Frank Brothers Solutions for ICSE Class 9 Biology Chapter 21 Health Personal And Social

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Answer 1: Hygiene is the science of preserving and promoting good health.
The major aspects of personal hygiene are:
Cleanliness
Physical exercise
Rest and sleep
Healthy habits
Balanced diet
Hygiene involves daily routines that keep our bodies clean and functioning well. By practicing these habits, we can stay energetic and avoid getting sick.
Teacher's Tip: Remember the acronym "C-P-R-H-B" (Cleanliness, Physical, Rest, Habits, Balanced) to recall the five aspects.
Exam Tip: Define hygiene first before listing its aspects to provide a complete answer for full marks.

Answer 2: The healthy habits one should develop are:
1. Eating a balanced diet. A diet in adequate quantity and well-balanced, protects a person from several diseases and keeps him fit to work with efficiency.
2. Getting sound sleep by waking up and sleeping at the regular times
3. Avoiding smoking and drinking of alcohol
4. Having proper control over emotions like anger and hatred.
Developing these habits helps in building a strong immune system and a focused mind. Consistency in these routines ensures long-term physical and mental well-being.
Teacher's Tip: Think of your body like a machine; it needs the right fuel (diet) and enough downtime (sleep) to work perfectly.
Exam Tip: Use a numbered list for habits to make your answer clear and easy for the examiner to read.

Answer 3: Maintaining personal cleanliness prevents us from getting infected with germs, thereby keeping us healthy.
Example - Our hands handle variety of things which may contain pathogens left by other infected persons. If these germs are not removed, they may enter our body and cause diseases. Hence it is important to wash hands with soap at regular intervals and especially before eating and after going to toilet.
Cleanliness acts as a primary barrier against bacteria and viruses that we encounter in daily life. Regular washing removes these microscopic threats before they can cause any harm.
Teacher's Tip: Use the "Hand-Wash Song" rule - wash your hands for at least 20 seconds, about the time it takes to sing "Happy Birthday" twice.
Exam Tip: Always include an example, like hand washing, to demonstrate your understanding of the concept.

Answer 4: (a) Flies transmit germs of many diseases and hence they should not be allowed to sit on edible things to prevent the spread of diseases.
(b) Our hands handle variety of things which may contain pathogens left by other infected persons. If these germs are not removed, they may enter our body and cause diseases. Hence it is important to wash hands with soap before eating to prevent spread of diseases.
(c) Clothes of another person may contain germs of various diseases left by that person. Wearing those clothes could cause the transmission of the disease to us. Hence it is not advisable to wear other people’s clothes.
(d) Nose has hair and mucus to filter the air coming through it while breathing. This traps dust, germs and other foreign particles and prevents them from reaching the lungs. Hence we should always breathe through nose.
(e) Flies and cockroaches transmit germs of many diseases. Hence they should be kept away from our kitchens so as to prevent spread of diseases.
These explanations show how diseases spread through common vectors like flies and physical contact. Understanding these risks helps us adopt better preventive measures in our daily environment.
Teacher's Tip: Think of your nose as a "natural air filter" for your body.
Exam Tip: For "Give Reason" questions, clearly state the cause (germs) and the effect (disease) for each point.

Answer 5: 1. Cockroaches. They can easily be controlled by spraying D.D.T., malathione or commercially available sprays like baygon etc.
2. Flies. They can be controlled in following ways:
Removing human faeces, stable manure and garbage at regular intervals and disposing them off
Killing adult flies by using fly swatters, spraying D.D.T, chlordane etc. or some other chemicals like pyrethrum, B.H.C etc.
Controlling pests requires both chemical treatments and maintaining a clean environment to remove their breeding grounds. Eliminating garbage is the most effective way to keep these insects away from our homes.
Teacher's Tip: Remember: No food/waste = No pests. Cleanliness is the best pesticide.
Exam Tip: Mention at least one chemical name like D.D.T. to show specific scientific knowledge.

Answer 6: If human excreta are not properly disposed off, the bacteria inhabiting the gut may reach open water bodies and make it contaminated. Such contaminated water when consumed can cause serious diseases, even fatal ones. Hence it is highly important to properly dispose human excreta.
Improper waste management leads to the pollution of vital resources like drinking water. This creates a cycle where diseases are easily spread throughout a community.
Teacher's Tip: Think of "Gut to Water" - bacteria from the body should never meet our drinking supply.
Exam Tip: Highlight the word "contaminated" as it is a key term in environmental health.

Answer 7: (a) Plague
(b) Cholera and dysentery
(c) Zinc phosphate
(d) Gastroenteritis, dysentery
These answers identify specific diseases and substances related to health and pest control. Knowing these terms helps in identifying health risks and their solutions quickly.
Teacher's Tip: Associate "Rat" with "Plague" and "Zinc" with "Raticide" to remember these pairs.
Exam Tip: For one-word answers, double-check your spelling to ensure no marks are lost.

Answer 8: The common mosquitoes are Anopheles, Culex and Aedes. Diseases transmitted by these mosquitoes are malaria, yellow fever, dengue, filariasis, encephalitis and dermatobia.
Mosquitoes act as carriers for many dangerous pathogens by biting infected individuals and passing the germs to others. Preventing mosquito bites is a key step in global disease prevention.
Teacher's Tip: Remember "Triple A" for mosquito names: Anopheles, Aedes, and (C)ulex.
Exam Tip: Be sure to match the mosquito type to the correct disease if asked specifically in the exam.

