Animal Physiology: Digestive system of a rat
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Animal Physiology: Digestive system of a rat Introduction Plants and animals are composed of many different types of complex organic molecules. When eaten as food, these molecules are too large to be simply absorbed into an animal's body. For food to be absorbed, the molecules must be small enough to pass into the cells lining the gut. This is the purpose of digestion. Digestion is the process of breaking down organic food into molecules that are small enough to enter cells. Chemical digestion involves enzymes that break complex molecules into simpler molecules Mechanical digestion is the physical breakdown of food into smaller pieces, to increase the surface area available for enzyme action. Unlike chemical digestion, it does not chemically change the molecules. The mammalian digestive system consists of the mouth, oesophagus, stomach, small intestine, large intestine, rectum, anus and associated glands. Aim To locate, identify and describe the digestive tract of a placental mammal, and; To compare and contrast the digestive system of different placental mammals and relate any differences in structure to function. Apparatus * Rat * Dissecting board * String * Forceps * Dissecting Scissors * Scalpel * Pins * Newspaper * Disposable Gloves * Disposable plastic bag * Disinfectant Procedure 1. The dissecting board was covered with newspaper.
It was red in colour and when cut open a brown substance came out. Large Intestine The walls were thin and easily stretched. It is not too long if comparing with small intestine: only 12 cm. It was light brown in colour. Data Analysis 1. Relate your observations about the various parts of the rat digestive tract to the functions that these parts perform. Discussion 2. Do you think the rat is a herbivore, omnivore or carnivore? Justify your answer in light of your observations. 3. A tiger is a predator that hunts and kills other animals for food. Suggest ways in which the digestive tract of a tiger would differ from that of the rat. Give reasons for these differences. 4. Suggest ways in which the digestive tracts of the tiger and the rat would be similar. Give reasons for your suggestions. Answers 1. The teeth of the rat could be divided in two groups. The first group includes the four teeth that appeared when his mouth was opened. They are known as incisors. The incisors have a sharp format that turns possible to the rat to catch and kill animals. The grinding teeth that are used to chew plant and seeds and eventually meat, form the second group. The oesophagus is long (about 4.5 cm in length)
A tiger than, spend less time eating and can not eat for days between meals. Another difference between the two digestive tracts is that the tiger should have bigger and stronger teeth in the front row to kill other animals, the canines, not present in the rats. The rats have more flat teeth to chew plants and seeds. The caecum of a carnivore, such as a tiger, is inactive, while the caecum of a rat is working. 4. All digestive systems have many similarities because all of them have the same purpose, the purpose of digestion - to rapidly break down organic food into molecules small enough to be able to pass through cell membranes and into cells. Both digestive tracts (rat's and tiger's) have two processes of digestion: the mechanical and chemical breakdown. The first one consists on the physical breakdown of food into smaller pieces, to increase the surface area available for enzyme action. The chemical digestion involves enzymes that break complex molecules into simpler molecules. Unlike chemical digestion, the mechanical breakdown not chemically changes the molecules. Conclusion The digestive tract of the rat was successful located, identified and described. With the observations, we could analyze why the rat is an omnivore, what parts of its digestive system are similar and what parts are different from a carnivore digestive tract and what are their functions in the digestion. We could discover also the difference between the types of feeding behaviour and why they are so essential to understand.
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