Darwin’s Theory outline notes

1. Darwin’s Theory outline notes Pages 138-145

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

3. A. Diversity • Species: grouping of similar organisms that can mate with each other and produce fertile offspring

4. B. Fossils • Fossil: preserved remains or traces of an organism that lived in the past

5. 2. Galapagos Organisms • In 1835, Darwin reached the Galapagos Islands. • Darwin compared the similarities and differences he saw in the Galapagos Island organisms to those from other parts of the world.

6. A. Comparisons to South American Organisms • Many organisms from the Galapagos Islands were similar to those from South America. • There were also many differences between the animals. • Darwin hypothesized that some different plants and animals had come to the Galapagos Islands from the mainland. Eventually the offspring became different from their mainland relatives.

7. B. Comparisons Among the Islands • Darwin noticed many difference between the organisms on each of the islands.

8. C. Adaptations • Darwin noticed that the finches on the islands were well suited for the food it ate. • Adaptation: a trait that helps an organism survive and reproduce **Think about the Bird Beak Lab that we did in class. We saw how certain beaks made it easier to pick up and “eat” the seeds.

10. 3. Evolution

11. A. Darwin’s Reasoning • Darwin reasoned that plants or animals that arrived on the Galapagos Islands faced conditions that were different from those on the mainland. Perhaps, Darwin hypothesized, the species gradually changed over many generations and became better adapted to the new conditions. • Evolution: gradual change in a species over time • Scientific theory: well-tested concept that explains a wide range of observations

12. B. Selective Breeding • Darwin also studied selective breeding of pigeons. By allowing only pigeons with many tail feathers to mate, breeders produced pigeons with 2-3 times the usual number of feathers. • Darwin thought a process similar to selective breeding might happen in nature.

14. 4. Natural Selection • Natural Selection: process by which individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species

15. A. Overproduction • Most species produce more offspring than can survive

16. B. Variations • Variation: members of a species differ from one another in many of their traits

17. C. Competition • Food and other resources are limited so members of a species must compete with each other to survive

18. D. Selection • Some variations make individuals better adapted to their environment. • Darwin proposed that, over a long time, natural selection can lead to change. Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear.

19. E. Environmental Change • A change in the environment can affect an organism’s ability to survive. Environmental change can lead to selection.

20. F. Genes and Natural Selection • Variations can occur from mutations. Only traits that are inherited, or controlled by genes, can be acted upon by natural selection.