A primitive streak forms during the early embryonic development of
A) birds, but not frogs or humans.
B) frogs, but not birds or humans.
C) humans, but not birds or frogs.
D) birds and frogs, but not humans.
E) humans and birds, but not frogs.
Answer: E) humans and birds, but not frogs.
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Which of the following animals has an incomplete digestive system?
a. bird b. flatworm c. goat d. amphibian
What is depicted in the above diagram?
a. a sensory neuron b. an interneuron c. a motor neuron d. a neuroglial cell e. none of these
When a cell makes a cell membrane bound growth factor that binds to receptors on neighboring cells causing them to proliferate this is an example of
A. autocrine signaling. B. endocrine signaling. C. paracrine signaling. D. contact-dependent signaling. E. direct intercellular signaling.
The large number of alveoli in lungs improve gas exchange by _____.
A. increasing the concentration difference B. changing the diffusion constant C. decreasing the distance for diffusion D. increasing the surface area for diffusion