Question 1: Define the Three Domain System and explain why it was developed as an alternative to the five-kingdom classification system.

Answer: The Three Domain System classifies all life into three primary groups: Archaea, Bacteria, and Eukarya, based on molecular differences, especially in ribosomal RNA sequences. It was developed to reflect evolutionary relationships more accurately than the five-kingdom system.

Question 2: Describe one key molecular difference between Archaea and Bacteria that supports their placement in separate domains.

Answer: Archaea have different membrane lipid structures and gene sequences, particularly in ribosomal RNA, compared to Bacteria, indicating a distinct evolutionary lineage.

Question 1: Explain how ribosomal RNA (rRNA) sequencing helps scientists classify organisms into the three domains.

Answer: Ribosomal RNA sequences are highly conserved within each domain but differ significantly between domains. Comparing these sequences allows scientists to determine evolutionary relationships and classify organisms accordingly.

Question 2: Calculate the percentage difference in rRNA sequences if two organisms have 95% similarity in their sequences.

Answer: Percentage difference = 100% - similarity percentage = 100% - 95% = 5%

Question 1: Design a basic experiment to identify whether a bacterial sample belongs to Bacteria or Archaea based on molecular techniques. Include key variables and safety precautions.

Answer: The experiment involves extracting DNA from the bacterial sample, performing PCR amplification of rRNA genes, and sequencing. Variables include type of bacteria (independent), DNA extraction method, and temperature (controlled). Safety precautions involve sterilising equipment, wearing gloves and lab coat, and disposing of biological waste properly.

Question 1: A scientist sequences the rRNA of four organisms and finds the following similarities: Organism A and B share 99%, A and C share 85%, B and D share 88%, and C and D share 80%. Based on these data, which organisms are most closely related, and to which domain might they belong?

Answer: Organisms A and B are most closely related, sharing 99% similarity, and likely belong to the same domain, probably Eukarya or Bacteria depending on their known characteristics.

Question 1: Explain how understanding the differences between Archaea and Bacteria can influence the development of antibiotics and biotechnological processes.

Answer: Knowing the molecular differences allows scientists to develop antibiotics that target specific bacterial features without affecting Archaea, which are often resistant to common antibiotics. It also aids in biotechnological applications like enzyme production from extremophilic Archaea.

Question 1: In your opinion, what is the most significant advantage of classifying organisms into three domains instead of five kingdoms?

Answer: Classifying organisms into three domains provides a clearer understanding of evolutionary relationships based on molecular data, leading to more accurate and meaningful classifications compared to the five-kingdom system, which is based primarily on physical and metabolic characteristics.