Evolution The process of biological change by which descendants come to differ from their ancestors. Nowicki, 2008.

Early beliefs In the 1700s scientists believed that organisms were fixed and did not change. At this time there were a few scientists who were making major contributions to the study of biology.

Carolus Linnaeus A Swedish botanist who proposed a new system of organization of plants, animals, and minerals based on their similarities.

Georges Buffon A French naturalist proposed that species shared ancestors instead of arising separately. Species: a group of organisms so similar to one another that they can reproduce.

Erasmus Darwin An English doctor and poet who proposed that all living things descended from a common ancestor. He believed that more complex things came from less complex things.

Lamarck Jean-Baptiste Lamarck was a French naturalistic He believed that all organisms evolved towards perfection and complexity. He proposed that changes in an environment caused an organism’s behaviour to change. This change could lead to greater use or disuse of a structure or organ.

Lamarck Inheritance of Acquired Characteristics The idea that the environment could cause a change in an organism’s behaviour leading to the disuse or greater use of a structure. The structure would then become larger or smaller, depending on its use. This change in the structure would then be passed on to the offspring.

Inheritance of Acquired Characteristics Example: Lamarck believed that giraffes’ long necks had evolved over generations because the giraffes were reaching for the leaves off of trees.

Charles Darwin Was born on February 12, 1809 in England. He came from a wealthy family, and was expected to follow a medical career. After he had graduated from Cambridge he was invited to go on a voyage on the H.M.S Beagle. He went on a five year voyage from

Beagle Voyage They travelled down to the Galapagos Islands, which are about 600 miles west of Ecuador.

Galapagos Islands These islands have species of organisms found no where else in the world. Darwin began to study the birds on the islands. As he studied the finches, he realized how different they were from one island to the next.

He identified 13 species of finches. There was only one species on the mainland

Darwin’s Finches They differed in beak size and shape.

Darwin’s Finches He concluded from this observations that as the birds dispersed to other islands they adapted to different environments and conditions. They changed in ways that allowed them to get enough food, in order to survive and reproduce.

Adaptive Radiation: Different populations of a species become reproductively isolated from each other by adapting to different ecological places. Different populations of a species become reproductively isolated from each other by adapting to different ecological places. Eventually they become separate species. Eventually they become separate species.

Darwin did not think that the environment was responsible for the variation. He believed that the variation existed before and that nature was just selecting the most suitable beak shape and size.

Survival of the Fittest Individuals who have variations that give them an advantage to survive and reproduce are the ones who will pass on their traits more frequently.

Darwin worked on his theory for more than 20 years! Darwin found out that another naturalist was also working on a similar theory.

Alfred Wallace was a British naturalist who was working on his own theory. After realizing how similar their ideas were, Darwin and Wallace made an announcement of their discoveries together. Darwin published The Origin of Species in 1858.

Evolution by Natural Selection There are five main ideas of Natural Selection: Overproduction Overproduction Struggle for existence (competition) Struggle for existence (competition) Variation Variation Survival of the fittest Survival of the fittest Origin of new species (Speciation) Origin of new species (Speciation)

Overproduction The number of offspring produced by a species is greater than the number that can survive, reproduce, and live to maturity. Example: Cod fish lay millions of eggs, yet the ocean is not completely filled with codfish because only a few survive. A bacterium can divide by binary fission every 20 minutes. In theory one bacterium could give rise to 4 x cells in just 24 hours!

Competition Due to overproduction, organisms of the same species, as well as those of a different species, must compete for limited resources, such as food, water, and a place to live. Example: Paramecium is a single-celled, ciliated protozoan that feeds on bacteria. There are a number of species of paramecium. Both species thrive when raised alone. When raised together, the growth rate is slowed for both, until one species declines. Evidently these two ciliates are competing for a limiting resource, share the same niche, and competition determines that only one persists.

Intra-specific Competition Competition occurring between organisms of the same species.

Inter-specific Competition Occurs when two different species compete for resources.

Variation Differences among traits occur among members of the same species. Therefore no two individuals are exactly alike. These variations are passed on to the next generation.

Variations We now know that variations arise by mutations. Mutations occur when there is a change in a gene’s sequence, or in the number of chromosomes.

Example Some jaguars are born with slightly larger jaws and teeth. This variation will be passed onto the next generation.

Survival of the Fittest Those individuals in a species with traits that give them an advantage (those that are well adapted to their environment) are better able to compete, survive, and reproduce. All others die off without leaving offspring. Only the strongest organisms survive, reproduce and consequently leave the strongest offspring.

Example: Peppered moth of the industrial revolution.

Speciation (Origin of a new species) Over numerous generations, new species arise by the accumulation of inherited variations. When a type is produced that is significantly different from the original, it becomes a new species.

Example: Darwin’s Finches