Free Biodiversity and Variety of Life MCQs with Answers

2651. Protists are considered a polyphyletic group because they probably originated from

• A. A common moneran ancestor
• B. More than one moneran ancestor
• C. The heritable genetic changes in viruses
• D. The organic substances of the environment

Explanation: Protists are polyphyletic because they arose from multiple independent evolutionary lines among the first eukaryotes, meaning they trace their ancestry back to more than one moneran (prokaryotic) line via various endosymbiotic events.The other options are wrong because: a single ancestor would be monophyletic; organic substances refer to the origin of life (abiogenesis); and viruses are not the ancestors, as endosymbiosis was the key event.

2652. Protists that form a monophyletic lineage with plants are

• A. Fucus and Ulva
• B. Ulva and Spirogyra
• C. Polysiphonia and Fucus
• D. Polysiphonia and Spirogyra

Explanation: The protist group closely related to land plants is green algae, including Ulva and Spirogyra. So option B is correct. All other combinations are incorrect, as Fucus is related to brown algae, and Polysiphonia is related to red algae.

2653. The groups of protists that act as the major producers of aquatic ecosystems are

• A. Diatoms and Dinoflagellates
• B. Green algae and Zooflagellates
• C. Foraminiferans and Euglenoids
• D. Brown algae and Water molds

Explanation: The correct answer is Option A:diatoms and dinoflagellatesThese groups of protists are primary producers in aquatic ecosystems, responsible for a significant portion of photosynthesis. Diatoms, with their silica cell walls, convert sunlight into energy efficiently, while dinoflagellates contribute to marine plankton. Option B is incorrect because zooflagellates are not photosynthetic. Option C is incorrect because foraminiferans are heterotrophs, and euglenoids, though photosynthetic, are not primary ecosystem producers. Option D is incorrect because water molds are decomposers, and brown algae, while producers, are not widespread enough to be considered major producers in all aquatic ecosystems.

2654. Select the wrong statement.

• A. The walls of diatoms are easily destructible.
• B. 'Diatomaceous earth' is formed by the cell walls of diatoms.
• C. Diatoms are chief producers in the"Diatoms are chief producers in the oceans."
• D. Diatoms are microscopic and float passively in water.

Explanation: The wrong statement is: "Diatoms are chief producers in the oceans."Explanation of the options:1. "The walls of diatoms are easily destructible." - This statement is generally true. Diatom cell walls, also known as frustules, are made of silica and are relatively fragile, making them easily destructible under certain conditions.2. "'Diatomaceous earth' is formed by the cell walls of diatoms." - This statement is accurate. Diatomaceous earth is a sedimentary rock composed of the fossilized remains of diatoms, specifically their cell walls. It is often used for various industrial and agricultural purposes.3. "Diatoms are chief producers in the oceans." - This statement is incorrect. Diatoms are important primary producers in aquatic ecosystems, including oceans, but they are not the chief producers. Phytoplankton, including diatoms, play a significant role in marine food chains, but other microorganisms and algae also contribute to primary production in the oceans.4. "Diatoms are microscopic and float passively in water." - This statement is true. Diatoms are indeed microscopic, single-celled algae that float passively in water. They are a type of phytoplankton and play a crucial role in ocean ecosystems as a food source for various marine organisms.

2655. Select the wrong statement.

• A. The term 'contagium vivum fluidum' was coined by M. W. Beijerinck.
• B. Mosaic disease in tobacco and AIDS in human being are caused by viruses.
• C. The viroids were discovered by D.J.Ivanowsky.
• D. W.M.Stanley showed that viruses could be crystallised.

Explanation: The wrong statement is: "Mosaic disease in tobacco and AIDS in human beings are caused by viruses."Explanation of each statement:1. "The term 'contagium vivum fluidum' was coined by M. W. Beijerinck." - This statement is correct. Martinus Beijerinck, a Dutch microbiologist, coined the term "contagium vivum fluidum" to describe infectious agents that are smaller than bacteria, which we now know as viruses.2. "Mosaic disease in tobacco and AIDS in human beings are caused by viruses." - This statement is incorrect. Mosaic disease in tobacco is indeed caused by a virus, but AIDS (Acquired Immunodeficiency Syndrome) is caused by HIV (Human Immunodeficiency Virus), not a virus in general. It's a more specific virus that leads to AIDS.3. "The viroids were discovered by D.J. Ivanowsky." - This statement is incorrect. The discovery of viroids is credited to the American pathologist Theodor O. Diener, not D.J. Ivanowsky. Viroids are small, infectious RNA molecules that are distinct from viruses.4. "W.M. Stanley showed that viruses could be crystallized." - This statement is correct. Wendell Meredith Stanley, an American biochemist, successfully crystallized the tobacco mosaic virus in 1935. His work provided important evidence that viruses are distinct entities that can be purified and studied like other biological molecules.

2656. Cell wall is absent in:

• A. Mycoplasma
• B. Nostoc
• C. Aspergillus
• D. Funaria

Explanation: Mycoplasma (KingdomMonera) are the simplest and smallest free living prokaryotes which are devoid of a cell wall. Plasma membrane forms the outer boundary of the cell of mycoplasma. Nostoc is a cyanobacterium (Kingdom Monera), in which cell wall comprises of peptidoglycans. Aspergillus is a fungus (KingdomFungi) in which cell wall is mainly made of chitin. Funaria is a bryophyte (KingdomPlantae) in which cell wall is cellulosic in nature.

2657. Which statement is wrong for viruses?

• A. All are parasites.
• B. All of them have helical symmetry.
• C. They don't have ability to synthesize nucleic acids and proteins.
• D. Antibiotics have no effect on them.

Explanation: "All are parasites": This statement is correct. Viruses are obligate intracellular parasites, meaning they depend on a host cell to replicate and reproduce. "All of them have helical symmetry": This statement is incorrect. Viruses can have different symmetries, including helical, icosahedral, or complex structures. The structure of a virus depends on its type and can vary. "They don't have the ability to synthesize nucleic acids and proteins": This statement is correct. Viruses do not have the cellular machinery to synthesize nucleic acids and proteins on their own. They must rely on the host cell's machinery to replicate and produce their genetic material and proteins. "Antibiotics have no effect on them": This statement is correct. Antibiotics are generally ineffective against viruses. Antibiotics target bacteria and not viruses because viruses lack the cellular structures and metabolic processes that antibiotics are designed to disrupt. So, in summary, the incorrect statements is the second.

2658. Kingdom protoctista includes:

• A. Prokaryotic organisms
• B. Fungi
• C. All unicellular organisms
• D. Eukaryotic organisms

Explanation: The kingdom Protoctista (also known as Protista) includes a diverse group of eukaryotic microorganisms. It is a diverse and heterogeneous group that encompasses various unicellular and simple multicellular organisms. Some examples of organisms in this kingdom include protozoans, algae, and slime molds.

2659. The component responsible for determination of shape of virus is:

• A. Type of nucleic acids
• B. Protein subunits
• C. Type of hosts
• D. Viral envelope

Explanation: The shape of the virus is determined by the shape of its capsid which is determined by its protein subunits.

2660. Which event of the life cycle of HIV occurs in the nucleus

• A. Uncoating
• B. Reverse Transcription
• C. Provirus
• D. Assembly

Explanation: "The explanation for this question will be added soon!"