Evidence & Relations

• Evolution


  Descent with modification, a process in which species change and give rise to new species over many generations
• Evolutionary history


  Forms a branching tree with many levels, all species can be traced back to an ancient common ancestor
• When the word "evolution" is mentioned, it is most likely interpreted as organisms evolving or changing to something different
• Scientists observe different patterns of evolution as they examine the diversity of life and their evolutionary history
• Chemicals used to prove relationships among organisms

  • DNA
  • Proteins
• Similarities in biomolecules


  Indicate closer relationships among organisms
• Cytochrome c


  An important enzyme found in virtually all organisms, known for its function in ATP synthesis, electron transport chain system, and apoptosis
• There are 104 amino acids in human cytochrome c, 37 of which are found at the same position in every sequenced cytochrome c
• Common structures are shared in the embryo stage and disappear by the time the embryo reaches the juvenile or adult form
• Chromosomes can be matched between humans and chimpanzees in a group activity
• Spot the difference activity


  Participants highlight or encircle different sequences in the given sequences
• Cladogram


  Diagram representing a hypothetical relationship between groups of animals
• Phylogeny


  Hypothetical relationship between groups of organisms, often depicted using a phylogenetic tree
• Cladogram vs Phylogenetic tree


  Cladogram shows relationships based on similarities, while a phylogenetic tree shows the evolutionary history of organisms with respect to the geological time scale
• Phylogenetic tree


  Diagram reflecting evolutionary relationships among organisms or groups of organisms
• Phylogenetic trees are considered a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships
• A phylogeny is often depicted using a phylogenetic tree
• Phylogenetic tree


  A diagram used to reflect evolutionary relationships among organisms or groups of organisms
• Scientists consider phylogenetic trees to be a hypothesis of the evolutionary past since one cannot go back to confirm the proposed relationships
• A "tree of life" can be constructed to illustrate when different organisms evolved and to show the relationships among different organisms. A phylogenetic tree can be read like a map of evolutionary history
• Many phylogenetic trees have a single lineage at the base representing a common ancestor
• Parts of a phylogenetic tree

  1. The point where a split occurs, that represents where a single lineage evolved into a distinct new one

  2. A lineage that evolved early from the root and remains unbranched

  3. When two lineages stem from the same branch point

  4. A branch with more than two lineages
• Lines of evidence to infer evolutionary relationships

  • Fossil evidence
  • Homologies
  • Developmental biology
  • Biogeography
  • Molecular clocks
• Homologies


  Similar characters due to relatedness, revealed by comparing anatomies, cellular similarities, embryological development, and vestigial structures
• Primitive (or ancestral) character

  Inherited from the common ancestor
• Derived traits


  Those that appeared by mutation in the most recent ancestor
• Symplesiomorphy


  A shared primitive character state
• Synapomorphy


  A shared, derived character common between an ancestor and its descendants
• At the end of this Module

  1. Explain the differences between the different kinds of evidences of evolution

  2. Perform different activities regarding evidences of evolution

  3. Realize the importance of the different evidences of evolution to support the existence of life
• The reason why Darwin’s findings were not accepted universally during his time was because of the lack of supporting pieces of evidence
• All Darwin had were observations
• Darwin’s hypothesis is now supported by considerable evidence from different disciplines without being refuted by counter evidence
• It is unfortunate that Darwin died several years before scientists could find supporting evidence for evolution
• Even in the present time, pieces of evidence have been added and validated the concept of evolution as first proposed by Darwin even more
• The Evidence for Evolution

  1. Anatomy and embryology: Darwin thought of evolution as "descent with modification," a process in which species change and give rise to new species over many generations

  2. He proposed an evolutionary history of life, the tree of life with many species can be traced back to a branching in which all species share an ancient common ancestor
• If two or more species share a unique physical feature, such as a complex body plan, they may all have inherited this feature from a common ancestor
• Homologous Features


  Physical features (a common shared history due to evolutionary ancestor) are said to be homologous
• Homologous physical features, due to a common shared ancestor, are said to be homologous
• Not all physical features that look alike are marks of common ancestry
• Analogous physical features are independently evolved similarities in organisms that lived in similar environments or experienced similar selective pressures