Free Biodiversity and Variety of Life MCQs with Answers

131. Thermococcus, Methanococcus and Methanobacterium examplify:

• A. Bacteria whose DNA is relaxed or positively supercoiled but which have a cytoskeleton as well as mitochondria
• B. Bacteria that contain a cytoskeleton and ribosomes
• C. Archaebacteria that contain protein homologous to eukaryotic core histones
• D. Archaebacteria that lack any histones resembling those found in eukaryotes but whose DNA is negatively supercoiled.

Explanation: Thermococcus, Methanococcus and Methanobacterium are examples of archaebacteria which are characterized by a unique cell wall that lack peptidoglycan and consist of polysaccharides and protein and closely resemble the eukaryotic cell in the mechanism of protein synthesis, structural protein and RNA compliments of the ribosomes.

132. Which one of the following is a slime mould?

• A. Physarum
• B. Thiobacillus
• C. Anabaena
• D. Rhizopus

Explanation: All options are explained below:a)Physarum is a genus of slime molds. Slime molds are unique organisms that belong to the group Amoebozoa. They have a complex life cycle that includes both single-celled amoeboid stages and multicellular stages. Physarum is known for its ability to form intricate patterns and make decisions based on environmental cues.b)Thiobacillus is not a slime mold. It is a genus of bacteria belonging to the phylum Proteobacteria. Thiobacillus species are known for their ability to oxidize sulfur compounds, which is important in various biogeochemical cycles.c) Anabaena is not a slime mold either. It is a genus of cyanobacteria, often referred to as blue-green algae. Cyanobacteria are photosynthetic prokaryotes that play a crucial role in the oxygenation of the Earth's atmosphere.d) Rhizopus is not a slime mold. It is a genus of fungi, specifically belonging to the group Zygomycota. Rhizopus species include bread molds and are common in decaying organic matter.Correct Option: PhysarumSummary: Physarum is a type of slime mold, which is an unusual organism with a unique life cycle that includes amoeboid and multicellular stages. It is known for its ability to make complex decisions and form intricate patterns based on environmental conditions. The other options, Thiobacillus, Anabaena, and Rhizopus, represent bacteria, cyanobacteria, and fungi, respectively, and are not classified as slime molds.

133. Which one of the following statements about mycoplasma is wrong?

• A. They are pleomorphic.
• B. They are sensitive to penicillin.
• C. They cause diseases in plants.
• D. They are also called PPLO.

Explanation: All options are explained below: a)They are pleomorphic: This statement is correct. Mycoplasma is known for its pleomorphic nature, meaning it can have various shapes and sizes. b) They are sensitive to penicillin: This statement is incorrect. Mycoplasma is typically resistant to antibiotics like penicillin because they lack a cell wall, which is the target of penicillin. Penicillin primarily acts on bacteria with cell walls, making it ineffective against mycoplasma. c) They cause diseases in plants:This statement is correct. Mycoplasma can indeed infect plants and cause diseases, often referred to as "phytoplasmas." These phytoplasmas are plant pathogens that are related to mycoplasma. d) They are also called PPLO (Pleuropneumonia-like organisms):This statement is correct. Mycoplasma was formerly referred to as Pleuropneumonia-like organisms (PPLO). The name was changed to reflect the unique characteristics of these microorganisms. Correct option: B. They are sensitive to penicillin. Summary: The incorrect statement is that mycoplasma is sensitive to penicillin. In reality, mycoplasma is generally resistant to penicillin and other antibiotics that target bacterial cell walls. Mycoplasma is pleomorphic, can infect both animals and plants, and was historically known as PPLO.

134. Which pair of the following belongs to basidiomycetes?

• A. Puffballs and Claviceps
• B. Peziza and stink horns.
• C. Morchella and mushrooms.
• D. Birds nest fungi and puffballs.

Explanation: All options are explained below: a)Puffballs and Claviceps:Puffballs belong to the Gasteromycetes group, and Claviceps is indeed a member of the Ascomycota group. Neither of these fungi belongs to basidiomycetes. b) Peziza and stinkhorns: Peziza is an ascomycete fungus, while stinkhorns are basidiomycetes. The pair contains one basidiomycete, stinkhorns, so this option is partially correct. c) Morchella and mushrooms: Morchella is a type of ascomycete, and mushrooms, in general, are examples of basidiomycetes. This pair includes one basidiomycete, which is mushrooms, so this option is also partially correct. d)Bird's nest fungi and puffballs: Bird's nest fungi belong to the class Nidulariaceae, which is a subgroup of basidiomycetes (specifically in the Agaricomycetes class). Puffballs are indeed basidiomycetes, but they belong to the Gasteromycetes group, which is a subgroup of basidiomycetes. Therefore, this pair includes two fungi that are both basidiomycetes. Correct Pair: D. Bird's nest fungi and puffballs Summary: The correct pair belonging to basidiomycetes is Bird's nest fungi and puffballs (option D). Both of these fungi are part of the basidiomycetes group. The other pairs include either non-basidiomycetes or a mix of basidiomycetes and non-basidiomycetes.

