Chapter 5 Analysis Of Natural Phenomena Long Answer Type Questions
Question 1. Describe in short how lightning occurs during a thunderstorm.
Answer:
Thunderstorm
A thunderstorm is a type of storm characterized by the presence of lightning and thunder accompanied by strong winds and heavy rain.
Thunderstorms result from the rapid upward movement of warm moist air. As the warm, moist air moves upward (called updraft of air), it cools, condenses, and forms cumulonimbus clouds that can gain heights of 12 km or more.
The upward movement of air in a storm cloud has been measured as more than 80 kilometres per hour. ‘ As the moist air reaches its dew point at the upper atmosphere, it converts to water droplets and tiny ice particles.
These particles begin to fall a long way through clouds and collide with other particles and thus become larger. Downdrafts of air are created by the falling water droplets because they don’t just drag other droplets down with them as they fall, they drag cooler air with them as well. The combined warm updraft and cool downdraft create a storm cell.
Read And Learn More WBBSE Solutions For Class 8 School Science Long Answer Type Questions
Question 2. Write about the characteristics of epidemic diseases.
Answer:
Characteristics Of Epidemic Diseases
- All epidemics have the following common characteristics:
- An unexpected number of cases of a particular disease occur at a particular point in time affecting a large segment of the population.
- Generally confined to a definite population or geographical area.
- Usually have a common source of infection,
- Epidemics generally tend to follow a pattern and repeat periodically when the conditions are favourable again.
Types Of Epidemic Diseases
Epidemics generally follow a pattern depending on the geographical and environmental conditions, the distribution and characteristics of the host population, and their cultural behaviour.
If there is no intervention or change in these conditions, those epidemics tend to repeat themselves. Therefore, knowledge about various types of epidemics and the conditions under which they occur can help in managing them.
Question 3. Write briefly about cholera.
Answer:
Cholera
Cholera is an acute intestinal infection caused by the
ingestion of food or water contaminated with the bacterium Vibrio cholera.
It has a short incubation period and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given.
Vomiting also occurs in most patients. Most persons infected with V. cholerae do not become ill, although the bacterium is present in their faeces for 7-14 days.
When illness does occur, about 80-90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhoea.
Less than 20% of ill persons develop typical cholera with signs of moderate or severe dehydration.
Question 4. Write the cause and symptoms of kala-azar.
Answer:
Kala-azar
Kala-azar is the second largest parasitic killer in the world – only Malaria is more deadly. It is also known as Dumdum fever.
Kala-azar is caused by bites from sandflies – which carry the Leishmania donovani parasite, a type of protozoa, responsible for the disease.
If blood containing Leishmania donovani parasites is drawn from an animal or human, the next person to receive a bite will then become infected.
Initially, Leishmania parasites cause skin sores or ulcers at the site of sand fly bites. If the disease progresses, it attacks the immune system.
Kala-azar presents after two to eight months, with more generalised symptoms including prolonged fever and weakness. Indian scientist Upendranath Brahmachari invented the medicine of Kala-azar.
Question 5. Write about an epidemic due to a non-infectious disease.
Answer:
Epidemic due to a non-infectious disease
Epidemics of non-infectious disease are often caused by exposure to industrial products, intermediates or byproducts, either in the workplace or as a result of the contamination of a wider environment.
The Global Status Report on Non-communicable Diseases 2010 is the first report on the worldwide epidemic of cardiovascular diseases, cancer, diabetes and chronic respiratory diseases, along with their risk factors and determinants.
Non-communicable diseases killed tens of millions of people in 2008, and a large proportion of these deaths occurred before the age of 60, so during the most productive period of life. The magnitude of these diseases continues to rise, especially in low- and middle-income countries.
Question 6. How can a common disease turn into an epidemic? What do you mean by zoonotic disease?
Answer:
The epidemic is due to the sudden rise of cases usually resulting from a new infectious agent or a change in an existing agent,
For example:
- An agent moving between host populations, for example, moving from animals to humans (zoonotic disease).
- A genetic change or mutation occurs in the infectious agent, eg. bacteria, viruses, fungi etc.
- Introduction of the new pathogen to a host population
- Initially, scattered or isolated incidences of small clusters of the disease occur in humans
- In the next step human to human transmission occurs at a rate that causes outbreaks in communities.
Zoonotic diseases are caused by germs that spread between animals and people. Examples include Covid-19, Plague, Rabies, Zoonotic influenza etc. Zoonotic diseases are caused by germs that spread between animals and people. Examples include Covid-19, Plague, Rabies, Zoonotic influenza etc.
