All Free Biology MCQs with Answers

2601. Escherichia coli is used extensively in biological research as it is

• A. Easily cultured
• B. Easily available
• C. Easy to handle
• D. Easily multiplied in host

Explanation: Let's explain each option individually: a) Easily cultured: This option is correct. Escherichia coli (E. coli) is easily cultured in the laboratory, making it a popular choice for biological research. It is a fast-growing bacterium that can be easily cultivated on various culture media, such as agar plates or in liquid media. Its rapid growth and simple nutrient requirements make it convenient for researchers to study and manipulate in the laboratory. b) Easily available: While E. coli is a commonly found bacterium in the environment, this option is not the primary reason it is extensively used in biological research. Its widespread presence in nature does contribute to its accessibility for researchers, but the main reason for its widespread use is its ease of culture and manipulation in the laboratory. c) Easy to handle: This option is related to the ease of culturing and manipulating E. coli in the laboratory. E. coli is indeed easy to handle due to its simple growth requirements, well-established protocols for transformation and manipulation of its genetic material, and well-characterized molecular biology tools available for studying this bacterium. d) Easily multiplied in the host: This option is not entirely accurate in the context of biological research. While E. coli is capable of multiplying rapidly in its natural host, the human intestine, the primary reason for its use in biological research is its ability to multiply rapidly and be easily cultured in the laboratory setting. The focus is on its laboratory applications, rather than its natural multiplication in the host. In summary, the correct answer is a) Easily cultured. Escherichia coli (E. coli) is extensively used in biological research because it is easily cultured in the laboratory due to its fast growth, simple nutrient requirements, and well-established protocols for manipulation and genetic engineering. Its ease of culture makes it a valuable model organism for studying various biological processes and conducting experiments in the field of molecular biology, genetics, and microbiology.

2602. Bacteria lack alternation of generation because there is

• A. Neither syngamy nor reduction division
• B. Distinct chromosomes are absent
• C. No conjugation
• D. No exchange of genetic materia

Explanation: Let's explain each option individually: a) Neither syngamy nor reduction division: This option is correct. Bacteria lack alternation of generations because they do not undergo the processes of syngamy (fusion of gametes) and reduction division (meiosis). Alternation of generations is a reproductive strategy observed in certain plants and algae, where the life cycle alternates between a haploid gametophyte phase and a diploid sporophyte phase. In the absence of sexual reproduction involving the fusion of gametes (syngamy) and the production of haploid spores through meiosis (reduction division), bacteria do not exhibit alternation of generations. b) Distinct chromosomes are absent: This option is not correct. Bacteria do possess distinct chromosomes. While bacterial chromosomes are different from those found in eukaryotes (such as humans or plants), they still contain the genetic material necessary for the bacterium's functions and reproduction. Bacterial DNA is present in a single, circular chromosome located in the nucleoid region of the cell. c) No conjugation: Conjugation is a specific type of bacterial genetic exchange, where genetic material (plasmids or parts of the chromosome) is transferred between two bacterial cells that are in physical contact. While conjugation is an important mechanism for bacterial genetic diversity, its absence does not directly relate to the lack of alternation of generations. d) No exchange of genetic material: This option is similar to option c and is not correct for the same reason. Bacteria can exchange genetic material through various mechanisms, including transformation (uptake of naked DNA from the environment) and transduction (transfer of genetic material through bacteriophages). However, the lack of alternation of generations in bacteria is not due to the absence of these genetic exchange mechanisms. In summary, the correct answer is a) Neither syngamy nor reduction division. Bacteria lack alternation of generations because they do not undergo the processes of syngamy (fusion of gametes) and reduction division (meiosis), which are essential for the alternation of generations life cycle observed in certain plants and algae.

