TLS Online TPP Program

#Question id: 11201


Why are action potentials usually conducted in one direction?

#Unit 7. System Physiology – Animal
  1. The nodes of Ranvier conduct potentials in one direction.
  2. The brief refractory period prevents reopening of voltage-gated sodium channels.
  3. The axon hillock has a higher membrane potential than the terminals of the axon.
  4. Voltage-gated channels for both Na+ and K+ open in only one direction.
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TLS Online TPP Program

#Question id: 8296

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species.


According to the phylogenetic tree in the figure above, G. intestinalis constitutes a ________ group.

TLS Online TPP Program

#Question id: 8680

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species


By examining the phylogenetic tree diagrammed in the figure above, what conclusion can you draw about the species G. microti?

TLS Online TPP Program

#Question id: 8682

#Unit 9. Diversity of Life Forms

Giardia intestinalis can cause disease in several different mammalian species, including humans. Giardia organisms (G. intestinalis) that infect humans are similar morphologically to those that infect other mammals, thus they have been considered a single species. However, G. intestinalis has been divided into different subgroups based on their host and a few other characteristics. In 1999, a DNA sequence comparison study tested the hypothesis that these subgroups actually constitute different species. The following phylogenetic tree was constructed from the sequence comparison of rRNA from several subgroups of G. intestinalis and a few other morphologically distinct species of Giardia. The researchers concluded that the subgroups of Giardia are sufficiently different from one another genetically that they could be considered different species


Which of the following changes would a modern systematist be most likely to make after learning of the results of the rRNA analyses?

TLS Online TPP Program

#Question id: 8683

#Unit 9. Diversity of Life Forms

Use the following information to answer the question.

Refer to the figure. Which of the following forms a monophyletic group?

TLS Online TPP Program

#Question id: 8684

#Unit 9. Diversity of Life Forms

Use the following information to answer the question.



Which of the following trees, if any, depicts the same relationship among species as shown above?

TLS Online TPP Program

#Question id: 8685

#Unit 9. Diversity of Life Forms

Which of the following would be most useful in creating a phylogenetic tree of a taxon?