The simplest eye structure, which is able to perceive light but not form an image, is called a
a. compound eye.
b. single-lens eye.
c. ocellus.
d. ommatidia.
e. photoreceptor.
C
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What molecule is composed only of chains and rings of hydrogen and carbon?
A) carbohydrate B) hydrocarbon C) polypeptide D) polysaccharide
What moves the food from your mouth to your stomach when you swallow?
A) Gravity B) Peristaltic muscle contractions C) Undulatory muscle contractions D) Pressure difference between zones
Under which of the following situations would receptor down-regulation most likely occur?
a. The number of G proteins is too high. b. The concentration of a hormone is too high. c. The cell is unable to manufacture cyclic AMP. d. The concentration of a neurotransmitter is too low. e. The number of receptors in the plasma membrane is too low.
Some organisms are capable of orchestrating alterations that are collectively termed antigenic variation. This allows the organism to __________.
A) rapidly move through the host's tissues B) drastically decrease its ID50 C) enter the host's body through more than one portal of entry D) evade the host's immune system