Darwin’s Theory of Evolution 15-1 Darwins Observations 15-3 Darwin Presents His case

Voyage of the Beagle During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time Evolution, or change over time, is the process by which modern organisms have descended from ancient organisms

Darwin's Observations Patterns of Diversity- so many plants and animals seemed remarkably well suited to whatever environment they inhabited. These patterns posed challenging questions: why were their no rabbits in Austria? Or Kangaroos in England? Despite the presence of habitats that seemed perfect for them?

Darwin’s Observations Living Organisms and Fossils – living animals represented just part of the puzzle posed by the natural world. Preserved remains of ancient organisms, fossils, resembled organisms still alive. Others look completely unlike any creature he had ever seen.

Darwin’s Observations The Galapagps Island – The islands were close together but had very different climates. Observed that the characteristics of animals and plants varied noticeably among the islands. Learned that the giant tortoise varied in predictable ways from one island to another. The shape of their shell could be used to identify which island they came from Collected several specimens of birds looking for seeds with different shaped beaks, came can to no conclusion about this at first.

Publication of On the Origin of Species In 1859 Darwin published the results of his work, On the Origin of Species. Proposed a mechanism for evolution that he called natural selection.

Inherited Variation and Artificial Selection Variation existed both in nature and on farms Naturally some plants in a species bear larger fruit then others and some cows give more milk than others. This is inherited variation When a breeder only selects the largest, fastest, or most productive, that is artificial selection In artificial selection, natural provided the variation, and humans selected those variations that they found useful

Evolution by Natural Selection The Struggle for Existence- members of each species compete regularly to obtain resourses. The predators that are faster or cunning, could catch more prey The prey that were faster, used camouflaged or protected themselves could avoid being caught.

Evolution by Natural Selection Survival of the Fittest- how well suited an organism is to its environment The ability of an individual to survive and reproduce in its specific environment is Fitness. Any inherited characteristic that increases an organism’s chance of survival is adaptation. Over time natural selection results in changes in the inherited characteristics of a population.

Evolution by Natural Selection Types of Adaptations Mimicry to copy other organisms for safety Carnivores plant to obtain nitrogen Camouflage to hide from predators or prey Long roots to increase surface area and large chance of gaining water in dry conditions

Evolution by Natural Selection Descent with Modification-Principle that each living species has descended, with changes from other species over time Ex: relations over time of the tigers, panthers, and cheetahs to horses, dogs, and bats Common descent- principle that all living species – living and extinct - have a common ancestor Ex: a ingle “tree of life” links all living things.