Ncert Solutions for Class 12 Biology Chapter 7 Human Health and Disease

Human Health and Disease ncert solutions: Class 12th biology chapter 7 ncert solutions

Textbook	NCERT
Class	Class 12
Subject	Biology
Chapter	Chapter 7
Chapter Name	Human Health and Disease class 12 ncert solutions
Category	Ncert Solutions
Medium	English

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Question 1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?

Solution 1: Here are the public health measures that can be suggested as safeguards against infectious diseases:

1. Vaccination: Promote widespread immunization programs to prevent diseases such as measles, polio, and influenza.
2. Hygiene Education: Educate the public on proper handwashing, sanitation, and personal hygiene.
3. Quarantine and Isolation: Implement quarantine measures for exposed individuals and isolation for infected patients to prevent the spread of infectious agents.
4. Surveillance and Early Detection: Strengthen disease surveillance systems for early detection and response to outbreaks.
5. Contact Tracing: Identify and monitor individuals who have come into contact with infected persons to break transmission chains.
6. Vector Control: Control and eliminate vectors like mosquitoes that spread diseases such as malaria and dengue.
7. Public Health Campaigns: Conduct awareness campaigns about preventive measures, such as avoiding close contact with sick people or wearing masks.
8. Nutrition and Immunity Support: Promote healthy diets and nutrition programs to strengthen immune systems.
9. Travel Restrictions: Implement travel advisories or restrictions during outbreaks to prevent the international spread of diseases.
10. Health System Strengthening: Improve healthcare infrastructure and ensure adequate resources for timely treatment and outbreak response.

Question 2: In which way has the study of biology helped us to control infectious diseases?

Solution 2: The study of biology has helped control infectious diseases by enabling the development of vaccines, antibiotics, and antiviral treatments. It has provided insights into how pathogens spread, infect, and interact with the immune system, allowing for improved prevention, diagnosis, and treatment strategies. Understanding microbial biology has also led to better sanitation, hygiene practices, and disease surveillance systems, all of which help reduce the spread of infectious diseases.

Vaccination programmes against several infectious diseases such as small pox, chicken pox, tuberculosis, etc. have helped eradicate these diseases. Biotechnology has helped in the preparation of newer and safer drugs and vaccines. Antibiotics have also played an important role in treating infectious diseases. 

Question 3: How does the transmission of each of the following diseases take place?
(a) Amoebiasis (b) Malaria (c) Ascariasis (d) Pneumonia

Solution 3:

(a) Amoebiasis (Amoebic Dysentery)

Cause: Entamoeba histolytica (a protozoan parasite)
Transmission: Amoebiasis is transmitted through the fecal-oral route. It typically spreads by consuming contaminated food or water that contains cysts of the parasite. Poor sanitation and hygiene practices, such as not washing hands after using the toilet or eating contaminated food, contribute to its spread.

(b) Malaria

Cause: Plasmodium species (a protozoan parasite)
Transmission: Malaria is transmitted through the bite of an infected female Anopheles mosquito. When the mosquito bites an infected person, it picks up the Plasmodium parasites from their blood. These parasites develop in the mosquito, and when it bites another person, the parasites are transmitted, causing malaria.

(c) Ascariasis

Cause: Ascaris lumbricoides (a parasitic roundworm)
Transmission: Ascariasis spreads through the fecal-oral route. People get infected by ingesting food or water contaminated with Ascaris eggs from human feces. Once inside the host, the eggs hatch into larvae in the intestines, where they mature and cause infection.

(d) Pneumonia

Cause: Various bacteria, viruses, or fungi (e.g., Streptococcus pneumoniae, Haemophilus influenzae, etc.)
Transmission: Pneumonia is transmitted through respiratory droplets from an infected person. When an infected person coughs, sneezes, or talks, they release droplets containing the pathogen into the air. These droplets can be inhaled by others, leading to infection, particularly in those with weakened immune systems or pre-existing health conditions.

Question 4: What measure would you take to prevent water-borne diseases?

