DARWIN’S THEORY

Charles Darwin ( ) A British scientist who went on a 5 year voyage around the world and studied nature. While travelling Darwin wanted to know why the plants and animals he observed were so different from the ones in England. Darwin's observations lead to develop one of the most important scientific theories of all time; the theory of evolution by natural selection.

Map of Charles Darwin’s Voyage

DARWIN’S OBSERVATIONS Key Concept What important observations did Darwin make on his voyage? Darwin’s important observations included the diversity of organisms, the remains of ancient organisms, and the characteristics of organisms on the Galapagos Islands.

DARWIN’S OBSERVATIONS Diversity Darwin learned that the plants and animals around the world were really diverse and different from country to country.. Species: a group of similar organisms that can mate with each other and produce fertile offspring. Fossils Darwin studied the fossil bones of animals that died long ago. Fossil: Preserved remains or traces of an organism that lived in the past. He was able to compare the fossil bones to current living animals

The iguanas on the Galapagos islands had large claws to grip slippery rocks while eating seaweed. The iguanas on the mainland had smaller claws that helped them climb trees to eat leaves. Many of the birds on the islands resembled those on the mainland. Many of the plants were similar to the ones collected on the mainland. GALAPAGOS ORGANISMS Similarities with South American Organisms Differences with South American Organisms

GALAPAGOS ORGANISMS Comparisons Among the Islands Tortoises on one island had dome shaped shells while on another island they had saddle shape shells Finches beaks were also different from island to island. Each beak was well suited to the life of the finch (food, area etc.) Beak shape is an example of an adaptation; a trait that helps an organism survive and reproduce in its environment.

EVOLUTION After gathering his data Darwin returned back to England and continued thinking about the diversity of species. He spent the next 20 years of his life studying data, consulting with other scientist, and gathering more information. Darwin’s ideas were often referred to as the Theory of Evolution Scientific Theory: a well tested concept that explains a wide range of observations

EVOLUTION Key Concept How did Darwin account for the diversity of species and the differences between similar species? Darwin reasoned that plants and animals that arrived on the Galapagos faced environment factors that were different from those on the mainland. Darwin hypothesized that the species gradually changed over many generations becoming better adapted for the environment.

EVOLUTION To study his hypothesis Darwin studied other examples of changes in living things He studied the offspring of animals produced by selective breeding. Sheep (Good wool) Pigeons (More tail feathers) Horses (Breed for speed and athletic ability) Charles Darwin believed that a process similar to selective breeding occurred in nature.

NATURAL SELECTION In 1859 Darwin Published a book called The Origin of Species by Natural Selection In the book he proposed that evolution occurred in nature through a process called natural selection. Natural Selection: A process by which individuals that are better adapted to their environment are more likely to survive and reproduce than others of the same species.

NATURAL SELECTION Factors of Natural Selection Overproduction Plants and animals sometimes tend to over reproduce leading to a very large population within an area Variations Genetic variation within a species may give an advantage over others within the species. Competition Since food and other resources are limited members compete to survive. Can be indirect like trying to find enough to eat or trying to not get caught by predators.

NATURAL SELECTION Factors of Natural Selection Environmental Factors Environmental factors can affect an organisms ability to survive. Thanks to genetic variation organisms within a species are more suited to survive in certain environmental conditions than others. Genes Without genetic variation all species would have the same traits and natural selection would not occur.

NATURAL SELECTION Key Concept How does natural selection lead to evolution? Over a long time natural selection can lead to change. Helpful variations may gradually accumulate in a species, while unfavorable ones may disappear.

VIDEO: CHANGES OVER TIME

POSTER ACTIVITY Using the Left Side page in your Science Notebook Complete the following activity. Imagine that you are a scientist exploring the Galapagos. Before With a partner describe and draw an animal that would be found on the mainland. Include specific traits that animal has that make it suited for that environment. After Describe and draw how that animal might have changed after it was transported to the Galapagos islands and managed to survive more many generations.