Natural Selection

Charles Darwin (1809-1882) Studied biology In 1831 at age 22, he accepted a job on the HMS Beagle as a scientist The HMS Beagle docked at the Galapagos Islands off the coast of South America

Charles Darwin (1809-1882) Based on fossil evidence, Darwin knew plants and animals change over time Believed organisms had changed slowly over time and would keep changing The environment and adaptability of the organisms controlled the changed.

What he saw in the Galapagos…

What he saw in the Galapagos… Each island had similar animals with slightly different traits Long or short necked tortoises depending on the plant height

What he saw in the Galapagos… Finches had many different beak sizes and shapes depending on diet

Natural Selection Darwin’s theory that organisms changed over time based on traits that helped them survive Survival of the fittest

Natural Selection Organisms with traits that help them survive grow and reproduce passing on those traits to their offspring Organisms with traits that don’t help them survive are usually eaten or die and don’t pass on their traits

Natural Selection Factors that can affect the process of natural selection Overproduction of offspring in a species Competition among organisms of same species Genetic variations within a population

Peppered Moths In England there is a species of peppered moth They come in two color variations Light dark The trees they lived on had a light bark color During the industrial revolution, factories were built that produced soot The soot stained the tree bark black

Peppered Moths light dark Use the moth and bark pictures on your desk to answer. Which moths were better adapted to the trees before pollution? Which moths were adapted to the trees after the pollution? light dark

Elephant Example Let’s say a group of elephants had mostly short trunks But a few of the elephants in the group had slightly longer trunks than others When food and water became scarce, the elephants with longer trunks could reach higher for food and deeper into holes for water

Elephant Example Elephants with shorter trunks would die of thirst and starvation Elephants with longer trunks would survive and reproduce passing on their longer trunks Over time, the group would consist mostly of long trunked elephants

Elephant Example Put the elephant cards in the right order