These are bounded opportunities, not learner attainment. Partial and blocked source requirements remain so.

• partial: Describe the Cretaceous–Palaeogene (K-Pg) extinction event approximately 66 million years ago, including the asteroid impact theory and its evidence (iridium layer, Chicxulub crater), and understand that this ended the reign of non-avian dinosaurs

  Bounded objective: Link evidence to the asteroid explanation of the K-Pg extinction. Primary study abstract/search excerpt checked; full article/data not reviewed. Older NASA 65-million wording preserved in research history, not used as the lesson date.

• partial: State that the K-Pg extinction happened about 66 million years ago and wiped out non-avian dinosaurs

  About 66 Ma and non-avian qualification stated.

• partial: Describe the asteroid impact hypothesis and name the Chicxulub crater in Mexico

  Impact/Chicxulub Mexico summary supplied.

• partial: Explain one piece of evidence: the iridium-rich layer found worldwide in rocks from that time

  Primary study excerpt connects iridium marker and crater boundary; full data not reviewed.

• partial: Can {{name}} explain what scientists think caused the dinosaurs to go extinct — and describe at least one piece of evidence for the asteroid theory?

  Try offers taught-source-evaluation for the bounded objective; it does not establish every part of the source assessment. Primary study abstract/search excerpt checked; full article/data not reviewed. Older NASA 65-million wording preserved in research history, not used as the lesson date.

• Primary study abstract/search excerpt checked; full article/data not reviewed. Older NASA 65-million wording preserved in research history, not used as the lesson date.