About this worksheet
Sea otters crack clams on rocks balanced on their bellies, stay warm with the thickest fur of any animal, and were hunted nearly to extinction for it before a 1911 treaty stopped the trade. The passage then explains why that matters: otters eat sea urchins, urchins eat kelp, and without otters whole kelp forests can disappear.
It goes further than our third grade sea otter sheet, which stays with fur and food. Here the point is the chain of cause and effect, and question four asks a child to explain what a keystone species is using details from the text. Question five asks for the main idea, which is harder than it sounds when a passage packs in this many good facts.
What students will practice
- Determine the main idea of a nonfiction passage
- Explain a cause and effect chain in an ecosystem
- Define a science term using details from the text
Details
- Grade level
- Grade 4
- Subject
- Reading · Comprehension
- Standard
- CCSS.ELA-LITERACY.RI.4.2
- Pages
- 1
- Format
- PDF · US Letter and A4 included
- License
- Free for classroom use · Attribution appreciated
- Last updated
- October 23, 2026