Question 7. Name the causative agents of cholera and tuberculosis.
Answer:
Some Common Infectious Diseases Induced Epidemics
1. Cholera
Cholera is an acute intestinal infection caused by the
ingestion of food or water contaminated with the bacterium Vibrio cholera.
It has a short incubation period and produces an enterotoxin that causes a copious, painless, watery diarrhoea that can quickly lead to severe dehydration and death if treatment is not promptly given.
Vomiting also occurs in most patients. Most persons infected with V. cholerae do not become ill, although the bacterium is present in their faeces for 7-14 days.
When illness does occur, about 80-90% of episodes are of mild or moderate severity and are difficult to distinguish clinically from other types of acute diarrhoea.
Less than 20% of ill persons develop typical cholera with signs of moderate or severe dehydration.
2. Malaria
Malaria is caused by a protozoan parasite called Plasmodium, which is transmitted via the bites of infected female Anopheles mosquitoes.
In the human body, the parasites multiply in the liver and then infect red blood cells. Symptoms of malaria include fever, headache, and vomiting, and usually appear between 10 and 15 days after the mosquito bite.
- If not treated, malaria can quickly become life-threatening by disrupting the blood supply to vital organs.
- Key interventions to control malaria include:
- prompt and effective treatment with artemisinin-based combination therapies,
- use of insecticidal nets and
- indoor spraying with insecticide.
3. Dengue
Dengue is transmitted by the bite of a mosquito. A type of mosquito called Aedes Egypt carries the germ of this disease. It is a febrile illness that affects infants, young children and adults with symptoms appearing 3-14 days after the infective bite.
Dengue is not transmitted directly from person to person and symptoms range from mild fever to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain, rash and lowering of platelet count to an alarming level.
It causes the oozing of blood in the skin due to the lowering of WBC. There is no vaccine or any specific medicine to treat dengue. People who have dengue fever should take rest, drink plenty of fluids and reduce the fever using paracetamol or see a doctor. It reduces the immunity power.
4. Plague
Plague is a bacterial disease, caused by Yersinia pestis, which primarily affects wild rodents such as rats. It is spread from one rodent to another by fleas (a type of insect).
Humans bitten by an infected flea usually develop a bubonic form of plague, which is characterized by a bubo, i.e. a swelling of the lymph node draining the flea bite site.
A type of fly called Xenopsylla cheopis carries the bacteria from the body of a rat afflicted with plague. If the bacteria reach the lungs, the patient develops pneumonia (pneumonic plague), which is then transmissible from person to person through infected droplets spread by coughing.
Initial symptoms of bubonic plague appear 7-10 days after infection. In 1987, Waldemar Haffkine invented the vaccine for the plague in Mumbai.
5. Smallpox
Smallpox is a disease caused by the Variola major virus. Some experts say that over the centuries it has killed more people than all other infectious diseases combined. Worldwide immunization stopped the spread of smallpox three decades ago The last case was reported in 1977.
Smallpox spreads very easily from person to person. Symptoms are flu-like. They include high fever, fatigue, headache, backache, and a rash with flat red sores.
There is no treatment. Fluids and medicines for pain or fever can help control symptoms. Most people recover, but some can die. Those who do recover may have severe scars. Edward Jenner, in 1976 used the cow-Pox virus in the human body to develop resistance against smallpox.
6. Kala-azar
Kala-azar is the second largest parasitic killer in the world – only Malaria is more deadly. It is also known as Dumdum fever.
Kala-azar is caused by bites from sandflies – which carry the Leishmania donovani parasite, a type of protozoa, responsible for the disease.
If blood containing Leishmania donovani parasites is drawn from an animal or human, the next person to receive a bite will then become infected.
Initially, Leishmania parasites cause skin sores or ulcers at the site of sand fly bites. If the disease progresses, it attacks the immune system.
Kala-azar presents after two to eight months, with more generalised symptoms including prolonged fever and weakness. Indian scientist Upendranath Brahmachari invented the medicine of Kala-azar.
7. Diarrhoea
Diarrhoea is the passage of loose or liquid stools 3 or more times per day, or more frequently than is normal for the individual.
Diarrhoea means ‘to flow/ It is usually a symptom of gastrointestinal infection, which can be caused by a variety of bacterial, viral and parasitic organisms.
Infection is spread through contaminated food or drinking water, or from person to person as a result of poor hygiene.
