All Free Biology MCQs with Answers

2581. The hereditary material present in the bacterium E.coli is.

• A. Single stranded DNA.
• B. Double stranded DNA.
• C. DNA
• D. RNA

Explanation: The hereditary material present in the bacterium Escherichia coli (E. coli) is primarily b. Double-stranded DNA. Let's explain each option and provide more details: Single-stranded DNA (a): While E. coli does contain single-stranded DNA during certain stages of DNA replication, the primary form of its hereditary material is double-stranded DNA. Double-stranded DNA is the stable form that carries the genetic information. Double-stranded DNA (b): This is the correct answer. E. coli, like most organisms, carries its genetic information in the form of double-stranded DNA. The double-stranded DNA molecule in E. coli is located in the nucleoid region within the bacterial cell. DNA (c): This option is essentially the same as option (b), which specifies "double-stranded DNA." DNA, in general, can be either single-stranded or double-stranded. In the context of E. coli, it primarily contains double-stranded DNA. RNA (d): While E. coli does contain RNA as well, especially for processes like transcription and translation, RNA is not its primary hereditary material. The genetic information in E. coli is stored in the form of double-stranded DNA. Correct Answer: The hereditary material present in the bacterium E. coli is primarily "Double-stranded DNA" (b). Summary: The primary hereditary material in the bacterium E. coli is double-stranded DNA. While E. coli does use RNA for various cellular processes, including protein synthesis, its genetic information is primarily encoded in the form of double-stranded DNA, which is located in the nucleoid region of the cell.

2582. Genes are packaged into a bacterial chromosome by:

• A. Acidic protein.
• B. Actin.
• C. Histones.
• D. Basic protein.

Explanation: In bacteria, genes are packaged into the bacterial chromosome by D. Basic protein. Let's explain each option and provide more details: Acidic protein (A): Acidic proteins are not typically involved in the packaging of genes into a bacterial chromosome. They are more commonly associated with other cellular processes and functions. Actin (B): Actin is a protein found in eukaryotic cells and plays a role in the cytoskeleton. It is not involved in the packaging of genes in bacterial chromosomes. Histones (C): Histones are proteins that are commonly associated with the packaging of DNA into chromatin in eukaryotic cells. They help condense and organize DNA in the cell nucleus. Bacteria, however, lack histones, and their DNA is organized differently. Basic protein (D): Basic proteins are involved in the packaging of genes into the bacterial chromosome. In bacteria, the DNA is organized by basic proteins that help condense and stabilize the genetic material. These proteins bind to the DNA, allowing it to be more compact and well-structured within the bacterial cell. Correct Answer: Genes are packaged into a bacterial chromosome by "Basic protein" (D). Summary: In bacteria, genes are packaged and organized within the bacterial chromosome with the help of basic proteins. These proteins interact with the DNA to ensure its stability, compaction, and proper function within the cell. Unlike eukaryotic cells, bacteria do not use histones for DNA packaging.

2583. Most of the lichens consist of:

• A. Green algae and ascomycetes.
• B. Brown algae and higher plant.
• C. Green algae and basidiomycetes.
• D. Red algae and ascomycetes.

Explanation: Most lichens consist of A. Green algae and ascomycetes. Let's explain each option and provide more details: Green algae and ascomycetes (A): This is the correct answer. Lichens are typically composed of a mutualistic relationship between a green algal partner and an ascomycete fungal partner. The green algae provide photosynthetic capabilities, while the ascomycete fungi provide a protective structure and absorb water and nutrients from the environment. Brown algae and higher plant (B): Brown algae are not typically involved in lichen associations. Lichens do not contain higher plants but instead consist of a fungal partner and a photosynthetic partner, which is often a green alga. Green algae and basidiomycetes (C): Lichens are not commonly composed of green algae and basidiomycetes. Basidiomycetes are another group of fungi, but lichen associations typically involve ascomycetes, not basidiomycetes. Red algae and ascomycetes (D): Lichens do not typically consist of red algae and ascomycetes. Red algae are not commonly involved in lichen partnerships. Correct Answer: Most lichens consist of "Green algae and ascomycetes" (A). Summary: Lichens are mutualistic associations between a green algal partner (providing photosynthesis) and an ascomycete fungal partner (providing a protective structure and nutrient absorption). This combination allows lichens to thrive in various environments, making them a unique and important ecological component.

2584. What is the genetic material in influenza virus?

• A. Double helical DNA.
• B. RNA
• C. Single helix DNA.
• D. None of these

Explanation: The genetic material in the influenza virus is B. RNA.Let's explain each option and provide more details:Double helical DNA (A):Influenza viruses do not have double-stranded DNA as their genetic material. They are classified as RNA viruses.RNA (B):This is the correct answer. Influenza viruses have single-stranded RNA as their genetic material. They belong to the Orthomyxoviridae family of viruses, which are RNA viruses responsible for causing influenza in humans and other animals.Single helix DNA (C):The concept of "single helix DNA" is not applicable in the context of viruses. DNA typically forms a double helix, and influenza viruses do not contain DNA as their genetic material.Correct Answer: The genetic material in the influenza virus is "RNA" (B).Summary:The genetic material in the influenza virus is single-stranded RNA. Influenza viruses are RNA viruses responsible for causing the flu in humans and other animals. This RNA serves as the blueprint for the replication and transcription of viral genes during the infection process.

