Short & Long Question Answers with Solution: Human Health & Diseases | Biology for Grade 12 PDF Download

Short Answer Type Questions

Q1: Which pathogenic virus would mutate faster, one with DNA or RNA? Why?
Ans: RNA viruses mutate at a faster rate compared to DNA viruses because DNA is more stable and equipped with more effective repair mechanisms. DNA viruses can promptly correct any alterations in their base pairs, whereas RNA viruses lack these repair mechanisms, leading to a higher mutation rate.

Q2: Describe the role of lymph nodes in the human immune response.
Ans: Lymph nodes serve as locations in the human body where lymphocytes and antigens engage with each other. When microorganisms invade the lymph nodes, the lymphocytes found there become activated and capture and eliminate the invaders.

Q3: What is a lifestyle disease? List two lifestyle diseases. What is their causative?
Ans: A lifestyle-related disease or disorder is linked to an individual's way of life. These conditions are brought about by factors such as work-related practices, posture, particular dietary habits, exposure to harmful substances or radiation, or even a lack of physical activity, exercise, and mental well-being. Examples of such conditions include heart disease, cancer, and obesity, among others.

Q4: Why is it recommended to avoid crowded and closed air-conditioned places during changing the weather?
Ans: This occurs because pathogens thrive in moist environments where they are most active, promoting their growth. Individuals can be more susceptible to illnesses when their bodies are adjusting to varying ambient temperatures and humidity levels.

Q5: Is it advantageous to have an identical twin for an organ transplant? If yes/no, why?
Ans: This is beneficial because the organ shares identical surface markers, which means the recipient's immune system won't identify it as foreign or transplanted and therefore won't mount an immune response against it. The immune system only attacks foreign tissues when it detects different surface markers.

Q6: What are allergens? How do they cause inflammatory responses inside the human body?
Ans: Allergens are substances that trigger an exaggerated immune system response known as hypersensitivity.
When an individual encounters an allergen regularly, the allergen binds with IgE antibodies on mast cells. Subsequently, these cells rupture and discharge histamines, resulting in an inflammatory reaction.


Q7: What is interferon? How do they monitor the infection of new cells?
Ans: Cells infected with viruses and those forming tumors release glycoproteins that shield healthy cells from attacks by pathogens. These glycoproteins are called interferons. Interferons stimulate macrophages, which are natural killer cells, and hinder viral replication. They also enhance the presentation of antigens to lymphocytes, leading to the continuous multiplication of lymphocytes aimed at eradicating foreign substances.

Q8: Detect the medical ailment in the following case – Strong hypersensitive reactions displayed by a person when exposed to a few substances in the air. Identify the cells causing this reaction. State a precautionary measure to avoid such a reaction.
Ans: The individual has an allergy to airborne substances. Allergic reactions occur because mast cells release chemicals like serotonin and histamine. One preventive measure could involve staying away from these allergens found in the atmosphere.

Q9: Where are B-lymphocytes and T-lymphocytes formed? How do they help develop immunity?
Ans: B-lymphocytes and T-lymphocytes originate in the human body's bone marrow.
B-lymphocytes safeguard the body through the production of antibodies, while T-lymphocytes support the immune system by assisting B-cells in antibody production.

Q10: State the significance of mother’s milk to a new-born infant.
Ans: Breast milk is highly valuable due to the presence of colostrum, a yellowish fluid produced by the mother during the initial days of breastfeeding. Colostrum contains a substantial amount of antibodies, particularly IgA, which plays a critical role in shielding the infant from infections.

Long Answer Type Questions

Q1: Define minerals and list out the essential minerals along with the deficiency diseases caused by the lack of essential minerals.
Ans: Minerals are essential inorganic nutrients, encompassing trace elements like copper, zinc, iodine, and iron, as well as macronutrients such as calcium, potassium, magnesium, and sodium. Key minerals required by our bodies include calcium, chloride, magnesium, phosphorus, potassium, sodium, and sulfur.
Below is a list of deficiency disorders arising from mineral deficiencies in our bodies:

• Anemia.
• Arthralgia (joint pain).
• Loss of appetite.
• Stunted growth.
• Excessive bleeding.
• Fragile and weakened bones.
• Diarrhea or vomiting.
• Dental cavities and gum disease.
• Goiter and enlargement of the thyroid gland.
• Purplish or blood spots beneath the skin.

