Chapter 1: Adaptation by Natural Selection  What is an Adaptation? Structures that are designed by Natural Selection Adaptations provide solutions to evolutionary problems (survival and reproduction). Evolutionarily Stable Problems. Best thought of in terms of function.

 Function: Ultimate: Why Question! To make copies of itself, Reproductive Success (RS) Proximate: What Question! What does the adaptation do?

Complex Design

Different Functions Different Designs

Natural Selection is a process of tinkering

Darwin’s Three Postulates 1. The ability of a population to expand is infinite, but the ability of any environment to support populations is always finite. “THE STRUGGLE FOR EXISTENCE.” 2. Organisms within populations vary and this variation affects the ability of individuals to survive and reproduce. “DIFFERENTIAL REPRODUCTIVE SUCCESS” 3. The variations are transmitted from parents to offspring. “SEX”

Darwin’s Finches (from the Beak of the Finch)

Darwin’s Finches: Selection (Darwin’s 1 st Postulate)

Darwin’s Finches: Selection (Darwin’s 2st Postulate)

Darwin’s Finches: Selection (Darwin’s 3 st Postulate)

Darwin’s Finches: Did Evolution Take Place?

Units of Selection Selection takes place at the level of Individuals Selection does not take place at the level of Groups or Populations Adaptations change through time not individuals or population Vehicles vs. Units of Selection

Inheritance of Traits Blending Inheritance –Mixing of traits undoes natural selection Discreet Units of Inheritance –Necessary to maintain adaptations (design features of traits)