2585. What are the sex organs provided in some bacteria?

• A. Sex pili
• B. Plasmid
• C. Circular DNA
• D. Gametes

Explanation: The term "sex organs" is not applicable to bacteria in the same way it is to sexually reproduce multicellular organisms. However, bacteria do have structures and mechanisms that facilitate genetic exchange. Let's explain each option and provide details: Sex pili (a): This is the correct answer. Bacteria often use sex pili (also known as conjugation pili) to facilitate the transfer of genetic material between cells during a process called conjugation. Sex pili are elongated, filamentous appendages that allow one bacterium to contact and transfer genetic material to another bacterium. Plasmid (b): Plasmids are small, circular DNA molecules that can carry extra genes. While plasmids play a role in the transfer of genetic material during conjugation (a process that involves sex pili), they are not sex organs themselves. Circular DNA (c): Circular DNA is a common form of bacterial genomic DNA. However, it is not a sex organ. Circular DNA refers to the structure of bacterial chromosomes and plasmids, but it does not serve as a sex organ in the traditional sense. Gametes (d): Gametes are reproductive cells involved in sexual reproduction in eukaryotic organisms. Bacteria do not produce gametes, as they primarily reproduce through asexual means like binary fission or through genetic exchange mechanisms such as conjugation. Correct Answer: In some bacteria, the structures involved in the genetic exchange are sex pili (a). Summary: Bacteria do not have sex organs in the way multicellular organisms do. Instead, they use structures like sex pili (conjugation pili) to facilitate genetic exchange during processes like conjugation. Plasmids and circular DNA are related to bacterial genetics but are not sex organs. Bacteria do not produce gametes, as they primarily reproduce asexually or through genetic exchange mechanisms.

2586. Which type of DNA is found in bacteria?

• A. Circular free DNA.
• B. Membrane bound DNA.
• C. Straight DNA.
• D. Helical DNA.

Explanation: The type of DNA found in bacteria is a. Circular free DNA. Let's explain each option and provide more details: Circular free DNA (a): This is the correct answer. Bacteria typically have a single circular DNA molecule that is free in the cytoplasm. This circular DNA contains the genetic information necessary for the bacterium's function and replication. Membrane-bound DNA (b): Bacteria do not have membrane-bound DNA. Unlike eukaryotic cells, bacteria lack a true nucleus and do not compartmentalize their DNA within a membrane-bound organelle. Straight DNA (c): The term "straight DNA" is not commonly used in the context of bacterial genetics. Bacterial DNA typically forms a circular structure within the bacterial cell. Helical DNA (d): While the DNA double helix is a common term in genetics, it is not specific to bacteria. The double helical structure of DNA is a fundamental characteristic shared by all organisms with DNA-based genomes. Correct Answer: The type of DNA found in bacteria is "Circular free DNA" (a). Summary: Bacteria typically contain a single circular free DNA molecule that resides in the cytoplasm of the bacterial cell. This circular DNA contains the genetic information necessary for the bacterium's functions and is distinct from the membrane-bound nucleus found in eukaryotic cells. The double helical structure of DNA is a fundamental feature of all DNA, regardless of the organism.

2587. Which one of the following statement about lichens is wrong?

• A. These grow very rapidly (2 cm per day).
• B. They show fungal and algal symbiotic relationships.
• C. Some of its species are eaten by reindeers.
• D. These are pollution indicators.

Explanation: The incorrect statement about lichens is a. These grow very rapidly (2 cm per day). Let's explain each option and provide more details: These grow very rapidly (2 cm per day) (a): This statement is incorrect. Lichens are known for their slow growth, and they typically grow much more slowly than 2 cm per day. Lichens are often used as indicators of environmental conditions, such as air quality, precisely because they grow slowly and are sensitive to environmental changes. They show fungal and algal symbiotic relationships (b): This statement is correct. Lichens are composite organisms consisting of a mutualistic relationship between a fungal partner (mycobiont) and an algal or cyanobacterial partner (photobiont). Some of its species are eaten by reindeers (c): This statement is correct. Lichens are an important food source for some animals, including reindeer, caribou, and certain insects. Lichens provide a winter food source for these animals in regions with limited vegetation. These are pollution indicators (d): This statement is correct. Lichens are often used as bioindicators of air quality and environmental pollution. Their sensitivity to air pollution, especially sulfur dioxide and heavy metals, makes them valuable in assessing environmental health. Correct Answer: The incorrect statement is "a. These grow very rapidly (2 cm per day)." Summary: Lichens are unique organisms that grow slowly and are composed of a mutualistic relationship between a fungal partner and an algal or cyanobacterial partner. Some lichen species are consumed by animals like reindeer, and lichens are used as bioindicators to assess environmental pollution and air quality due to their sensitivity to pollutants.

