Natural Selection

evolution = a change in inherited characteristics over a long period of time

helpful variations in a species replace unfavorable ones

Charles Darwin =

• English naturalist who published a book on the process of evolution by natural selection

• most notable part of his journey was his visit to the Galapagos islands where he studied finches and determined that the shape of the bird’s beaks had changed over time in response to food availability

• each of the Galapagos islands have a unique ecosystem

• Darwin published “origin of species” in 1859 about biodiversity in the islands; outlined how living things change over time in evolution by natural selection

natural selection = individuals in a population that exhibit the traits that best enable them to survive in their environment will be able to and will pass on their genetic information to future generations through reproduction

survival of the fittest = natural selection results in changes in the inherited characteristics of a population

mutations = random changes in DNA that causes variations within a species; can be caused during replication, exposure to radiation, or chemicals

adaptation = variations that help the organism to survive long enough to reproduce and pass on the genetic information to offspring; can be structures, functions, or behaviors that enable a species to survive

the mechanism through which evolution takes place by connection mutation, adaptation, and natural selection is that random variations or mutations occur during DNA replication. if the mutation helps an organism survive and reproduce, it is an adaptation. over time, adaptations are selected through the process of natural selection

extinction = all of the organisms within a species die out

fossil = the remains or impressions of a prehistoric organism in a petrified fork or a s a mold or cast in rock

paleontologist = scientists who study fossils

not everything becomes a fossil. shells and bones typically do become fossilized, but plants and tissues of soft-bodied organisms very rarely become fossilized

imprints = traces fossils left behind by the plants or animals lacking bones or shells

evidence for evolution:

• relative dating (approximate age) = the lower in the rock layer fossils are found, the older they are

• radiometric dating (actual age) = using carbon; carbon 14 is radioactive and takes a long time to break down, scientists determine fossil age by seeing how much carbon 14 is in the sample

• anatomical similarities (homologous structures)

• developmental similarities (embryology)

• DNA = most reliable source of determining how related organisms might be

• geographic distribution = similar animals that live in different locations but are the products of different lines of descent