Name_______________________________ Bio 44, Sect 1-2, First Exam, Feb. 16,2004

 

Answer all questions, Each is worth 5 points.  ANSWERS in Bold

 

1. A recessive allele occurs with a frequency of 80% in a population.  If Hardy-Weinberg equilibrium applies, what is the frequency of heterozygote individuals in the population?

           q = .8,      p = .2   2pq = .32

 

2. Blue eye, a recessive trait, occurs in 64% of the individuals in a population.  What is the percentage of individuals in the population that carry at least one recessive gene?

              q2 = .64  , q = .8,  p = .2    2pq + q2 =  .32 + .64 = .96

 

3. If, over several generations, the frequency of an allele in a population changes from 20% to 80%, do we know that it was selected for?  Why or why not?

          it could be selected for – selection can change frequencies quickly. However, if the population is small, drift could also do this.

 

4. How can a gene with obviously bad effects on a species occur in a population at a higher frequency than the mutation rate?  Give at least two answers.

            - pleiotropy – the gene also has good effect.

            - environmental change. The gene was valuable in a past environment and has not

                  decreased yet in the new environment

-         takes a long time to get rid of harmfull recessives

-         sexual selection – if the gene is favored in mating

 

5. Give at least two reasons why sympatric speciation doesn’t occur commonly in animals? 

            the only sympatric speciation we know involves hybridization in plants

             in animals – hybridization rare due to courtship behavior (select mates)

             hybrids usually sterile,  and  have no similar individual to mate with

 

Under what conditions should the increase in the number of species in an area be most rapid?   Answer this question for

6.   Animals

               animals speciate allopatrically – need lots of isolating barriers – varying                                  environments would also help

                   if you said – in an area with few species – high colonization rate, low                                     extinction rate - accepted

7.   Plants

              plants speciate sympatrically – need lots of closely related species so hybridization can occur.     if you said – in an area with few species – high colonization rate, low extinction rate - accepted

 

8.   Asexual organisms

              each new individual is a potential species – need new environments (food sources, for instance) that they can use – mutation will then create differences and new species.

 

9  Both Darwin’s natural selection and Lamarck’s theory of acquired characteristics explain evolution on the basis of variation.  What is the difference?

Lamarck – variation acquired during life is inherited

Darwin – variation already in the population. the best variants survive.(selected for)

 

 

 

 

10. Many people think they are “perfect” and want their children to be just like them, even to the point of cloning themselves.  In evolutionary terms, is this a good idea?

         if true that you are perfect, then its ok if the environment doesn’t change – if it does, what is perfect today may not be perfect tomorrow -

 

11. If you were searching for fossil organisms on Antarctica, what kind of  animals would you expect to find (who would they be related to and why)?

           related to organisms on any continent that was once connected to Antarctica = Gondwanaland land areas – could walk to Antarctica at one time.  It was not cold then.

 

12.  What are the possible consequences of  interspecific (between species) competition on organisms?   

           competition leads to specialization – character displacement, resource partitioning, competitive exclusion – could lead to extinction if competition overlap is great.

 

13.  If most mutations are harmful, what factors (name 2) allow haploid (asexual) organisms to evolve as rapidly as sexual organisms?

 - very large population size – so there are enough beneficial mutations to improve the species 

 - because they reproduce quickly – good mutations can spread through a population quickly

-  duplication errors can give an individual 2 sets of information – mutation affects only one

 

14.  What features (list several) make DNA the ideal material for the basis of life?

                 it can replicate, carry information, and mutate (change through time)

 

15. Gause’s principle says that no two species can coexist if competing for resources?  If this is so, how come so many species live together in the tropics?

             very stable environment allows extreme specialization of species = narrow niches.

 

16.  What evidence was Darwin lacking (what couldn’t he explain) when he presented his theory of evolution?

            didn’t know how variation was reconstituted after selection had reduced it.

 

17.  Under what circumstances can two individuals whose egg and sperm form viable offspring be considered to belong to different species?

              - if they don’t mate in nature = prezygotic barrier

              - if offspring aren’t able to reproduce = postzygotic barrier (sterile hybrid)

              - all sympatric speciation involves this.

18.  Antibiotics are given to cattle to increase meat and milk production.  Although the antibiotics are gone by the time we ingest the milk and meat, could this practice be harmful to us in other ways?  How?

             if bacteria in cows become resistant to the antibiotics, those bacteria could infect us, and the antibiotics then would not work

           

19-20.  Does evolution improve organisms?  What does improvement mean? Discuss.

 

        improve means to become more fit = leave more offspring – genes to the next generation. This is the “goal” of evolution, but since all organisms are trying to improve, it means that you may change but not necessarily get ahead of predators, prey, diseases, etc. = Red queen – run fast to stay in the same place.