All Free Biology MCQs with Answers

• 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…

• 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…

• 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…

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

Explanation: Bacteria are classified based on the arrangement of their flagella, which affects their motility.

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

Explanation: The microbes also contain the same chlorophyll a compound used by plants.

• 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…

• 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…

• 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…

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

Explanation: After the lag phase, bacterial cells enter the exponential or log phase.

• A. Excrete
• B. Reproduce
• C. Decline phase
• D. Stop phase

Explanation: At the decline phase, bacterial growth decreases exponentially and many bacteria begin dying due to lack of nutrients or unfavorable…

• A. Extremophile
• B. Methanogen
• C. Extremophyte
• D. Extremogeus

Explanation: The correct term for organisms that live in extreme environments is extremophile.

• A. Alpha proteobacteria
• B. Beta proteobacteria
• C. Gamma proteobacteria
• D. Delta proteobacteria

Explanation: The correct answer is Gamma proteobacteria. This group includes chemolithotrophic sulfur bacteria, which are capable of oxidizing H2S to…

• A. Cyanobacteria
• B. Phototrophic organisms
• C. Anaerobic organisms
• D. All of the above

Explanation: It is a fact that the first organisms that oxygenated the atmosphere were cyanobacteria

• A. Beta-protobacteria
• B. Gama-protobacteria
• C. Alpha-protobacteria
• D. Delta-protobacteria

Explanation: Rhizobium belongs to alpha proto-bacteria, this is a fact and has to be learnt

• A. Fungi
• B. Bacteria
• C. Algae
• D. Plants

Explanation: Myxospores are actually not spores produced by fungi, but rather by certain groups of bacteria called Myxobacteria.

• A. Bacill
• B. Spirilla
• C. Vibrio
• D. Cocci

Explanation: Bacillus is an example of bacteria that can be atrichous, meaning they do not have flagella or hair-like structures for movement.

• A. Bacteria
• B. Algae
• C. Fungi
• D. Both (A) & (B)

Explanation: The peptidoglycan layer is found in the cell wall of bacteria. It is a unique structural component that provides strength and rigidity to…

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

Explanation: A bacterium with a single polar flagellum is classified as Monotrichous.

• A. Diatoms
• B. Dinoflagellates
• C. Water molds
• D. Myxomycota

Explanation: The rapid increase in the population of red dinoflagellate (a type of algae), causes the sea to appear red, which is responsible for the…

• A. Merozoites
• B. Sporozoites
• C. Gametocytes
• D. Oocytes

Explanation: The well-matured sporozoites are injected into the human host through the saliva of an Anopheles mosquito when it bites to feed on the…