Free Biodiversity and Variety of Life MCQs with Answers

2221. Approximately how many species of bacteria are known to cause diseases in humans?

• A. 100
• B. 150
• C. 200
• D. 250

Explanation: 200 species of bacteria are pathogenic, i.e can cause disease like cholera and tuberculosis in humans.

2222. Some bacteria have resistant organelles called as:

• A. Spores
• B. Cysts
• C. Granules
• D. All of these options are correct

Explanation: Option A is correct since spores are considerably more resistant to moist and dry heat than non-sporulating bacteria. Spores are more resistant to unfavorable environmental conditions. Cysts are less resistant compared to spores.

2223. Sex pili are formed in which of the following processes?

• A. Sexual reproduction
• B. Binary fission
• C. Mitosis
• D. Conjugation

Explanation: Conjugative or sex pili are special projections originating from many bacteria's cytoplasmic membranes. They are involved in the exchange of genetic material between the bacteria. This method is known as conjugation. It is analogous to sexual reproduction, hence also called 'sex' pili.

2224. The structure of prokaryotes which is involved in attachment:

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

Explanation: Pili are hollow, nonhelical, filamentous appendages. They are primarily involved in a mating process between cells called conjugation. It helps the bacteria to stick to each other and to surfaces such as rocks in the flowing streams or to the lining of human intestines. Flagella helps with the motility of the bacteria while cilia are not present in prokaryotic cells. The cytoplasm also helps in the transport of material by cyclosis, the movement of cytoplasm.

2225. Which one of the following edible products is widely pasteurized?

• A. Soft drinks
• B. Mango squash
• C. Milk
• D. Orange Juice

Explanation: Milk: This option is the correct answer. Milk is widely pasteurized to kill harmful bacteria and increase its shelf life. Pasteurization involves heating the milk to a specific temperature for a set period of time and then rapidly cooling it. This process helps to eliminate pathogenic bacteria while retaining the nutritional value of the milk.

2226. Cyanobacteria are:

• A. Photoautotrophic bacteria
• B. Chemosynthetic bacteria
• C. Saprotrophic bacteria
• D. Parasitic bacteria

Explanation: Cyanobacteria synthesize their own food from inorganic substances and this fall into the category of photoautotrophs.

2227. When the division of cells is in three planes, the arrangement is known as:

• A. Diplococcus
• B. Sarcina
• C. Streptococcus
• D. Staphylococcus

Explanation: Option A is incorrect because Division in one plane that form a pair of coocci is called diplococcus.Option B is correct since Division in three planes produces an arrangement called sarcina that is a cube of 8 cocci.Option C is incorrect because Streptococcus is division in one plane and has more than 2 cocci.Option D is incorrect because Staphylococcus is arrangement in which cocci are arranged in irregular , often grape like cluster.

2228. Pasteurization technique is widely used for preservation of:

• A. Water
• B. Heat
• C. Milk products
• D. Vaccines

Explanation: Pasteurization is a technique to remove pathogenic organisms in certain foods and liquids. In water, bacteria is killed through the process of chlorination. Hence, the only remaining viable option is option C : Milk products.

2229. A bacterium which has a group of two or more flagella inserted at one pole of the cell

• A. Monotrichous
• B. Peritrichous
• 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 - Tufts of flagella extend from one end or both ends of the cell. 4. Peritrichous - Multiple flagella randomly distributed over the entire bacterial cell. Thus, the correct answer is 'Lophotrichous.'

2230. The following are sexual reproduction methods in bateria except

• A. Transformation
• B. Transduction
• C. Binary fission
• D. Conjugation

Explanation: In bacteria,genetic recombination takes place. Genetic recombination is primitive type of sexual reproduction. There are three types of genetic recombination: Transformation,Transduction, Conjugation.