Human Population and Health Disorders

Human population growth has several serious consequences:

1. Depletion of natural resources — The rapid increase in human numbers puts heavy pressure on land, water, forests, fossil fuels and minerals. Forests are cleared for settlement and agriculture, groundwater is over-extracted, and fossil fuels are consumed faster than they are formed.

2. Environmental pollution and degradation — More people mean more waste, sewage, industrial effluents, and vehicular and industrial emissions. This causes air and water pollution, soil degradation, and contributes to global warming and climate change.

3. Food and resource scarcity — Although food production has increased, it has not kept pace with population growth in many regions, leading to malnutrition, hunger and food insecurity, especially in developing countries.

4. Unemployment and poverty — Population growth outpaces the creation of jobs, leading to unemployment, underemployment, low per capita income and widespread poverty.

5. Pressure on health, education and other services — Hospitals, schools, housing, transport and sanitation facilities become inadequate for the growing number of people, reducing the quality of life and increasing disease and mortality.

6. Loss of biodiversity — Expansion of human settlements, agriculture and industries destroys natural habitats, causing extinction of many plant and animal species and disturbing ecological balance.

(a), (c) and (d)

Psychotropic drugs act on the brain and alter mood, thought or behaviour. Opiates (morphine, heroin) are narcotic CNS depressants, mescaline is a hallucinogen, and bhang (cannabis) is psychoactive, so all three are psychotropic. Antihistamines act against allergy and are not primarily psychotropic.

Four respiratory disorders prevalent in the community:

1. Asthma – A chronic allergic condition in which the bronchioles and bronchi become inflamed and narrowed, causing difficulty in breathing, wheezing and coughing. It is triggered by dust, pollen, smoke and cold air.

2. Bronchitis – Inflammation of the bronchi and bronchioles, usually caused by viral or bacterial infection or by cigarette smoke. It is marked by persistent cough with thick sputum and shortness of breath.

3. Tuberculosis (TB) – A bacterial disease caused by Mycobacterium tuberculosis that damages the lungs and produces a long-lasting cough, chest pain, fever and blood in sputum. It spreads through droplets released by an infected person while coughing or sneezing.

4. Pneumonia – An infection of the alveoli caused by bacteria, viruses or fungi, in which the air sacs fill with fluid and pus. It causes fever, chest pain and rapid, difficult breathing.

(Other acceptable answers: emphysema, lung cancer, COVID-19, common cold.)

Methods of prevention:

1. Avoid smoking and exposure to second-hand smoke, and discourage smoking in public places.
2. Keep the home and surroundings dust-free and well ventilated; use masks in dusty or polluted areas and during heavy air pollution.
3. Avoid contact with allergens such as pollen, animal dander and strong fumes; keep asthma patients away from known triggers and use prescribed inhalers regularly.
4. Ensure BCG vaccination of children to prevent tuberculosis, and isolate and treat TB patients under DOTS so that infection does not spread.
5. Maintain good personal hygiene — cover the mouth while coughing or sneezing, wash hands frequently, and avoid crowded places during outbreaks of respiratory infection.
6. Eat a balanced diet rich in vitamins A and C, drink clean water and take regular exercise to keep natural immunity strong.
7. Control air pollution by planting trees, using cleaner fuels and reducing vehicular and industrial smoke.

(b) Immigration

Immigration is the movement of individuals into a population from another area or population, which adds to the population size. (Emigration is the opposite — individuals leaving the population.)

Risk factors responsible for kidney disorders (any two):

1. Diabetes and high blood pressure (hypertension): Persistently high blood sugar and high blood pressure damage the tiny blood vessels (glomerular capillaries) of the nephrons. This is the leading cause of chronic kidney disease, as the filtering units gradually lose their function.

2. Unhealthy diet and inadequate water intake: A diet high in salt, processed food and excess protein increases the solute load on the kidneys and raises blood pressure. Taking too little water concentrates the urine, which favours the formation of kidney stones and urinary infections.

(Other acceptable risk factors: smoking, alcohol consumption, obesity, prolonged use of painkillers such as NSAIDs, repeated urinary tract infections, family history of kidney disease, and exposure to nephrotoxic chemicals or heavy metals.)

Healthy habits to protect the kidneys (any two):

1. Drink plenty of water and eat a balanced, low-salt diet: Taking 2–3 litres of water daily keeps the urine dilute and flushes out wastes, preventing stone formation. A diet low in salt, with controlled protein and plenty of fruits and vegetables, keeps blood pressure and the workload on the kidneys normal.

2. Exercise regularly and avoid self-medication, smoking and alcohol: Regular physical activity maintains healthy body weight and normal blood pressure and blood sugar. Avoiding unnecessary painkillers and other nephrotoxic drugs, and staying away from smoking and alcohol, prevents direct damage to kidney tissue.

