The embryonic membrane that completely encloses the embryo in a watery sac is the
A. yolk sac.
B. amnion.
C. allantois.
D. chorion.
E. ectodermal sac.
B
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Which papillae, distributed on the anterior two-thirds of the tongue surface, lack taste buds?
A. Papiform B. Filiform C. Fungiform D. Vallate E. Foliate
The ________ or preen gland in birds, which is lateral to the tail feather attachment, secretes oil that is used to waterproof feathers
A) tertiary B) remige C) uropygial D) pteryla
Answer the following questions true (T) or false (F)
1. During the absolute refractory period, production of an additional action potential is not possible no matter how strong the stimulus. 2. Saltatory conduction is slow due to the presence of insulating myelin around an axon. 3. Conduction speed of a nerve impulse is influenced by the diameter of the axon and the presence or absence of a myelin sheath.
Which of the following statements is NOT true of diffusion?
A. It requires the energy of ATP. B. It is a type of physical transport process. C. It is considered to be a type of passive transport. D. It occurs due to random molecular motion. E. It moves substances from higher to lower concentration.