Process of evolution

• OBJECTIVES: After going through this module, you are expected to: Describe how the present system of classification of organisms is based on evolutionary relationships; Interpret and explain the phylogenetic tree; Explain the importance of phylogenetic tree to evolutionary relationship of organisms.
• Evolution


  A process of gradual change that takes place over many generations, during which species of animals, plants, or insects slowly change some of their physical characteristics
• Charles Darwin


  The first person who explained how evolution happens through his scientific theory of natural selection
• In 1835, when Darwin visited the Galapagos Islands, evidence has been found to indicate that living things have changed gradually during their natural history.
• With the theory or study of Charles Darwin, there are pieces of evidence that evolution occur in nature.
• Pieces of evidence that evolution occur in nature

  • Fossils
  • Biogeography
  • Embryology
  • Molecular Evidence
  • Comparative Anatomy
• Fossils


  The remain or a piece of evidence of a living thing
• Biogeography


  The study of the geographic distribution of plants, animals, and other forms of life. It is concerned not only with habitation patterns but also with the factors responsible for variations in distribution.
• Embryology


  The study of the development of the anatomy of an organism to its adult form, provides evidence for evolution as embryo formation in widely divergent groups of organisms tends to be conserved.
• Molecular Evidence


  Some of the best evidence comes from examining the molecules and DNA found in all living things. Organisms of the same group should have the same DNA sequence for a specific protein structure.
• 3 Types of Comparative Anatomy

  • Homologous structure
  • Analogous structure
  • Vestigial structure
• Homologous structure


  Similar physical features in organisms that share a common ancestor, but the features serve completely different functions
• Analogous structure


  Features of different species that are similar in function but not necessarily in structure and which do not derive from a common ancestral feature (compare to homologous structures) and which evolved in response to a similar environmental challenge.
• Vestigial structure


  Structures that have no apparent function and appear to be residual parts from a past ancestor
• Phylogeny

  From the Greek word phylon which means "tribe" and genesis which means "origin". It is the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.
• Phylogenetic tree


  Biologist traditionally represent the genealogy or organism's line of evolutionary development of organisms as phylogenetic trees, which are diagrams that trace evolutionary relationships and connections among organisms.
• Parts of a rooted phylogenetic tree


  • Branch point
  • Basal taxon
  • Sister taxa
  • Polytomy
  • Root
• Branch point


  The point where split occurs
• Basal taxon


  Lineage that evolved early from the root and remains unbranched
• Sister taxa


  Point of two lineages stem from the same branch
• Polytomy


  Branch with more than two lineages
• Root


  Indicates that an ancestral lineage gave rise to all organisms on the tree
• Four groups of evolutionary tree

  • Monophyletic
  • Paraphyletic
  • Polyphyletic
  • Soft polytomy
• Monophyletic


  Also called clade which shows common ancestor
• Paraphyletic


  Group refers to recent common ancestor but not all descendants are included
• Polyphyletic


  Group includes recent common ancestors are not included only distant relative
• Soft polytomy


  Indicates more than two immediate descendants