Selina Concise Solutions for ICSE Class 9 Biology Chapter 16 Diseases Cause And Control

Exercise 1

Question A:
Answer: 1. (c) pandemic
2. (d) Bacillus
3. (d) AIDS
4. (c) Anopheles mosquito
5. (d) Entamoeba
These terms describe various types of disease outbreaks and the specific organisms that cause or carry them. Knowing these classifications helps scientists and doctors track how illnesses move through a population.
Teacher's Tip: Remember "Pan" in pandemic means "all," referring to a disease that spreads across the whole world.
Exam Tip: In multiple-choice questions, always write the option letter and the corresponding word for total clarity.

Question B.1:
Answer: (a) F (False). Filariasis is transmitted by the Culex mosquito.
(b) T (True)
(c) F (False). BCG vaccine is used for tuberculosis.
(d) F (False). Louis Pasteur discovered a cure for rabies.
(e) F (False). AIDS is caused by a virus.
(f) T (True)
(g) T (True)
(h) F (False). Chicken pox and hepatitis are viral diseases.
(i) T (True)
(j) F (False). AIDS is caused by HIV virus.
(k) T (True)
(l) F (False). Smallpox has been eradicated from India.
(m) F (False). The disease filariasis is caused by the filarial worm Wuchereria bancrofti.
These statements help distinguish between different pathogens like viruses and bacteria and the specific ways they are treated or transmitted. Understanding which diseases have been eradicated, like smallpox, shows the success of global vaccination efforts.
Teacher's Tip: Link the vaccine "BCG" directly to "Tuberculosis" in your mind to avoid confusion.
Exam Tip: If a statement is False, always provide the corrected statement to ensure you get full marks.

Question B.2:
Answer: AIDS : Acquired Immunodeficiency Syndrome
This full form describes a condition where the body's immune system becomes too weak to fight off common infections. It is acquired during a person's lifetime rather than being inherited from birth.
Teacher's Tip: Break it down: "Immuno" refers to the immune system and "Deficiency" means a lack of strength.
Exam Tip: Spelling is crucial for scientific full forms; practice writing "Immunodeficiency" several times.

Question B.3:
Answer: (a) Viruses
(b) BCG
(c) Lungs
(d) AIDS
(e) Vaccine
(f) Tsetse fly
(g) Virus
(h) Elephantiasis
This list identifies specific causative agents, vaccines, and the physical symptoms of various medical conditions. For instance, elephantiasis is the visible swelling of limbs caused by a parasitic worm infection.
Teacher's Tip: Associate the "Tsetse fly" with "Sleeping Sickness" as it is the primary carrier of that disease.
Exam Tip: Use the specific scientific terms provided in the textbook rather than general or common names.

Question C.1:
Answer: Infection: The transmission of disease from one person to another is called infection.
Pathogen: Disease-causing micro-organism is called a pathogen.
Incubation period: Incubation period is the period between the entry of germs and the appearance of the first symptoms of the disease.
Allergen: An antigenic substance capable of producing immediate hypersensitivity allergy is called an allergen.
These definitions form the basis of understanding how we get sick and how our bodies react to foreign substances. The incubation period is particularly important because a person can be infectious even before they feel ill.
Teacher's Tip: Think of a "Pathogen" as a "Pain-generator" to remember it causes disease.
Exam Tip: When defining "Incubation period," make sure to mention both the "entry of germs" and the "first symptoms."

Question C.2:
Answer: The different ways in which infectious diseases can spread are as follows:
Direct contact: Person to person, animal to person and expected mother to child
Indirect contact: Doorknob, phone, etc.
Droplet transmission: Sneezing, coughing, etc.
Particle transmission: Air particles can transfer infectious diseases
Bites and Stings: Mosquitoes, lice, ticks, etc.
Food Contamination: Food, beverages, etc.
Infectious diseases move through various pathways to find new hosts, making hygiene and sanitation very important. Simple actions like washing hands or covering your mouth when coughing can block many of these routes.
Teacher's Tip: Think of these routes as the "Germ Highway" and handwashing as the "Roadblock."
Exam Tip: If the question asks for a list, use a clear format with each method on a new line.

