• Giraffes with longer necks could reach more food.
• Some giraffes in the past had shorter necks.
• The trees are part of the environment.
• Over time, only giraffes with long necks remain.
• The timeline shows changes across millions of years.

EXTENDING THE DISCUSSION
After the observational question, randomly call on one or more students to share what they or their partner answered. Then ask the class, “Did anyone notice…?” using the suggestions above or anything else you’ve noticed.

• Why did some giraffes survive and others did not?
• How did the variations first appear?
• Could other animals experience natural selection the same way?
• How long does it take for a new descendant species to form?
• Does the environment always determine which traits are helpful?

EXTENDING THE DISCUSSION
After students have shared what they notice, ask the class, “Did anyone wonder…?” using the suggestions above or anything else you might think is interesting or relevant to the lesson.

To the observational question, What occurs in natural selection?

LOW-LEVEL

In natural selection, some organisms survive and others do not.

HIGH-LEVEL

In natural selection, individuals with traits better suited to the environment survive and reproduce, passing on those traits to future generations.

RESPONDING TO RESPONSES
Emphasize and celebrate each student’s use of the key vocabulary to support a culture of “no wrong answers.”