Q2: What is vaccination? Why is it important to take a vaccine?
Ans: Vaccination is the process of stimulating the body's immune system to build protection against harmful pathogens.
A vaccine consists of a weakened or inactive form of a pathogen that is introduced into the body. This triggers the production of antibodies that can neutralize the injected pathogens. If the vaccinated person encounters the same pathogen in the future, even in a more potent form, their B lymphocytes and T lymphocytes will recognize and combat it to defend the body. This form of immunity is termed active immunity. Conversely, if an individual is severely affected by a pathogen, they can receive antibodies directly through a vaccine, resulting in passive immunity. Therefore, vaccination is of utmost importance in the development of immune protection within the body.

Q3: What causes adolescents to start using drugs? How can the use of drugs be avoided?
Ans: Several factors contribute to adolescents initiating drug use:

• Curiosity and experimentation.
• Pursuit of excitement and adventure.
• Peer pressure.
• Attempting to test one's physical and mental limits or increase productivity.
• Coping with depression and frustration stemming from various failures.
• Lack of family support.

To prevent drug use among adolescents, the following preventive actions can be taken:

• Avoid imposing excessive academic expectations on children.
• Provide education and counseling to help adolescents manage stress and life disruptions.
• Encourage seeking assistance from family and peers.
• Stay vigilant for warning signs and take appropriate measures to address them.
• Consider seeking medical or professional support for rehabilitation and overcoming addiction.

Q4: Write a brief note on the role of lymphoid organs in the immune response. Elaborate on the different types of lymphoid organs in the human body with examples.
Ans: Lymphoid organs within the human body play a crucial role in monitoring and initiating immune responses against foreign substances and microbes.
These organs can be categorized as follows:

• Primary Lymphoid Organs: Also known as central lymphoid organs, these organs are responsible for producing immune system cells. They include the bone marrow and thymus.
  • Bone Marrow: The primary lymphoid organ, the bone marrow, actively generates various blood cells, including lymphocytes. It creates a micro-environment essential for the development and maturation of T lymphocytes and B lymphocytes. Mature B cells travel to the bloodstream to detect pathogens.
  • Thymus: Located beneath the breastbone near the heart, the thymus serves as the site for the production and nurturing of T lymphocytes. While it is relatively large at birth, it gradually diminishes in size with age.
• Secondary Lymphoid Organs: These organs facilitate interactions between lymphocytes and antigens, enabling the immune system to target and eliminate them.
  • Spleen: A sizeable bean-shaped organ predominantly composed of lymphocytes and phagocytes, the spleen is often referred to as the "graveyard" of red blood cells. It acts as a blood filter, capturing blood-borne microorganisms.
  • Lymph Nodes: These nodes are responsible for capturing microorganisms and antigens entering the lymphatic and tissue fluids. Lymphoid tissues located within major passages are known as mucosa-associated lymphoid tissue (MALT).

Q5: State the behavioural changes observed in an alcohol addict and remedial measures to overcome the problem.
Ans: Several observations have been made:

• Alcoholic beverages can be expensive and may lead to the deprivation of a family's basic necessities.
• Drinking is linked to criminal activities and the erosion of cultural and moral values.
• Some corrupt practices and acts of violence are often directly or indirectly connected to alcohol consumption.

To address these issues, the following remedial actions can be taken:

• Refrain from succumbing to peer pressure.
• Counseling and education play a crucial role in addressing issues such as stress, failure, and disturbances.
• Seek support from both family members and peers.
• Stay vigilant for warning signs, especially when in the company of people consuming alcohol.
• For individuals grappling with addiction, seeking medical or professional assistance is a viable option to lead a healthy and normal life.

Q6: What is Ringworm? What are the different types of ringworm?
Ans: Ringworm is a type of skin infection, caused by the fungus. It is a contagious skin disorder, which can spread by the skin contact with an infected person. There are different types of ringworm and are mainly classified based on the body parts which get infected. The most common forms of ringworm are tinea pedis, tinea capitis, tinea cruris and tinea corporis.  
Types of Ringworm are: Ringworm is classified based on the part of the body it affects.

