Free Kingdom Prokaryotae MCQs with Answers

381. Pesticide and insecticides are made up of:

• A. Physical agents
• B. Biological agents
• C. Chemical agents
• D. All of these

Explanation: Pesticides and insecticides are the chemicals which kill the unwanted pests and insects for the welfare of humans. In some cases a microorganism or a biological agent can also be used as a pesticide. But most of the insecticides and pesticides are chemical agents. Hence this is the correct option.

382. What is the main role of bacteria?

• A. CO2 cycle
• B. Nitrogen cycle
• C. Phosphorus cycle
• D. All of above

Explanation: Bacteria play vita role(s) in all of the above mentioned cycles be it in the form of decomposition, nitrogen fixation , denitrification or converting phosphates to other organic forms.

383. Rapid growth at exponential rate occurs in which phase of bacterial growth?

• A. Lag
• B. Log
• C. Stationary
• D. Decline

Explanation: Exponential Phase (Logarithmic Phase): In the exponential phase, the bacteria experience rapid and continuous growth at an exponential rate. Under favorable conditions with an abundant supply of nutrients, bacterial cells divide and multiply at their maximum rate during this phase.

384. Which of the following refers to the region of RNA responsible for binding ribosomes during prokaryotic translation?

• A. TATA box
• B. Promoter
• C. Terminator
• D. Shine-Dalgarno sequence

Explanation: The correct answer is D) Shine-Dalgarno sequence. The Shine-Dalgarno sequence is a short RNA sequence found in the mRNA of prokaryotic cells, specifically in the 5' untranslated region (UTR). It is located upstream of the start codon (AUG) that signals the beginning of translation. The Shine-Dalgarno sequence base pairs with the complementary sequence on the 16S rRNA of the small ribosomal subunit during the initiation of translation. This interaction positions the ribosome correctly on the mRNA to start translation. The Shine-Dalgarno sequence is essential for the efficient initiation of translation in prokaryotic cells.

385. Compound Microscope was first used by:

• A. A.V. Leeuwenhoek
• B. Pasture
• C. Janssen and Hans
• D. None of these

Explanation: It had long been suspected that small creatures exist which are too small to be seen with the naked eye. However, their discovery was linked to the invention of the microscope. A Dutch Scientist "Antonie van Leeuwenhoek" (1673) was the first to report the microbes such as bacteria and protozoa. He used a simple microscope to describe bacteria and protozoa with accurate drawings and descriptions and called these small creatures as "animalcules". He first observed small creatures in rainwater and then confirmed these in saliva, vinegar, infusions, and other substances.

386. The nitrifyng bacteria are an example of which of the following?

• A. Heterotrophic Bacteria
• B. Saprotrophic Bacteria
• C. Chemosynthetic Bacteria
• D. Parasitic Bacteria

Explanation: Chemosynthetic bacteria obtain their energy by converting inorganic substances into organic compounds. Nitrifying bacteria are a type of chemosynthetic bacteria, as they obtain energy by oxidizing ammonia and nitrites to produce nitrates.

387. DNA replication in bacteria occurs:

• A. Within nucleolus
• B. Prior to fission
• C. Just before transcription
• D. During SDuring S phase:

Explanation: DNA replication in bacteria occurs just before fission. Here's an explanation for each of the options you mentioned:1. Within nucleolus: The nucleolus is a substructure found within the nucleus of eukaryotic cells, not in bacteria. Bacteria lack a defined nucleus and nucleolus.2. Prior to fission: Bacterial DNA replication occurs just before the process of binary fission. Binary fission is the method by which bacteria reproduce, where a single bacterial cell divides into two genetically identical daughter cells. DNA replication is a crucial step in this process to ensure that each daughter cell receives a copy of the genetic material.3. Just before transcription: DNA replication and transcription are separate processes. DNA replication must occur before transcription in both bacteria and eukaryotic cells. Replication generates a copy of the DNA, while transcription is the process of synthesizing RNA from DNA.4. During S phase: The concept of an S phase is relevant to eukaryotic cell cycle regulation. In eukaryotic cells, the cell cycle is divided into phases, and S phase is the specific phase where DNA replication occurs. Bacteria do not undergo a defined cell cycle like eukaryotic cells, so they do not have an S phase.In summary, DNA replication in bacteria occurs prior to fission, ensuring that each daughter cell receives a complete copy of the genetic material, which is critical for their reproduction.

