Section 1: Darwin’s Theory Changes Over Time Section 1: Darwin’s Theory What important observations did Darwin make on his voyage? How did Darwin account for the diversity of species and the differences between similar species? How does natural selection lead to evolution?

Changes Over Time Darwin’s Voyage Charles Darwin sailed on the Beagle, from England to the Galápagos Islands.

Darwin’s Observations Darwin’s important observations included the diversity of organisms, the remains of ancient organisms and the characteristics of organisms on the Galapagos Islands.

Diversity Today, scientists have identified more than 1.7 million organisms. MUCH more than Darwin could have ever imagined. A species is a similar group of organisms that can mate with each other and produce fertile offspring.

Fossils Darwin saw the fossil bones of animals that had died long ago. A fossil is the preserved remains or traces of an organism.

Galapagos Organisms Many of the plants and animals resembled those on the mainland. However there were important differences between the mainland iguanas and the Galapagos marine iguanas.

Can you spot some differences below?

Darwin’s Finches Darwin noticed differences in finches from island to island

Tortoises too! Some islands had tortoises with dome shaped shells, some with saddle shaped and some that were more flat.

Adaptation An adaptation is any trait that helps an organism survive and reproduce in its environment. Finches beak structure helps it get food Flowers are brightly colored to attract bees and other insects

Evolution Darwin reasoned that plants and animals that arrived on the Galapagos Islands faced environmental factors that were different from those on the mainland. He hypothesized that species gradually changed over many generations to become better adapted to the new environments. The gradual change in species over time is called evolution.

Overproduction and Variation Changes Over Time Overproduction and Variation Natural selection is the process by which individuals who are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

Competition and Selection Changes Over Time Competition and Selection Variations among turtles make some of them better able to survive. Turtles that survive to become adults will be able to reproduce.

Galapagos and Google Maps And now a video!

Questions Give me 5! Outline your hand and give me five things you learned today… one on each finger!

End of Section: Darwin’s Theory Changes Over Time End of Section: Darwin’s Theory