No. If they didn't open and close their mouths, water couldn't flow through their body, and then out their gills. Thus, they wouldn't survive.
by opening their mouths then closing it then opening it again, then closing it:-)
yes they do, by opening their mouths.
Scallops open their mouths and shut them so then they start to move, so that's how they get away the open and close their mouths.
we can open our mouths
Actually... YES they CAN! The muscles of their jaws are VERY strong for CLOSING their mouths, but VERY WEAK for OPENING their mouths. This why the average man can hold the croc's mouth closed (once it is already closed) while someone else wraps duct tape around the snout, or the person holding the croc's mouth closed can tape it shut.
with their mouths
Fish open and close their mouths to breathe, eat, and communicate. Gill slits are openings on the sides of the fish's head that enable water to pass over the gills, where oxygen is absorbed and carbon dioxide is released. This process is essential for respiration in fish, allowing them to extract oxygen from water to survive.
walruses get their food by rushing in the water quickly and opening their mouths like whales.
it defends the plant from animals who do not want to put the prickles in their mouths (and also, please learn how to spell survive)
The chances for an Elephant to survive without a trunk are next to nothing. They use their trunk to smell, touch, pick up objects and food, signal each other and bring water to their mouths. Without being able to do these things, an Elephant would have to rely on a Human or other Elephant to feed them, and they would lead miserable lives.
Some fish swim with their mouths open to help them breathe better. By opening their mouths, they can take in more water and extract oxygen from it as it passes over their gills. This can be especially helpful in low-oxygen environments or when they are swimming at high speeds.
I know the snails have mouths on the heads, but not really ON. It's like kind of BENEATH their heads. It's under their eyes, on the bottom. It's the same for both water snails and garden snails. That way when it crawls on food it can just eat it, not position the head so the mouth is actually at the food. When the snails crawl on the glass or something transparent, you can sometimes see their tiny mouths opening and closing and they're so cute!