Evolutionary Theory

Some Definitions to Remember… Evolution is the process by which species change over time A theory is a broad explanation that has been scientifically tested and supported The Theory of Evolution explains the evidence suggesting that life on Earth has changed The Theory of Evolution was proposed by Charles Darwin

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: The Voyage of the Beagle 5 year trip around the world He collected & observed natural objects from each place that he visited

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: The Voyage of the Beagle 5 year trip around the world He collected & observed natural objects from each place that he visited Fossils of extinct armadillos were similar but not identical to living armadillos in the area

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: The Voyage of the Beagle 5 year trip around the world He collected & observed natural objects from each place that he visited Fossils of extinct armadillos were similar but not identical to living armadillos in the area Finches from the Galapagos Islands were similar, except for their beaks

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: The Voyage of the Beagle 5 year trip around the world He collected & observed natural objects from each place that he visited Fossils of extinct armadillos were similar but not identical to living armadillos in the area Finches from the Galapagos Islands were similar, except for their beaks He noticed that all organisms were well suited to their environments and diets

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: Years of Reflection After returning from his voyage on the Beagle, Darwin (27 at the time) studied his data for many years. He did not report his data until much later

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: Breeding and Selection Darwin noticed that humans take advantage of the variations among organisms of the same species as they breed them In other words, humans choose to breed the organisms with the “best” traits Darwin called this artificial selection What examples of artificial selection can you think of?

The Evolutionary Theory was Influenced by Darwin’s Life Experiences: Examples of Artificial Selection Horses are bred for strength, speed, beauty, and size Flowers are often bred for brighter and more varied colors. Corn is bred to have many full kernels in straight rows and to taste great. Strawberries are bred for color, size, and durability. Wild berries taste better.

The Evolutionary Theory was Influenced by Darwin’s Peers: Lamarck First prominent scientist to defend the idea that species could change Thought that species passed on acquired traits due to use and/or disuse

The Evolutionary Theory was Influenced by Darwin’s Peers: Malthus Economist Stated that the human population is limited by resources Darwin applied this idea to all populations

The Evolutionary Theory was Influenced by Darwin’s Peers: Cuvier Argued that fossils in rock layers showed differences in species over time Said that species from the past differed from those in the present

The Evolutionary Theory was Influenced by Darwin’s Peers: 4. Lyell His research pointed out that the Earth was old enough for species to have evolved gradually

Evolution by Natural Selection Darwin’s theory predicts that over time, the number of individuals that carry advantageous traits will increase in a population due to nature SELECTING FOR those traits.

Aspects of Darwin’s Theory: Overproduction: Every population produces more offspring than survive Variation: There is variation in every population (some inherited, some random) Selection: In a given environment, some traits give an organism a better chance at survival, so that organism lives and reproduces Adaptation: Traits that improve survival become more common in the population

Publication of his Theory After many years, Darwin wrote an outline of his theory of evolution by natural selection He didn’t publish it because he was afraid that his ideas would be controversial UNTIL…

Publication of his Theory Darwin received a letter from Alfred Wallace In the letter, Wallace wanted Darwin’s opinion on his new theory… one JUST like his! This prompted Darwin to publish a book of his ideas In his book, Darwin: Explained his Theory Offered evidence that suggested that evolution had occurred