Support for Evolution Today, scientists use evolution to mean cumulative change in a group of organisms through time. Evidence for evolution comes from: The fossil record Homologies a. Anatomical -homologous structures b. Molecular- Comparative biochemistry c. Developmental-Comparative embryology Geographic distribution Copyright © McGraw-Hill Education Evidence of Evolution

Support for Evolution: Fossil Record Fossils are thought to be the same age as the rock they are found in. Horses do not look the same as they did many years ago. Fossil Records show evidence that animals have changed over time and that they share a common ancestor based on similarities in their skeletons. Which of the following fossils (W, X or Y) is the youngest? Why? Which layer of earth is the oldest? Why?

Support for Evolution: Developmental-Comparative embryology Support for Evolution: Homologous structures Homologous structures are anatomically similar structures inherited from a common ancestor. Similar structures with different function (similar bones = common ancestor) Support for Evolution: Developmental-Comparative embryology Organisms that are closely related may also have physical similarities before they are even born. Embryos of many animals with back-bones are very similar. Evidence of Evolution Copyright © McGraw-Hill Education

Similarities in DNA and protein sequences suggest relatedness. Support for Evolution: Molecular- Comparative Biochemistry The more closely related species are to each other, the greater the biochemical similarity. Similarities in DNA and protein sequences suggest relatedness. Copyright © McGraw-Hill Education Evidence of Evolution

Support for Evolution: Geographic distribution Closely related species are usually found in areas that are geographically close to each other Copyright © McGraw-Hill Education Evidence of Evolution

2 populations are separated by geographic barriers Support for Evolution: Geographic distribution Geographic Isolation 2 populations are separated by geographic barriers Examples: rivers, mountains, bodies of water Formation of barriers can cause new species to form (speciation) Evidence of Evolution Copyright © McGraw-Hill Education

Cladogram: a chart that is composed of many different clades or branches. Organisms listed are all related, but the cladogram depicts the successive points of species divergence from common ancestral lines. Which species developed first: Ferns or Mosses? How long ago was the development of vascular tissue? Assuming this cladogram is correct, would we find a fossil for a fern that is in rock 425 million years old?

Dendrogram – a branching diagram representing a hierarchy of categories based on degree of similarity or number of shared characteristics. Who is most closely related to the Brown bear? Who is most closely related to the Lesser panda? Who is furthest related to the Brown bear?