Biology 120 Handout: Natural Selection and Antibiotic Resistance

Antibiotic Resistance:

Natural selection: Important Features of Natural Selection/Adaptation: More on Causes, Mechanisms, Prevention of Antibiotic Resistance: How Natural Selection Affects Populations:



 

PRACTICE QUESTIONS:

1.  List the four main properties of populations that result in natural selection:
 1.________________________________________________
 2.________________________________________________
 3.________________________________________________
 4.________________________________________________
Explain why they result in natural selection.

2.  Describe how each of the properties you listed in the previous question applies to peppered moths.  Describe what has happened to peppered moths as a result of these properties.

3.  Traits that have evolved through natural selection, because they result in high survival and therefore reproduction in their particular environments, are called _________________
4.  The degree to which individuals with a certain trait survive and reproduce is called _______________

5.  Genetic change in a population over time is called ____________________

6. True or False: Evolution is the same thing as natural selection

7.  The form of evolution that has resulted in antibiotic resistance in bacteria is __________________

8.  Evolution occurs:
 a. when an individual changes and develops, during its life
 b. when the genetic characteristics of populations change from generation to generation
 c. when one species survives and another goes extinct, so that the species that are present in an area change over time (even though the characteristics of each species may not change.)

9. Natural selection:
 a. results in populations of individuals with higher fitness
 b. occurs to benefit a species
 c. increases the genetic variation present in a population
 d. is the same thing as evolution

10. Which of the following is/are examples of evolution?
a. as the climate grows colder, an individual mouse grows more fur
b. two species of mouse occur in the same area; one reproduces more than the other and eventually drives the other extinct
c. as the climate grows warmer, more and more members of a population of mice have shorter fur; differences in fur length are genetic
d. both a and b
e. both b and c

 11.  In a population of fish, some individuals have upturned mouths and others have down-turned mouths.  These fish feed on the bottom of lakes and those with down-turned mouths obtain food better and therefore survive better.  Each generation, many fish hatch from eggs but because there is only a limited amount of food, not all survive.

 i. to know whether natural selection will affect mouth orientation (up or down-turned) in this population, you need to know one more thing.  What is it? ____________________

 ii. suppose that natural selection DOES affect mouth orientation in this population.  Over time, you would expect to see:
a. an increase in genetic variation in the population
b. a decrease in genetic variation in the population

12.  State whether each of the following examples is most likely to illustrate directional, stabilizing, or disruptive selection.  For each, also explain what you would need to know in addition to what you are told in the question to know that natural selection really does occur in each population (hint: what are the aspects of a population that result in natural selection?)
a. In a population of sparrows, individuals whose wings are too long suffer from wing damage in storms.  Individuals whose wings are too short can not fly fast enough to escape from predators.  Individuals with intermediate length wings are not harmed by storms and can escape from predators.
b. In a population of butterflies, individuals vary in how much green or red color there is in the wings.  Individuals with all green wings survive well because they are hard to see against their background.  Individuals with all red wings survive well because they look like a poisonous species that is red, and predators avoid them.  Individuals with mixed green and red wings are easy to see and often eaten by predators.
c. In a population of wild horses, the longer the lower leg bones are with respect to body size, the faster the horses can run, and the better they escape from predators.

13.  Through what form of evolution does antibiotic resistance arise?  What can we do to help prevent antibiotic resistance from arising?

HOMEWORK QUESTIONS FOR RUSSELL PAPER: ANTIBIOTIC: Overuse of Cipro can breed lethal bacteria

1. The Russell paper argues that Cipro was overused in the 2001 anthrax cases, since the strain of anthrax that was present could be killed with penicillin.  Why is the use of Cipro for anthrax treatment more likely to lead to antibiotic resistance than the use of Cipro for other diseases?  What is the most serious potential problem related to the evolution of antibiotic resistance for an individual that can result from this use of Cipro?  Why can this problem arise?

2.  The guidelines described by the Russell paper state that Cipro should be used first in a suspected anthrax attack, but that once it is determined that the anthrax strain  "can be treated with something other than ciprofloxacin, it should be."  Explain the rationale for these guidelines with regard to the following points: why should Cipro be used first, and why, in terms of public health (not just the health of the individual), should something other than Cipro be used as soon as possible.