Free Biodiversity and Variety of Life MCQs with Answers

31. Motile zygote of Plasmodium occurs in:

• A. Gut of female Anopheles
• B. Salivary glands of Anopheles
• C. Human RBCs
• D. Human liver

Explanation: Plasmodium, a tiny protozoan parasite causes malaria in humans and is transmitted through the bite of an infected female Anopheles mosquito. When female Anopheles sucks the blood of an infected human it takes up gametocytes (sexual stages of parasite) with blood meal. The gametocytes come out of the RBCs into the lumen(cavity) of the stomach of the mosquito. In the stomach, the male gametocyte divides and forms 6 to 8 long, motile, whiplike microgametes(male gametes). The female gametocyte does not divide but undergoes a process of maturation to become the macrogamete(female gamete). A microgamete penetrates a macrogamete and fertilization(syngamy) takes place, resulting in the formation of a zygote. The zygote elongates and becomes a worm-like motile organism called an ookinete. Ookinete further changes into sporozoites(mature infective stage of Plasmodium).

32. Which one of the following is not a property of cancerous cells whereas the remaining three are?

• A. They compete with normal cells for vital nutrients
• B. They do not remain confined in the area of formation
• C. They divide in an uncontrolled manner
• D. They show contact inhibition

Explanation: Contact inhibition is a property of normal cells by virtue of which contact withother cells inhibits their uncontrolled growth. Cancerous cells lack this property. One of the hallmarks of cancer is the loss of contact inhibition not gain of it. Cancer cells often ignore the signals from neighboring cells and continue to divide and grow uncontrollably, leading to the formation of tumors. This loss of contact inhibition is a crucial aspect of cancer development and progression.

33. Cirrhosis of liver is caused by the chronic intake of:

• A. Opium
• B. Alcohol
• C. Tobacco(chewing)
• D. Cocaine

Explanation: Cirrhosis is a condition in which the liver responds to injury or death of some of its cells by producing interlacing strands of fibrous tissue between which are nodules o regenerating cells. The liver becomes tawny and characteristically knobbly(due to the nodules). One of the causes include alcoholism(alcoholic cirrhosis). Chronic infection with hepatitis B or hepatitis C viruses can lead to liver inflammation and fibrosis, eventually progressing to cirrhosis.

34. Where will you look for the sporozoites of the malarial parasite?

• A. Saliva of infected female Anopheles mosquito
• B. Red blood corpuscles of human suffering from malaria
• C. Spleen of infected humans
• D. Salivary glands of freshy moulted female Anopheles mosquito

Explanation: Sporozoites represent the infective forms of malarial parasites. A healthy person acquires infection, when a female Anopheles mosquito, containing sporozoites, bites the person for sucking his blood. The mosquito punctures the host's skin by its proboscis and first introduces some saliva into the bloodstream. Along with saliva, thousands of sporozoites are inoculated in the host. The motile zygote then undergoes further development in the mosquito's gut to produce sporozoites, which migrate to the mosquito's salivary glands.

35. Common cold is not cured by antibiotics because it is:

• A. Caused by a virus
• B. Caused by a Gram positive bacterium
• C. Caused by a Gram negative bacterium
• D. Not an infectious disease

Explanation: Common cold is caused by some 100 types of Rhinoviruses. It is one of the most common infectious diseases in humans. Antibiotics are substances that destroy or inhibit the growth of microorganisms, particularly disease-producing bacteria and fungi. Antibiotics are obtained from microorganisms(especially molds) or synthesized. Many antibiotics interfere with the pathogen protein synthesis. Some (e.g. Penicillin) prevent cross-linking of the glycan chains of peptidoglycan molecules in bacterial cell walls. Since the viruses do not possess cell walls and their own protein-synthesizing apparatus, antibiotics do not attack them.

36. Ringworm in humans is caused by:

• A. Bacteria
• B. Fungi
• C. Nematodes
• D. Viruses

Explanation: Ringworm (tinea) is a fungal infection of the skin, the scalp, or the ails. Ringworm is caused by the dermatophyte fungi species of Microsporum, trichophyton, and epidermophyton ringworms and also affects animals, a source of infection for humans. It can be spread by direct contact or via infected materials. The lesions of ringworm may form partial or complete rings and may cause intense itching. The disease is treated with antifungal agents taken by mouth or applied locally. These fungi can infect the skin, hair, and nails, leading to the development of ringworm, also known as dermatophytosis.

37. Widal test is used for the diagnosis of:

• A. Malaria
• B. Pneumonia
• C. Tuberculosis
• D. Typhoid.

Explanation: Widal test (developed by G.F.I Widal) is an agglutination test for the presence of antibodies against the Salmonella organism that causes typhoid fever. It is used to diagnose the presence of the disease in a patient. If the patient has been exposed to Salmonella bacteria and has developed antibodies against them, a reaction called agglutination occurs. Agglutination causes the clumping together of the bacterial antigens and antibodies in the test solution, which is visible to the laboratory technician.

38. Infectious protein are present in:

• A. Gemini viruses
• B. Prions
• C. Viroids
• D. Satellite viruses.

Explanation: Prions are named by Stanley Prusiner (who got the Nobel Prize in 1997). Prions are infectious agents which are made of proteins only(without nucleic acid). Prions are the causal agents of scrapie disease of sheep. Prion diseases are a unique and challenging category of infectious diseases due to their unconventional nature and lack of traditional genetic material. They continue to be a subject of scientific research to better understand their mechanisms and develop potential treatments.

39. Which one of the following technique is safest for the detection of cancers?

• A. Magnetic Resonance Imaging (MRI)
• B. Radiography (X-Ray)
• C. Computed tomography (CT)
• D. Histopathological studies

Explanation: The histopathological study is an invasive technique. Radiography and CT involve X-rays which are harmful. In MRI strong magnetic fields and nonionizing radiations are used to detect any physiological changes in the concerned tissue. Hence it is safe for the detection of cancers.

40. A person suffering from a disease caused by Plasmodium, experiences recurring chill and fever at the time when:

• A. The sporozoites released from RBCs are being rapidly killed and broken down inside spleen
• B. The trophozoites reach maximum growth and give out certain toxins
• C. The parasite after its rapid multiplication inside RBCs ruptures them, releasing the stage to enter fresh RBCs
• D. The microgametocytes and megagametocytes are being destroyed by the WBCs.

Explanation: Plasmodium is a tiny protozoan that is responsible for malaria in humans. In malaria, the patient experiences high fever which periodically rises, and also experiences recurring chills with fever. Such symptoms are seen because when the RBCs carrying Plasmodium (one of the stages in the life cycle of the parasite) ruptures it releases a toxic substance called hemozoin which is chiefly responsible for the chill and high fever recurring every three to four days.