Solution 4: Water borne diseases can be prevented by –

1. Ensure Safe Drinking Water: Use water purification methods such as boiling, filtration, or chemical treatment (e.g., chlorine) to kill pathogens.
2. Improve Sanitation: Promote proper waste disposal and sanitation facilities to prevent fecal contamination of water sources.
3. Hygiene Practices: Encourage regular handwashing with soap, especially before eating and after using the toilet.
4. Educate Communities: Raise awareness about the importance of clean water and hygiene to prevent disease transmission.
5. Regular Testing: Monitor and test water quality regularly for contaminants and pathogens to ensure it is safe for consumption.
6. Protect Water Sources: Implement measures to safeguard rivers, lakes, and groundwater from pollution and contamination.

Question 5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.

Solution 5: In the context of DNA vaccines, ‘a suitable gene’ refers to a specific segment of genetic material that encodes for an antigen, which is a substance that can provoke an immune response. This gene is chosen because it corresponds to a protein found on the surface of a pathogen, such as a virus or bacteria.

When this gene is introduced into the body through a DNA vaccine, it instructs cells to produce the antigen, thereby training the immune system to recognize and combat the actual pathogen if encountered in the future. A suitable gene must be effective in eliciting a strong immune response while being safe and non-harmful to the host.

Question 6: Name the primary and secondary lymphoid organs.

Solution 6: The primary lymphoid organs are the sites where lymphocytes (a type of white blood cell) are produced and mature. The main primary lymphoid organs are the bone marrow and the thymus. In the bone marrow, both B cells and T cells are generated, while T cells migrate to the thymus to mature.

The secondary lymphoid organs are where lymphocytes become activated and proliferate in response to pathogens. Key secondary lymphoid organs include the lymph nodes, spleen, and mucosa-associated lymphoid tissues (MALT), such as the tonsils and Peyer’s patches in the intestines. These organs play a crucial role in the immune response by facilitating interactions between lymphocytes and antigens.

Question 7: The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form:
(a) MALT (b) CMI (c) AIDS (d) NACO (e) HIV

Solution 7: The expansion is as follows:

(a) MALT – Mucosa-Associated Lymphoid Tissue
(b) CMI – Cell-Mediated Immunity
(c) AIDS – Acquired Immunodeficiency Syndrome
(d) NACO – National AIDS Control Organisation
(e) HIV – Human Immunodeficiency Virus

Question 8: Differentiate the following and give examples of each:
(a) Innate and acquired immunity (b) Active and passive immunity

Solution 8: The differences are as follows:

(a) Innate Immunity vs. Acquired Immunity

Innate Immunity	Acquired Immunity
Definition: Innate immunity is the body’s first line of defense, providing immediate but non-specific protection against pathogens.	Definition: Acquired immunity, also known as adaptive immunity, develops more slowly and provides specific protection against particular pathogens after exposure.
Characteristics: It is present at birth and includes physical barriers (like skin and mucous membranes), inflammatory responses, and immune cells (such as macrophages and neutrophils).	Characteristics: It involves the activation of lymphocytes (B cells and T cells) and is characterized by memory, allowing for a faster and stronger response upon re-exposure to the same pathogen.
Examples: Physical barriers (skin), inflammatory responses, phagocytic cells (like macrophages).	Examples: Immunity developed after vaccination (e.g., measles vaccine) or after recovering from an infection (e.g., immunity after chickenpox).

(b) Active Immunity vs. Passive Immunity

Active Immunity	Passive Immunity
Definition: Active immunity occurs when the immune system produces antibodies in response to exposure to an antigen, either through infection or vaccination.	Definition: Passive immunity involves the transfer of antibodies from one individual to another, providing immediate but temporary protection without the recipient’s immune system being actively involved.
Characteristics: It is usually long-lasting (sometimes lifelong) because the immune system retains a memory of the pathogen.	Characteristics: It provides immediate but short-term protection (typically lasting a few weeks to months) since no memory cells are formed.
Examples: Immunity gained from natural infection (e.g., recovering from flu) or through vaccination (e.g., tetanus vaccine).	Examples: Maternal antibodies transferred to a baby through the placenta or breast milk, or antibodies received through intravenous immunoglobulin (IVIG) therapy.