(Other acceptable habits: get blood sugar and blood pressure checked regularly, treat urinary infections promptly, and drink boiled or filtered water.)

Motives (why youngsters take drugs)

1. Curiosity and experimentation — adolescence brings a natural urge to try new experiences, and peer pressure pushes them to "fit in" with friends who use drugs.
2. Peer influence and imitation — friends, seniors or idols who use drugs make it seem normal and "cool".
3. Escape from stress — exam failure, family conflict, unemployment, heartbreak or emotional distress drives them to drugs for temporary relief from tension and depression.
4. Pleasure-seeking and false belief — drugs like cocaine, heroin and morphine give a short-lived feeling of euphoria, and youngsters wrongly believe they can stop whenever they wish.
5. Easy availability and curiosity about the forbidden — cheap, easily available drugs near schools and colleges, plus the thrill of doing something prohibited.
6. Family and social factors — broken homes, neglect, lack of parental care, or a family history of drug use.

Preventive measures

1. Education and awareness — health education in schools and colleges about the harmful effects of drug abuse on the nervous system, health, family and society.
2. Parental care and communication — a loving, watchful family environment; parents should guide children, know their friends and address problems early.
3. Avoiding bad company — keeping away from drug-using peers and choosing good friends.
4. Healthy recreation — sports, yoga, music, hobbies and extracurricular activities to channel energy positively and relieve stress.
5. Counselling and rehabilitation — psychological counselling, de-addiction centres and rehabilitation for those already addicted.
6. Legal and administrative control — strict enforcement of laws against drug trafficking, banning sale near educational institutions, and rehabilitation of addicts rather than punishment alone.
7. Public campaigns — mass media, NGOs and government programmes (e.g. awareness campaigns) to build social disapproval of drug use.

Conclusion: The main motivators are curiosity, peer pressure and the desire to escape stress; prevention works best through a combination of education, family support, healthy recreation and strict legal control.

(c) Moderate

Mesolecithal eggs contain a moderate amount of yolk — the frog's egg is a typical example, with yolk concentrated toward the vegetal pole.

(b) Candidiasis

Candidiasis is a fungal infection caused by Candida albicans, which spreads through kissing and sexual contact. Tuberculosis and influenza spread through air droplets, and cholera through contaminated food and water.

J-shaped growth curve

When a species enters a new habitat with plenty of food and space and few predators or diseases, its population grows without any limit for a time. This is exponential growth, and the model is

$\frac{dN}{dt} = rN \qquad\Rightarrow\qquad N_t = N_0 e^{rt}$

where $N_0$ is the starting number, $N_t$ the number after time $t$, $e$ the base of natural logarithms and $r$ the intrinsic rate of natural increase (birth rate minus death rate).

Model of the curve: plot time on the x-axis and population size on the y-axis. The curve rises slowly at first (lag phase), then climbs steeply upward, giving a J shape. It does not level off; growth stops abruptly when a limiting factor such as food, space or disease suddenly acts and the population crashes. Example: a few rabbits or water hyacinth introduced to a new area, or algal blooms.

Two activities to control population growth

1. Family planning and awareness programmes: use of contraceptives, spacing of births and education about small families to lower the birth rate.
2. Raising the age of marriage and educating girls and women: delayed marriage and female education reduce the number of births, together with better employment and health services so that families choose to have fewer children.

(For a wildlife or pest species: controlled culling, introducing predators, or sterilisation programmes.)

Hepatitis-B

Causative agent: Hepatitis-B virus (HBV), a DNA virus of the family Hepadnaviridae.

Mode of infection: It spreads mainly through contact with infected blood and body fluids. Common routes are:

• Transfusion of infected blood or blood products.
• Use of contaminated syringes and needles (e.g. among drug addicts).
• Sexual contact with an infected person.
• From an infected mother to her baby during childbirth (vertical transmission).

Tuberculosis

Causative agent: Mycobacterium tuberculosis, a rod-shaped bacterium (also called Koch's bacillus).

Mode of infection: It spreads through the air by droplet infection. When a patient coughs, sneezes or spits, tiny droplets containing the bacteria are released into the air and inhaled by a healthy person, reaching the lungs. It can also spread by drinking infected milk (bovine TB) or by using articles contaminated by the patient's sputum.

Vaccines used

BCG is given in early infancy and gives protection mainly against severe forms of childhood TB.

(c) Family planning

Family planning (use of contraceptives, spacing of births, and limiting family size) directly controls over population. Early marriage and polygamy increase birth rates, while food supply only supports a larger population.

Hepatitis is an inflammation of the liver, usually caused by viral infection but also by alcohol, drugs, or toxins. It is marked by damage and impaired function of liver cells. The most common types are hepatitis A, B, C, D and E.

