All Free Biology MCQs with Answers

2531. In the five kingdom classification, Chlamydomonas and Chlorella have been included in:

• A. Protista
• B. Algae
• C. Plantae
• D. Monera

Explanation: In order to develop phylogenetic classification, R.H. Whittaker (1969), an American taxonomist, divided all the organisms into five kingdoms. Whittaker has used five criteria for delimiting the different kingdoms. (i) Complexity of cell structure, prokaryotic and eukaryotic (ii) 19 Complexity of body structure or structural organization, unicellular and multicellular. (iii) Mode of nutrition which is divergent in multicellular kingdoms. (iv) Ecological life style like producers (plantae), decomposers (fungi) and consumers (animalia), (v) Phylogenetic relationship. When such characteristics were considered, the fungi were placed in a separate kingdom - Kingdom Fungi. All prokaryotic organisms were grouped together under Kingdom Monera and the unicellular eukaryotic organisms were placed in Kingdom Protista. Kingdom Protista has brought together Chlamydomonas, Chlorella (earlier placed in Algae within Plants and both having cell walls) with ParamoeciumandAmoeba(which were earlier placed in the animal kingdom which lack cell wall). It has put together organisms which, in earlier classifications, were placed in different kingdoms. This happened because the criteria for classification changed

2532. Which one of the following also act as as a catalyst in a bacterial cell?

• A. 5S rRNA
• B. snRNA
• C. hnRNA
• D. 23S rRNA

Explanation: Among the options you provided, 23S rRNA also acts as a catalyst in a bacterial cell. Here's an explanation of each option:1. 5S rRNA: 5S ribosomal RNA is a component of the ribosome, which is involved in protein synthesis in both bacterial and eukaryotic cells. It plays a structural role in the ribosome but does not act as a catalyst.2. snRNA (small nuclear RNA): snRNAs are a class of RNA molecules found in the nucleus of eukaryotic cells. They are involved in processes like pre-mRNA splicing and do not typically act as catalysts.3. hnRNA (heterogeneous nuclear RNA): hnRNA is an intermediate molecule in the processing of pre-mRNA in eukaryotic cells. It undergoes modifications to become mature mRNA and does not act as a catalyst.4. 23S rRNA: 23S ribosomal RNA is part of the large subunit of the bacterial ribosome. It has peptidyl transferase activity, which catalyzes the formation of peptide bonds during protein synthesis. This catalytic activity makes it an essential component for the translation of genetic information into proteins in bacterial cells.So, 23S rRNA is unique among the options in that it acts as a catalyst in a bacterial cell, specifically in the ribosome during protein synthesis.

2533. In eubacteria, a cellular component that resembles eukaryotic cell is:

• A. Plasma membrane
• B. Nucleus
• C. Ribosomes
• D. Cell wall

Explanation: Plasma membrane of eubacteria resembles plasma membrane of eukaryotic cell. But nucleus, ribosomes and cell wall are little different in eukaryotic cell in their structure and organization from eubacterial cell. Plasma Membrane: The plasma membrane, also known as the cell membrane, is a structure shared by both eubacteria (prokaryotes) and eukaryotic cells. It serves as a selective barrier that controls the passage of substances in and out of the cell, just like in eukaryotic cells. Nucleus: Eubacteria do not possess a true nucleus. Unlike eukaryotic cells, which have a distinct membrane-bound nucleus housing their genetic material, eubacteria have a nucleoid region where their DNA is located, but it lacks a membrane. Ribosomes: Ribosomes are cellular structures responsible for protein synthesis. Both eubacteria and eukaryotic cells have ribosomes, but there can be some differences in their ribosome structure and organization. Cell Wall: Eubacteria typically have a cell wall, which is a rigid outer layer providing structural support and protection to the cell. This is a feature shared with some eukaryotic cells, such as plant cells and fungi, but not all eukaryotic cells have cell walls.

2534. Which one of the following organisms is not an eukaryote?

• A. Paramecium caudatum
• B. Escherichia coli
• C. Euglena viridis
• D. Amoeba proteus

Explanation: 1. Paramecium caudatum: Paramecium caudatum is a eukaryotic organism. Eukaryotes are characterized by having a true nucleus enclosed within a membrane, and Paramecium fits this description.2. Escherichia coli: Escherichia coli, commonly known as E. coli, is a prokaryotic organism. It is a bacterium, which means it lacks a true nucleus and other membrane-bound organelles. Instead, its genetic material is found in a single circular chromosome in the cytoplasm.3. Euglena viridis: Euglena viridis is a eukaryotic organism. It is a single-celled organism with a well-defined nucleus and other membrane-bound organelles, which are characteristics of eukaryotes.4. Amoeba proteus: Amoeba proteus is also a eukaryotic organism. Like Paramecium and Euglena, it possesses a true nucleus enclosed by a nuclear membrane, confirming its classification as a eukaryote.So, among the options provided, Escherichia coli is the one that is not a eukaryote. It is a prokaryotic bacterium.