Severe diarrhoea leads to fluid loss, and may be life-threatening, particularly in young children and people who are malnourished or have impaired immunity. A quick intake of ORS (Oral Rehydration Solution) is an effective remedy for diarrhoea.
8. Tuberculosis
Tuberculosis, or TB, is an infectious bacterial disease caused by Mycobacterium tuberculosis, which most commonly affects the lungs.
It is transmitted from person to person via droplets from the throat and lungs of people with active respiratory disease.
In healthy people, infection with Mycobacterium tuberculosis often causes no symptoms, since the person’s immune system acts to “wall off” the bacteria.
The symptoms of active TB of the lung are coughing, sometimes with sputum or blood, chest pains, weakness, weight loss, fever and night sweats. It is possible to control the disease by proper treatment through DOTS or Directly Observed Treatment, a short course.
9. Hepatitis
Hepatitis is an inflammation of the liver, most commonly caused by a viral infection. There are five main hepatitis viruses, referred to as types A, B, C, D and E.
These five types are of greatest concern because of the burden of illness and death they cause and the potential for outbreaks and epidemic spread.
In particular, types B and C lead to chronic disease in hundreds of millions of people and together, are the most common cause of liver cirrhosis and cancer.
Hepatitis A and E are typically caused by the ingestion of contaminated food or water. Hepatitis B, C and D usually occur as a result of contact with infected body fluids.
Common modes of transmission for these viruses include receipt of contaminated blood or blood products, invasive medical procedures using contaminated equipment and hepatitis B transmission from mother to baby at birth, from family member to child, and also by sexual contact.
Acute infection may occur with limited or no symptoms or may include symptoms such as jaundice (yellowing of the skin and eyes), dark urine, extreme fatigue, nausea, vomiting and abdominal pain.
10. Influenza/Flu
Influenza is a viral infection that affects mainly the nose, throat, bronchi and occasionally, lungs. Infection usually lasts for about a week and is characterized by sudden onset of high fever, aching muscles, headache and severe malaise, non-productive cough, sore throat and rhinitis.
The virus is transmitted easily from person to person via droplets and small particles produced when infected people cough or sneeze.
Influenza tends to spread rapidly in seasonal epidemics. Most infected people recover within one to two weeks without requiring medical treatment.
However, in the very young, the elderly and those with other serious medical conditions, the infection can lead to severe complications of the underlying condition, pneumonia and death.
11. AIDS
The Human Immunodeficiency Virus (HIV) is a retrovirus that infects cells of the immune system, destroying or impairing their function.
As the infection progresses, the immune system becomes weaker, and the person becomes more susceptible to infections. The most advanced stage of HIV infection is Acquired Immuno Deficiency 9/ndrome (AIDS).
It can take 10-15 years for an HIV-infected person to develop AIDS; antiretroviral drugs can slow down the process even further.
HIV is transmitted through unprotected sexual relations, transfusion of contaminated blood, sharing of contaminated needles and between a mother and her infant during pregnancy, childbirth and breastfeeding.
12. COVID-2019
Coronaviruses are a large family of viruses that cause illnesses ranging from the common cold to Middle East Respiratory Syndrome (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS- CoV).
A novel coronavirus (nCoV) is a new strain that has not been previously identified in humans. Coronaviruses are zoonotic. SARS-CoV was transmitted from civet cats to humans and MERS- CoV from dromedary camels to humans with infected body fluids.
Common modes of transmission for these viruses include receipt of contaminated blood or blood products, invasive medical procedures using contaminated equipment and hepatitis B transmission from mother to baby at birth, from family member to child, and also by sexual contact.
Acute infection may occur with limited or no Common signs of infections including respiratory symptoms, fever, cough, shortness of breath and breathing difficulties.
In severe cases, the infection can cause pneumonia, severe acute respiratory syndromes, kidney failure and death. Standard recommendations to prevent infection spread include regular hand washing, covering mouth and nose when coughing and sneezing, avoiding close contact with people or social gatherings etc.
Epidemic due to a non-infectious disease
Epidemics of non-infectious disease are often caused by exposure to industrial products, intermediates or byproducts, either in the workplace or as a result of the contamination of a wider environment.
The Global Status Report on Non-communicable Diseases 2010 is the first report on the worldwide epidemic of cardiovascular diseases, cancer, diabetes and chronic respiratory diseases, along with their risk factors and determinants.
Non-communicable diseases killed tens of millions of people in 2008, and a large proportion of these deaths occurred before the age of 60, so during the most productive period of life. The magnitude of these diseases continues to rise, especially in low- and middle-income countries.