Question 1: Briefly explain what the Three Domain System is and why it was developed.

Answer: The Three Domain System classifies all living organisms into three major categories: Bacteria, Archaea, and Eukarya, based on genetic differences. It was developed to reflect evolutionary relationships more accurately than previous systems.

Question 2: Which domain includes organisms that are prokaryotic and often found in extreme environments?

Answer: Archaea

Question 3: Fill in the blank: The domain ________ includes all multicellular organisms, such as plants and animals.

Answer: Eukarya

Question 1: Define 'prokaryotic' and explain how it differs from 'eukaryotic'.

Answer: Prokaryotic organisms lack a nucleus and membrane-bound organelles, whereas eukaryotic organisms have a nucleus and membrane-bound organelles.

Question 2: Describe one characteristic that distinguishes Archaea from Bacteria.

Answer: Archaea often live in extreme environments and have different genetic sequences compared to Bacteria.

Question 1: If two organisms share 85% of their genetic sequences, what is their genetic difference percentage?

Answer: 15%

Question 2: A DNA analysis shows that an organism's DNA has a melting temperature of 85°C. If the melting temperature of a known species in the same domain is 80°C, what might this suggest about their genetic similarity?

Answer: The higher melting temperature suggests the organism's DNA is more GC-rich, possibly indicating closer genetic similarity within the same domain.

Question 1: Design a simple experiment to test whether a newly discovered microorganism belongs to the Archaea or Bacteria domain. Describe the main variables and safety precautions.

Answer: The experiment could involve analyzing the microorganism's genetic material for specific markers unique to Archaea or Bacteria. The main variables include the type of genetic sequences tested. Safety precautions include working in a biosafety cabinet, wearing protective gear, and sterilizing equipment to prevent contamination.

Question 1: A scientist isolates two organisms. Genetic analysis shows 70% similarity in their ribosomal RNA sequences. One is known to be a plant, and the other is an animal. To which domain do these organisms most likely belong, and why?

Answer: Both most likely belong to the Eukarya domain because they are multicellular organisms, and their genetic similarity indicates they are eukaryotes.

Question 2: An environmental sample contains microorganisms with genetic sequences matching 95% to known Archaea species. What does this suggest about the organisms' classification and their possible habitats?

Answer: This suggests the microorganisms are Archaea, and they likely inhabit extreme environments such as hot springs or salt lakes.

Question 1: Explain how the Three Domain System helps scientists understand evolutionary relationships among organisms. (6 marks)

Answer: The Three Domain System groups organisms based on genetic and evolutionary differences, reflecting their common ancestors. It helps scientists trace evolutionary paths, understand genetic diversity, and classify organisms more accurately than previous systems that relied only on physical characteristics.

Question 2: In which domain would you classify a virus, and why? Provide a brief explanation.

Answer: Viruses are not classified in any of the three domains because they are not considered living organisms; they lack cellular structure and cannot reproduce on their own.