Summarize the main ideas of each paragraph from the provided text about Killer Whales.

Here are the main ideas from each paragraph of "The Killer Whale":

• Paragraph 1: Greg's fascination with Killer Whales at the aquarium.
• Paragraph 2: The Killer Whales' intelligence and playfulness during training sessions.
• Paragraph 3: The surprising speed, agility, and classification of Killer Whales as part of the dolphin family.
• Paragraph 4: Killer Whales' predatory nature and their position at the top of the food chain.
• Paragraph 5: Greg's inspiration to become a marine biologist due to his interest in Killer Whales.