3.  In observing ephemeral ponds (ponds that fill in the spring, with snow melt, then dry up in late June – early July), you note the following organisms:

small arthropods (herbivores),  frog larvae (herbivores), dragonfly larvae (predators) (no fish occur in these pods because they dry up).  In a few ponds you also find salamander larvae (predators).  You hypothesize that the presence of the salamander larvae will have an indirect affect on small arthropod abundance, because they will eat both frog larvae and dragonfly larvae.

a.  sketch the community, indicating direct interactions among species (competition, predation).

b.  Would the arthropod abundance go up or down when salamander larvae are present?  Why?

c.  Using a grant, you propose to dig several depressions that will serve as experimental ponds to test your hypothesis.  Design this experiment by indicating:

manipulated variable(s):

response (measured) variable(s):

variable(s) controlled for:

4.  What is the “carrying capacity” of a species?  How is it altered by competition?  How is it altered by resource availability?

Ecology of transgenics:

1.  We discussed two experiments concerning possible ecological affects of the planting of transgenics:  persistence of transgenic crops in the wild, and escape and persistence of transgenes in the wild.  Which do you consider a more likely problem?  Support your answer using information from the models of population growth and competition within a trophic level.

2.   The spread of Bt transgenes into wild relatives through pollen flow would be influenced by the abundance of herbivores.  Explain why herbivory would influence the persistence of the Bt transgene in wild plants

3.  Why are other transgenes, such as herbicide resistance or production of vitamins, unlikely to pose an ecological risk?

Evolution

1. We discussed three mechanisms for evolution:  drift, sexual selection, and natural selection.  Why is it said that only natural selection can produce adaption?

2.  A butterfly species lives along an altitudinal gradient on the west coast, from mid-altitude warm and dry areas to high altitude damp, chilly areas. This species of butterflies have two alleles for a protein that influences flight temperature (the temperature that the butterflies must achieve through shivering before they can fly).  In the high-altitude population, most butterflies have the allele that allows flight at a lower body temperature.  In the lower altitude populations, most butterflies have the regular allele, which requires higher body temperature for flight. The closest relative of this butterfly lives only in the lower altitudes.  Have these butterflies evolved an adaptation to  higher elevation?  Support your answer using the three requirements for evolution through natural selection.

3.  There is a common, introduced, lady-bug in the North East, the variable lady bug.  These lady bugs get their name from the variable number of spots on their orange elytra (the shiny modified wings that beetles have):  the spots vary from none to 6 or sometimes 8.  The number of spots is genetically determined.  What information would you need to determine whether the number of spots was evolving?  (hint:  recall the three things that are required for a population to evolve through natural selection)

4.  Evolution, via any mechanism, requires variation in phenotype that is genetically determined.  What is the source of this initial variation?

Evolution and transgenic crops

1.    a. Why is the exposure of an insect population to natural disease described as ‘soft’ selection?
b.  Why is exposure to a pesticide described as ‘hard’ selection?
c.  Which of the above will cause more rapid evolution, and why?

2.  Describe the pesticide tread-mill. 
b.  Integrated pest management involves spraying only when a sudden increase in pest number is detected by a farmer.  Why would this slow down the pesticide tread-mill?

3.  In Europe, crops are often planted in strips with “wild” vegetation (mixed wild flowers) in between.  What are two reasons that this would reduce insect damage on the crops?

4.  a.  It is argued that the movement of the Bt gene into crops will greatly speed the evolution of Bt resistance in pest insects.  Provide two mechanisms behind this prediction (i.e., two reasons it is expected to happen).

b.  Would movement of the Bt transgene into wild relatives through pollen flow increase or decrease the likelihood of Bt resistance in herbivorous insects?  Explain your answer.