- Tue Nov 14, 2017 7:57 pm
#41601
Hi Etsevdos,
This question is difficult in that it requires synthesizing information from all three paragraphs in order to get to the correct answer. The passage itself is concerned with how bacteria reach attractants, given that they exhibit erratic motion consisting of straight lines and tumbles. We are told that bacteria tumble less and travel in straight lines more as the get closer to an attractant, and vice versa. So scientists tested how the bacteria are sensing the attractants: uniformly or at different times? The evidence suggests they sense the attractants at different times, on both sides of their bodies, moving towards whichever side has a higher sense of attractant. This explains the tumbling, as the bacteria change direction whenever they sense more attractant in a direction they are not traveling in.
Putting all that information together leads to the inference that the erratic motion is actually based upon bacteria's response to attractant stimuli, and that it reflects the relative strength of attractant in a given direction and the bacteria's movement towards that attractant as it senses the attractant at different intervals.
This is essentially what answer choice (A) states, that the erratic motion is in fact a controlled mechanism responding to the attractant. So (A) is the correct answer.
(B) is a sweeping claim totally unsupported by the passage. Nowhere does the passage describe scientists' tendency to overstate complexity.
(C) is at least dealing with the subject of the passage, but the passage actually suggests this is an Opposite Answer: if bacteria are making different measurements of attractant at different times on different parts of the cell body, then there must be some memory of prior measurements in order to gauge relative strength and direction of the attractant.
(D) Again, an Opposite Answer: the information in the passage suggest that bacteria actually are not flailing around wildly, but responding to attractant stimuli. This is the opposite to (A), and incorrect.
(E) No distinction is made in the passage between photosynthetic and non-photosynthetic bacteria, so this answer is incorrect.
