Free Biodiversity and Variety of Life MCQs with Answers

91. Viroids differ from viruses in having:

• A. DNA molecules without protein coat.
• B. RNA molecules with protein coat.
• C. RNA molecules without protein coat.
• D. DNA molecules with protein coat.

Explanation: RNA molecules without a protein coat: This is the correct description of viroids. Viroids are small, circular RNA molecules that lack a protein coat. They are unique infectious agents that can cause disease in plants.

92. Which among the following are the smallest living cells, known without a definite cell wall, pathogenic to plants as well as animals and can survive without oxygen?

• A. Pseudomonas
• B. Mycoplasma
• C. Nostoc
• D. Bacillus

Explanation: Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:Mycoplasma is the smallest living cells known without a definite cell wall, pathogenic to both plants and animals, and capable of surviving without oxygen. Here's an explanation of each option:1. Pseudomonas: Pseudomonas is a type of bacteria that possesses a cell wall and cannot be considered the smallest living cell without a definite cell wall. It is not pathogenic to animals and is aerobic, requiring oxygen for survival.2. Mycoplasma: Mycoplasma is a genus of bacteria that lacks a rigid cell wall and is known to be one of the smallest living cells. Some species of Mycoplasma are pathogenic to both plants and animals. They are also facultative anaerobes, meaning they can survive with or without oxygen.3. Nostoc: Nostoc is a genus of cyanobacteria (blue-green algae) that have a definite cell wall and do not fit the description of the smallest living cells without a cell wall. They are photosynthetic and can fix nitrogen.4. Bacillus: Bacillus is a genus of bacteria that possess a cell wall, and they are not the smallest living cells without a cell wall. They are aerobic bacteria and are not typically pathogenic to both plants and animals.So, Mycoplasma meets all the criteria mentioned in your question.

93. Which of the following components provides sticky character to the bacterial cell?

• A. Nuclear membrane
• B. Plasma membrane
• C. Glycocalyx
• D. Cell wall

Explanation: The component that provides the sticky character to the bacterial cell is the Glycocalyx. Here's an explanation of each option:1. Nuclear membrane: The nuclear membrane, also known as the nuclear envelope, is found in eukaryotic cells and surrounds the nucleus. Bacterial cells are prokaryotic and do not have a defined nucleus or nuclear membrane.2. Plasma membrane: The plasma membrane, also known as the cell membrane, is present in both eukaryotic and prokaryotic cells, including bacterial cells. It plays a crucial role in controlling the passage of substances into and out of the cell but is not primarily responsible for the sticky character of the cell.3. Glycocalyx: The Glycocalyx is a gel-like layer of carbohydrates that surrounds the cell membrane of many bacterial cells. It is responsible for the sticky character of the cell and plays a significant role in adhesion, protection, and biofilm formation.4. Cell wall: The cell wall in bacterial cells provides structural support and protection but is not primarily responsible for conferring a sticky character to the cell.So, in this context, the Glycocalyx is the component that provides the sticky character to the bacterial cell.

94. Methanogens belong to:

• A. Eubacteria
• B. Archaebacteria
• C. Dinoflagellates
• D. Slime moulds

Explanation: Methanogens belong to the archaebacteria group. Here's an explanation for each of the options:1. Eubacteria: Methanogens are not part of the eubacteria group. Eubacteria are the typical bacteria that are commonly found in various environments.2. Archaebacteria: Methanogens fall under the archaebacteria group. Archaebacteria are a distinct domain of microorganisms that are known for their ability to thrive in extreme environments, and methanogens are a subgroup of these archaebacteria that produce methane as a metabolic byproduct.3. Dinoflagellates: Dinoflagellates are a type of unicellular protist, not bacteria, so they are not related to methanogens.4. Slime molds: Slime molds are also not related to methanogens. Slime molds are part of the kingdom Protista and have a different biological classification compared to methanogens.

