Free Biodiversity and Variety of Life MCQs with Answers

2041. In which of the following growth phases, the number of bacteria increases the most rapidly?

• A. Lag phase
• B. Log phase
• C. Stationary phase
• D. Death/Decline phase

Explanation: The exponential or the log phase is the phase during which the bacterium increases the most rapidly as shown in the figure below:

2042. Which of the following bacteria are able to release oxygen into the environment?

• A. Saprotrophic bacteria
• B. Parasitic bacteria
• C. Cyanobacteria
• D. Pathogenic bacteria

Explanation: The answer is tiny organisms known as cyanobacteria or blue-green algae. These microbes conduct photosynthesis using sunshine, water, and carbon dioxide producing carbohydrates and oxygen.

2043. Which of the following is true about the structure of a typical bacterium?

• A. It has cell wall
• B. It has cytoplasm
• C. It has genetic material
• D. All of the above

Explanation: A typical bacterium has all the structures listed from opinion A-C, including cell wall, cytoplasm and genetic material. Although some bacterias dont have cell walls, the question asks about a typical bacteria, hence option D is correct. Diagramatic representation of all the structures is given below:

2044. Tuberculosis is caused by?

• A. Bacterium
• B. Allergy
• C. Nicotine
• D. Virus

Explanation: Tuberculosis (TB) is caused by a bacterium called Mycobacterium tuberculosis. The bacteria usually attack the lungs, but TB bacteria can attack any part of the body such as the kidney, spine, and brain.

2045. Bacteria having a tuft of flagella at one end are called:

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

Explanation: There are four types of flagellar arrangements based on the number and placement of flagella on the cell. These are, 1. Monotrichous - A single flagellum extends from one end of the cell. 2. Amphitrichous - A single flagellum or multiple flagella extend from two ends of the cell. 3. Lophotrichous - Tuft of flagella extend from one end of the cell. 4. Peritrichous - Multiple flagella randomly distributed over the entire bacterial cell. Thus, the correct answer is 'Lophotrichous.' Option A, B and D are incorrect as their description does not match the requirement of the question i.e. bacteria having a tuft of flagella at one end of the cell.

2046. Which one of the following sets includes the bacterial diseases?

• A. Cholera, typhoid, mumps
• B. Tetanus, tuberculosis, measles
• C. Malaria, mumps, poliomyelitis
• D. Diphtheria, leprosy, plague

Explanation: Cholera is a bacteria infection caused by eating food or drinking water contaminated with Vibrio cholerae. Typhoid fever is caused by Salmonella typhi bacteria. Mumps is a viral disease caused by the mumps virus. Tetanus is bacteria infection caused by Clostridium tetani. Tuberculosis is caused by bacterium Mycobacterium tuberculosis. Measles is caused by virus paramyxovirus. Malaria is a disease caused by Plasmodium parasite. Poliomyelitis is infectious disease caused by the poliovirus. Diphtheria is an infection caused by the Corynebacterium diphtheriae bacterium. Leprosy is caused by bacteria Mycobacterium leprae. Plague is a bacterial infection caused by bacterial strain Yersinia pestis. Thus, the correct answer is 'Diphtheria, Leprosy, Plague.'

2047. Spirochaete bacterium Treponema Pallidum causes _.

• A. Gonorrhea
• B. Syphilis
• C. Genital herpes
• D. AIDS

Explanation: Treponema Pallidum causes a disease called Syphilis.

2048. Which of the following is not a component of extracellular matrix in bacteria?

• A. Cell wall
• B. Slime
• C. Capsule
• D. Cell membrane

Explanation: "Bacterial surface and walls are very diverse. Collectively complexes of layer external to the cell protoplasm are called as cell envelope and include capsule, slime and cell wall"

2049. What are labelled phases A, B, and C in the below given sigmoidal growth curve?

• A. A: Stationary, B: Log, C: Lag
• B. A: Lag, B: Stationary, C: Log
• C. A: Log, B: Lag, C: Stationary
• D. A: Lag, B: Log, C: Stationary

Explanation: When a graph is plotted taking into consideration time on one hand and growth rate, on the other hand, an S-shaped curve is obtained. It is called the "grand period of growth". This curve mainly shows four phases of growth: 1. Initial slow growth (lag phase). 2. The rapid period of growth (log phase), where maximum growth is seen in a short period. 3. The diminishing phase, where growth will be slow. 4. Stationary phase, where finally growth stops.

2050. Genetic recombination in bacteria can occur through:

• A. Conjugation
• B. Transformation
• C. Transduction
• D. All of the above

Explanation: Bacteria increase their genetic diversity through three recombination techniques: transduction, transformation and conjugation.