Precision will be reduced, but yield will be increased

Optimisation of a PCR reaction is often a compromise between the competing demands for precision, efficiency and yield. Although the specific effects may vary, generally, increasing the annealing temperature will increase non-specific primer binding and reduce precision. Increasing the length of the elongation phase will reduce the proportion of incomplete newly-synthesised strands and therefore increase yield. In this case, the potential effect on efficiency is unclear. Increasing the elongation phase would increase the reaction time, but the time taken to ramp down to a lower annealing temperature would be reduced.

Which of the following will provide least specific amplification in qPCR?

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#Question id: 12236

#Unit 10. Ecological Principles

A  plant species arrives at  an  island  for the first time, where it  is  exposed to  a  new set of  pollinators.  Over the course of 20 generations, the characteristics of its flowers change. The figures above show the frequency distribution of petal length in the original colonizing population (Figure 1) and 20 generations later (Figure 2). Which of these explanations is consistent with the observed change in petal length?

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#Question id: 12237

#Unit 10. Ecological Principles

Which of the following occurred first during the separation of the elements of Pangaea through continental drift? 

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#Question id: 12238

#Unit 10. Ecological Principles

The mussel Mytilus edulis thrives in saline habitats, in both the highly salty seawater of tidal zones and the less salty estuaries. This results in two kinds of populations: one adapted to the higher salt concentrations of the tidal zone, and one adapted to the lower salt concentrations of the estuary. It has been found that the more salt-tolerant populations have high frequencies of an allele that produces an enzyme involved in maintaining osmotic equilibrium. Conversely, estuarine mussels having the same enzyme seem to be disfavoured and have a much higher death rate than mussels without the allele. Adult estuarine populations do have lower frequencies of this allele. Each spring, large numbers of larvae from  the salty habitats pour into the estuaries.

The invasion of the seawater larvae would be expected to facilitate change in the genetic structure of the estuarine population by a process called

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#Question id: 12239

#Unit 10. Ecological Principles

The figures above show the results of an experiment in which two microbial species, A and B, were grown in three treatments. In treatment I, species A was grown alone. In treatment II, species B was grown alone. In treatment III, both species were grown together at the same starting densities as in (I) and (II). The results suggest the interaction is best described as

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#Question id: 12240

#Unit 10. Ecological Principles

Two plant species co-occur in a prairie. Species X always occurs near species Y. However, species    often occurs in isolation from species X and produces more seeds when alone than when growing next to species X. Which of the following interactions between species X and Y could generate this pattern?

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#Question id: 12241

#Unit 10. Ecological Principles

The process of speciation can be prevented by