Phylogeny, Reproduction, Development

Question 1

Why study development?

Answer 1

• developmental homologies are evidence for common descent

- developmental patterns can help with construction of phylogenies

Question 2

An outdated view

Answer 2

• Ontogeny recapitulates Phylogeny (Ernst Haeckel)
  phylogeny: evolutionary history of a species
  ontogeny: developmental history of an organism throughout
  its entire life
• Theory: successive stages of development represented adult form from its evolutionary history
• This idea was based on the flawed premise that evolutionary change occurs by successively adding new stages to ancestral ontogenies

Question 3

An updated view

Answer 3

• “Ontogeny Recapitulates Phylogeny” is compelling, but wrong
• Nevertheless, ontogeny does provide evidence for common descent
• Many developmental features are shared among animal groups (i.e. many homologies)
• Not universal
  There are also important differences among species, even very
  early in development

Question 4

What is the evidence for common descent?

Answer 4

• developmental homologies