Question C.3:
Answer: NON-INFECTIOUS DISEASES - CAUSE OF THE DISEASE
Asthma - Allergy
Cataract - Ageing
Beri-Beri - Nutritional deficiency
Cancer - Carcinogens like chemicals, tobacco smoking, pollution etc.
Non-infectious diseases are not passed from person to person but are caused by internal factors or lifestyle choices. For example, Beri-Beri is strictly caused by a lack of specific vitamins in your daily diet.
Teacher's Tip: Remember: Non-infectious means "Not Catchy."
Exam Tip: Match the disease to its primary cause exactly as listed in the textbook table.

Question C.4:
Answer: It is important to know how the germs leave the body of a patient as there are some diseases and infections which are transmitted through air, water or just by direct contact. Therefore, to take precautions and protect others from further infections, it is a must to know how the germs leave the body of an infected person.
Understanding the exit route of a pathogen helps in creating effective barriers to stop the spread of an illness. For example, if we know germs leave through breath, we can use masks to keep the air clean.
Teacher's Tip: Think of this as "Knowing the Enemy's Escape Route" to trap them.
Exam Tip: Mention "precautions" and "protection" as the main reasons for needing this knowledge.

Question C.5:
Answer: Causative germ of AIDS:
HIV (Human immunodeficiency virus)
Transmission of AIDS:
(a) Sexual intercourse
(b) Mother to child transmission
(c) Contaminated blood transfusions
AIDS is caused by a specific virus that attacks the body's defense cells through very specific contact routes. It cannot be spread through casual contact like hugging, shaking hands, or sharing food.
Teacher's Tip: Remember that HIV is the name of the "Virus," and AIDS is the name of the "Condition" it causes.
Exam Tip: List all three modes of transmission to provide a complete answer for full marks.

Question D.1:
Answer: (a) BCG: It is a vaccine which is effective against the bacterial disease tuberculosis (TB). It develops immunity to TB. BCG stands for Bacillus Calmette Guerin.
(b) Incubation period: It is the period between the entry of germs and the appearance of the first symptoms of the disease. Example: Incubation period of pneumonia is 1-3 days.
(c) Chicken pox: It is a viral disease caused by the Herpes Varicella zoster virus. It spreads rapidly by close contact with an infected person. A live attenuated vaccine containing Varicella is administered to children of 12-18 months for active immunisation.
(d) Hepatitis A: It is a viral disease caused by Hepatitis A virus which results in inflammation of the liver. It has an incubation period of 14-45 days. It is mainly transmitted through contaminated food and water.
These notes explain how vaccines work to build immunity and provide details on common viral infections. They emphasize that different diseases have different timeframes for showing symptoms and different ways of spreading.
Teacher's Tip: For "Hepatitis A," remember "A" for "Alimentary" (Digestive) because it spreads through food and water.
Exam Tip: Always include an example (like the 1-3 days for pneumonia) when explaining the incubation period.

Question D.2:
Answer: Disease - Causative agent - Symptoms - Prevention
Malaria - Protozoan, Plasmodium - Chills, high fever, profuse sweating, severe headache, nausea, vomiting, fatigue and body pain - Destruction of mosquitoes at all stages and avoid mosquito bites by using mosquito nets or repellents
Chicken pox - Virus, Varicella zoster - Highly irritating rashes near the chest and back, gradually spreading to the arms, legs, face and head - Active immunisation by administering live attenuated vaccine containing Varicella
Tuberculosis - Bacterium, Mycobacterium\ tuberculosis - Persistent cough, afternoon fever, bloody mucus, loss of weight, fatigue and chest pain - BCG vaccination and isolation of the patient
This table compares three major diseases by looking at what causes them, how they make us feel, and how to stop them. It shows that prevention can involve both physical barriers like mosquito nets and medical solutions like vaccines.
Teacher's Tip: Use the keyword "Isolation" specifically for Tuberculosis to remember how to stop it from spreading through the air.
Exam Tip: When writing symptoms, list at least three distinct ones to demonstrate a thorough understanding of the disease.