In: Biology
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a.The difference between the eyes of most animals we are familiar with and the eyespots of Dugesia is that in humans, the eyes have specialised structures with functions such as iros, cornea , retina to name a few whereas in Dugesia, the eyespots the eyespot consists of only photosensitive cells.
a.The movement of the head is from side to side while the tail just follows where the head moves.
a.The feeding tube location is in the middle of the body ,mostly on the head side.This is unusual for bilaterally symmetrical organisms due to cephalization due to which sensory organs are confined to head region mostly.
a.No, the gastrovascular cavity of Dugesia is not a simple sac .Rather it is divided to have branches with small diverticula.The advantage with this is that it increases the surface area for absorption of nutrients.
b.Being monoecious would increase the reproductive success as searching out for mates is ruled out and chances of fertilization is more to produce more offsprings.
c.Having head means anterior and posterior distinction of the body is clear.With head,presence of sensory organs is a a must like the eyespots in Dugesia.
d.Planarians accomplish this task via process of simple diffusion of the gases through their body wall.