Unit 9: Evolution 9.3 What is Evolution?

Question for Thought Earth has millions of other kinds of organisms of every imaginable shape, size and habitat. This variety of living things is called Biological Diversity. How did all these different organisms arise? How are they all related?

What is Evolution? A change in a species over time. The process by which modern organisms have descended from ancient organisms.

The Theory of Evolution A scientific theory: Well-supported, testable, explanation of a phenomena that occurs in the natural world.

The Theory of Evolution The theory has been around for more than 2,000 years (since Roman time) Scientists once believed that each species was of divine creation and lived as it was originally designed. In 1831, Charles Darwin came along and provided evidence for the Theory of Evolution.

Darwin’s Voyage on the HMS BEAGLE In 1831, Charles Darwin was selected to be the naturalist on a voyage of the HMS Beagle.

Darwin’s Voyage on the HMS BEAGLE On this voyage he discovered: Fossils of Armadillos in South America that were similar but not identical to modern day Armadillos. Similar grassland ecosystems in Argentina and Australia but inhabited by very different animals. The Galapagos Islands: very different ecosystems on each island and similar but different species of animals between the islands. Giant Tortoises, marine Iguanas and Finches

Darwin’s Voyage on the HMS BEAGLE Darwin made two major points in his book, On the Origin of Species: He presented evidence that many species of organisms presently inhabiting the Earth are descendants of ancestral species He viewed the history of life like a tree: with multiple branching's from a common trunk to the tips of the youngest twigs that represent the diversity of living organisms.

Darwin’s Voyage on the HMS BEAGLE Example: Humans and chimpanzees share a recent common ancestor and therefore have DNA that is 98.8% similar. Humans did NOT evolve from chimpanzees.

Darwin’s Voyage on the HMS BEAGLE 2. He proposed a mechanism for the evolutionary process: natural selection.

Evolution by Natural Selection Natural Selection: The process by which organisms with variations most suited to their environment survive and leave more offspring. Occurs naturally Does not make organisms “better” Could not occur without genetic variation.

Natural Selection Requirements The struggle for existence: More individuals are produced that can survive, therefore members of a population must compete.

Natural Selection Requirements Variation: Individuals vary, and some are better suited to life in an environment to others.

Natural Selection Requirements Adaptation: Any heritable characteristic that increases an organism’s ability to survive and reproduce in its environment- may be physical, physiological, or behavioral.

Natural Selection Requirements Survival of the Fittest: Differences in rate of survival AND reproduction to pass on adaptations.

Natural Selection If conditions change faster than a species can adapt, the species may go extinct.

Artificial Selection Artificial Selection: the intentional reproduction of individuals in a population that have desirable traits. In organisms that reproduce sexually, two adults that possess a desired trait are bred together Considered “artificial” because people, instead of nature, select which organisms get to reproduce. Examples: Crops and domesticated animals

Artificial Selection

Artificial Selection