Causes

1. Viral infection — Hepatitis A and E spread through contaminated food and water (faecal–oral route); hepatitis B, C and D spread through infected blood, semen, and other body fluids (parenteral route), e.g. transfusion of infected blood, use of unsterilised syringes and needles, and unsafe sexual contact. Hepatitis B and C can also pass from mother to child.
2. Alcohol — chronic heavy drinking causes alcoholic hepatitis.
3. Drugs and toxins — overdose of drugs such as paracetamol, and exposure to chemicals like carbon tetrachloride.
4. Autoimmune and metabolic disorders — the body's own immune system attacks liver cells.

Symptoms

• Loss of appetite, nausea, vomiting, and fatigue
• Yellowing of skin and eyes (jaundice), dark urine, and pale stools
• Pain or tenderness in the upper right abdomen
• Low-grade fever, headache, and joint pain
• In severe cases, liver cirrhosis, liver failure, and even death

Control measures

• Isolate the patient and use separate utensils and linen.
• Disinfect stools and urine properly; maintain strict personal hygiene.
• Screen blood before transfusion and use only disposable or properly sterilised syringes and needles.
• Avoid sharing razors, toothbrushes, and needles.
• Provide a high-carbohydrate, low-fat diet with plenty of fluids and rest.
• Give antiviral drugs and, where needed, supportive treatment for liver failure.

Prevention

• Drink boiled, filtered, or chlorinated water and eat freshly cooked, clean food.
• Wash hands with soap before eating and after using the toilet.
• Improve sanitation and dispose of sewage safely.
• Vaccinate against hepatitis A and B (and hepatitis B for newborns).
• Avoid unprotected sex and multiple sexual partners.
• Avoid alcohol and unnecessary drugs; do not share personal items such as needles and razors.

Health hazards of tobacco smoking

Tobacco smoke contains nicotine, tar, carbon monoxide and many carcinogens.

• Respiratory system: chronic bronchitis, emphysema, reduced lung function and lung cancer.
• Circulatory system: raised blood pressure, atherosclerosis, heart attack and stroke (nicotine narrows blood vessels and CO reduces oxygen carried by haemoglobin).
• Cancers: of the mouth, throat, oesophagus, bladder and pancreas.
• Other effects: stained teeth, gum disease, reduced fertility, low birth weight in babies of smoking mothers, and addiction to nicotine. Passive smokers are also harmed.

Preventive measures

• Awareness campaigns in schools, media and communities about the risks.
• Laws banning smoking in public places and sale to minors, higher tax on tobacco products, and warnings on packs.
• Counselling, nicotine replacement and rehabilitation for those who wish to quit, and support from family and friends.
• Encouraging healthy habits such as sports, yoga and hobbies, and avoiding peer pressure.

(b) Exposure to pollutants

Chronic obstructive pulmonary disease (chronic bronchitis and emphysema) is mainly caused by long exposure to smoke, dust and air pollutants, which damage the airways and alveoli. Caffeine, tranquilizers and narcotics do not cause COPD.

Health disorder: any condition in which the normal structure or function of the body is disturbed, so that a person is not in a state of complete physical, mental and social well-being.

Cardiovascular disorders

• Hypertension (high blood pressure): persistent blood pressure above about 140/90 mm Hg; it strains the heart and damages the brain, heart and kidneys.
• Atherosclerosis: deposits of cholesterol and fat (plaques) on artery walls narrow the lumen and reduce blood flow.
• Coronary artery disease / angina pectoris: narrowing of the coronary arteries gives chest pain due to insufficient blood to heart muscle.
• Heart attack (myocardial infarction): a blocked coronary artery causes death of part of the heart muscle.
• Heart failure: the heart cannot pump enough blood to meet the body's needs.
• Stroke: a blocked or burst blood vessel in the brain cuts off blood supply to brain tissue.

(b) Syncope

Syncope (fainting) is a temporary loss of consciousness due to a sudden fall in blood supply to the brain. Asthma is a respiratory disorder, oedema is fluid accumulation in tissues, and a heart attack is caused by blocked coronary flow to the heart.

(a) Activities with the help of senior students

1. Peer education programme: trained senior students hold small group sessions in junior classes, explaining the harm of tobacco to lungs, heart and finances, and teaching how to refuse a cigarette politely ("assertive refusal" role plays).
2. Awareness campaign: seniors organize a poster, slogan and street-drama competition on a "Smoke-free school" theme, and form a student club that watches for smoking near the school gate and supports classmates who want to quit.

(b) Activities for the school authorities

1. Rules and environment: declare the school and its surroundings a tobacco-free zone, display warning notices and take regular, fair action against sale or use nearby.
2. Guidance and health education: arrange a school counsellor, parent-teacher meetings, and talks by doctors, together with sports, music and other co-curricular activities that keep adolescents busy and give healthy ways to gain acceptance.