Two Eyes, One Picture: teacher key

Hammerhead Sharks, grade 9 edition, written for 9th grade. A hammerhead's eyes sit at the two ends of its wide head, yet a 2009 study found a wide arc in front covered by both eyes. Scientists have proposed ideas for the head's shape, and scalloped hammerheads dive deep.

Read the book. Print this page for the key.

Questions and answers

1. How wide was the winghead shark's arc covered by both eyes in the 2009 study?
   • 13 degrees
   • 34 degrees
   • 48 degrees (answer)
2. Which shark had the smallest binocular overlap in that study?
   • The bonnethead (answer)
   • The winghead
   • The scalloped hammerhead
3. What does the National Science Foundation grant say about the wide head?
   • Its function is unclear, and hypotheses include maneuverability and lift (answer)
   • It is only for digging
   • It is only for swimming slowly
4. The winghead had a 48-degree arc covered by both eyes. What does that show about its eyes?
   • Their views overlap in front (answer)
   • They cannot see ahead
   • They point only backward
5. What is a hypothesis?
   • A proven fact
   • A proposed explanation (answer)
   • A kind of fish

Words

• binocular: using both eyes
• hypotheses: proposed explanations
• maneuverability: turning skill
• lift: an upward push
• solitary: living alone
• nomadic: wandering