One Orca or Many?: teacher key

Orcas, grade 11 edition, written for 11th grade. Scientists use teeth, clicks and counts to ask whether the orca is one species or several. Read the evidence, from Antarctica to the Pacific Northwest.

Read the book. Print this page for the key.

Questions and answers

1. What did researchers write in 2024 about Bigg's and resident orcas?
   • They should be recognized as two separate species (answer)
   • They are the same animal
   • They live only in Antarctica
2. What do worn teeth show about an orca?
   • Its age
   • Its diet (answer)
   • Its home ocean
3. Why might Bigg's orcas be hard to detect by their clicks?
   • They never use sound
   • They live deep
   • Their clicks can be buried in background sound (answer)
4. What happened to the Southern Residents after the peak of 98 whales in 1995?
   • They fell by almost 20 percent in the late 1990s (answer)
   • They doubled by 2001
   • They moved to Chile
5. What does "interbred" mean?
   • Learned a call
   • Moved together
   • Had young together (answer)

Words

• ecotypes: habit groups
• interbred: had young together
• species: animal kind
• contaminants: harmful leftovers
• menopause: end of calves