Question 9: Draw a well-labelled diagram of an antibody molecule.

Solution 9: The diagram is as follows:

Question 10: What are the various routes by which transmission of human immunodeficiency virus takes place?

Solution 10: The various routes by which transmission of the human immunodeficiency virus (HIV) takes place are as follows:

• Unprotected sexual contact with an infected person.
• Organ transplantation from an infected person
• Transfusion of contaminated blood products and blood
• Sharing infected needles and syringes.
• From an infected mother to a child through the placenta.

Question 11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?

Solution 11: Upon managing to enter the body, this virus enters into macrophages, where the RNA genome of the virus duplicates for the formation of viral DNA by the action of the reverse transcriptase enzyme. The viral DNA is then incorporated into the DNA of the cells of the host, which targets the infected cells to synthesize virus particles. The macrophages continue to produce the virus, serving as an HIV factory.

On the other hand, HIV enters the helper T-lymphocytes, replicating and producing progeny viruses, which when released in the blood, target other helper T-lymphocytes, which is reiterated, causing a progressive decrease in the count of helper T-lymphocytes in the patient’s body. In the long run, there is a significant decline in the count of helper T-lymphocytes resulting in the weakening of the defence mechanism of the body. This is referred to as acquired immunodeficiency.

Question 12: How is a cancerous cell different from a normal cell?

Solution 12: Cancerous cells differ from normal cells in several key ways:

Uncontrolled Growth:

• Cancerous Cells: They divide uncontrollably, leading to tumors. They can bypass normal regulatory mechanisms that limit cell division.
• Normal Cells: They grow and divide in a controlled manner, responding to signals that regulate the cell cycle.

Loss of Apoptosis:

• Cancerous Cells: They often evade programmed cell death (apoptosis), allowing them to survive longer than they should.
• Normal Cells: They undergo apoptosis when damaged or no longer needed, preventing the accumulation of abnormal cells.

Genetic Mutations:

• Cancerous Cells: They typically contain multiple mutations in their DNA that contribute to their aggressive growth and survival. These mutations can affect oncogenes (promote cell growth) and tumor suppressor genes (inhibit growth).
• Normal Cells: They maintain stable genetic integrity, with mechanisms in place to repair DNA damage.

Altered Metabolism:

• Cancerous Cells: They often exhibit altered metabolism, such as the Warburg effect, where they preferentially use glycolysis for energy production even in the presence of oxygen (aerobic glycolysis).
• Normal Cells: They use oxidative phosphorylation for energy when oxygen is available, which is more efficient.

Abnormal Cell Structure:

• Cancerous Cells: They may have an irregular shape, larger nuclei, and abnormal chromosome numbers (aneuploidy). The cytoskeleton may also be disorganized.
• Normal Cells: They have a uniform structure, regular shape, and stable nuclear characteristics.

Invasion and Metastasis:

• Cancerous Cells: They can invade surrounding tissues and spread to other parts of the body (metastasis).
• Normal Cells: They typically adhere to their original location and do not invade other tissues.

Immune Evasion:

• Cancerous Cells: They can develop mechanisms to evade the immune system, allowing them to grow without being detected.
• Normal Cells: They are usually recognized and regulated by the immune system.

Cell Communication:

• Cancerous Cells: They can disrupt normal signaling pathways, leading to a lack of response to growth factors and other signals that regulate cell proliferation.
• Normal Cells: They communicate properly with other cells and respond appropriately to signals that control growth and division.

Question 13: Explain what is meant by metastasis.

Solution 13: The property of metastasis is exhibited by malignant tumors. It is the pathological process of spreading cancerous cells to the different parts of the body. These cells divide uncontrollably, forming a mass of cells called tumor. From the tumor, some cells get sloughed off and enter into the blood stream. From the blood stream, these cells reach distant parts of the body and therefore, initiate the formation of new tumors by dividing actively. 

Question 14: List the harmful effects caused by alcohol/drug abuse.

