• previous unit
• unit index
• next unit

• quick read
• in english
• print

A Little Bit More

The “ inhalation” technique of capturing prey often means that a fisherman’s hook reaches much more deeply into the mouth, where softer tissue is located. Those fishes that use this method to catch food, such as the basses and sunfishes, often are hooked deep inside the mouth, making hook removal difficult.

This technique is responsible for the “popping” sound fishermen often hear at the water’s surface. It is quite impressive to watch because it happens so quickly – if you even see it. The predator’s mouth opens rapidly, and simultaneously the throat cavity enlarges by lifting the head and lowering the floor of the mouth. The sudden pressure reduction within the oral cavity (mouth plus) causes an inrush of water along with the hapless prey. Once the prey is in the mouth, the moth closes and contractions of the oral cavity expel the water through the gill slits. Now the prey can be swallowed.

Black Crappy

We use a related system ourselves, every time we drink. Our lips form a seal on the top of the water in our glass. By lowering our jaw or even moving our tongue slightly, we increase the size of our oral cavity. This reduces the pressure inside our mouth, and outside air pressure pushes water into our mouth from the glass. If our lips do not completely seal on the water surface, we will suck in air rather than water. We can suck water in along with air, without a complete seal, if we provide a more dramatic pressure difference by using our lungs as well as our oral cavity. It’s called slurping – an effective way of mixing cool air with a hot drink before it hits our sensitive mouth, but certainly not very polite!

Not all animals are able to drink by sealing their lips on the water’s surface. Horses and cows can but other animals, such as dogs and cats, are unable to do this and must resort to lapping with their tongues to carry water to their mouths.

Activities

Can You Drink This?

We all do it everyday but few, if any, of us has ever thought about how we accomplish this simple process. To understand the process better, students will need to closely monitor their own behavior so they can interpret exactly what is happening.

Have your students move through this 3-step process and they should be much better acquainted with how their lips make drinking possible.

1. Fill a glass close to the rim with drinking water. Ask each student to drink from their glass but do so slowly as they carefully monitor what they’re doing. This will initiate lots of giggles and there will probably be some false starts until they actually focus on what they’re doing.

Now have the students see if they can describe exactly what they did. They may need to drink a time or two more to figure this out. You may have to help them verbalize this process. For the most part, students will reduce the air pressure in their mouths by dropping their tongue, thus creating more space and less pressure. Just as with the fish, outside pressure(air in this case) will force water into their mouths. Your students may not understand about the pressure difference but should be able to discuss what they’re doing with their tongue as they drink.

2. Now have the students refill their glasses and try to drink WITHOUT allowing their upper lip to make contact with the water’s surface. They’ll quickly realize that they can pour it in or they can inhale lots of air and the inrush of air will pull in some water too, but they can’t drink as in step 1.

3. Now have the students refill their glasses and slurp water (as if the water if very hot) from the glass by keeping their upper lip close to, but not making a seal on, the surface of the water.

Once finished, your students should have a much better understanding how they drink –probably one they’ve never thought through before!

Actividad: ¿Puede beber esto?

Todos nosotros bebemos a diario, pero pocos, han pensado sobre como logramos este proceso básico. Para entender este proceso mejor, los estudiantes tienen que observar su propio comportamiento para interpretar exactamente lo que esta pasando.

Pida que los estudiantes pasen por los tres pasos del proceso y al final deben entender mejor que hacen sus labios para que sea posible beber.

1. Llena un vaso al borde con agua potable. Pida que cada niño bebe de su vaso pero que lo haga muy lento para observar lo que están haciendo con mucho cuidado. Esto iniciará mucha risa y probablemente empezará con una salida falsa hasta que realmente pueden enfocarse en lo que estan haciendo.

Ahora, pida que los estudiantes observen si pueden describir exactamente que hicieron. Quizás, necesitan beber una vez o dos más para entenderlo. Por lo tanto, los estudiantes reducirán la presión de aire en sus bocas bajando su lengua, por eso, creando mas espacio y menos presión. Como los peces, la presión de afuera (aire en este caso) forzará el agua dentro de sus bocas. Es posible que sus estudiantes no entiendan la diferencia de la presión pero deben poder discutir lo que están haciendo con su lengua cuando beben.

Ahora, pida que los estudiantes rellenen sus vasos y traten de beber sin permitir que su labio superior haga contacto con la superficie del agua. Se darán cuenta muy rápido que pueden llenar su boca o inhalar mucho aire y el torrente de aire va a extraer agua también, pero no pueden beberlo como hicieron durante el primer paso.

3. Ahora, pida que los estudiantes rellenen sus vasos y beban aspirando del vaso dejando el labio superior cerca de la superficie del agua, pero sin hacer un sello.

Cuando terminen, los estudiantes tendrán un mejor conocimiento de como beben – probablemente algo que no han pensado anteriormente.

Questions

Do you have a question for a naturalist? Go ahead and ask!

It's easy -- just fill out this form, submit your question and you'll receive an answer shortly.