Use the following information to answer the question(s) below. 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. (T. Monis et al. 1999. Molecular systematics of the parasitic protozoan Giardia intestinalis. Mol. Biol. Evol. 16[9]:1135-44.)
According to the phylogenetic tree in the figure above, G. intestinalis constitutes a _____ group.
A) paraphyletic
B) monophyletic
C) polyphyletic
Answer: A
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Who invented the first crude microscope by grinding glass?
A. Pasteur B. Schultz and Schwann C. Redi D. Lister E. Leeuwenhoek
These vertebrates are unique in that they:
1.have skeletons made of cartilage
2.do not have jaws
3.lack appendages
4.lay amniotic eggs
Which of the following statements about predation are true? Check all that apply.
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