2588. Mycorrhiza is correctly described as:

• A. Parasitic association between roots and some fungi.
• B. Symbiotic relationship between fungi and roots of some higher plants.
• C. Symbiosis of algae and fungi.
• D. Relation of ants with the stem of some trees.

Explanation: Mycorrhiza is correctly described as b. Symbiotic relationship between fungi and roots of some higher plants. Let's explain each option and provide more details: Parasitic association between roots and some fungi (a): This statement is not accurate. Mycorrhizal associations are typically mutualistic rather than parasitic. In mycorrhizal symbiosis, both the fungi and the plant benefit from the relationship. Symbiotic relationship between fungi and roots of some higher plants (b): This statement is correct. Mycorrhiza is a mutually beneficial association between certain fungi and the roots of many higher plants. The fungi assist in nutrient uptake, especially phosphorus and other minerals, while the plant provides the fungi with carbohydrates. Symbiosis of algae and fungi (c): This statement is not accurate. Mycorrhiza involves fungi and plant roots, not algae. The association you are describing is more closely related to lichens, which involve algae and fungi. Relation of ants with the stem of some trees (d): This statement is unrelated to mycorrhiza. It describes a different ecological interaction, which is not connected to the mycorrhizal symbiosis. Correct Answer: Mycorrhiza is correctly described as a "Symbiotic relationship between fungi and roots of some higher plants" (b). Summary: Mycorrhiza is a mutualistic association between certain fungi and the roots of many higher plants. In this symbiotic relationship, fungi assist plants in nutrient uptake, especially phosphorus and other minerals, while plants provide carbohydrates to the fungi. This mutually beneficial association is essential for the health and growth of many plants.

2589. The tailed bacteriophages are:

• A. Motile on surface of bacteria.
• B. Non-motile.
• C. Motile on surface of plant leaves.
• D. Actively motile in water.

Explanation: The tailed bacteriophages are B. Non-motile.Let's explain each option and provide more details:Motile on the surface of bacteria (A):This statement is not accurate. Tailed bacteriophages are viruses that specifically infect and replicate within bacterial cells. They do not have the ability to move on the surface of bacteria.Non-motile (B):This is the correct answer. Tailed bacteriophages do not exhibit motility. They rely on random encounters with their bacterial hosts and do not have the ability to actively move or swim.Motile on the surface of plant leaves (C):This statement is not related to tailed bacteriophages, which are viruses that infect bacteria, not plants.Actively motile in water (D):Tailed bacteriophages are not actively motile in water. They are passive particles that rely on diffusion and random encounters to come into contact with their bacterial hosts.Correct Answer: The tailed bacteriophages are "Non-motile" (B).Summary:Tailed bacteriophages are non-motile viruses that infect bacterial cells. They do not possess the ability to move actively on the surface of bacteria or in the environment. Instead, they rely on chance encounters with their bacterial hosts for the infection and replication process.

2590. A large number of organic compounds can be decomposed by:

• A. Azotobacter
• B. Chemolithotrophs
• C. Mycoplasma
• D. Pseudomonas

Explanation: Let's explain each option individually: a) Azotobacter: Azotobacter is a genus of free-living, nitrogen-fixing bacteria. While they play an essential role in nitrogen fixation by converting atmospheric nitrogen into a usable form for plants, they are not primarily known for their ability to decompose a large number of organic compounds. Their main significance lies in their contribution to nitrogen cycling and plant growth. b) Chemolithotrophs: This option is correct. Chemolithotrophs are organisms, including certain bacteria and archaea, that can decompose a large number of organic compounds using inorganic substances as a source of energy. These organisms derive their energy from the oxidation of inorganic compounds, such as ammonia, nitrite, sulfur, iron, or hydrogen, rather than organic carbon sources. They are essential players in various biogeochemical cycles, such as the nitrogen, sulfur, and iron cycles, as they help decompose and recycle a wide range of organic compounds in the environment. c) Mycoplasma: Mycoplasma is a genus of bacteria that are characterized by their small size and lack of a cell wall. While they can cause various diseases in animals and plants, they are not typically associated with decomposing a large number of organic compounds. Mycoplasma species are more commonly known for their parasitic or pathogenic nature. d) Pseudomonas: Pseudomonas is a diverse genus of bacteria that includes many species capable of breaking down a wide range of organic compounds. They are well-known for their metabolic versatility and ability to degrade various complex organic molecules, such as hydrocarbons, aromatic compounds, and pollutants. Some Pseudomonas species are valuable in bioremediation, where they help clean up environmental contamination by breaking down harmful substances. In summary, the correct answer is b) Chemolithotrophs. These organisms can decompose a large number of organic compounds using inorganic substances as a source of energy. While Pseudomonas can also decompose organic compounds, chemolithotrophs have a broader ability to break down various organic substances using inorganic compounds for energy.