95. The primitive prokaryotes responsible for the production of biogas from the dung of ruminant animals, include the

• A. Methanogens
• B. Sulphate reducing bacteria
• C. Halophiles
• D. Thermoacidophiles

Explanation: Sure, I can explain each of these options:1. **Methanogens**: Methanogens are a type of archaea, which are primitive prokaryotic microorganisms. They are responsible for the production of biogas from the dung of ruminant animals. Methanogens are unique in that they produce methane (CH4) as a metabolic byproduct. They are often found in the digestive systems of ruminant animals like cows, where they help break down cellulose and other organic matter, producing methane in the process.2. **Sulfate-Reducing Bacteria (Sulfate-Reducing Prokaryotes)**: Sulfate-reducing bacteria (SRB) are a group of bacteria responsible for the production of hydrogen sulfide gas (H2S) as part of their metabolism. While they play a role in biogas production, they are not as directly involved as methanogens. SRB can compete with methanogens in anaerobic environments and can influence the composition of biogas.3. **Halophiles**: Halophiles are prokaryotes that thrive in high-salinity environments, such as salt flats or saline lakes. They are not directly involved in biogas production from ruminant dung but have unique adaptations to saline conditions.4. **Thermoacidophiles**: Thermoacidophiles are prokaryotes that can thrive in extremely high-temperature and acidic environments, such as hot springs or volcanic areas. They are not typically associated with biogas production from ruminant dung but have adapted to harsh conditions.To summarize, methanogens are the primary prokaryotes responsible for producing biogas (methane) from the dung of ruminant animals due to their ability to digest organic matter and produce methane gas during their metabolic processes. Other prokaryotes, like sulfate-reducing bacteria, may also play a role in biogas production but are not as directly involved as methanogens. Halophiles and thermoacidophiles have specific environmental preferences and are not typically associated with biogas production.

96. Which one of the following statements is wrong?

• A. Eubacteria are also called false bacteria.
• B. Phycomycetes are also called algal fungi.
• C. Cyanobacteria are also called bluegreen algae.
• D. Golden algae are also called desmids.

Explanation: The statement "Eubacteria are also called false bacteria" is incorrect. Eubacteria are commonly referred to as "true bacteria" or "common bacteria," not "false bacteria."Here are explanations for each option:1. Eubacteria are indeed called "true bacteria" or "common bacteria" because they represent the vast majority of known bacteria and are not "false bacteria."2. Phycomycetes are also called "algal fungi" because they share characteristics with both algae and fungi, so this statement is correct.3. Cyanobacteria are indeed called "blue-green algae" because they resemble algae, even though they are actually a type of bacteria, so this statement is accurate.4. Golden algae are also known as "desmids." Desmids are a specific type of unicellular green algae, so this statement is correct.Therefore, the incorrect statement is the first one about Eubacteria.

97. Which of the following statements is wrong for viroids?

• A. They cause infections.
• B. Their RNA is of high molecular weight.
• C. They lack a protein coat.
• D. They are smaller than viruses.

Explanation: RNA of viroid has low molecular weight. The statement "Their RNA is of high molecular weight" is wrong for viroids.Here are explanations for each option:1. "They cause infections": This statement is correct. Viroids are small, infectious RNA molecules that can cause disease in plants. They do not infect animals or humans, but they can have a significant impact on agriculture by causing diseases in crops.2. "Their RNA is of high molecular weight": This statement is incorrect. Viroids have RNA that is of very low molecular weight. In fact, one of the distinguishing features of viroids is their small size, as they consist of a single-stranded RNA molecule with a low molecular weight. This sets them apart from viruses, which typically have larger and more complex genomes.3. "They lack a protein coat": This statement is correct. Viroids do not have a protein coat, which is another characteristic that distinguishes them from viruses. Viruses usually have a protein coat called a capsid that surrounds their genetic material, while viroids consist solely of the RNA molecule itself.4. "They are smaller than viruses": This statement is correct. Viroids are indeed smaller than viruses. They are among the smallest infectious agents known and consist of a single circular RNA molecule, typically around a few hundred nucleotides in length, whereas viruses can be much larger and more complex in structure.

