Chapter 5, Section 1 Darwin’s Voyage

1. Chapter 5, Section 1Darwin’s Voyage Wednesday, January 6, 2010 Pages 146 -- 156

2. Objectives • State how Darwin explained variations among similar species. • Explain how natural selection leads to evolution, and explain the role of genes in evolution. • Describe how new species form.

3. Species Adaptation Evolution Scientific theory Natural selection Variation Vocabulary Words

4. Who is Charles Darwin? • He was a scientist who came up with the idea of evolution by natural selection. • Ideas began when we worked as a young naturalist aboard a British naval ship. • His travels brought him to the Galapagos Island.

5. Darwin’s Observations • The voyages brought Darwin to many interesting places such as Argentina and the Galapagos Islands. • Darwin was amazed at the diversity of living things he saw. • Today, there are over 1.7 million species of organisms on Earth. • A species is a group of similar organisms that can mate with each other and produce fertile offsprings.

6. Similarities and Differences • While on the Galapagos Island, Darwin noticed that many of the plants and animals were the same as those organisms found on the mainland. • Even though many of the plants and animals, there were slight differences. • Small vs. large claws. • Shape of the shells on the tortoises

7. Adaptation • An adaptation is the ability of an organism to take on a trait that will help it survive and reproduce. • Example: The size of a bird’s beak.

8. Evolution • Evolution is the gradual change in a species over time. • Darwin thought that species gradually changed over many generations and became better adapted to the new condition. • Darwin’s ideas are often referred to as the theory of evolution. • A scientific theory is a well-tested concept that explains a wide range of observations.

9. Natural Selection • Darwin published a book called The Origin of Species in 1858. • This book proposed an explanation for how evolution occurs. • Darwin explained that evolution occurs by means of natural selection.

10. Natural Selection -- cont’d • Natural selection is a process by which individuals are better adapted to their environment and these individuals are more likely to survive and reproduce than other members of the same species. • Factors that affect the process of natural selection are: • Overproduction, competition, and variations. • Over time, natural selection can lead to evolution. Helpful variations gradually accumulate in a species, while unfavorable ones disappear.

11. Role of Genes in Evolution • Without variations, all the members of a species would have the same traits. • Evolution by natural selection would not occur because all individuals would have the same chance of survival. • Variations come from mutations in genes.

12. How do New Species Form? • New species may come about from separation from the rest of its species. • Once a group is isolated, members of the isolated group can no longer mate with members of that species. • These separated members might be away for so long that different traits evolve.

13. Continental Drift • Continental drift affected the evolution of species. • Evident when examining the fossils from various continents. • The split of Pangaea accounts for species being separated from one another and caused them to evolve independently.

14. Homework • Workbook 5.1 (1/8) • Worksheet 5.1 (1/7) • Vocabulary quiz 5.1 (1/8)