Evolution

Evolution Change over time Change in allele frequency The process by which modern organisms have descended from ancient organisms Macroevolution—large changes Microevolution—small changes

Charles Darwin Darwin traveled on the HMS Beagle to the Galapagos Islands as ship naturalist Made observations about how species change over time Darwin observed that the characteristics of many animals and plants varied noticeably among the different islands of the Galapagos.

Darwin’s Theory Published On the origin of Species in 1858 Abandoned theory that species were perfect and unchanging Argued that different variations are brought out through a process called natural selection

Natural Selection The Struggle for Existence Members of each species compete regularly to obtain Food Living space Other necessities of life

Natural Selection Survival of the Fittest Fitness = result of adaptations Adaptation = any inherited characteristic that increases an organism’s chance of survival Over time natural selection results in changes in the inherited characteristics of a population.

Antibiotic-Resistant Bacteria

Natural Selection Descent with Modification Each living species has descended from other species over time Changes that increased ability to survive are maintained

Evolution of Populations Population = group of individuals of the same species that live in the same area Species = group of organisms that can breed and produce fertile offspring Gene Pool = the combined genetic information of all the members of a particular population

Sources of Genetic Variation Mutations Changes in DNA sequence; results in different characteristics Genetic Shuffling Chromosomes move independently during Meiosis Crossing-over swaps genes on homologous chromosomes

Hardy-Weinberg Principle Relative Frequency of an Allele = number of times that allele occurs in a gene pool compared with the number of times other alleles occur Genetic Equilibrium (constant allele frequencies) will be maintained unless one or more factors cause the frequencies to change

Conditions of Hardy-Weinberg Random Mating Large Population No movement in or out of the population No mutations No natural selection