10.3 Theory of Natural Selection KEY CONCEPT Darwin proposed natural selection as a mechanism for evolution.

10.3 Theory of Natural Selection Charles Darwin - Biography Born – England, February Sailed around the world as a naturalist (scientist who studies nature) Well educated and interested in natural history Curious with an analytical nature Made observations and collected evidence which later supported his hypothesis about how life changes over time

10.3 Theory of Natural Selection Charles Darwin - Travels Sailed on the ship H.M.S. Beagle in 1831 –From Europe to South America, the Galapagos Islands, New Zealand, Austrailia, the southern tip of Africa, back to South America, and then home to England The Galapagos Islands –Islands are close together; climates are very different: hot, dry and barren vs. more rainfall and vegetation

10.3 Theory of Natural Selection Darwin observed differences among island species. Variation is a difference in a physical trait. –Galápagos tortoises that live in areas with tall plants have long necks and legs. –Galápagos finches that live in areas with hard-shelled nuts have strong beaks.

10.3 Theory of Natural Selection Several key insights led to Darwin’s idea for natural selection. –Darwin observed a lot of variation in domesticated plants and animals. Artificial selection is the process by which humans select traits through breeding. neck feathers crop tail feathers

10.3 Theory of Natural Selection Artificial selection in dogs

10.3 Theory of Natural Selection Artificial selection in horses

10.3 Theory of Natural Selection Natural selection is when individuals that have inherited beneficial adaptations produce more offspring on average than do other individuals.

10.3 Theory of Natural Selection Heritability is the ability of a trait (beneficial adaptations) to be passed down. –There is a struggle for survival due to overpopulation and limited resources. Darwin proposed that adaptations arose over many generations.

10.3 Theory of Natural Selection There are four main principles to the theory of natural selection. Variation – differences in organisms Natural selection explains how evolution can occur. VARIATION

10.3 Theory of Natural Selection Natural selection explains how evolution can occur. There are four main principles to the theory of natural selection. Adaptation – changes caused by evolution in an organism to better survive in their environment ADAPTATION

10.3 Theory of Natural Selection Natural selection explains how evolution can occur. There are four main principles to the theory of natural selection. Overproduction – producing more offspring than will survive OVERPRODUCTION

10.3 Theory of Natural Selection Natural selection explains how evolution can occur. There are four main principles to the theory of natural selection. DESCENT with MODIFICATION Traits that are heritable and beneficial (like big jaws and teeth) will be passed down to further generations.

10.3 Theory of Natural Selection Fitness is the measure of survival ability and ability to produce more offspring.

10.3 Theory of Natural Selection Natural selection can act only on traits that already exist. Structures take on new functions in addition to their original function. Natural selection acts on existing variation. wrist bone five digits