Which stage would show the development of the ectoderm and endoderm germ layers?

A. early gastrulation
B. blastulation
C. neurulation
D. late gastrulation


Answer: A

Biology & Microbiology

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Mechanoreceptors that react to changes in pressure are part of the _____

A) human sense of taste B) pain receptors in birds C) human sense of smell D) lateral line systems in fish E) eyes in arthropods

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Tetrad analysis shows that crossing-over occurs at the four-strand stage (i.e., after replication) because, when two genes are linked,

A) NPD > T. B) T > NPD. C) T > PD. D) PD > NPD. E) PD > T.

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Is the following statement true or false? "Vertebrates can never get ahead in the evolutionary race against their microbial pathogens."

a. True, vertebrate mutation rates are not high enough. b. True, vertebrate population sizes are too small. c. False, "real" evolution occurs only at the population level. d. False, the population size of immune system cells in an individual host can be similar to that of microbial pathogens.

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Botulism will always be a threat for people who

A. are meat eaters. B. are vegetarians. C. have a weakened immune system. D. consume home-preserved foods. E. eat a lot in restaurants.

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