Biology Notes Life on Earth + Digestive System

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Topic: patterns in nature

Compare the digestive systems of mammals.
Include: grazing herbivore, carnivore and a predominantly nectar feeding animal

Major parts of mammalian digestive systemsgrazing herbivore GOAT
carnivore
CATpredominantly nectar feeding animal
HONEY-POSSUM
Mouth- no incisor or canine teeth
- depend on firm dental pad in
front of hard palate, lower incisors, lips, and tongue to take food into mouths - use molar teeth to grind food to increase surface area so that it is more exposed to digestive chemicals that help to break it down. These molars are used again to chew even further when the cud is regurgitated.- mouth of a cat contains a pharynx, soft palate, hard palate and variety of teeth (incisors, canine, premolars and molars) - takes its food in with teeth and lips

- Some chew the pieces, others swallow them whole
- saliva moistens food so it is easier to swallow
- tongue pushes food back through the pharynx into the esophagus - tongue has range of papillae, including filiform (doesn’t contain taste buds), fungiform, vallate and foliate- elongated snout and long tongue covered in papillae that collect the pollen - tongue moves in and out of mouth 2-3 times a second and is supported by the teeth, which are all very tiny, except for the two front teeth in the bottom jaw which act as main supporters for the tongue - When tongue re-enters the mouth it scrapes against roof of mouth which contains ridges that scrape off the pollen Teeth- no upper teeth incisor or canines

- teeth they use are lower incisor teeth, along with the dental pad in front of the hard palate, tongue and lips which are all depended on to take food into mouth- mouth of a cat contains a variety of different teeth: Canines– grab, hold & tear prey

Incisors– scrape meat off bones
Molars and premolars– crush meat so it is easier to swallow See picture 1- only a few, tiny teeth
- incisors and canines are narrow and pointed
- cheek teeth flat with round tips
- lack of strong teeth because of no need to bite or crush food See picture 6
Esophagus- tube-like passageway from mouth to stomach
- opens into the stomach at the point where rumen and reticulum meet - helps transport both gases and cud- begins at end of pharynx, continues down neck next to the trachea, through diaphragm, finally connecting with the stomach - first passageway in digestive system, so often exposed to rough food which has not been fully chewed i.e. pieces of bone - surface therefore has to be resistant to damage, so is lined with stratified squamous epithelium. See picture 2- simple tube that moves food from mouth to stomach - At entry from esophagus to stomach the lining of the esophagus changes from stratified squamous (picture 2) to tall column shaped cells

StomachGoat’s stomach has four compartments (see picture 3): 1) rumen: largest compartment. Here food is moistened and churned around to break down into smaller pieces Capacity: 11 -22 litres depending on food eaten 2) honey-combed reticulum: located just below entrance from esophagus into stomach. Part of the rumen, only separated by thin fold. Bacterial cellulases act on food here and food is made into round balls called cud which is regurgitated into mouth and chewed into small particles. Capacity: 1-2 L 3) omasum: after cud has been regurgitated and cellulose broken down, it is re-swallowed and moves into the omasum, consisting of layers of tissue that grind up cud and remove some water from it. Capacity: approx 1L 4) abomasum ‘true stomach’: functions similarly to human stomachs. Contains hydrochloric acid and enzymes that break down food particles before entering small intestine. Capacity: approx. 4L- stomach of a cat is designed to store large amounts of food and begin digestive process - esophagus carries food into the stomach, where it enters through a valve called the cardiac sphincter - lining of stomach has many folds called gastric folds, which help...
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