388. In chlorophyceae, the mode of sexual reproduction is

• A. Isogamy
• B. Anisogamy
• C. Oogamy
• D. All of these

Explanation: d. In Chlorophyceae, the mode of sexual reproduction can be all of these-Isogamy, Anisogamy, and Oogamy. The specific reproductive mode may vary among different species within this group, and they can exhibit various reproductive strategies depending on the species and environmental conditions. Isogamy involves the fusion of gametes that are similar in size and structure, anisogamy involves the fusion of gametes that are dissimilar in size, and oogamy involves the fusion of a large, non-motile egg cell with a smaller, motile sperm cell. These modes offer flexibility in reproduction and adaptability to different ecological niches.Other options are explained below:a. Isogamy: In isogamy, the gametes (reproductive cells) are similar in size and structure. Both the male and female gametes are morphologically alike. The fusion of isogametes results in the formation of a zygote.b. Anisogamy: Anisogamy involves the production of gametes that differ in size or structure between the male and female. One type of gamete is typically smaller (male), and the other is larger (female). The fusion of these dissimilar gametes leads to the formation of a zygote.c. Oogamy: Oogamy is a more specialized form of sexual reproduction where one gamete (usually the egg or ovum) is large and non-motile, while the other gamete (sperm) is small and motile. Oogamy is common in many green algae, including Chlorophyceae.

389. The sexual reproduction is absent in

• A. Spirogyra
• B. Nostoc
• C. Ulothrix
• D. Volvox

Explanation: b. Nostoc belongs to Cyanophyceae. In this entire class sexual reproduction is completely absent. It reproduces by colony formation, hormogonia, akinetes, heterocysts, and endospores. However genetic recombination has been observed. It may be probably through transformation or conjugation. The other three algae­ Spirogyra, Ulothrix andVolvox belong to Chlorophyceae. The members of this class show isogamous, anisogamous, and oogamous types of sexual reproduction. Explain other options too: a. Spirogyra: Spirogyra reproduces both sexually and asexually. It undergoes a process called conjugation for sexual reproduction, where two filaments come into contact, and a conjugation tube forms between them. However, it doesn't involve the formation of specialized reproductive structures like gametes. c. Ulothrix: Ulothrix is a filamentous green alga. It reproduces both sexually and asexually. Asexual reproduction involves the formation of zoospores, and sexual reproduction involves the formation of isogametes (similar-sized gametes). d. Volvox: Volvox is a colonial green alga. It also reproduces both sexually and asexually. Asexual reproduction occurs through the formation of daughter colonies, while sexual reproduction involves the formation of specialized reproductive cells, including eggs and sperm.

390. Auxospores and hormogonia are formed, respectively, by

• A. Some diatoms and several cyanobacteria
• B. Some cyanobacteria and many diatoms
• C. Everal cyanobacteria and several diatoms
• D. Several diatoms and a few cyanobacteria.

Explanation: d. Until 1907, auxospore formation was regarded as asexual process but now it is considered as an act of sexual process. The auxospores may be autogamous, isogamous, anisogamous or oogamous. Their pattern of formation differs in pennate and centric diatoms. Formation of hormogonia is the common method of reproduction in Nostoc which are produced by accidental breaking of trichome into several pieces. It may also be formed by death and decay of ordinary intercalary cells. Soon, the hormogonium escapes from mucilage and grows into a new filament and then into a new colony. Auxospores are formed by several diatoms, and hormogonia are produced by a few cyanobacteria. a. Some diatoms and several cyanobacteria: This option is incorrect. Auxospores are formed by diatoms, but hormogonia are not associated with cyanobacteria. b. Some cyanobacteria and many diatoms: This option is also incorrect. Auxospores are typically formed by diatoms, while hormogonia are mainly a feature of cyanobacteria. c.Several cyanobacteria and several diatoms: This option is incorrect as well. While diatoms do produce auxospores, the term "hormogonia" is more commonly associated with cyanobacteria. Summary: Auxospores are primarily produced by diatoms, while hormogonia are a feature of a select group of cyanobacteria. Option 4 correctly identifies the organisms associated with the formation of these structures.