Science 20 – Biology Ch. 2 Populations Section 3

Galapagos Finches  Charles Darwin observed a chain of volcanic islands off the Pacific coast of South America called the Galapagos Islands  There were a variety of different climatic regions, each with their own unique ecosystem along the islands with a variety of food sources  Darwin observed that the same animals had adapted differently to take advantage of the local conditions

E.g. Several varieties of finches had different beak types that were adapted for a diet specific to their regions Darwin suggested that all varieties of finches came from a common seed-eating finch ancestor

Darwin’s Theory of Evolution Published “On the Origin of Species by Means of Natural Selection” to describe his theory of evolution – theory stating that the nature of population gradually changes form over time

Darwin also described his theory of natural selection based on the following observations: Organisms usually produce more offspring than can survive There is a variation among individuals with respect to any trait in a population Organisms within a population compete for limited resources

The best adapted individuals in the population are considered to have greater Darwinian fitness because they’ll be able to survive, breed, & pass on traits Reproductive success of an organism

More Evidence The fossil record indicates that organisms did not remain static

Many organisms have vestigial structures – structures that serve no function. (i.e. appendix in humans, undeveloped hind legs in a whale.)

Homework Case Study in readings: James Lamark (Incorrect Hypothesis) and The Peppered Moth Assignment: p #36-40a, 42-46