NGSS
MS-ESS3-4
3 lessons teach this standard. Every lesson is interactive, and every one prints as a worksheet with a separate answer key.
Grade 6 Science · Chapter 7 · Lesson 3
Nothing comes out for free.
Grade 6 Science · Chapter 7 · Lesson 4
More people, and more each.
Grade 8 Science · Chapter 8 · Lesson 3
Human Activity and Rising Carbon Dioxide
Where the extra carbon came from.