In Chapter 4 starting on page 60, Neil Shubin briefly talks about the role of teeth in mastication and the importance of good teeth in fish of every size. Since teeth have evolved over time to support the function of initiating the digestive cycle in humans and other mammals, please explain this relationship of tooth structure to its function. Does the shape/type of teeth (blade-like molars, flatter teeth) directly affect what type of role that organism will play in the food web? Do different types of teeth shift food preferences of animals towards plants or other sources? Also, use this passage as a way to review the process of digestive initiation and use of enzymes to help teeth start to break down food before digestion.
Christine Lin
choco_cat11@comcast.net
According to Shubin, “teeth are a powerful window into an animal’s lifestyle” (Shubin 61). When finding teeth that have been fossilized, scientists can tell the species’ position in the food chain, and they can determine the food that the organisms ate based on the size and shape of the teeth. Mammals have teeth that can “grind, stab, scissor, dig, chisel, sieve and lift (elephants tusks)” (http://www.earthlife.net/mammals/teeth. html). Animals that are carnivores tend to develop with sharper teeth to tear apart the meat that they eat. Herbivores will have flatter teeth necessary for grinding up plants.
ReplyDeleteIncisors are teeth that are located at the front of the jaw. These teeth are sharp and used for animals that gnaw at their food, such as rodents. Canines are the “stabbing teeth” that work with the incisors to kill prey. Canines are mostly found in carnivores because they are useful for cutting through meat, whereas herbivores do not have use for sharp canine teeth. Premolars are the teeth used to crush and grind up food. Molars benefit herbivores and omnivores, but if they are found in carnivores, they are usually thinner for biting meat. Molars are large and flatter like premolars, but they have cusps in them. Because premolars and molars are so flat, plants can easily be crushed when these teeth rub together. If herbivores had sharper teeth, the canines or incisors might be able to tear right through the plant, but it would be difficult to actually grind the plant into smaller, digestible pieces. Likewise, if carnivores had flat molars, these teeth would be too big to do much damage to flesh, and if the prey isn’t immediately killed, it could have a chance of escaping its predator if it isn’t wounded too badly. (http://www.earthlife.net/mammals/teeth.html)
When food enters the oral cavity, teeth that are specific for different functions of tearing and grinding food break down the food into smaller particles with mechanical digestion. At the same time, the salivary glands produce saliva to help with chemical digestion. Salivary amylase is the enzyme in saliva that “hydrolyzes starch and glycogen into smaller polysaccharides and the disaccharide maltose” (Campbell 884). After the teeth works with saliva in breaking down the food, the food is swallowed, where it will be further digested.
Claire Yao (claire.yao521@gmail.com)
The shape/type of teeth completely affect what type of role that organism will play in the food web. If one has a mouth full of canines and incisors then one is most likely a carnivore. On the other hand, if one has a mouth of molars, one is most likely a herbivore. Omnivores have a mixture of both. Canines and incisors are necessary for slicing through meat, while molars are more efficient for the simple chewing of grasses, so depending on the teeth is what the animal will eat. In fact, Shubin explained that “teeth are such a great clue to an animal’s diet…” (61).
ReplyDeleteThere are four distinctive sort of teeth types that Claire already thoroughly explained: incisors, canines, premolars, and molars. But also what is just as important in dealing with death is their precise occlusion -- the fit between upper and lower teeth. Reptiles lack it, while humans and other mammals have this. When Shubin observed the tritheledonts, he saw that the individual cusps do not interlock in a precise way as mammals do. Instead, the inner and outer surface sheer against one another like scissors. The was the distinct transition from the lack of a matching pattern of occlusion in crocodiles and lizards and the pattern we see in mammals today. The way teeth fit together is another factor that leans animals toward or away from certain prey.
To continue, the material the teeth is made out of changes the role the organism will play in the food chain. Shubin explains how a molecule knows as hydroxyapatite “impregnates the molecular and cellular infrastructure of both teeth and bones, making them resistant to bending, compression, and other stresses” (74). The hardness hydroxyapatite gives the teeth, especially the enamel, is what makes our teeth so strong and powerful to crush into food and chew it. Animals like clams and lobsters, on the other hand, don’t use hydroxyapatite for their teeth, but instead use calcium carbonate or chitin. These leads them to be further down the food chain than mammals would be because mammals have harder, stronger teeth.
In digestion, teeth is what drives the entire system. When food enters the mouth, teeth begin the process of mechanical digestion by grinding down the food. And just as Claire explained, salivary amylase plays a role in chemical digestion. The salivary glands release salivary amylase that hydrolyzes starch and glycogen (Campbell 884). Then the food travels down the esophagus where it is further digested in the stomach and onward.
-Michelle Layvant, mlayvan2@students.d125.org