are far safer and more effective:
  • They create a continuous physical barrier that stops mosquitoes from entering without exposing family members to toxic chemical fumes.
  • Chemical repellent coils and sprays emit harmful fumes containing pyrethroids, which irritate children's lungs and trigger asthma attacks.
  • Mosquitoes develop genetic resistance to repeated chemical sprays over time, whereas physical screens never lose effectiveness.
CBSE Step-by-Step Marking Scheme
Physical barrier safety without toxic inhalants 1.5 Marks
Health hazards of chemical coils and insect resistance 1.5 Marks
Q6 Think and Discuss • Environmental Science & Ecology • A Treat for Mosquitoes
[Textbook Activity & Question 1] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q7 Find Out and Write • Observational Field Study • A Treat for Mosquitoes
[Textbook Activity & Question 2] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q8 Scientific Investigation • Ecosystem Relationships • A Treat for Mosquitoes
[Textbook Activity & Question 3] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q9 Traditional Wisdom & Community Stewardship • Conservation • A Treat for Mosquitoes
[Textbook Activity & Question 4] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q10 Survey & Data Collection • Experiential Inquiry • A Treat for Mosquitoes
[Textbook Activity & Question 5] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q11 Health, Diet & Human Biology • Nutritional Science • A Treat for Mosquitoes
[Textbook Activity & Question 6] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q12 Disaster Preparedness & Climate Resilience • Geography • A Treat for Mosquitoes
[Textbook Activity & Question 7] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q13 Biodiversity & Habitat Adaptations • Wildlife Protection • A Treat for Mosquitoes
[Textbook Activity & Question 8] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q14 Think and Discuss • Environmental Science & Ecology • A Treat for Mosquitoes
[Textbook Activity & Question 9] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q15 Find Out and Write • Observational Field Study • A Treat for Mosquitoes
[Textbook Activity & Question 10] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q16 Scientific Investigation • Ecosystem Relationships • A Treat for Mosquitoes
[Textbook Activity & Question 11] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q17 Traditional Wisdom & Community Stewardship • Conservation • A Treat for Mosquitoes
[Textbook Activity & Question 12] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q18 Survey & Data Collection • Experiential Inquiry • A Treat for Mosquitoes
[Textbook Activity & Question 13] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q19 Health, Diet & Human Biology • Nutritional Science • A Treat for Mosquitoes
[Textbook Activity & Question 14] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q20 Disaster Preparedness & Climate Resilience • Geography • A Treat for Mosquitoes
[Textbook Activity & Question 15] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q21 Biodiversity & Habitat Adaptations • Wildlife Protection • A Treat for Mosquitoes
[Textbook Activity & Question 16] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
Q22 Think and Discuss • Environmental Science & Ecology • A Treat for Mosquitoes
[Textbook Activity & Question 17] In 'A Treat for Mosquitoes', describe how students can conduct an empirical investigation or discussion on this topic and explain the scientific principles involved.
[3 Marks]
✅ Step-by-Step Solution & Working
Scientific Model Answer & Environmental Analysis:
1. Field Inquiry / Observation: In A Treat for Mosquitoes, students examine real-world ecological relationships, habitat dependencies, and sustainable environmental practices.
2. Scientific Core Principles: Applying primary scientific methods—such as formulating a hypothesis, measuring field parameters, and recording observations in a nature journal—reveals direct linkages between human communities and natural cycles.
3. Stewardship Conclusion: Understanding these concepts cultivates empathy for living organisms and empowers students to implement eco-friendly conservation measures in daily life.
CBSE Step-by-Step Marking Scheme
Observation methodology & identification of ecological concepts 1.0 M
Scientific explanation of natural cause-and-effect processes 1.0 M
Actionable conservation recommendations stated clearly 1.0 M
🌟 NEP 2020 Competency-Based Case Study

Preventing Dengue, Malaria, and Chikungunya

During the rainy season, stagnant water collected in old car tires, broken flowerpots, and cooler trays in a residential colony. Within two weeks, multiple residents fell sick with dengue and malaria.

Analytical Task: Explain four practical actions community residents must take to prevent mosquito breeding around their homes.
Evaluation & Model Answer:
Four Essential Vector Control Actions: 1. Eliminate Stagnant Water: Empty, scrub, and dry out water coolers, flowerpot trays, buckets, and bird baths every week. 2. Cover Water Storage: Keep overhead and underground water storage tanks tightly sealed with lids. 3. Use Oil or Kerosene Film: If water cannot be drained from a pit or puddle, pour a few drops of kerosene or oil on top; this creates a thin film that stops mosquito larvae from breathing air. 4. Biological Control (Gambusia fish): Put small Gambusia fish into local decorative ponds and ditches; they voraciously consume mosquito larvae.
Rubric: 1 Mark each for 4 preventive actions + 1 Mark for biological control explanation = 5 Marks