All Free Biology MCQs with Answers

2901. Poliomyelitis mostly occurs in:

• A. Childhood
• B. Adulthood
• C. In old age
• D. Difficult to say

Explanation: Polio is most commonly observed in children under five years old, although adults can also be affected.

2902. Viruses can be classified on the basis of:

• A. Shape
• B. Nucleic acid
• C. Envelope
• D. All of these

Explanation: Viruses are grouped by their overall shape, the type of genetic material they carry, and whether or not they have an outer envelope. These features help distinguish one group of viruses from another and hint at how they replicate and spread.

2903. Which of the following kingdoms, the eukaryotic multicellular autotrophs are classified?

• A. Plantae
• B. Animalia
• C. Monera
• D. Protista

Explanation: Plants are made up of many cells, and each of these cells has a true nucleus, which puts them in the eukaryotic group. They're also autotrophic, meaning they can make their own food using sunlight through photosynthesis. As a group, all these features place them in the kingdom Plantae.Members of this kingdom usually have cell walls made of cellulose, contain chlorophyll for capturing light energy, and show a clear pattern of growth and development. They range from tiny mosses to huge trees, but they all share the same basic characteristics that define them as plants.

2904. A Russian scientist discovered that certain diseases could be transmitted by an agent that could pass through a very fine filter, which is called:

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

Explanation: Dmitri Ivanovsky discovered that viruses could pass through filters that trapped bacteria, leading to the discovery of these infectious agents.

2905. Examples of reverse transcribing diploid single-stranded RNA viruses are:

• A. Hepatitis B
• B. HIV
• C. Rabies
• D. Chicken Pox

Explanation: HIV (Human Immunodeficiency Virus) is a retrovirus that has diploid single-stranded RNA and uses reverse transcription.

2906. Viruses are called non-cellular infectious entities because:

• A. They are pathogens and cause infections
• B. They can replicate inside as well as outside the living cells
• C. They cause infections and can only replicate inside living cells
• D. They have a capsid to infect the host

Explanation: They cause infections and can only replicate inside living cells - Correct. Viruses are obligate intracellular parasites, meaning they need a host cell to reproduce.

2907. The following are viral diseases except:

• A. Hepatitis
• B. Polio
• C. Syphilis
• D. AIDS

Explanation: Syphilis is caused by the bacterium Treponema pallidum, not a virus.It spreads mainly through sexual contact and can progress through several stages if untreated.

2908. Cirrhosis of the 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 of regenerating cells. The liver becomes tawny and characteristically knobbly (due to the nodules). One of the causes includes alcoholism (alcoholic cirrhosis). Chronic infection with hepatitis B or hepatitis C viruses can lead to liver inflammation and fibrosis, eventually progressing to cirrhosis.

2909. If a person shows production of interferons in his body, the chances are that he has an infection of

• A. Tetanus
• B. Malaria
• C. Typhoid
• D. Measles

Explanation: Interferons are antiviral proteins that increase a cell's resistance to viral attacks. Since measles is a viral disease, the body produces interferons. Measles is an acute infectious eruptive viral disease of childhood caused by the RNA-containing Rubeola virus (Polynosa morbillorum). Typhoid and tetanus are bacterial diseases caused by Salmonella typhi and Clostridium tetani, respectively. Malaria is a protozoan disease caused by Plasmodium species.

2910. Below is the diagram of a bacteriophage. In which one of the options are all four parts, A, B, C, and D, correct, respectively?

• A. Tail fibres, Head, Sheath, Collar
• B. Sheath, Collar, Head, Tail fibres
• C. Head, Sheath, Collar, Tail fibres
• D. Collar, Tail fibres, Head, Sheath

Explanation: A-Head, B-Sheath, C-Collar, D-Tail fibreThe head contains the genetic material of the bacteriophage, usually in the form of DNA or RNA, enclosed within a protein coat. It plays a vital role in protecting the genetic material and injecting it into the host cell during infection.The sheath is a contractile structure surrounding the tail tube that helps in injecting the phage DNA into the bacterial cell. When the phage attaches to the host, the sheath contracts to push the DNA through the bacterial membrane.The collar is a small structure that connects the head to the tail and helps in stabilizing the phage during attachment. It also assists in the transfer of genetic material from the head to the tail during infection.The tail fibres are long, thin structures that help the phage recognize and attach to specific receptor sites on the bacterial surface. They play a crucial role in determining the host range and initiating the infection process.