Unlike most other animals, sponges lack?

Question

a) a digestive tract.
b) a symmetrical body plan.
c) nerve cells.
d) a digestive tract, an a symmetrical body plan.
e) a digestive tract, a symmetrical body plan, and nerve cells.


--[I'm almost sure it's E ... what do you guys all think??]

Answer 1

It depends on how picky you are.

If the sponges had any kind of system at all (a debatable prospect), it would be a digestive system. Water does flow through them for feeding in one direction only and allows all the cells access for feeding.

Likewise, some sponges do seem to be radially symmetric, though they're usually classified as a group in the 'asymmetric' category.

So if you (or your teacher) is really picky, then C is the only correct answer. Certainly comparatively sponges have virtually no digestive tract nor symmetry to speak of (sponges are too primitive to even have proper tissues), so E would be correct in that sense.

Answer 2

Planets produce food using photosynthesis where as sponges filter feed, they also lack the cellulose found in plants . Sponges are the simplest form of animal, it has a specialised cell called the choanocyte which forms an very basic digestive system something else not found in plants and being able to digest food is important in determined an animal. No brain is not unusual in an animal, jelly fish and flatworms both lack brains and some that do have brains can survive quite happily with out them (like crabs).

Answer 3

E is absolutely correct. The cells of a sponge are not specialized -- meaning not nerve cells or a digestive tract. Their body "plan" is asymmetric, meaning that they have not defined shape/form/symmetry.

Answer 4

if you took all of the sponges out of the ocean would the water level drop?