1. Chapter 15 Section 1 finish

2. Charles Darwin Born Feb. 12, 1809 Naturalist Joined Crew of HMS Beagle, 1831 5 Year Voyage around world Astounded By Variety of Life Avid Collector of Flora & Fauna

3. Common Descent with Modification Darwin proposed that organisms descended from common ancestors Idea that organisms change with time, diverging from a common form Caused evolution of new species

4. Darwin Left England in 1831 Darwin returned 5 years later in 1836

5. The Galapagos Islands Small Group of volcanic Islands 1000 km West of South America Very Different Climates Island species varied from mainland species & from island-to-island species  Tortoises  Iguanas  Finches

6. Each island had long or short neck tortoises

7. Darwin’s Finches Finches on the same island resembled each other closely However, those from neighboring islands were different Available food on each island was different seeds, nuts, berries, insects… Finches had different types of beaks adapted to their type of food gathering

9. Darwin’s Observations Individuals of a population vary extensively in their characteristics no two individuals being exactly alike. Much of this variation between individuals is inheritable.

10. Darwin’s Observations Left unchecked, the number of organisms of each species will increase exponentially, generation to generation In nature, populations tend to remain stable in size Environmental resources are limited

11. Darwin’s Conclusion Production of more individuals than can be supported by the environment leads to a struggle for existence among individuals Only a fraction of offspring survive each generation Survival of the Fittest

12. Darwin’s conclusions Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals Called Natural Selection

13. Overproduction More offspring are produced then can survive to maturity Genetic Variation Within a population, individuals have different traits Ex. Deer can have longer legs Struggle to survive Individuals compete with each other to survive and reproduce Differential Reproduction Organisms with the best adaptations are most likely to survive and reproduce

14. Natural Selection Adaptation – A trait that makes an individual successful in it’s environment Ex. Thick fur in winter, longer legs to run faster Organisms with best adaptations are more likely to survive and reproduce Through inheritance, adaptations will become more frequent in the population  Populations may begin to differ when they become adapted to different environments

15. Darwin’s Theory of Evolution The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection)The unequal ability of individuals to survive and reproduce leads to a gradual change in a population, with favorable characteristics accumulating over generations (natural selection) New species evolveNew species evolve

16. Definition Evolution - the slow, gradual change in a population of organisms over time