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Mechanisms of Speciation

Through natural selection, evolution is the result of a change in allele frequency in a population’s gene pool over a number of generations.  This change in allele frequency can be caused by a number of different factors, ultimately resulting in the process of speciation: inability of two organisms to produce fertile offspring.

PART A: Barrier Between Gene Pools

In order for two groups to become individual species, isolation between the two groups must occur in one form or another.  These forms of isolation are not just physical barriers, generally first thought of example.  To demonstrate different forms of we will simulate each type of isolation: Geographical, Temporal, Behavioural, Reproductive/Hybrid.

PART B: Barriers Between Gene Pools

Barriers between individuals that can cause speciation are often thought of as physical barriers in which the two different population groups change independently from one another due to separate environments.  However, speciation can occur within the same environmental region.  Compare the differences between allopatric and sympatric speciation.

PART C: Divergent & Convergent Evolution

Numerous species exhibit similarities in traits.  For example, both insects and birds have wings to allow for flight.  But, are insects and birds related and derived from a common ancestor?  DNA analysis would suggest they are not of similar ancestors.  What explains these similarities?  Provide an example for each of the follow types of evolution:

PART D: Speciation in the Wild: Reproductive isolation caused by color pattern mimicry

Speciation has been observed in nature through a variety of different species.  As discussed previously and examined in this lab, a variety of factors can induce speciation.  Read the provided (short) scientific article from Nature entitled Reproductive isolation caused by color pattern mimicry and complete the following questions.

  1. Briefly describe observations (analytical data collected) during this experiment?

  1. What does the data suggest concerning  Heliconius melpomene and Heliconius cydno?

  1. What type of isolation is represented in this example?

  1. What do the authors suggest is the cause of this observed case of speciation?