Free Biodiversity and Variety of Life MCQs with Answers

3091. Salmonella typhosa is a

• A. Coccus bacterium
• B. Bacillus bacterium
• C. Spirillus bacterium
• D. Nitrobacterium

Explanation: Salmonella typhosa is the scientific name for the bacillus bacterium responsible for causing typhoid fever, a severe and potentially life-threatening illness. It belongs to the genus Salmonella, which comprises gram-negative bacteria that are rod-shaped or bacillus.

3092. A bacterium that converts NO2 to NO3 is:

• A. Rhizobium
• B. Bacillus
• C. Nitrosomonas
• D. Nitrobacter

Explanation: Nitrobacter is the correct answer because it is involved in the second step of nitrification, where it converts nitrite (NO2) to nitrate (NO3). This is an essential step in the nitrogen cycle, making nitrogen available to plants in a more accessible form. Rhizobium is involved in nitrogen fixation, Bacillus is known for endospore production, and Nitrosomonas converts ammonia to nitrite, not nitrite to nitrate.

3093. Pigeon odour is released from the water bloom of:

• A. Slime mold
• B. Water mold
• C. Cyanobacteria
• D. Cyanobacteria Algae ponds

Explanation: The correct answer is Cyanobacteria Algae ponds. Cyanobacteria, often called blue-green algae, can form dense blooms in water, releasing odors due to the organic compounds they produce. These blooms can make the water smell unpleasant and affect its quality. Slime molds and water molds, while they exist in moist environments, do not typically contribute to offensive odors in water bodies. Cyanobacteria, due to their ability to proliferate rapidly in nutrient-rich waters, are the main culprits behind such issues.

3094. Bacteria maintain their survival by the formation of:

• A. Hormogonia
• B. Akinetes
• C. Endospores
• D. Zygospores

Explanation: Endospores are the correct answer because they are specialized, durable structures that allow bacteria to survive in unfavorable conditions. Unlike akinets or hormogonia, endospores can withstand extreme environmental stresses such as heat, desiccation, and chemicals. Zygospores, on the other hand, are related to fungi and protists and are not relevant to bacterial survival.

3095. When the entire body of a bacterium is covered by flagella, such a bacterium is called:

• A. Atrichous
• B. Lophotrichous
• C. Amphitrichous
• D. Peritrichous

Explanation: Bacteria are classified based on the arrangement of their flagella, which affects their motility. Peritrichous bacteria have flagella all over their surface, enabling them to move in various directions efficiently. This is in contrast to atrichous bacteria, which lack flagella entirely and are non-motile. Lophotrichous and amphitrichous bacteria have flagella localized to specific areas, either in bundles at one end or at both ends, respectively. Thus, the correct answer is D: Peritrichous.

3096. Blue green algae, besides chlorophyll also possess another pigment known as:

• A. Phycocyanin
• B. Phycoerythrin
• C. Phycobillirubin
• D. Phycobilliprotein

Explanation: The microbes also contain the same chlorophyll a compound used by plants. Some blue-green algae possess a different photosynthetic pigment, which is known as phycoerythrin.

3097. Murein cell-wall is composed of:

• A. Sugar and amino acids
• B. Calcium pectate
• C. Glycoprotein
• D. Peptidoglycan

Explanation: Bacterial cell walls are made of peptidoglycan, also called as murein, which is made from polysaccharide chains cross-linked by unusual peptides containing D-amino acids.

3098. Rhizobium belong to sub group of bacteria called:

• A. Alpha-Protobacteria
• B. Beta-Protobacteria
• C. Gamma-Protobacteria
• D. Delta-Protobacterla

Explanation: Proteobacteria is a phylum of gram-negative bacteria. The Proteobacteria are further divided into 5 classes: Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, Deltaproteobacteria, and Epsilonproteobacteria.The first class of Proteobacteria is the Alphaproteobacteria, many of which are obligate or facultative intracellular bacteria. Some species are characterized as oligotrophs, organisms capable of living in low-nutrient environments such as deep oceanic sediments. Rhizobium is a genus of alphaproteobacteria. Rhizobium are gram-negative nitrogen-fixing bacteria that occur either as free-living soil bacteria or in interaction with the roots of leguminous plants.

3099. The interval between two successive division of bacteria is called:

• A. Ecological time
• B. Population time
• C. Growth time
• D. Generation time

Explanation: Generation time is the time it takes for a population of bacteria to double in number or the interval between two successive divisions in bacteria. For many common bacteria, the generation time is quite short, 20-60 minutes under optimum conditions.

3100. Most disease symptoms appear during.

• A. Lag phase
• B. Log phase
• C. Die
• D. Generation time

Explanation: After the lag phase, bacterial cells enter the exponential or log phase. This is the time when the cells are dividing by binary fission and doubling in numbers after each generation time. Metabolic activity is high as DNA, RNA, cell wall components, and other substances necessary for growth are generated for division. In humans, the disease symptoms develop during the log phase because the bacterial production attains such a high level which damages the tissues.