98. One of the major components of cell wall of most fungi is:

• A. Cellulose
• B. Hemicellulose
• C. Chitin
• D. Peptidoglycan

Explanation: Certainly! The major component of the cell wall of most fungi is chitin. Here's an explanation of each of the options:1. Cellulose: - Cellulose is a structural polysaccharide found in the cell walls of plants and some algae, but it is not a major component of fungal cell walls. Fungi have chitin in their cell walls, which is different from cellulose.2. Hemicellulose: - Hemicellulose is another complex carbohydrate found in plant cell walls, but it is not a primary component of fungal cell walls. Fungal cell walls primarily consist of chitin.3. Chitin: - Chitin is the primary structural component of fungal cell walls. It is a complex carbohydrate made up of long chains of N-acetylglucosamine (GlcNAc) molecules. Chitin provides strength and rigidity to the fungal cell wall, similar to how cellulose functions in plant cell walls.4. Peptidoglycan: - Peptidoglycan is a structural component of bacterial cell walls, not fungal cell walls. Fungi and bacteria have distinct cell wall compositions, with fungi having chitin in their cell walls and bacteria having peptidoglycan.So, in summary, chitin is the major component of the cell wall of most fungi, while the other options (cellulose, hemicellulose, and peptidoglycan) are not typically found in fungal cell walls.

99. Chrysophytes, Euglenoids, Dinoflagellates and Slime moulds are included in the Kingdom:

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

Explanation: Certainly, let me explain the classification of these microorganisms:1. **Fungi**: None of the mentioned organisms belong to the Fungi kingdom. Fungi are a separate kingdom that includes organisms like mushrooms, yeasts, and molds. They are characterized by their cell walls made of chitin and their mode of nutrition, which is typically absorptive.2. **Animalia**: Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds are not part of the Animalia kingdom. Animals are multicellular, heterotrophic organisms that exhibit a wide range of characteristics, including the ability to move and a lack of cell walls.3. **Monera**: The Monera kingdom, which is now considered obsolete, included unicellular prokaryotic organisms like bacteria. The organisms you mentioned are eukaryotic and thus do not fall under the Monera category.4. **Protista**: The Protista kingdom is where you'll find Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds. These are all eukaryotic microorganisms that don't fit neatly into the categories of animals, plants, or fungi. Protists are a diverse group, and they can be unicellular or multicellular, photosynthetic or heterotrophic. This kingdom is often considered a "catch-all" for eukaryotes that don't fit elsewhere in the classification system.So, the correct answer is **Protista** for Chrysophytes, Euglenoids, Dinoflagellates, and Slime molds.

100. The imperfect fungi which are decomposers of litter and help in mineral cycling belong to:

• A. Phycomycetes
• B. Ascomycetes
• C. Deuteromycetes
• D. Basidiomycetes

Explanation: Imperfect fungi that are decomposers of litter and play a role in mineral cycling can belong to various fungal groups. Let me explain each of the options you provided:1. **Phycomycetes:** - Phycomycetes are commonly referred to as water molds and belong to the phylum Zygomycota.While some Zygomycetes are parasitic, many can act as saprophytes, decomposing dead organic matter, including litter, and participating in mineral cycling.2. **Ascomycetes:** - Ascomycetes are a diverse group of fungi that include the morels, truffles, and yeast, among others. Some ascomycetes, such as those in the genus Penicillium, are well-known decomposers of organic material and play a significant role in breaking down litter and recycling nutrients.3. **Deuteromycete (anamorphic fungi):** - Deuteromycetes, also known as fungi imperfecti, are fungi that do not have a known sexual reproductive stage and have been classified based on their asexual structures. Some deuteromycetes are decomposers and can contribute to the decomposition of litter, although their classification is based on the absence of a sexual reproductive cycle.4. **Basidiomycetes:** - Basidiomycetes are a diverse group that includes mushrooms, toadstools, and bracket fungi. Many basidiomycetes are involved in the decomposition of organic matter, particularly in forest ecosystems. They help break down litter and recycle nutrients.It's important to note that while these groups may contain species with decomposer roles, the specific ecological functions of fungi can vary within each group, and they are not limited to a single ecological niche. Fungi play a crucial role in nutrient cycling and decomposition processes in various ecosystems.