Biologists performed an experiment with flies to examine the effects of population size on the maintenance of genetic variation  and  on  egg-to-adult survival.  From  a  large  source  population, they  randomly  assigned  eggs  to  three experimental  populations  of  size  N,  equal  to  20,  60,  and0100.  For  later  generations,  they  collected  N  eggs  from each  population  and  moved  them  into  identical  vials  that  co0ntained  f2re0sh  me4d0ium.  Th6e0y  coun8te0d  the  number  of adult flies that emerged and used tissue samples from the adults for genetic analyses. Genetic variation was measured by  scoring  alleles  at  several  polymorphic  loci  and  expressed  as  the  average  number  of  alleles  at  those  loci.  The results are summarized in Figure 1 and Figure 2 below.

The numbers of adult flies that emerged from the three populations in the first generation are closest to which of the following?

#Question id: 4650

#Unit 9. Evolution & Diversity of Life Forms

DDT was once considered a ʺsilver bulletʺ that would permanently eradicate insect pests. Today, instead, DDT is largely useless against many insects. Which of these would have been required for this pest eradication effort to be successful in the long run?

#Question id: 4651

#Unit 9. Evolution & Diversity of Life Forms

Some members of a photosynthetic plant species are genetically resistant to an herbicide, while other members of the same species are not resistant to the herbicide. Which combination of events should cause the most effective replacement of the non-herbicide-resistant strain of plants by the resistant strain?

1. The presence of the herbicide in the environment

2. The absence of the herbicide from the environment

3. The maintenance of the proper conditions for one generation

4. The maintenance of the proper conditions for many generations

#Question id: 4652

#Unit 9. Evolution & Diversity of Life Forms

The graph depicts four possible patterns for the abundance of 3TC-resistant HIV within an infected human over time. If 3TC resistance is costly for HIV, then which plot (I—IV) best represents the response of a strain of 3TC-resistant HIV over time, if 3TC administration begins at the time indicated by the arrow?

#Question id: 4653

#Unit 9. Evolution & Diversity of Life Forms

 If two modern organisms are distantly related in an evolutionary sense, then one should expect that

#Question id: 4654

#Unit 9. Evolution & Diversity of Life Forms

Structures as different as human arms, bat wings, and dolphin flippers contain many of the same bones, these bones having developed from very similar embryonic tissues. How do biologists interpret these similarities?

#Question id: 4655

#Unit 9. Evolution & Diversity of Life Forms

Over evolutionary time, many cave-dwelling organisms have lost their eyes. Tapeworms have lost their digestive systems. Whales have lost their hind limbs. How can natural selection account for these losses?