High School Department
Molino 3, Bacoor, Cavite
Jerome Richard Tan
II – Jupiter
1. What do you think is the function of the nictating membrane, and why ? The nictitating membrane is a protective, semi-transparent third eyelid. It allows vision while giving the eye extra protection. In the case of frogs, the protection is needed when the frog is out of the water. The clear nictitating membrane allows the frog to keep looking for prey - and looking out for herons and other hunters! - while its eyes are protected from dust and from the drying effects of the air. 2. A frog does not chew its food, what do the positions of its teeth suggest about how the frog uses them ? That they are intended for gripping, not for chewing. The 4 teeth a frog has, are positioned with 2 on the sides and 2 in the center, and are angled toward the throat. This helps keep the food going in the direction of the digestive tract...but unable to back out of the mouth. 3. Trace the path of food through the digestive tract.
In the frog's mouth there is a front hinged tongue. This flips food into the gullet, which is the entrance to the esophagus. The food is moved down into the stomach by muscle contraction. The stomach breaks food down mechanically using its multiple muscle layers. It also secretes enzymes to convert complex nutrients into simpler ones. The enzymatic breakdown continues in the small intestine where the simpler nutrients are also then absorbed. The left over material is passed on to the large intestine where water may be absorbed from the mixture. 4. Trace the path of blood through the circulatory system. The Deoxygenated blood flows from the body into the right atrium. Oxygenated blood from the lungs flows into the left atrium. Since frogs have only one ventricle, the oxygenated and deoxygenated blood mixes in the ventricle. From there, blood flows into the truncus arteriosus that...