135. Curing of tea leaves is brought about by the activity of:

• A. Fungi
• B. Bacteria
• C. Mycorrhiza
• D. Viruses

Explanation: The curing of tea leaves, also known as tea fermentation or oxidation, is a critical step in the post-harvest processing of tea leaves. This process is especially important for certain types of tea, such as black tea and oolong tea, as it significantly influences the flavor, aroma, and overall quality of the final tea product. All options are explained below: a)Fungi: While fungi can play a role in some fermentation processes, such as in the production of certain fermented teas, they are not primarily responsible for the curing of tea leaves. b)Bacteria: Bacteria are the microorganisms that are mainly involved in the fermentation and curing of tea leaves. Specific strains of bacteria are responsible for the chemical changes that occur during the curing process, leading to the development of tea's flavors and aromas. c)Mycorrhiza: Mycorrhiza is a symbiotic association between fungi and plant roots and is not directly related to the curing of tea leaves. d)Viruses: Viruses do not have a role in the curing of tea leaves. They are not involved in the fermentation or processing of tea. Summary: The correct answer is Bacteria. Bacteria are the microorganisms responsible for the fermentation and curing of tea leaves, a critical step in tea processing that influences the flavor and quality of the final tea product. Fungi, mycorrhiza, and viruses are not the primary agents involved in the tea curing process.

136. Which of the following environmental conditions are essential for the optimum growth of Mucor on a piece of bread? A. Temperature of about 25° C B. Temperature of about 5° C C. Relative humidity of about 5% D. Relative humidity of about 95% E. A shady place F. A brightly illuminated place Choose the answer from the following options.

• A. B, C and F only
• B. A, C and E only
• C. A, D and E only
• D. B, D and E only

Explanation: The environmental conditions essential for the optimum growth of Mucor on a piece of bread typically include: A. Temperature of about 25°C: Mucor tends to grow well at moderate temperatures. D. Relative humidity of about 95%: Mucor thrives in humid conditions. E. A shady place: Mucor prefers dark or shaded environments. Therefore, the correct answer is: A, D, and E only: These conditions are conducive to the growth of Mucor on bread. Options B and C are not typically favorable for the growth of Mucor. A low temperature (5°C) and low relative humidity (5%) are not ideal for its growth. Option F, a brightly illuminated place, is also not conducive to Mucor growth, as it prefers darkness or shade.

137. All of the following statements concerning the actinomycetous filamentous soil bacterium Frankia are correct except that Frankia

• A. Can induce root nodules on many plant species
• B. Can fix nitrogen in the freeliving state
• C. Cannot fix specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids
• D. Like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host's cortex.

Explanation: a)Can induce root nodules on many plant species: This statement is correct. Frankia is known for its ability to induce root nodules on a wide range of plant species, particularly actinorhizal plants. These nodules provide a symbiotic environment for Frankia to fix nitrogen. b)Can fix nitrogen in the free-living state: is the incorrect statement. Frankia, like many nitrogen-fixing bacteria, cannot fix nitrogen in the free-living state, unlike some other nitrogen-fixing bacteria, such as free-living diazotrophs. Frankia typically forms symbiotic relationships with host plants and fixes nitrogen within root nodules. c)Cannot fix specialized vesicles in which the nitrogenase is protected from oxygen by a chemical barrier involving triterpene hopanoids: is the correct statement. Frankia can fix nitrogen within specialized vesicles, and triterpene hopanoids are involved in maintaining low oxygen levels in these vesicles. d)Like Rhizobium, it usually infects its host plant through root hair deformation and stimulates cell proliferation in the host's cortex : This statement is correct. Similar to Rhizobium, Frankia often initiates the infection of its host plant by inducing deformation of root hairs. It also stimulates the proliferation of plant cells in the root cortex, leading to the formation of nodules where the bacterium resides and performs nitrogen fixation. Summary: The correct statements are A and D, which describe Frankia's ability to induce root nodules on various plant species and its infection process through root hair deformation and cortex cell proliferation, similar to Rhizobium. Option B is the incorrect statement, as Frankia cannot fix nitrogen in the free-living state, and it relies on symbiotic associations for nitrogen fixation. Option C is also incorrect as Frankia does indeed form specialized vesicles and employs mechanisms like triterpene hopanoids to protect nitrogenase from oxygen during nitrogen fixation.

