All Free Biology MCQs with Answers

2191. A group of 8 cocci is called______________?

• A. Diplococci
• B. Octococci
• C. Tetrad
• D. Sarcina

Explanation: A group of eight cocci arranged as a cubical packet is called a sarcina, produced by division in three planes. Tetrad refers to four cocci, while diplococci refers to pairs, so choosing either confuses the number of cells in the arrangement.

2192. Which of the following bacteria are thick rigid and spiral______________?

• A. Vibrio
• B. Spirillum
• C. Spirochete
• D. Coccus

Explanation: Spirilla are rigid, thick-walled, spiral-shaped bacteria and usually move with polar flagella. Spirochetes are also spiral but are thin and flexible, which is why they are the likely alternative distractor.

2193. The first bacterium isolated was_________________?

• A. Coccus
• B. Bacillus
• C. Vibrio
• D. Spirochete

Explanation: Bacillus anthracis was among the earliest bacteria isolated and studied in pure culture, especially through Robert Koch's work on anthrax. Students may choose coccus because cocci are a common bacterial form, but the question refers to the historical isolate Bacillus rather than a general shape.

2194. Coccobacillus has a shape similar to________________?

• A. Diplobacillus
• B. Sarcina
• C. Egg
• D. None of these

Explanation: A coccobacillus is an intermediate form between a coccus and a bacillus, appearing short, oval, or egg-shaped. Diplobacillus describes paired rod-shaped cells, so it refers to an arrangement rather than the egg-like shape.

2195. Some bacteria ranging occasionally a size of 500 ?m in length are___________________?

• A. Escherichia coli
• B. Spirochetes
• C. Mycoplasma
• D. Epulopiscuim

Explanation: Some spirochetes are exceptionally long and may reach about 500 μm, despite being very thin spiral cells. Epulopiscium is also a giant bacterium, so students may select it when focusing only on size, but the stated range is commonly given for certain spirochetes.

2196. In bacterial categories the bacteria smaller in number are_______________?

• A. Gram-ive bacteria
• B. Eubacteria
• C. Ancient bacteria
• D. Gram +ive bacteria

Explanation: Ancient bacteria, or archaea, represent a much smaller and more specialized group than the broad group of eubacteria in traditional classifications. The likely alternative is Gram-positive bacteria, but Gram-positive and Gram-negative are cell-wall categories, not the major-versus-minor evolutionary groups intended here.

2197. E. coli and example of entrobacteriace is important for causing diarrheal diseases its size is____________?

• A. 0.1-600 um
• B. 100-200 nm
• C. 1.1-1.5 um (width) 2.0-6.0 um (length)
• D. 0.75-1.25 um

Explanation: E. coli is a short rod approximately 1.1-1.5 μm wide and 2.0-6.0 μm long, so option c gives the appropriate bacterial dimensions with units. Students may choose 100-200 nm because bacteria are microscopic, but nanometres describe much smaller structures such as ribosomes, not the whole E. coli cell.

2198. Which of the following structure is not present in all the bacteria_____________?

• A. Cell membrane
• B. Chromatin bodies
• C. Ribosomes
• D. Capsule

Explanation: All bacteria possess a plasma membrane, genetic material in a chromatin-like nucleoid, and ribosomes, but a capsule is present only in some species. Students may choose the cell membrane because bacterial diagrams differ in how it is drawn, but it is an essential structure of every bacterial cell.

2199. Other name for Kingdom monera is_______________?

• A. Protoctista
• B. Prokaryotae
• C. Archae
• D. None of these

Explanation: Kingdom Monera traditionally includes organisms with prokaryotic cells, so it is also called Prokaryotae in older five-kingdom classifications. These organisms lack a membrane-bound nucleus and other membrane-bound organelles. Students may choose c because archaea are a major prokaryotic group, but Archaea is not the complete alternative name for Monera in this classification.

2200. Which of the following organisms have Chitin as a major structural component of their cell wall________________?

• A. Prokaryotae
• B. Protoctista
• C. Plantae
• D. Fungi

Explanation: Fungi have cell walls made mainly of chitin, a nitrogen-containing polysaccharide that also occurs in arthropod exoskeletons. Plant cell walls are mainly cellulose, so students may choose Plantae by confusing chitin with the common structural material of plants.