Mass Extinctions Through History

What You'll Learn

Extinction occurs when the last member of a species dies. Mass extinctions have occurred several times in Earth's history, the most famous killing the dinosaurs 66 million years ago.

Key Words

heredity
allele
cell

Steps

Step 1 — Read

Read the introduction and identify the main idea of this lesson.

Step 2 — Do

Extract DNA from a strawberry using dish soap, salt, water, and rubbing alcohol. Observe the stringy white substance—that's DNA!

Step 3 — Observe

Look for patterns in your observations.

Step 4 — Record

Make a graph or chart showing your results.

Check Your Understanding

Question 1

1 of 3

What is an allele?