138. For retting of jute the fermenting microbe used is

• A. methanophilic bacteria
• B. butyric acid bacteria
• C. Helicobactor pylori
• D. Streptococcus lactis

Explanation: The fermenting microbe used for retting jute is not methanophilic bacteria, Helicobacter pylori, or Streptococcus lactis. The correct microbe used in the retting process is butyric acid bacteria. Here's an explanation of all the options and a summary: Methanophilic bacteria: Methanophilic bacteria are not used in the retting of jute. They are specialized bacteria that produce methane and are typically found in anaerobic environments, such as certain wetlands and the digestive systems of animals. Helicobacter pylori: Helicobacter pylori is a bacterium associated with stomach ulcers and gastritis in humans. It has no role in the retting of jute. Streptococcus lactis: Streptococcus lactis is a lactic acid bacteria used in the fermentation of dairy products, but it is not used in the retting of jute. Summary: Butyric acid bacteria are the fermenting microbes used in the retting process of jute. They help break down the pectin substances in jute fibers, facilitating the separation of the fibers from the plant's woody core. Methanophilic bacteria, Helicobacter pylori, and Streptococcus lactis are not involved in this specific industrial process.

139. There exists a close association between the alga and the fungus within a lichen. The fungus

• A. Provides protection, anchorage and absorption for the algae
• B. Provides food for the alga
• C. Fixes the atmospheric nitrogen for the alga
• D. Releases oxygen for the alga.

Explanation: In a lichen, the association between the alga and the fungus is a mutualistic one, where both partners benefit: The fungus provides protection, anchorage, and absorption for the algae: The fungal partner forms a protective structure around the algal cells, which helps shield them from harsh environmental conditions and provides a stable substrate to grow on. The fungal partner also aids in the absorption of water and nutrients from the environment. The alga provides food for the fungus: The algal partner, through photosynthesis, produces organic compounds (such as sugars) using sunlight and carbon dioxide. These compounds serve as a source of nutrition for the fungal partner. The association typically does not involve nitrogen fixation: Nitrogen fixation is not a primary role of the fungus in the lichen symbiosis. The association does not involve the release of oxygen: While photosynthesis by the algal partner generates oxygen, the primary benefit to the fungus is the food produced by the alga. So, the correct statement is that the fungus provides protection, anchorage, and absorption for the algae, and the algae provide food for the fungus.

140. Which of the following statements is not true for retroviruses?

• A. DNA is not present at any stage in the life cycle of retroviruses.
• B. Retroviruses carry gene for RNA dependent DNA polymerase.
• C. The genetic material in mature retroviruses is RNA.
• D. Retroviruses are causative agents for ertain kinds of cancer in man.

Explanation: a) "DNA is not present at any stage in the life cycle of retroviruses" - This statement is not true. Retroviruses have a unique life cycle that involves the conversion of their RNA genome into DNA. They carry the gene for reverse transcriptase, an enzyme that allows them to synthesize a DNA copy of their RNA genome once they infect a host cell. This DNA form is integrated into the host cell's genome.b) "Retroviruses carry the gene for RNA-dependent DNA polymerase" - This statement is true. Retroviruses carry the gene for reverse transcriptase, which is also known as RNA-dependent DNA polymerase. This enzyme is responsible for transcribing the viral RNA into DNA.c) "The genetic material in mature retroviruses is RNA" - This statement is true. Retroviruses store their genetic information as RNA. However, during the replication process, they reverse transcribe this RNA into DNA, which becomes integrated into the host cell's genome.d) "Retroviruses are causative agents for certain kinds of cancer in man" - This statement is true. Some retroviruses are known to be oncogenic, meaning they can cause cancer in humans. For example, the human T-cell lymphotropic virus type 1 (HTLV-1) is associated with the development of adult T-cell leukemia (a form of cancer).Summary: The correct answer is option A. Retroviruses do have DNA at some stages in their life cycle, specifically in the form of a DNA copy of their RNA genome, which is integrated into the host cell's genome. This process is mediated by reverse transcriptase (RNA-dependent DNA polymerase). Retroviruses are indeed linked to certain types of cancer in humans.