Chapter 16: Darwin’s Theory of Evolution 16.1 Darwin’s Voyage of Discovery 16.2 Ideas That Shaped Darwin’s Thinking 16.3 Darwin Presents His Case 16.4 Evidence of Evolution
Big Idea: EVOLUTION • What is NATURAL SELECTION?
Chapter 16.1 • General Question: • What patterns of biodiversity did Darwin observe while traveling aboard the Beagle?
Darwin’s Epic Journey • Key Question: • What was Charles Darwin’s contribution to science? • Charles Darwin • born in England, 1809 • 1831 • 5 year journey on the HMS Beagle • Ship’s mission is to map South America • See Fig 16-1
Darwin’s Epic Journey • Galapagos Islands • West coast of South America, at the Equator • Coordinates: Latitude: 0°40′0″S Longitude: 90°33′0″W
Darwin’s Epic Journey • This is where Darwin developed a scientific theory of biological evolution that explains how modern organisms evolved over long periods of time through descent from common ancestors.
Observations Aboard the Beagle • Key Question: • What three patterns of biodiversity did Darwin note? • While on the Galapagos Islands, Darwin noticed three distinctive patterns of biological diversity: • Species vary globally • Species vary locally • Species vary over time
Species Vary Globally • Darwin noticed that different, yet ecologically similar, animal species inhabited separated, but ecologically similar, habitats around the globe.
Species Vary Globally • Example: • flightless, ground-dwelling birds are found in the grasslands around the globe: • Rheas in South America • Ostriches in Africa • Emu in Australia
Question: • Why is it significant that many of the stops the Beagle made were near the equator?
Species Vary Locally • Darwin noticed that different, yet related, animal species often occupied different habitats within a local area.
Species Vary Locally • Example: • Galapagos Islands • Several islands were home to distinct forms of giant land tortoises.
Species Vary Over Time • Darwin noticed that some fossils of extinct animals were similar to living species.
Species Vary Over Time • Fossil: preserved remains of ancient, extinct organisms. • Example: Glyptodonts (giant, armored, land-dwelling animal) • Fossils of glyptodonts are found today in regions inhabited by present-day armadillos.
Putting the Pieces of the Puzzle Together • The great variety of species of animals found on the Galapagos Islands must have come from a common ancestor on the mainland of South America and changed over time to the demands of each individual habitat.
Assessment Questions 16.1 • 1. What is evolution?
Assessment Questions 16.1 • 2. What three kinds of variations among organisms did Darwin observe during the voyage of the Beagle?
Assessment Questions 16.1 • 3. Darwin found fossils of many organisms that did not resemble any living species. How might this finding have affected his understanding of life’s diversity?
Assessment Questions 16.1 • 4. 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
Assessment Questions 16.1 • 5. What was Charles Darwin’s contribution to science?
Assessment Questions 16.1 • 6. What three patterns of biodiversity did Darwin note?