Ch 15 Evolution

Chapter 15: Evolution Evolution: (to change) modern organisms have descended from ancient organisms •

•

•

1831: Charles Darwin takes H.M.S. Beagle around the world (5 years) 1. Official company of the captain 2. Collected every new plant and animal he could Questions (after 3 voyages): 1. Why have so many species disappeared over time? (99% of species are extinct) 2. Where did they come from? 3. How did they become so fit? o Fitness: the ability of an organism to survive based on its traits and behavior 30 years later, Darwin writes The Origin of Species by Means of Natural Selection 1. Modern species were produced through evolution, a very long/slow process 2. Each new species came from a pre-existing one (Common Descent) 3. Fitness comes from adaptation (Survival of the Fittest) a. Fitness drives Evolution

Genetics and Evolution: 1. Mutations (chromosomal or gene) 2. Meiosis (variety of combinations) • Gene Pool: all the alleles available in the population for a specific trait • Relative Frequency: number of times an allele occurs vs. number of times another occurs • Any change in relative frequency of alleles on the gene pool of a population (evolution) Homologous Features: • Originated in a common ancestor • Similar in skeletal structure • Come from the same embryological structure Analogous Features: • Serve identical functions • Similar appearance • Different embryological associations • Different internal anatomy