Charles Darwin, 1831, at 22 years old Was sent on a 5 year trip around the world by ship He learned as much as he could about the organisms he saw on the trip.

He saw and thought about…. Differences between the organisms on each island Differences between the organisms on the Islands and the Mainland Differences between the organisms on the Islands and in England

Differences Between Islands Pointed and Smooth Shells, Bird Varieties

Differences between the organisms on the Islands and the Mainland nearby Genetic Difference between Galapagos and South American Yellow Finches.

Organisms different from those studied at home

Galapagos and England Doves

More Diversity 1.7 million species of organisms identified on Earth Grizzly Bear here AND Panda and Polar elsewhere California King Snake, Western Rattlesnake, California Redwood, California Bay Laurel Tree California Bay Laurel, Valley Oak

Darwin was amazed at this diversity He noticed that iguanas that lived in trees and ate leaves on the mainland had smaller claws. He noticed that iguanas with larger claws were able to grip the slippery rocks of the Galapagos Islands.

More and More Differences He also saw differences in the pointed or smooth tortoise shells between the islands He saw differences in the color of the Finches in South America and on the islands He saw differences in the color of the Doves on the Islands and those from his home His observations led him to develop a theory

Darwin wondered why there were these differences and variations Darwin hypothesized that a small number of species came to the islands by floating on a log… Once there, they reproduced and their offspring became different from their mainland relatives.

Differences to Adaptations The differences Darwin noticed are examples of ADAPTATIONS An adaptation is a trait that helps an organism survive and reproduce in its environment. Some adaptations keep organisms from being eaten. Some adaptations aid in reproduction: the color of flower petals attract pollinators. Darwin wanted to understand adaptations better!!

After 20 years of thinking Darwin reasoned that: Plants and animals that arrived on the Islands faced new environmental factors than those on the mainland. He hypothesized that the species gradually changed over many generations and became better adapted to the new environment. This gradual change in a species over time is called evolution.

Darwin’s ideas are often referred to as the theory of evolution. A theory is not a casual thought or a hypothesis. A scientific theory is a well-tested concept that explains a wide range of observations. From the evidence he gathered, Darwin concluded that organisms on the Galapagos Islands are changing over time.

“On the Origin of Species by Natural Selection” was published by Darwin 28 years after his trip. In it, Darwin proposed that: Evolution occurs in nature through a mechanism called Natural Selection In Natural Selection: Individuals that are better adapted to their environment are more likely to survive and reproduce than other members of the same species.

Factors that affect the process of Natural Selection 1. Overproduction 2. Genetic Variation: A difference between individuals of the same species 3. Competition

Selection Some variations make individuals better adapted to their environment. Those individuals are more likely to survive, and reproduce. The offspring may inherit the helpful characteristics, making the offspring more likely to survive and reproduce, and pass on those characteristics to their offspring……….

Results of Selection After many generations, more members of the species will have the helpful characteristic. The environment has selected organisms with helpful traits to become parents of the next generation. Over time, Natural selection can lead to change. Helpful variations may gradually accumulate, and Unfavorable variations may disappear.

Environmental Factors Environmental factors can affect an organisms ability to survive. Environmental factors can therefore lead to selection. For Example: With a change in the environment, some individuals may be able to survive in the new conditions. These individuals will grow and reproduce.

Genes and Natural Selection Genetic variation also leads to selection. Without variations, all members of a species would have the same traits. So…. Natural Selection would not occur because all individuals would have an equal chance of surviving and reproducing.

Inherited Traits and Natural Selection Variations can result from mutations and shuffling of alleles during meiosis. Genes are passed from parents to offspring. Because of this…… Only traits that are inherited, or controlled by genes, can be acted upon by natural selection.