• Tinea corporis: This fungal infection might occur in any part of the body. 
• Tinea capitis: It is also called scalp ringworm. This fungal infection affects the scalp.
• Tinea cruris: This fungal infection affects the skin around the buttocks, inner thighs, and groin. It is also known as the Jock itch.
• Tinea pedis: This fungal infection affects both the foot, in between the fingernails and toenails. It is also known as Athlete’s foot. 

Q7: Which protozoa cause malaria? Write a short note on the life cycle of the malarial parasite.
Ans: Plasmodium vivax is the protozoan responsible for causing malaria. This protozoan is a parasite and relies on hosts for its growth and development. When a female Anopheles mosquito bites an infected individual, the protozoa enter its body. Subsequently, when the mosquito bites another person, it transmits the protozoa's sporozoites into their bloodstream, thus infecting the healthy individual. Malaria is caused by four different types of malarial protozoa: Plasmodium falciparum, Plasmodium vivax, Plasmodium ovale, and Plasmodium malariae.
The life cycle of the Plasmodium protozoa within the human body comprises four stages: pre-erythrocytic schizogony phase, erythrocytic schizogony phase, gametogenic phase, and exoerythrocytic schizogony phase.

• Sporozoites of the protozoa reside in the salivary glands of Anopheles mosquitoes and are transmitted into the human bloodstream during a mosquito bite.
• These sporozoites reach the human liver and multiply rapidly to form schizonts containing merozoites.
• The merozoites are attracted to glycoproteins present in red blood cells (RBCs).
• Inside the RBCs, they reproduce, produce gametes, and eventually rupture the RBCs.
• The ruptured RBCs release toxic haemozoin, leading to symptoms like high fever and shivering.
• Malaria symptoms become evident after an incubation period of nine to fourteen days, during which the patient may not exhibit any illness.
• When a mosquito bites a malaria-infected person, it ingests the gametes present in their blood.
• Within the mosquito's gut, these gametes fertilize.
• Newly formed sporozoites are stored in the mosquito's salivary glands.
• When this mosquito bites another individual, it injects the sporozoites into their bloodstream, perpetuating the cycle of infection.

Q8: What Is Typhoid? List out the symptoms of Typhoid?
Ans: Typhoid is an infectious illness resulting from the invasion of the intestinal tract and bloodstream by Salmonella typhi or S. Typhi bacteria.
Here are some typical symptoms of Typhoid:

• Headache
• Dry cough
• Sweating
• Skin rashes
• Muscle pains
• Abdominal discomfort
• Fatigue and weakness
• Diarrhea or constipation
• Decreased appetite and weight loss
• Prolonged or spiking fever with a rising body temperature.

Q9: How to detect cancer? What are a few approaches to treat cancer?
Ans: Early detection is crucial in identifying cancer, and there are various areas where diagnosis and detection can take place:

• Blood cell count tests for blood cancer screening.
• Histopathological examination and biopsy of blood, tissues, or bone marrow.
• Radiography, CT scans, and MRI scans for detecting internal organ cancers.
• Identification of cancer-specific antigens.
• Utilization of molecular biology techniques to identify genes associated with an inherited predisposition to certain cancers.

When it comes to cancer treatment, several approaches can be employed:

• Surgical procedures to excise the tumor.
• Immunotherapy aimed at enhancing the body's ability to target and destroy cancer cells.
• Radiotherapy to eliminate cancerous cells.
• Chemotherapy.
• Administration of biological response modifiers like alpha-interferons, which activate the immune system and aid in tumor destruction.

Q10: What is a recombinant DNA vaccine? List two such vaccines. State their advantages.
Ans: Recombinant DNA vaccines are composed of small, circular DNA molecules called plasmids. These plasmids contain specific pathogen DNA segments responsible for producing one or two particular pathogen proteins. To harness the cellular machinery needed for generating these pathogen proteins, this DNA is inserted into yeast or bacterial cells.
These vaccines are employed to initiate immune responses in the body and are widely used in the production of:

• Hepatitis-B vaccine (produced using yeast)
• DNA vaccines for bird flu

Some of the advantages associated with these vaccines include:

• They are more advantageous than attenuated vaccines because they do not revert to a virulent form.
• They are highly pure and specific, leading to robust immune responses.