Sponges
The simplest animals. A sponge lives fixed to the sea floor, and its body is a hollow sac whose wall is full of tiny pores. Cells lining the inside beat little whips that pull water in through the pores; they catch the bits of food in it, and the water leaves through a big opening at the top. A sponge has no mouth, stomach, nerves or muscles, yet it is an animal: it eats food rather than making it.
Depth 1 · Foundation
You can say how a sponge feeds by pumping water through its pores, and why it counts as an animal though it never moves.
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- 1
Foundation
You can say how a sponge feeds by pumping water through its pores, and why it counts as an animal though it never moves.
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