2535. The pathogen Microsporum responsible for ringworm disease in humans belongs to the same kingdom of organisms as that of

• A. Taenia, a tapeworm
• B. Wuchereria, a filarial worm
• C. Rhizopus, a mold
• D. Ascaris, a round worm

Explanation: Rhizopus, a mold:Rhizopus is a genus of fungi, specifically a type of mold. Molds are also classified under the kingdom Fungi, similar to Microsporum.

2536. Virus envelope is known as:

• A. Capsid
• B. Virion
• C. Nucleoprotein
• D. Core

Explanation: The nucleic acid of a virus is surrounded by a protein coat called the capsid. The capsid is composed of protein subunits called capsomeres. In some viruses, the capsid is covered by an envelope, which usually consists of some combination of lipids, proteins and carbohydrates.

2537. Single celled eukaryotes are included in:

• A. Protista
• B. Fungi
• C. Archaea
• D. Monera

Explanation: Protista is a kingdom in the classification of life forms. It consists of a diverse group of eukaryotic microorganisms that are primarily single-celled but can also be multicellular.Protists include various organisms like amoebas, paramecia, diatoms, and algae. Many of these single-celled eukaryotes do not fit neatly into the other major kingdoms (Animalia, Plantae, and Fungi).

2538. Some hyperthermophilic organisms that grow in highly acidic (pH 2) habitats belong to the two groups:

• A. Eubacteria and archaea
• B. Cyanobacteria and diatoms
• C. Protists and mosses
• D. Liverworts and yeasts

Explanation: Explanations for each of the given options:1. Eubacteria and Archaea: - Eubacteria and Archaea are two distinct domains of microorganisms. Some hyperthermophilic organisms that grow in highly acidic (pH 2) habitats can belong to these groups.Eubacteria are a diverse group of bacteria that can thrive in extreme environments, including highly acidic conditions.Archaea are also single-celled microorganisms, and some of them are known to be hyperthermophiles, meaning they can live in extremely high-temperature environments, including acidic ones.2. Cyanobacteria and Diatoms: - Cyanobacteria are a group of photosynthetic bacteria that are often found in various environments, including acidic habitats. They can tolerate a range of pH levels.Diatoms are a type of photosynthetic microalgae, and while they are not typically associated with highly acidic conditions, some diatom species can adapt to a wide range of pH levels.3. Protists and Mosses: - Protists are a diverse group of eukaryotic microorganisms, including single-celled organisms like amoebas and algae. Some protists can be found in acidic environments.Mosses are small, non-vascular plants that typically grow in moist and shaded habitats. They are not typically associated with highly acidic conditions.4. Liverworts and Yeasts: - Liverworts are small, non-vascular plants similar to mosses. They can grow in a variety of habitats but are not specifically known for thriving in highly acidic environments.Yeasts are unicellular fungi and are not typically associated with highly acidic habitats. They are commonly used in various industrial and scientific applications.In summary, Eubacteria and Archaea are more likely to include hyperthermophilic organisms adapted to highly acidic conditions. The other options may have representatives that can tolerate acidic environments to some extent, but they are not as specialized for extreme acidity as Eubacteria and Archaea.

2539. One of the freeliving, anaerobic nitrogen fixer is:

• A. Beijernickia
• B. Rhodospirillum
• C. Rhizobium
• D. Azotobacter

Explanation: Rhodospirillum is a free living photosynthetic anaerobic nitrogen fixing nonsulphur bacteria. It is capable of synthesizing its organic food in presence of light and in absence of O2 by a process known as bacterial photosynthesis. Beijernickia and Azotobacter are free living but aerobic nitrogen fixing bacteria. Rhizobium is a symbiotic nitrogen fixing bacteria.

2540. Give below is the diagram of a bacteriophage. In which one of the options all the four parts A, B, C and D are correct?

• A. Tail fibres, Head, Sheath, Collar
• B. Sheath, Collar, Head, Tail fibres
• C. Head, Sheath, Collar, Tail fibres
• D. Collar, Tail fibres, Head, Sheath

Explanation: A-Head, B-Sheath, C-Collar, D-Tail fibre