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Which of the following is not necessary for designation as a chordate?
I. A notochord
II. Vertebrae
III. A post-anal tail
IV. Gill arches
V. A dorsal, tubular nervous system
Chordates must have, at some point in their embryogenesis, all features except vertebrae. Although the vast majority of chordates are vertebrates, Amphioxus has only a notochord. This primitive organism never develops vertebrae. Man has gill arches, and remnants of these are seen in certain congenital malformations. The notochordal remnants can give rise to the tumor known as a chordoma. The brain has ventricles (it is tubular) and it is certainly dorsal. Finally, human tail persists in about one per million live births.
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Which of the following statements about chordates is true?
The phylum chordata has a few key characteristics. They are deuterostomes, meaning that the anus arises from the blastopore. They have a coelom that arises from the mesoderm during development, and at some point they have a tail, pharyngeal slits, and a notochord.
Vertebrata is a subphylum of chordata, so not all chordates are vertebrates (though all vertebrates are chordates).
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Which of the following organelles is/are mainly present in animal cells?
I. Peroxisome
II. Centrioles
III. Flagella
Centrioles are generally only found in animal cells, but have been found in a variety of eukaryotes. There are a small subset of plants that do contain centrioles. Some plant cells have flagella and peroxisomes.
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