Natural Selection “Survival of the Fittest”

Charles Darwin Fresh out of college young Charles Darwin started a 5 year voyage on the HMS Beagle which became the foundation for his theory of Natural Selection.

In 1859, Darwin proposed a theory to explain how organisms changed over time. He based his theory on his observation of plants and animals that he studied all over the world. The HMS Beagle traveled all over the world and Darwin collected thousands of plant and animal samples and kept detailed notes of his observations.

His most important work was during his visit on the Galapagos Islands.

Natural Selection The process by which organisms with favorable traits survive and reproduce at a higher rate than organisms without the trait.

Natural Selection Examples Would the large tree finch and the large ground finch compete for the same resource? They would not compete for the same resource because one goes for plant food while the other goes for animal food.

Four Parts of Natural Selection Overproduction: Each species produce more offspring that will survive to maturity 2) Genetic Variation: Individuals in a population are slightly different from each other with slightly different traits. Some traits increase the chances of the individual to survive and reproduce 3) Struggle for Survival: Environment does not have enough food, water and other resources to support every individual. Some are killed by other organisms 4) Successful Reproduction: Individuals that are able to adapt to their environment reproduce offspring that will have the traits to also be able to adapt.

HUMAN IMPACT -Genetic Resistance in Insects How can natural selection be seen in a population of insects on a farm? The pesticide kills off the weaker insects, leaving the stronger ones with a resistance to the chemical. They reproduce and then the pesticide is not as effective in killing the insects next time.

-Selective Breeding In selective breeding humans select desired traits in animals to be passed from 1 generation to another. Ex: corn or breeding dogs

Speciation Allopatric speciation due to geographic separation of the Grand Canyon. Harris's antelope squirrel (Ammospermophilus harrisi) inhabits the canyon's south rim (left). Just a few miles away on the north rim (right) lives the closely related white-tailed antelope squirrel (Ammospermophilus leucurus). Another example is the Tassel-eared Squirrel, where Abert's Squirrel (Sciurus aberti) lives on the south rim and the Kaibab Squirrel (Sciurus aberti kaibabensis) lives on the north rim.