Diversity of Life - Early Beliefs It was believed that the earth was young. Bishop James Ussher ( ) – using references from scripture – determined that the 1 st day of creation was October 23, 4004 B.C. His work was incorporated into an authorized version of the Bible in 1701.

Diversity of Life – Early Beliefs All organisms on Earth were created at once, in a center of creation. All organisms were created perfectly, well- designed for the environment they lived in. Organisms shared no common ancestors.

Scientific evidence began to show that this explanation was not completely accurate: Evidence showed that Earth is very old. Evidence showed that Earth has changed a great deal over time.

Diversity Evolution: Genetic changes in a species over time. These changes produce new phenotypes within a species and lead to the formation of new species from ancestral forms.

Jean-Baptist de Lamarck ( ) Law of Use and Disuse: organisms become suited to their environment by creating adaptations within their lifetime. Inheritance of Acquired Characteristics: Those acquired traits are then passed on to future offspring.

Charles Darwin

The Galapagos Islands are volcanic islands located 500 miles west of Ecuador. The organisms Darwin observed there were all descendants of those brought by wind or currents. Darwin’s Journey

A Galapagos tortoise and one of the thirteen finch species found among the islands. Galapagos Islands

Charles Darwin ( ) Recognized the vast biological diversity found on Earth. The earth is very old and has changed a great deal over time. Organisms have traits that make them well-suited to a particular environment. Applied the ideas of Malthus to all organisms.

Charles Darwin Variation exists in a population. Populations tend to over-produce. This creates a struggle for survival. Those members of a population with variations well-suited to the environment will survive and pass their traits to future offspring. Over time – due to environmental changes, some populations will change, leading to the formation of new species.

Species A group of organisms that naturally interbreed to produce fertile offspring. Organisms that are of different species will not interbreed, or if they do their offspring typically are not fertile.

Natural Selection A mechanism where those organisms with features best suited to an environment will survive and reproduce. The result of natural selection is a population with phenotypes suited to a local environment.

Alfred Wallace, who independently developed the same theory as Darwin. Wallace

Evidence for Evolution Radiometric Dating Fossil Evidence Comparative Morphology and Embryology Gene Modification Evidence Experimental Evidence

Radiometric Evidence How do we know how old the earth really is? A technique for determining the age of objects by measuring the decay of the radioactive elements they contain A technique for determining the age of objects by measuring the decay of the radioactive elements they contain Uraium-238 vs Lead-206 The transformation proceeds at a fixed rate.

The John Day beds of central Oregon. Sedimentary rocks are formed as layers, one atop another. The oldest rock is deepest and the newest layers are closest to the surface.

Fossil Evidence Compare fossils from the same geologic layers of sediment, scientists expect to find similar types of fossils. When we compare fossil placement with the dates we get from radiometric dating, they are very close to being the same.

Fossils

Bird Fossils

Homology Homologous – the same in structure owing to inheritance from a common ancestor. It is believed that all four groups of mammals descended from the same ancestor.

Comparative Morphology Morphology is the study of physical forms. Forelimbs of a diverse group of mammals are homologous. The structure has been adapted by the four different groups of mammals in accordance with their varying needs. The structure has been adapted by the four different groups of mammals in accordance with their varying needs.

Whale, Cat, Bat, Gorilla The bones in the forearm are similar in structure despite their variable actions.

Python bones corresponding to the bones of the pelvic girdle in humans. In most vertebrates, the pelvic girdle is attached to the hind limbs but pythons don't have limbs. Comparative morphology

Comparative Embryology Embryology is the study of how animals develop from fertilization to birth. At a certain point in their development, diverse species all have structures known as pharyngeal slits. In fish these become gills, in humans they become the Eustachian tubes. In fish these become gills, in humans they become the Eustachian tubes. All of these animals shared a common ancestor. All of these animals shared a common ancestor.

Comparative embryology

Gene modification Evidence Evolutionary theory predicts that there should be fewer DNA base-pair differences between the genes of similar organisms as compared to those of very different organisms. Human vs. yeast Human vs. yeast Human vs. pig Human vs. pig

Many diverse organisms have the same enzyme. Over time the genetic sequence of the enzyme has been altered. This chart is a measure of the amount of difference between the enzymes of these organisms.

Experimental evidence Evolutionary change takes place over long periods of time but a carefully planned experiment can provide evidence.

Sex and the Male guppy In the absence predators, male guppies grow larger in size and more brightly colored. Female guppies prefer to mate with brightly colored males but these males are more visible to predators. In the presence of predators, the male guppy was smaller and drab in color. These males live longer and produce more offspring because they live longer.