Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies The Evidence for Evolution Chapter Copyright © McGraw-Hill Companies Permission required for reproduction or display

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies The Fossil Record Case for evolution based on two pillars:  Evidence natural selection can produce evolutionary change.  Evidence from fossil record that evolution has occurred. Three events of fossilization:  Organism buried in sediment.  Calcium in material must mineralize.  Surrounding sediment hardens.

Evidence 1-The Fossil Record Dating Fossils Radioactive isotopes have decayed more in older rocks. Steady decay rate allows measurement. History

The Fossil Record Arraying fossils according to age provides evidence of successive evolutionary change (gradual change over time) One of strongest lines of evidence for evolution.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies

The Evolution of Horses Modern members of Equidae (horses, zebras, donkeys) are descendents of lineage originating in the Eocene Period 55 mya.  Earliest known members were species in genus Hyracotherium. - Small size - Multiple toes - Small, simple teeth.  Evolutionary change has not occurred at a constant rate.

Evidence 2-Natural Selection Changes Populations Evidence of branching evolution Darwin collected a closely related group of 13 finch species in the Galapagos Islands.  All similar except for beak characteristics. - Beak correspondence suggested to Darwin that they were shaped by evolution.  Nature of available food supply. Example: Beaks of Darwin’s Finches

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Natural selection continued Peppered Moths and Industrialized Melanism Until the mid-nineteenth century, Peppered Moths, Biston betularia, had predominately light-colored wings.  Industrial smog helped turn lichens on tree trunks dark.  Subsequently, dark individuals became predominant. - Predators see them! Second half of the twentieth century saw widespread implementation of pollution controls, thus trends reversed and light colored moths again dominated. But, caution must be taken, as the selective agent could be some factor other than wing coloration.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Artificial Selection Agriculture  Kernel characteristics of corn.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Artificial Selection Domestication  Breeds and characteristics of dogs.

Evidence 3-The Anatomical Record Homology  Evidence of branching evolution  Structures with different appearances and functions that all derived from a common ancestor.

The Anatomical Record Development  Evidence of branching evolution  Different organisms exhibit similar embryological forms.

The Anatomical Record Vestigal Structures  Organs with no apparent modern function, but resemble ancestral structures.  Evidence of branching evolution and branching evolution

Evidence 4-The Molecular Record (DNA, RNA, proteins) Distantly related organisms are expected to accumulate a greater number of evolutionary differences than closely related species. Evidence of branching evolution and common descent

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Types of Evolution Convergent Evolution - Selection that favors changes making two or more groups more similar.  Similar solutions to similar problems. - Marsupial-Placental Convergence Divergent Evolution - Selection that favors changes making two or more groups less similar.  Exposure to different selective pressures.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies When two groups of the same species are separated, changes may occur in each population that eventually causes them to be so different that speciation occurs Geographic Isolation  separated by land formations such as rivers, mountains, valleys, etc Reproductive Isolation  separated due to inability to mate with each other - Structural, mating time is different, etc Temporal Isolation  Separated by time factors such as circadian rhythms Behavioral Isolation  Separated by behavioral differences such as courtship dances or sounds

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Darwin’s Critics Evolution is not solidly demonstrated. There are no fossil intermediates. Intelligent Design. Evolution violates Second Law of Thermodynamics. Proteins are too improbable. Natural Selection does not imply evolution. The irreducible complexity argument.

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Review The Fossil Record The Evolution of Horses Beak’s of Darwin’s Finches Peppered Moths and Industrial Melanism Artificial Selection The Anatomical Record The Molecular Record Convergent and Divergent Evolution Darwin’s Critics

Raven - Johnson - Biology: 6th Ed. - All Rights Reserved - McGraw Hill Companies Copyright © McGraw-Hill Companies Permission required for reproduction or display