First sentence: Why this is the first line? This paragraph is the first sentence because it introduces the main topic of the text, which is the Northern Pike. It does not refer to any previous information and gives a broad overview of the subject. This follows the rule of Topic Sentence. Why other lines are not chosen? The other paragraphs are not chosen because they do not stand alone. For example, Paragraph 2 starts with 'This aggressive predator,' which uses a pronoun and needs context. Paragraph 3 starts with 'Scientists have observed,' which is not general and assumes prior knowledge. Paragraph 4 starts with 'The rapid consumption,' which uses 'the' and refers to a specific idea. Paragraph 5 starts with 'Without intervention,' which is not a general statement.

Concluding sentence: Why this is the last line? This paragraph is the last sentence because it summarizes the main concern of the text. It gives a clear warning about the future of native fish species, which wraps up the discussion. This follows the Conclusive Words rule, as it provides a final thought on the topic.

Paragraph pairs:

• Pair 1 (Paragraph 1 → Paragraph 2): Paragraph 2 connects with Paragraph 1 because it gives more details about the Northern Pike. This follows the Broader to Specific Strategy, where the first paragraph introduces the topic and the second paragraph provides specific information about its feeding habits.
• Pair 2 (Paragraph 2 → Paragraph 3): Paragraph 3 connects with Paragraph 2 because it shows the effect of the Northern Pike's feeding on local fish. This follows the Cause and Effect Relationship rule, where the feeding habits lead to a decline in fish populations.
• Pair 3 (Paragraph 3 → Paragraph 4): Paragraph 4 connects with Paragraph 3 because it explains why there is a decline in fish populations. This follows the Logical Order rule, where the observation leads to an explanation of the disruption in the food chain.
• Pair 4 (Paragraph 4 → Paragraph 5): Paragraph 5 connects with Paragraph 4 because it shows the consequence of the disruption in the food chain. This follows the Cause and Effect Relationship rule, where the disruption leads to the risk of extinction.