Answer 9: Using one’s own towel and comb prevents spread of diseases. Towel used by another person may contain germs of diseases if the person is infected. This may get transmitted to us. Also using comb of another person may transmit lice and other organisms present on another person’s head to ours.
Personal items often carry skin cells, oils, and microbes that are unique to the owner. Sharing these items bypasses the natural protection of our skin and directly introduces foreign germs.
Teacher's Tip: Think of towels and combs like toothbrushes - they are strictly for personal use only!
Exam Tip: Use the term "transmission" to describe how germs move from one person to another.

Answer 10: Three ways of controlling mosquitoes are:
1. Mosquitoes can be controlled by spraying liquid insecticides like flit or D.D.T.
2. The breeding places of mosquitoes are sprayed with petroleum oils. The oil-film formed on the surface of water is toxic to the mosquito larvae.
3. Mosquito-repellents like mosquito cream, citronella, odomos and indalone help to keep mosquitoes away and protect us from getting bitten.
Controlling the population of mosquitoes involves attacking them at different life stages, such as larvae in water and adults in the air. Protective creams provide a personal shield against those that survive chemical treatments.
Teacher's Tip: Remember the three levels: Spraying (adults), Oiling (larvae), and Repelling (personal protection).
Exam Tip: Mentioning the "oil-film" method is important because it specifically targets the breeding stage.

Answer 11: Raticide - Insecticide
Culex - Encephalitis
Rat flea - Plague
DDT - Contamination
Housefly - Filaria
Cockroach - Gastroenteritis
Cholera - Vibrio
Giardia - Protozoan
Faeces - Cholera
This list matches common pests and substances with the diseases or conditions they are associated with. It serves as a quick reference for understanding environmental health risks.
Teacher's Tip: Link "Vibrio" directly to "Cholera" as it is the specific name of the bacteria.
Exam Tip: In matching questions, read both columns entirely before drawing lines or writing pairs.

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Answer 12: Contamination of water is the addition of any substance, natural or synthetic that enters the water making it unfit for human use or that of animals too.
Water contamination occurs when pollutants change the chemical or biological makeup of water. This makes it dangerous to drink, wash with, or use for farming.
Teacher's Tip: Contamination = Water + Unwanted Stuff.
Exam Tip: Define "unfit for use" to show you understand the impact of contamination.

Answer 13: Water is contaminated by microbes when animal or human faecal waste or urine is disposed off in near or in water bodies.
Microbes from waste products can quickly multiply in water sources used by communities. This often happens due to poor sanitation systems or open drainage near rivers and lakes.
Teacher's Tip: "Near or in" - even waste placed near water can wash into it during rain.
Exam Tip: Use the term "microbes" to refer to the tiny organisms that cause disease.

Answer 14: No. If contaminated water is consumed, it can cause serious diseases, even fatal ones.
Drinking impure water introduces harmful pathogens directly into the digestive system. This can lead to severe dehydration and other life-threatening symptoms.
Teacher's Tip: Always boil or filter water if you are unsure about its purity.
Exam Tip: A simple "No" is not enough; always explain the consequences (serious/fatal diseases).

Answer 15: (a) Cholera - It is caused by Vibrio cholera. It is caused by consuming contaminated water or food. The patient passes frequent white watery stools and has repeated vomiting. Several preventive measures can be taken to prevent spread of cholera like anticipatory inoculations, consuming boiled water, health education, isolation of infected person etc.
(b) Typhoid - It is caused by the bacterium Salmonella typhi I . Infection occurs through consuming of contaminated food and water. Symptoms include headache, high fever, tender and distended abdomen, diarrhea with water green stools and eruption of rash on body of patient. Prevention methods include proper sanitation and disposal of faecal matter and vaccination.
(c) Amoebiasis - It is caused by a protozoa, Entamoeba Histolytica. It is commonly spread by water contaminated by faeces or from food served by contaminated hands. Symptoms include - lower abdominal pain, diarrhoea and later develop dysentery and fever. Prevention methods include proper sanitation and drinking clean water.
(d) Giardiasis - It is caused by the protozoan flagellate Giardia intestinalis, which lives in upper parts of human intestine. It perches on living cells of intestinal wall with adhesive discs, absorbing nutrition from food passing by, growing and multiplying. They interfere with digestion, causing pain, diarrhea, headache and fever. Preventive measures include consuming boiled water, maintaining hygiene and sanitation as well as practicing personal hygiene.
(e) Hepatitis - It is caused by hepatitis virus. There are six varieties hepatitis A, B, C, D, E and F. Symptoms include enlarged liver in early stage, fever, anorexia, vomiting, epigastric, discomfort, pain in muscles and joints. Later on liver becomes smaller and yellowish or greenish. Some forms of hepatitis spreads through contaminated water and food whereas others spread through body fluids.
Each of these diseases targets the body differently but most are spread through poor hygiene and contaminated resources. Knowing the specific symptoms helps in early detection and treatment.
Teacher's Tip: Notice that "Boiled Water" and "Sanitation" are common prevention methods for almost all of these.
Exam Tip: When describing a disease, always include the causative agent (e.g., bacterium, virus, or protozoa).

Answer 16:
(i) (d) All the above
(ii) (c) Health for all
(iii) (b) Gambusia
These selections identify key concepts in public health and biological control. For example, Gambusia fish are used to eat mosquito larvae to naturally reduce their numbers.
Teacher's Tip: Gambusia is often called the "Mosquito-fish" because it loves to eat larvae.
Exam Tip: Read all options in multiple-choice questions before picking "All of the above."