Evolution

Populations evolve, Individuals DO NOT evolve! Evolution is . . . A change in a kind of organism over time A process by which modern organisms have descended from ancient organisms Populations evolve, Individuals DO NOT evolve!

Charles Darwin Born on February 12, 1809 in England Proposed that evolution occurs via natural selection.

Voyage of the Beagle (1831-1836) Darwin sailed around the world Made many observations and collected lots of evidence about how life is changing

Galapagos Islands

Galapagos Islands Darwin's finches share similar size, coloration, and habits. One difference among finches was beak size Key Observation: organisms are remarkably suited to their environment

Examples of some of the Finch Species

Common Thought in Darwin’s Time Earth is only a few thousand years old Neither planet nor living things have changed

Hutton & Lyell (Discoveries ~1785 - 1833) Earth is much older than only a few thousand years Cited formation of rock layers as evidence Rattlesnake Canyon in Colorado

Malthus (1798) Reasoned that if the human population continues to grow unchecked, sooner or later there would be insufficient living space and food for everyone Forces working against growth = war + famine + disease

Lamarck (1809) Tendency towards perfection Use & disuse Inheritance of acquired traits

Darwin Publishes His Work (1858) “It was evident that such facts as these . . . Could be explained on the supposition that species gradually became modified, and the subject haunted me.”

Artificial Selection Members of each species vary from one another Variable traits are passed from parent to offspring Humans select organisms with variations that they find to be most useful

The Struggle for Existence Organisms produce many offspring, few survive Members of each species compete regularly for food, living space, and other necessities

Natural Selection / Survival of the Fittest Fitness = the ability of an individual to survive and reproduce in its specific environment

Fitness results from adaptations Adaptation = any inherited characteristic that increases an organisms chance for survival

Natural Selection / Survival of the Fittest Individuals with low fitness (those not well suited for environment) either die or leave few offspring

Evidence of Evolution - - The Fossil Record Countless species have come into being, lived for a long time, and then vanished Fossils document stages in evolution of modern species from organisms that are now extinct

Archaeopteryx – thought to be first bird, wings are very primitive.

Homologous Body Structures Structures that have different mature forms in different organisms but develop from the same embryonic tissue

Alligator Mammal Turtle Bird

Why do vestigial organs remain? Organ that serves no useful function in an organism Ex: tailbone in humans, legs in skinks Why do vestigial organs remain?

Similarities in Embryology The same groups of embryonic cells develop in the same order and in similar patterns to produce the tissues and organs of all vertebrates

Summary of Darwin’s Theory Species alive today are descended with modification from ancestral species that lived in the distant past. This process, by which diverse species evolved from common ancestors, unites all organisms on Earth into a single tree of life.