2603. Which one of the following organisms are indicator of SO2 pollution of air?

• A. Mosses
• B. Lichens
• C. Mushrooms
• D. Puffballs

Explanation: Let's explain each option individually: a) Mosses: Mosses are sensitive to air pollution, including sulfur dioxide (SO2) pollution, but they are not the primary indicator species for SO2 pollution. While mosses can be affected by air pollutants and can show signs of stress or damage in polluted environments, their response to SO2 pollution is not as specific or pronounced as some other organisms, like lichens. b) Lichens: This option is correct. Lichens are excellent indicators of SO2 pollution in the air. Lichens are unique organisms composed of a symbiotic association between a fungus and an alga or a cyanobacterium. They are highly sensitive to air pollution, particularly sulfur dioxide (SO2) and other sulfur-containing compounds. Lichens are efficient at absorbing and accumulating airborne pollutants, including SO2, from the atmosphere. As a result, they are particularly useful as bioindicators in air quality monitoring programs. The presence, absence, or health of certain lichen species in a given area can provide valuable information about the level of air pollution, especially SO2 pollution. c) Mushrooms: Mushrooms, as fruiting bodies of fungi, do not directly serve as indicators of SO2 pollution. However, fungi, including mushrooms, can be impacted by air pollution in general, depending on the type and severity of pollutants in the environment. d) Puffballs: Puffballs are a type of fungi that produce spores inside an enclosed fruiting body. Similar to mushrooms, puffballs do not directly function as indicators of SO2 pollution. While fungi, including puffballs, can be influenced by air quality, they are not specific indicators of SO2 pollution. In summary, the correct answer is b) Lichens. Lichens are excellent indicators of SO2 pollution in the air due to their high sensitivity to sulfur dioxide and their ability to accumulate airborne pollutants, making them valuable bioindicators in air quality monitoring programs. The other options (mosses, mushrooms, and puffballs) may also be influenced by air pollution but are not as specific or reliable indicators of SO2 pollution as lichens.

2604. In Amoeba and Paramecium osmoregulation occurs through

• A. Pseudopodia
• B. Nucleus
• C. Contractile vacuole
• D. General surface

Explanation: In both Amoeba and Paramecium, osmoregulation occurs through a specialized organelle called the contractile vacuole. The contractile vacuole is responsible for regulating the water content and maintaining the osmotic balance within these single-celled organisms. As they live in aquatic environments, water constantly moves into their cells by osmosis, and the contractile vacuole helps them remove excess water to prevent bursting or lysing.

2605. African sleeping sickness is due to

• A. Plasmodium vivax transmitted by tsetse fly
• B. Trypanosoma lewsii transmitted by bed bug
• C. Trypanosoma gambiense transmitted by Glossina palpalis
• D. Entamoeba gingivalis spread by housefly

Explanation: Trypanosoma gambiense is one of the subspecies of Trypanosoma brucei that causes African sleeping sickness in West and Central Africa. Glossina palpalis is one of the tsetse fly species responsible for transmitting this subspecies. So, this option accurately identifies one of the causative agents (T. gambiense) and one of the vectors (G. palpalis) responsible for transmitting the disease.

2606. Malignant tertian malarial parasite, belongs to class

• A. Plasmodium falciparum
• B. P. vivax
• C. P. ovale
• D. P. malariae

Explanation: Malignant tertian malarial parasite is caused by Plasmodium falciparum. Plasmodium falciparum is one of the species of protozoan parasites responsible for causing malaria in humans. It is known for causing severe and potentially fatal cases of malaria, especially in young children and non-immune individuals. The disease caused by Plasmodium falciparum is often referred to as "malignant tertian malaria."

2607. Plasmodium, the malarial parasite, belongs to class

• A. Sarcodina
• B. Ciliata
• C. Sporozoa
• D. Dinophyceae

Explanation: Plasmodium, the malarial parasite, belongs to class Sporozoa. This class is a group of parasitic protozoans that are characterized by forming spores during some part of their life cycle. Plasmodium species, which are responsible for causing malaria in humans and other animals, are obligate intracellular parasites belonging to the class Sporozoa.

2608. Amoebiasis is prevented by

• A. Eating balanced food
• B. Eating plenty of fruits
• C. Drinking boiled water
• D. Using mosquito nets

Explanation: Amoebiasis, also known as amebiasis, is a gastrointestinal infection caused by the protozoan parasite Entamoeba histolytica. One of the primary modes of transmission of this parasite is through contaminated water sources, especially those containing cysts of the parasite. Drinking boiled water is an effective preventive measure because boiling water can kill the cysts and other harmful microorganisms, reducing the risk of infection.

2609. Which is true about Trypanosoma?

• A. Polymorphic
• B. Monogenetic
• C. Facultative parasite
• D. Nonpathogenic

Explanation: Trypanosoma is polymorphic. Polymorphism refers to the existence of different forms or morphological variations within a species. Trypanosoma species exhibit polymorphism, meaning they can have varying morphological forms during different stages of their life cycle. For example, Trypanosoma brucei, the species responsible for causing African trypanosomiasis, displays different morphological forms in its mammalian host and the tsetse fly vector.

2610. Genetic information in Paramecium is contained in

• A. Micronucleus
• B. Macronucleus
• C. Both micronucleus and macronucleus
• D. Mitochondria

Explanation: Paramecium contains a single large macronucleus and one small micronucleus. The macronucleus controls metabolism such as feeding and maintaenance, whereas the micronucleus takes an important role in reproduction and stores genetic information, hence it is also termed as reproductive nucleus whereas macronucleus is termed as vegetative nucleus.