Question 1: Briefly explain what the Three Domain System is and why it was developed as an alternative to the Five Kingdom system.

Answer: The Three Domain System classifies all life into three broad groups: Bacteria, Archaea, and Eukarya, based on genetic and molecular differences, providing a more accurate understanding of evolutionary relationships than the Five Kingdom system.

Question 2: Identify which of the following organisms belongs to the domain Archaea: A) Escherichia coli B) Methanogens C) Yeast D) Human

Answer: B) Methanogens

Question 3: Fill in the blank: The domain __________ contains organisms that are prokaryotic and often live in extreme environments.

Answer: Archaea

Question 4: Describe one key difference between bacteria and archaea in terms of their genetic material.

Answer: Archaea have genetic sequences and membrane lipid structures that are more similar to eukaryotes, whereas bacteria have different ribosomal RNA sequences and membrane lipids.

Question 1: Design a simple experiment to determine whether a sample of bacteria belongs to the Bacteria or Archaea domain. Include variables to control and safety precautions.

Answer: Students should isolate the bacteria, test for growth in extreme conditions (e.g., high temperature or salinity), and perform genetic analysis such as PCR. Variables to control include temperature, pH, and salinity. Safety precautions include wearing gloves, lab coat, eye protection, and sterilising equipment to prevent contamination.

Question 2: In industry, certain microorganisms classified under the Three Domain System are used in biotechnology. Name one application for Archaea and explain its importance.

Answer: Methanogens are used in waste treatment to produce biogas, which is an important renewable energy source, reducing reliance on fossil fuels.

Question 3: A scientist finds a microorganism that has cell walls but does not have peptidoglycan. To which domain is this microorganism most likely to belong?

Answer: B) Archaea

Question 4: Explain how the genetic differences among the three domains support their classification as separate groups.

Answer: Genetic analyses reveal distinct rRNA gene sequences and differences in core metabolic genes among Bacteria, Archaea, and Eukarya. These molecular differences reflect separate evolutionary paths, justifying their classification into three domains rather than the older five-kingdom system.

Question 1: A new microorganism is discovered that thrives in hot springs with high sulphur content. Genetic analysis shows it has unique ribosomal RNA sequences different from known bacteria and archaea. To which domain is it most likely to belong, and why?

Answer: It is most likely to belong to the domain Archaea because it thrives in extreme conditions and has distinct genetic sequences different from known bacteria, fitting the characteristics of Archaea.

Question 2: Calculate the number of years it would take for 10^6 bacteria to double if the bacteria's doubling time is 30 minutes. Use the formula: Number of bacteria after t minutes = initial amount × 2^(t / doubling time).

Answer: Initial bacteria = 1; Doubling time = 30 minutes; Find t when bacteria = 10^6. 10^6 = 1 × 2^(t / 30) 2^(t / 30) = 10^6 t / 30 = log2(10^6) t = 30 × log2(10^6) t ≈ 30 × 19.93 ≈ 597.9 minutes (~10 hours).

Question 3: Discuss how understanding the Three Domain System can help in developing antibiotics and other treatments.

Answer: Knowing the differences among the three domains allows scientists to target specific genetic and structural features unique to bacteria or archaea when developing antibiotics, reducing harm to beneficial organisms and improving effectiveness. It also helps in understanding resistance mechanisms and developing treatments for infections caused by organisms in different domains.