Which respiratory surface lacks physical protection from the external environment?
a. tracheal system tubes
b. human lungs
c. external gills
d. internal gills
e. bird lungs
C
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The most important feature of a protein is its
A. secondary structure. B. side group. C. shape. D. electric charge.
An invertebrate statocyst contains ____, which surround movable ____. Changes in body position
move the latter and thus trigger action potentials.
a. statoliths; sensory hair cells b. sensory hair cells; statoliths c. otoliths; sensory hair cells d. efferent neurons; otoliths e. efferent neurons; statoliths
Which of the following is NOT one of the key adaptations to land shared by all land plants?
A) A means of taking up nutrients from the soil B) Waxy cuticle C) Stomata D) Water transport by xylem E) Protected embryos
Agricultural companies have developed the ability to control the genetic characteristics of their crops. Genetic engineering techniques have been used to produce all of the following effects except
A. grow salt-tolerant crop plants B. decrease harvesting time C. make crop plants resistant to disease D. decrease soil nitrogen levels