Introduction to Evolution Section 5.1

Charles Darwin (1809-1882) a. “Father of Evolution” b Charles Darwin (1809-1882) a. “Father of Evolution” b. Much of his research comes from the Galapagos Islands, off the coast of South America

What did Darwin’s Travels reveal? The diversity of living species was far greater than anyone had previously known!! The species, while different, had similarities to one another and to other species found in South America

What Sparked Darwin’s Theory? Each island had its own type of tortoises and birds that were clearly different from other islands However, similarities existed between them

Galapagos Tortoises

What is Evolution? Defined as change in a species over time It proposes that organisms descended from a common ancestor Organisms in a population differ slightly in form, function, and/or behavior. These differences are due to hereditary changes in DNA passed down from parent to offspring.

Darwin’s Theory of Evolution Darwin proposed that the environment exerts a strong influence over which individuals will survive to produce offspring (“Survival of the Fittest”) These individuals have certain traits that make them more likely to survive and reproduce. (based on genes) Over time (many generations), natural selection causes the characteristics of a population to change.

Evolution by Natural Selection Organisms produce more offspring than can survive. The environment is hostile and contains limited resources. Organisms differ in the traits they have. Some inherited traits provide organisms with an advantage. Each generation contains proportionately more organisms with advantageous traits.

Other Mechanisms of Biological Evolution: Mutation, Migration, and Genetic Drift Accidental change in DNA that can give rise to variation among individuals Migration Movement of individuals into (immigration) or out of (emigration) a population

Genetic Drift Evolution that occurs by chance In each generation, some individuals may, just by chance, leave behind a few more descendents (and genes, of course!) than other individuals. 

Artificial Selection Nature provides variation- humans select the variations that are useful to them. Example - a farmer breeds only his best livestock

Speciation Process by which new species are generated Can occur in a number of different ways; the most important way is called allopatric speciation Has resulted in every form of life on Earth-today and in the past

Extinction The disappearance of species from Earth Generally occurs gradually, one species at a time, when environmental conditions change more rapidly than the species can adapt There are 5 known mass extinction events, each of which wiped out a large proportion of Earth’s species.