Question

all \symmetrical\ organisms develop asymmetries. a fruit fly, no larger than the tip of a lead pencil, having developed while stuck to the inside of a glass culture vessel, has different numbers of sensory bristles on its left and right sides, some flies having more on the left, some more on the right. moreover, this side - to - side variation is as large as the difference among different flies. but the genes on the left and right sides of a fly are the same, and it seems absurd to think that the temperature, humidity, or concentration of oxygen was different between left and right sides of the tiny developing insect. the variation between sides is a result of random events in the timing of division and movement of the individual cells that produce the bristles, so - called developmental noise.

1. why does the author put symmetrical in quotation marks?

a it is a scientific term.
b it is a new word that the author made up.
c the author is referring to another authors use of the term.
d the usual meaning of the word is not completely accurate in this context.

1. in this passage, the vessel is

a a boat.
b a container.
c a vein or artery.
d a window.

1. the passage implies that differences such as that between right - and left - hand fingerprints could be a result of

a differences in genes.
b differences between individuals.
c asymmetry.
d unpredictable variations in the way cells divide.

1. how does the number of bristles on the right side affect the number of bristles on the left?

a it has no effect.
b it makes the left side have fewer bristles.
c it makes the left side have an equal number of bristles.
d it makes the left side have more bristles.

Explanation:

Question 20:

The author uses quotation marks around "symmetrical" because the actual biological phenomena don't fully conform to the typical meaning of symmetry, suggesting the usual meaning isn't completely accurate in this context.

Question 21:

The text mentions the fly being "stuck to the inside of a glass culture vessel", indicating that a vessel here is a container.

Question 22:

The passage states that differences such as between right - and left - hand fingerprints could be due to unpredictable variations in the timing of division and movement of individual cells that produce features like bristles, which is developmental noise.

Question 23:

The passage implies that the number of bristles on the right side has no effect on the number of bristles on the left as the variation between sides is due to random events in cell division (developmental noise).

Answer:

1. D. The usual meaning of the word is not completely accurate in this context.
2. B. a container.
3. H. unpredictable variations in the way cells divide.
4. I. It has no effect.