Solution 14: Here are some harmful effects caused by alcohol and drug abuse:

Physical Effects

1. Liver Damage: Alcohol can lead to fatty liver, hepatitis, and cirrhosis.
2. Cardiovascular Problems: Increased risk of heart disease, high blood pressure, and stroke.
3. Respiratory Issues: Impaired lung function and increased risk of infections.
4. Neurological Damage: Cognitive impairments, memory loss, and increased risk of dementia.
5. Gastrointestinal Disorders: Issues like gastritis, ulcers, and pancreatitis.
6. Cancer: Increased risk of various cancers, including liver, breast, and esophagus.

Psychological Effects

1. Addiction: Development of substance use disorders and dependency.
2. Mental Health Issues: Increased risk of anxiety, depression, and psychosis.
3. Cognitive Impairment: Reduced attention span, poor decision-making, and memory issues.

Social Effects

1. Relationship Strain: Conflicts with family, friends, and colleagues.
2. Legal Problems: Increased likelihood of arrests, DUI charges, and legal issues.
3. Job Loss: Decreased work performance, absenteeism, and unemployment.

Behavioral Effects

1. Risky Behaviors: Increased likelihood of engaging in dangerous activities, such as unprotected sex and driving under the influence.
2. Violence and Aggression: Higher risk of involvement in violent situations or domestic abuse.

Question 15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?

Solution 15: Yes, friends can have an influence on friends to start taking drugs and consuming alcohol. The following actions can be taken as precautionary measures to protect oneself from alcohol/drug abuse, they are:

• One must have a strong control over his/her will. One should refrain from experimenting with alcohol just for the sake of trying/curiosity/fun, etc.
• Stay away from people who are into drugs.
• Seek elderly advise, peer or medical assistance.
• Enlighten yourself with enough knowledge about the consequences of drug abuse.
• Go in for a counselling session.
• Take up some hobby/extracurricular activity.
• If depression or frustration levels persist or heighten, seek immediate medical or professional help.

Question 16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.

Solution 16: Drug and alcohol consumption has an inherent addictive nature associated with euphoria and a temporary feeling of well-being. Repeated intake of drugs increases the tolerance level of the body’s receptors, leading to more consumption of drugs. 

Question 17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?

Solution 17: Youngsters may be motivated to use alcohol or drugs for various reasons. Understanding these motivations can help in developing effective strategies to prevent substance abuse. Here are some common motivations and ways to avoid them:

Motivations for Substance Use

1. Peer Pressure: Desire to fit in with friends or social groups who engage in substance use can lead to experimentation.
2. Curiosity and Experimentation: Youngsters may be curious about the effects of drugs or alcohol, leading them to try them.
3. Escape from Stress or Problems: Many young people use substances to cope with stress, anxiety, depression, or other emotional challenges.
4. Social Acceptance: Engaging in drinking or drug use may be seen as a rite of passage or a way to enhance social status among peers.
5. Media Influence: Movies, music, and advertisements can glamorize substance use, creating the impression that it is a normal part of life.
6. Family Influence: Exposure to alcohol or drug use in the home can normalize such behaviors, making it more likely for youngsters to adopt them.
7. Rebellion: Some may use substances as a form of rebellion against authority or societal norms.

Ways to Avoid Substance Use

1. Education and Awareness: Providing accurate information about the risks and consequences of alcohol and drug use can help youngsters make informed decisions.
2. Strong Communication: Encouraging open discussions about feelings, challenges, and peer pressure can help young people feel supported and understood.
3. Promoting Healthy Coping Mechanisms: Teaching young people alternative ways to cope with stress, such as exercise, art, or mindfulness, can reduce reliance on substances.
4. Encouraging Positive Peer Relationships: Helping youngsters build friendships with peers who share healthy values and interests can decrease the likelihood of engaging in substance use.
5. Involvement in Extracurricular Activities: Encouraging participation in sports, clubs, and community service can provide healthy outlets and reduce the temptation to experiment with substances.
6. Setting Clear Expectations: Parents and guardians should set clear rules and expectations regarding substance use and discuss the reasons behind these guidelines.
7. Role Modeling: Adults can serve as positive role models by demonstrating healthy behaviors and attitudes toward alcohol and drug use.