9.2 Establishing Phylogenetic Relationships

• Phylogeny establishes evolutionary

  relationships among species and groups of species.
• Cladograms can be produced by

  examining shared derived characters
• Evidence of hominid evolution comes from the fossil record.
• Phylogeny: The evolutionary history of a group of organisms.
• Phylogenetic Tree: A diagram that shows the evolutionary relationships between organisms.
• Clade: An evolutionary branch in a

  phylogenetic tree
• Cladistics: A method of determining the sequence of branches in a phylogenetic tree
• Cladogram: A phylogenetic diagram that specifies the derived characters of

  clades
• Derived Characteristics: Homologous

  structures that are common to all the

  organisms in a clade(e.g. amniotic egg)
• Homologous structures are one of the

  best clues to assess how closely

  related organisms are
• Adaptations can hide homologous

  structures
• Convergent evolution can produce

  analogous structures that can be

  mistaken for homologous ones.
• Relatedness of species can be

  measured by comparing their genes

  and the proteins that genes code for
• The more similar the genes the more

  closely the species are related (e.g. fossil data indicates whales are

  closely related to hippos, cows, deer,

  and pigs).

  • Molecular data now also supports this.
• Molecular Data: DNA, RNA, and Protein Sequencing
• HIV mutates at a fast rate (it’s a virus). HIV can evolve into 5 new strains per year.
• Possible scenarios for HIV:

  • HIV developed from a single strain after 1998
  • Medics could have infected the children
  • HIV not similar enough to have a common ancestor after 1998 (this the lineages split before 1998)
  • Medics could NOT have caused the infection
• HIV was blamed on tainted needles and poor hygiene practices by the hospital, not the medics
• Early primates gave rise to two distinct

  lines:

  1. Prosimians
  2. Anthropoids
• Anthropoids branch into:

  1. old world monkeys
  2. new world monkeys
  3. hominoids
• Hominids: Humans and all their ancestral species that arose after the split from ancestral chimpanzees
• Bipedalism: Ability to walk on two feet
• Oldest H. sapiens fossil found in Ethiopia. Indicates modern day humans evolved in Africa
• Founder Effect visible in human

  populations outside Africa