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BIO102: Introduction to Evolutionary Biology and Ecology

Unit 5: Speciation   When certain events occur in history, a population of organisms will undergo what is called “speciation,” a process in which two species emerge from one.  There are many reasons why speciation can occur, and we will talk about the major ones in this unit.  Darwin first became aware of speciation when he studied the birds of the Galapagos, including his famous finches, and noticed how many of them resembled one another and at the same time had very important differences.

Unit 5 Time Advisory
This unit should take approximately 4.5 hours to complete.

☐    Subunit 5.1: 2 hours

☐    Subunit 5.2: 2 hours

☐    Assessment: 0.5 hours

Unit5 Learning Outcomes
Upon successful completion of this unit, the student will be able to: - Define a species. - List types of isolating mechanisms. - Identify which isolating mechanism(s) would be operating under given circumstances. - Understanding that most hybrids have much lower fitness that their parents. - Distinguish between allopatric and sympatric speciation and recognize examples of each. - Distinguish between punctuated equilibrium and gradualist models of evolution.

5.1 Prezygotic Isolating Mechanisms (Habitat Isolation, Temporal Isolation, Behavioral Isolation, Mechanical Isolation, Gametic Isolation), Postzygotic Isolating Mechanisms (Zygotic Mortality, Hybrid Inviability, Hybrid Sterility, Hybrid Breakdown), and Speciation (Allopatric, Sympatric, and Adaptive)   - Reading: John Kimball’s Biology Pages: “Speciation” Link: John Kimball’s Biology Pages: “Speciation” (HTML)

 Instructions: Read the entirety of the webpage. Please note that
there are prezygotic and postzygotic isolating mechanisms listed in
the reading, but they are not clearly defined.  The prezygotic
isolating mechanisms include Habitat/Geographical Isolation,
Temporal Isolation, Behavioral Isolation, Mechanical Isolation, and
Gametic Isolation.  The postzygotic isolating mechanisms include
Zygotic Mortality, Hybrid Inviability, Hybrid Sterility, Hybrid
Breakdown, and Hybrid Sterility.  

 **Habitat/Geographical:** Occupy different geographic areas  
 **Temporal:** Mate at different times  
 **Behavioral:** Behavior does not elicit mating  
 **Mechanical:** Differences in sex organs  
 **Gametic:** Failure of sperm to meet egg.  
 **Zygote mortality:** Fertilization occurs and zygote does not
develop.  
 **Hybrid inviability:** Embryo forms but viability is reduced (A
mule is the offspring of two different species of animals – a female
horse and a male donkey – and is a result considered a “hybrid”
animal).  
 **Hybrid breakdown:** First generation fertile but subsequent
generations are sterile.  
 **Hybrid sterility:** Hybrid offspring are sterile.  

 Reading this webpage should take approximately 1 hour.  

 Terms of Use: This resource has been reposted by the kind
permission of Professor John Kimball and can be viewed in its
original form
[here](http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html). 
Please note that this material is under copyright and may not be
reproduced in any capacity without the explicit permission of the
copyright holder.
  • Lecture: Yale University: Stephen C. Stearns’ Principles of Evolution, Ecology, and Behavior: “Species and Speciation” Link: Yale University: Stephen C. Stearns’ Principles of Evolution, Ecology, and Behavior“Species and Speciation” (YouTube)

    Also available in:
    MP4

    MP3
    iTunes U Video
    iTunes U Audio

    Instructions: Watch Lecture 14, titled “Species and Speciation.” Adaptive radiation is a process through which many species arise from a single initial species.  It occurs when a single species migrates to a new area in which there are many different ecological niches unoccupied; populations of the initial species evolve to exploit those different niches, eventually resulting in many new species.  Darwin’s finches were thought to have undergone adaptive radiation.

    Watching this lecture and pausing to take notes should take approximately 1 hour.

    Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.  It is attributed to Stephen C. Stearns and Yale University's Open Yale Courses.  The original version can be found here.

5.2 Rate of Speciation: Gradualist Model and Punctuated Equilibrium Model   Note: Although there is still some debate about the frequency through which evolutionary change occurred via gradualism or punctuated equilibrium, it is worth noting that one model does not discount the other and that the two models do not have to be mutually exclusive.  Punctuated equilibrium very often may have occurred in combination with gradualism, and both models still recognize that the changes occurring were slow in human terms.

  • Reading: PBS’s Evolution Library: “Punctuated Equilibrium”

    Link: PBS’s Evolution Library: “Punctuated Equilibrium” (HTML)

    Instructions: First click on the larger image of the figure at the top of the article and read the figure legend, which will explain some differences between gradualism and punctuated equilibrium.  Then read the article on punctuated equilibrium.

    Reading this article and taking notes should take approximately 30 minutes.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: Dr. Niles Eldredge’s “Species, Speciation, and the Environment”

    Link: Dr. Niles Eldredge’s “Species, Speciation, and the Environment” (HTML)

    Instructions: Read the section titled “Evolution of Ideas on Speciation” to learn about the “Gradualist” Model of speciation.

    Reading this section and taking notes should take approximately 1 hour.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above.

  • Reading: The Saylor Foundation’s “Uniformitarianism versus Punctuated Equilibrium” Link: The Saylor Foundation’s “Uniformitarianism versus Punctuated Equilibrium” (PDF)

    Instructions: Read this article, which discusses the main differences between the two leading hypotheses of mode and tempo of evolution.  This should give you an overview of the two hypotheses as well as some of the history that led to their formation.

    Reading this article and taking notes should take approximately 30 minutes.

Unit 5 Review and Assessment   - Assessment: The Saylor Foundation’s “Unit 5 Review” Link: The Saylor Foundation’s “Unit 5 Review” (PDF)

 Instructions: Please click on the link above and work through the
questions. When you are finished, check your work against The Saylor
Foundation’s [“Unit 5 Review Answer
Key”](http://www.saylor.org/site/wp-content/uploads/2012/11/BIO102_Unit_5_Review_ANSWER_KEY-FINAL.pdf)
(PDF).  

 Completing this assessment should take approximately 30 minutes.
  • Assessment: The Saylor Foundation’s “Unit 5 Assessment” Link: The Saylor Foundation’s “Unit 5 Assessment” (HTML)

    Instructions: Please complete the linked assessment.
     
    You must be logged into your Saylor Foundation School account in order to access this quiz.  If you do not yet have an account, you will be able to create one, free of charge, after clicking the link.