Free Biodiversity and Variety of Life MCQs with Answers

2431. How many organisms in the list given below are Photoautotrophs? Lactobacillus, Nostoc, Chara, Nitrosomonas, Nitrobacter, Streptomyces, Saccharomyces, Trypanosoma, Porphyra, Wolffia.

• A. Four
• B. Five
• C. Six
• D. Three

Explanation: Photoautotrophs are organisms that can synthesize their own food using sunlight as an energy source. In the list provided, the photoautotrophs are:Nostoc: A cyanobacterium capable of photosynthesis.Chara: A green alga that performs photosynthesis.Porphyra: A type of red alga known for photosynthesis.Wolffia: A type of aquatic plant that is photosynthetic.The other organisms in the list are not photoautotrophs:Lactobacillus: A heterotrophic bacterium.Nitrosomonas: A chemoautotrophic bacterium involved in the nitrogen cycle, relying on inorganic compounds for energy.Nitrobacter: Similar to Nitrosomonas, it is also chemoautotrophic.Streptomyces: A heterotrophic bacterium that decomposes organic matter.Saccharomyces: A heterotrophic yeast.Trypanosoma: A parasitic protozoan that is heterotrophic.Therefore, the correct answer is that four organisms are photoautotrophs, while the rest are not.

2432. A bacterium divides every 36 minutes. If a culture containing 105 cells/ml is grown for 180 minutes, what will be cell concentration after that period?

• A. 175 x 10^5 cells/ml
• B. 5 x 10^5 cells/ml
• C. 35 x 10^5 cells/ml
• D. 32 x 10^5 cells/ml

Explanation: The bacterium divides every 36 minutes. The total time given is 180 minutes. To find out how many times the bacterium divides during this period, divide 180 by 36, which equals 5. The formula for exponential growth is N(t) = N0 * 2n, where N0 is the initial number of cells, and n is the number of divisions. Here, N0 = 105 cells/ml and n = 5. Therefore, N(t) = 105 * 25 = 105 * 32 = 32 x 105 cells/ml. Thus, the correct answer is 32 x 105. The other options are incorrect as they do not account for the accurate number of divisions or exponential growth.

2433. Bacterial ribosome lie in/on:

• A. Cytoplasm
• B. Nuclear membrane
• C. RER
• D. Cell Wall

Explanation: The correct answer is A) Cytoplasm, as bacterial ribosomes are found in the cytoplasm of the cell where they carry out protein synthesis.

2434. Bacteria and cyanobacteria very closely resemble in their:

• A. Mode of nutrition
• B. Mode of respiration
• C. Pigment composition
• D. Cell wall composition

Explanation: The correct answer is D) Cell wall composition, as bacteria and cyanobacteria both have cell walls containing peptidoglycan, making them closely resemble each other in this aspect.

2435. Basophilic prokaryotes :

• A. Grow and multiply in very deep marine sediments
• B. Occur in water containing high concentrations of barium hydroxide
• C. Readily grow and divide in sea water enriched in any soluble salt of barium
• D. Grow slowly in highly alkaline frozen lakes at high altitudes

Explanation: All options are explained below:a)Basophilic prokaryotes are known for their ability to grow and multiply in very deep marine sediments:This is the correct option. These microorganisms have adapted to extreme conditions in deep ocean sediments where high pressure, low temperature, and unique mineral compositions are common. They thrive in such environments where barium is often present.b)Occur in water containing high concentrations of barium hydroxide: Basophilic prokaryotes are not typically found in water with high concentrations of barium hydroxide. They thrive in environments with soluble barium salts, but high concentrations of barium hydroxide are not a common condition in nature.c)Readily grow and divide in sea water enriched in any soluble salt of barium: Basophilic prokaryotes are known for their ability to grow and multiply in seawater enriched with various soluble salts of barium. This is a characteristic feature of these organisms and this option is partially correct for it.d)Grow slowly in highly alkaline frozen lakes at high altitudes: Basophilic prokaryotes are not commonly associated with highly alkaline frozen lakes at high altitudes; they are more commonly found in barium-rich marine environments.

