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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: 1. 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: 1. 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: 1. 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: 1. 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: 2. 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: 3. 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 Flowers are often bred for brighter and more varied colors. Horses are bred for strength, speed, beauty, and size 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: 1. 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: 2. 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: 3. 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: 1. Overproduction: Every population produces more offspring than survive 2. Variation: There is variation in every population (some inherited, some random) 3. Selection: In a given environment, some traits give an organism a better chance at survival, so that organism lives and reproduces 4. 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