Biology 120                Handout: Genetic Variation in Conservation and Agriculture              R. Irwin

Loss of genetic variation:

Sources of variation: Summary of causes and consequences of the main forms of evolution:
 
Form of Evolution Cause Significance Does it increase or decrease genetic variation in populations? Does it make different populations of the same species like each other or different from each other?
Natural Selection   
 
 		         
Mutation   
 
 		         
Sexual Selection   
 
 		         
Genetic Drift   
 
 		         
Gene Flow   
 
 		         

PRACTICE QUESTIONS:

1.  Evolution that occurs through random chance changes in the frequency of alleles existing in a population is called ____________________.  Does this form of evolution typically increase or decrease the amount of genetic variation in a population?  Why?
2.  Evolution that occurs when individuals move from population to population is called __________________. Does this form of evolution typically increase or decrease the amount of genetic variation in a population?  Why?
3.  Two forms of evolution that typically result in the loss of genetic variation in populations are _______________ and ______________________.  Which of these results in loss of variation that is adaptive?  Which of these results in loss of variation that is NOT adaptive?
4.  Small populations of endangered species typically lose genetic variation.   The main form of evolution that causes this to occur specifically in small populations is _______________________.  Give two reasons why this loss of genetic variation is something to worry  about, if your goal is to conserve these small populations.
      1. _____________________________________________________
      2. _____________________________________________________

5.  Two forms of evolution that typically increase genetic variation in populations are __________________and ______________________.  One of these is very slow so that we can usually not observe its effects, which one?  One of these is more rapid so that we can observe its effects, which one?

6.  What are some things that people managing endangered species can try to do to prevent loss of genetic variation in small populations?  What form of evolution are they causing when they take these actions?

 QUESTIONS FOR QUIZ ON RALOFF PAPER:

1. What is generally happening to the genetic diversity  of animals used as livestock? Explain why this is happening in dairy cattle and in chickens.  Changes in genetic diversity mean that evolution is occurring in these livestock breeds.  Name two forms of evolution that are observed in NATURAL populations that result in the kind of change in genetic diversity that is observed in livestock, and explain how the way humans breed dairy cattle and chickens may be causing something similar to one or both of these forms of evolution to occur.

2.  In "Dying Breeds", by Raloff, it is argued that even though Holstein cattle produce most milk, that other forms of dairy cattle should be conserved.  Give two potential problems discussed in the paper that might occur if other forms of dairy cattle are allowed to go extinct.  Could the same kinds of problem also apply to natural populations of wildlife where genetic variation is lost?  Why or why not?