Which statement best reflects the current understanding of pollen-tube elongation?
a. It is not even known if pollen tube growth uses chemical signals or is completely random.
b. Pollen-tube elongation will occur as long as the pistil provides moisture and energy.
c. While it is known that chemical cues from female tissues help guide pollen tube growth,
the identity of these chemicals is not known.
d. Nearly all of the details of the chemical interactions between the pollen tube and pistil
tissue are known.
e. Pollen-tube elongation will occur only when pistil chemical cues are suppressed.
C
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If a patients ability to create the bilayer that surrounds the cells has been disrupted, the processes likely to be affected would be
_____ controlling the gradients of Na+. _____ collecting fatty acids and making lipids. _____ holding proteins that aid active transportation. _____ dividing work between different cell types. _____ packing proteins into vesicles for exocytosis.
Which of the following best describes transpiration?
A) the loss of oxygen from a plant B) evaporation from a plant's roots C) the bulk flow movement of water in a plant D) the loss of water from plant leaves through evaporation
The muscles of your lower leg are arranged in antagonistic pairs so that you
A) can both flex and extend your leg. B) can stand upright. C) obtain a stronger contraction than you would with a single muscle. D) have a backup when one muscle is not strong enough.
Which of the following statements about vertebrate eyes is true?
A. Most predators have monocular vision. B. Most predators have eyes on the sides of their heads. C. Binocular vision helps prey animals scan their surroundings for predators. D. Most prey animals have eyes on the sides of their head and monocular vision. E. Monocular vision allows for better depth perception.