Artificial Selection aka Selective Breeding  Darwin noted that plant and animal breeders would breed only the largest hogs, the fastest horses, or the cows that produced the most milk.  Darwin termed this process artificial selection or selective breeding. Copyright Pearson Prentice Hall

Evidence of Evolution Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process include: 1. Fossils 2. Comparative anatomy 3. Biochemistry of different life forms

Fossil Evidence  Paleontology: Study of the fossil record.  Fossils: Remains or traces of organisms that lived in past ages, to understand past life forms.

Fossil Evidence  By comparing fossils from older rock layers with fossils from younger layers, scientists could document that life on Earth has changed over time. Copyright Pearson Prentice Hall

Fossil Evidence in sedimentary rock

Fossil Evidence  Some scientists have found transitional fossils.  Transitional fossils: Show a transition from one species to another.  For example: Whales

Transitional Fossils of Whales Older whales were hoofed mammals that lived on land. These animals were able to walk on land and swim. Later, fossils suggest that over time, the hind limbs of the whales’ ancestors shrank. Their forelimbs became flippers. Their hind limbs became a tail called a fluke.

Comparative Anatomy/Physical Features: Homologous Structures  Body parts of different organisms that have a similar structure but may have different functions. Copyright Pearson Prentice Hall

Comparative Anatomy: Homologous Structures Composed of similar bones. Must mean they all shared an ancestor that had a similar structure.

Comparative Anatomy: Analogous Structures Copyright Pearson Prentice Hall Analogous Structures  Body parts that have a similar function but not a similar structure.  They do not indicate shared ancestry.

Comparative Anatomy: Analogous Structures Bird wing and butterfly wing

Comparative Anatomy: Vestigial Structures Vestigial Structure: A body part that does not seem to play a major role in an organism’s life functions but was more important in the organism’s ancestors. Rats also have an appendix suggesting we share a common ancestor. Copyright Pearson Prentice Hall

Comparative Anatomy: Embryology Embryology: Study of embryos. Embryo: Early stage of development in an organism. Embryos of related organisms develop in similar ways. Copyright Pearson Prentice Hall Chick embryo (LM) Human embryo Pharyngeal pouches Post-anal tail

Biochemical Evidence of Evolution  Recall that all organisms contain the nucleic acid: DNA.  DNA directs the production of proteins which are made of amino acids.  The more similar an amino acid sequence is, the more closely related organisms are and most likely shared an ancestor.  We can compare hemoglobin: a protein found in RBC’s to determine this.

Biochemical Evidence

 In addition to hemoglobin, Cytochrome C is another protein that determines how closely related species are to one another.