1. You have learned that both biotic and abiotic factors affect ecosystems. Give some examples of each and explain how biotic and abiotic factors could have affected the tortoises that Darwin observed on the Galapagos Islands

2. Ch 16 Darwin’s Theory of Evolution
16.1 Darwin’s Voyage of Discovery

3. Evolution The process of change over time
Change in allele frequency in a population over time.

4. Geologists were suggesting that Earth was ancient and had changed over time
Biologists were suggesting that life on Earth had also changed.

5. Darwin’s Epic Journey
Darwin was invited to sail on the HMS Beagle’s five- year voyage mapping the coastline of South America in 1831
Darwin planned to
collect specimens
of plants and
animals on the
voyage.

6. Observations Aboard the Beagle
Species vary around the world
Species vary locally
Species vary over time
Darwin wanted to explain the biological diversity he observed in a scientific way
He looked for larger patterns into which his observations might fit.

7. Species vary Globally
Darwin found flightless, ground- dwelling birds called rheas living in South America
Rheas look and act a lot like ostriches (live in Africa).

8. Species vary Locally
These islands are close to one another, yet they have different ecological conditions
Different islands had distinct tortoises, mockingbirds, and finches.

9. Hood Island is flat, dry, and has sparse vegetation
Isabela Island has high peaks, is rainy, and has abundant vegetation that is close to the ground
Tortoise has a dome-shaped shell and short neck
Hood Island is flat, dry, and has sparse vegetation
Long neck and a shell that is curved and open around the neck and legs allow them to reach sparse, high vegetation.

10. Darwin also observed that different islands had different varieties of mockingbirds
All were similar to those in South America
Darwin noticed several types of small brown birds on the islands with beaks of different shapes
He didn’t think they were important.

11. Species Vary Over Time Darwin collected fossils
Preserved remains or traces of ancient organisms
Some fossils of extinct animals were similar to living species.

12. Darwin collected MANY specimens
He actually kept poor records
Darwin sent plant and animal specimens to experts for identification
Mockingbirds turned out to belong to three separate species unique to the Galapagos
The little brown birds were actually all species of finches.

13. Some specimens he took back to England were living.

14. Putting the Pieces Together
Darwin began to wonder if different Galápagos species evolved from South American ancestors
He spent years researching and filling notebooks with ideas on species and evolution
Evidence suggested that species are not fixed and that they could change by some natural process.

15. Using a world map and page 381, count the number of lines of 10° latitude the Beagle crossed
Using the biome map from Ch 4 as a reference, identify three different biomes Darwin visited on his voyage
How did the geography of Darwin’s voyage give him far greater exposure to species variability than his fellow scientists back home had?