Which of the animals would travel toward the top of the page if they began moving in a straight line? A is a spider, b is a kind of sea urchin, c is a turtle and d is a planarian.

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Expert Answers
lynn30k eNotes educator| Certified Educator

I can't see the last choice on your sheet but I will assume it is J) animals A and C because that would be the correct answer. Choice A is an insect, and choice C is a turtle. They both exhibit bilateral symmetry (only one way to divide the animal into halves) and cephalization (major sense organs at one end). When they move forward, they move in the direction of the cephalized end, which for these two is toward the top of the page. Choice D is a planarian, which is a type of flatworm. It also exhibits bilateral symmetry and cephalization, but the cephalized end is pointing towards the bottom of the page. When it moves forward it will go to the bottom. Choice B appears to be a sea urchin. Whatever type of animal it is, it has radial symmetry (many ways to divide the animal in half), and is not cephalized. There is no real "forward" for this animal, so when it begins to move in a straight line it is no more likely to move in one direction than any other.