First sentence: Why this is the first line? This paragraph is the first because it introduces the main topic of the research. It shows the purpose of the study, which is to compare sea lives and land lives. This is an introductory sentence that sets the stage for the following information. Why other lines are not chosen? The other paragraphs do not qualify as the first sentence. For example, Paragraph 2 starts with 'They' which is a pronoun, so it cannot stand alone. Paragraph 3 starts with 'The range' which uses the definite article 'the', meaning it refers to something already known. Paragraph 4 starts with 'This' which is also a pronoun and cannot stand alone.

Concluding sentence: Why this is the last line? This paragraph is the last because it wraps up the information. It shows the result of the research and how it was shared with others. This is a clear conclusion to the discussion.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it explains what the biologists did for their research. This shows a logical order where the first paragraph introduces the research and the second paragraph gives details about the work done.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it describes the results of the counting done in Paragraph 2. This shows a logical order where the second paragraph gives details and the third paragraph explains the wide range of what was counted.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it concludes the discussion about the research. It shows that the analysis of the wide range was important enough to be published, which is a logical flow from results to conclusion.