2436. Some antibiotics are synthesized in:

• A. Bacteria
• B. Actinomycetes
• C. Fungi
• D. Laboratory

Explanation: Answer is "Laboratory"Explanation: Synthetic antibiotics.

2437. Antibiotics are synthesized by:

• A. Actinomycetes
• B. Fungi
• C. Bacteria
• D. Actinomycetes, Bacteria and Fungi

Explanation: Answer is "Actinomycetes, bacteria and fungi"Explanation: Biological antibiotics are produced by certain fungi actinomycetes and bacteria, whereas synthetic antibiotics are usually derived from dyes.

2438. Oxygenic photosynthesis occurs in:

• A. Oscillatoria
• B. Rhodospirillum
• C. Chlorobium
• D. Chromatium

Explanation: In summary, oxygenic photosynthesis occurs in organisms like cyanobacteria (e.g., Oscillatoria), which produce oxygen as a byproduct, while Rhodospirillum, Chlorobium, and Chromatium are examples of bacteria that perform anoxygenic photosynthesis and do not produce oxygen during photosynthesis.

2439. Which of the following is a symbiotic nitrogen fixer?

• A. Azotobacter
• B. Frankia
• C. Azolla
• D. Glomus

Explanation: Azotobacter: Azotobacter is a free-living nitrogen-fixing bacterium. It forms a symbiotic relationship with some plants, especially in the rhizosphere (root zone), where it provides them with fixed nitrogen in exchange for organic carbon compounds. However, it is primarily considered a free-living nitrogen fixer.Frankia: Frankia is a genus of actinomycete bacteria that forms symbiotic relationships with certain types of plants, particularly woody plants like alders, Elaeagnus, and others. These associations are called actinorhizal symbiosis, and the plants are referred to as actinorhizal plants. Frankia helps these plants fix atmospheric nitrogen and provides them with essential nutrients.Azolla: Azolla is a water fern that can host the cyanobacterium Anabaena azollae in cavities on its upper leaf surface. This cyanobacterium is capable of nitrogen fixation and provides fixed nitrogen to the Azolla plant. This symbiotic relationship is often used in rice cultivation as a natural fertilizer.Glomus: Glomus is a genus of arbuscular mycorrhizal fungi (AMF). These fungi form mutualistic relationships with the roots of most land plants. In these relationships, the AMF assist the plant in nutrient uptake, including phosphorus, and, to some extent, nitrogen. Although they are not direct nitrogen fixers like Azotobacter or Frankia, they play a crucial role in nutrient acquisition and overall plant health.So among these, Frandia is symbiotic nitrogen fixer.

2440. Bacterial leaf blight of rice is caused by a specie:

• A. Alternaria
• B. Erwinia
• C. Xanthomonas
• D. Pseudomonas

Explanation: Bacterial leaf blight of rice is primarily caused by a species of Xanthomonas. Here's an explanation of each of the options:1. Alternaria: Alternaria is a fungal pathogen that is not typically associated with bacterial leaf blight in rice. It is more commonly known for causing diseases in various other plants, such as Alternaria leaf spot in crops like tomatoes and potatoes.2. Erwinia: Erwinia is a genus of bacteria, but it is not the primary causative agent of bacterial leaf blight in rice. Erwinia species are often associated with diseases in a variety of plants, including soft rot in vegetables.3. Xanthomonas: Xanthomonas or Xanthomonas oryzae is the primary bacterium responsible for bacterial leaf blight of rice. This pathogen can lead to severe damage to rice crops, causing characteristic leaf blight symptoms.4. Pseudomonas: Pseudomonas is a diverse genus of bacteria, but it is not commonly associated with bacterial leaf blight of rice. Pseudomonas species can cause diseases in a range of plants, but they are not the primary causative agent for this specific rice disease.So, in the context of bacterial leaf blight in rice, the correct answer is Xanthomonas.