Free Biodiversity and Variety of Life MCQs with Answers

2261. Methanopyrus kandleri is an organism that lives in a hydrogen-carbon dioxide environment and was first discovered in a hydrothermal vent where temperatures reached 230°F. What sort of organism is this?

• A. Protist
• B. Cyanobacteria
• C. Archaea
• D. Bacteria

Explanation: Methanopyrus kandleri is classified as an archaeon because it thrives in extreme environments, such as hydrothermal vents, where temperatures and chemical conditions are extreme. Archaea are known for their ability to survive in such harsh conditions. Protists, being eukaryotic, are not suited to such environments. Cyanobacteria are photosynthetic and not adapted to high-temperature environments like hydrothermal vents. Bacteria, although diverse, do not encompass Methanopyrus kandleri, which is specifically categorized under Archaea due to its unique characteristics and environmental adaptations.

2262. The flagella originate from which part of the cell?

• A. Basal body
• B. Cell membrane
• C. Cell wall
• D. Capsule

Explanation: In prokaryotic cells, the flagella originate from the basal body, which is embedded in the cytoplasm and serves as the anchoring point for the flagellum. This structure is responsible for the rotation and movement of the flagella, aiding in cell motility. The basal body has a similar structural arrangement to centrioles, featuring microtubule triplets. The cell membrane, cell wall, and capsule, while important for cellular integrity and protection, do not serve as the origin of the flagella.

2263. The presence of which of these cell structures would confirm that the cell is prokaryotic?

• A. Cytoplasm
• B. Ribosomes
• C. Flagella
• D. Peptidoglycan cell wall

Explanation: The presence of a peptidoglycan cell wall is a unique characteristic of most prokaryotic cells, distinguishing them from eukaryotic cells, which do not have peptidoglycan. This rigid layer provides structural support and protection, making it a strong indicator of prokaryotic cells. In contrast, cytoplasm, ribosomes, and flagella are found in both prokaryotic and eukaryotic cells, and thus their presence cannot confirm that a cell is prokaryotic.

2264. Photosythetic bacteria have the ability to release:

• A. Sulphur
• B. Oxygen
• C. Hydrogen
• D. Carbon dioxide

Explanation: Prokaryotes use H2S instead of water so they release sulphur, unlike plants and algae which use water as a hydrogen source and thus release hydrogen.

2265. Many bacteria are motile due to the presence of:

• A. Flagella
• B. Pili
• C. Cilia
• D. Microtubules

Explanation: The correct answer is Flagella. Flagella are specialized structures that provide motility to bacteria by rotating like propellers, allowing them to move towards or away from various stimuli. This is a key feature distinguishing motile bacteria from non-motile ones. Other structures like Pili are involved in adhesion rather than movement, Cilia are not present in bacteria, and Microtubules are eukaryotic cell structures unrelated to bacterial motility.

2266. The plasma membrane of eukaryotes differ from that of bacteria in having:

• A. Peptidoglycan
• B. Respiratory enzymes
• C. Cholesterol
• D. Phospholipids

Explanation: Cholesterol is a lipid molecule that is an essential component of the plasma membrane in eukaryotic cells. It is primarily found in the animal kingdom, as plants have different types of sterols. Cholesterol plays a crucial role in maintaining the fluidity and stability of the plasma membrane, allowing it to function properly. It helps regulate membrane permeability and protects the membrane from extreme temperatures.

2267. Moist heat causes_and kills the microbes:

• A. Oxidation of proteins
• B. Coagulation of proteins
• C. Degeneration of nucleic acids
• D. Bursting up of cells

Explanation: Moist heat primarily kills microbes by causing the coagulation or denaturation of proteins. This process disrupts the protein's three-dimensional structure, leading to the loss of their functional shape, which is crucial for microbial survival. The coagulation of proteins results in the inactivation or destruction of essential microbial enzymes and structures, ultimately leading to cell death. Although moist heat can also cause damage to nucleic acids and, in extreme cases, lead to cell lysis, these are secondary effects. Thus, the coagulation of proteins is the most significant mechanism by which moist heat kills microbes.

2268. Pick up the component which is comparatively in greater amount in Gram Negative cell wall:

• A. Lipids
• B. Peptidoglycan
• C. Teichoic acid
• D. Lipoteichoic acid

Explanation: The correct answer is Lipids. Gram-negative bacteria have a unique cell wall structure characterized by an outer membrane rich in lipids, including lipopolysaccharides (LPS), phospholipids, and lipoproteins. This lipid-rich outer membrane provides a protective barrier and plays a significant role in the bacteria's interaction with its environment. In contrast, the peptidoglycan layer in Gram-negative bacteria is much thinner than in Gram-positive bacteria, and teichoic and lipoteichoic acids are absent as they are specific to Gram-positive bacteria.

2269. The structure that contains the gene responsible for drug resistance in bacteria is:

• A. Nucleoids
• B. Mesosomes
• C. Chromatin Bodies
• D. Plasmids

Explanation: Plasmids are extrachromosomal DNA found in many bacteria and are known for carrying genes that can provide resistance to antibiotics. This capability makes them crucial for the survival of bacteria in environments with antibiotics. Unlike the nucleoid, which contains the main genetic material of the bacterium, plasmids are smaller DNA structures that can replicate independently and often carry genes beneficial for bacterial adaptation.Nucleoids, mesosomes, and chromatin bodies do not typically carry genes for drug resistance. The nucleoid contains the essential genetic material of the bacterial cell, mesosomes are associated with cell membrane processes, and chromatin bodies are involved in phosphate metabolism, not in storing genetic information for drug resistance.

2270. Photosynthetic bacteria utilize H₂S instead of water and liberate one of the following instead of oxygen:

• A. Sulphur
• B. Phosphorus
• C. Calcium
• D. Magnesium

Explanation: Photosynthetic bacteria is mistakenly typed as photosynthesis bacteria. Option A: Sulphur is correct. Photosynthetic bacteria utilize H2S instead of water and liberate sulfur instead of oxygen. CO2 + H20 → (CH2O)n + H2S + 2S STB Pg 105.