Feeding in man – Grinding and Chewing system

GRINDING AND CHEWING MECHANISM

This method is common among mammals e.g. man, cattle, sheep, goat, e.t.c. These animals are capable of grinding their food before swallowing. The grinding is aided by the presence of hard and strong teeth make up of enamel and dentine. Mammal like man has four different type of teeth mainly incisor, canine, premolar and molar. The incisor has a sharp edge that is used to cut food, the canine are pointed and they are used for tearing of flesh or other material. The premolars and molars are flat teeth with cusps that grind and mash food. The molars are for vigorous chewing                            

 STRUCTURE OF A TOOTH

DENTITION: – Is the arrangement of teeth dental formula shows the number of each typed of teeth possession by a mammal, the number of teeth in one side the jaw is given with the number in the upper jaw before that in the lower jaw

Mammal	Dental formula	Total No of teeth
Man	I=2/2, C=1/1, P=2/2, M=3/3	32
Dog	I=3/3, C=1/1, P=4/4, M=2/3	42
Cow & Sheep	I=0/3, C=0/1, P=3/0 M=3/3	32
Rat	I=1/1, C=0/0, P=0/0, M=3/3	16

(3) TRAPPING AND ABSORBING MECHANISM

This system is common among insectivorous and carnivorous plant such as bladderwort, pitcher, sundew, Venus fly trap. They have structure which enables them to adapt to this mode of feeding.

FEATURES

• The plants have special devices for attracting and trapping flies and other insect; such features are: bright colour flowers, scent and sugary secretion/nectar
• The plant possesses digestive juice which when a prey is trapped will trigger off to kill and digest the prey.
• The leaves of these plants have long hairs which carry digestive glands. Bladderwort is a floating aquatic plant with tiny leaves and small bladder.
• Venus fly trap have leaves which are folded inward but leaving some gap between the sensitive hairs.
• Pitcher plants have leaves that are modified with pitcher like vessels which contain a digestive juice. The rim of the vessel is brightly coloured with a sugary nectar.

                                                                    FEEDING HABIT IN AMOEBAS

Amoebas are found in the bottom of muddy ponds. It feeds on food particles smaller than itself. There is no  mouth or alimentary canal. When it comes across a food particle e.g. diatom, it shoots out 1 or 2 pseudopodia which flows around the food particle. On contact with the food particle, the pseudopodia becomes cup-shaped and engulf the food. The process is called PHAGOCYTOSIS or ENGULFMENT. By the retraction of the pseudopodia, the food is taken into the cytoplasm in food vacuole in which digestion of food take place. Digestion of food is intracellular and necessary digestive enzymes are poured into the food vacuole. From the surrounding cytoplasm. The absorption of the digested food into the cytoplasm mark the end of the feeding process. Undigested food material is egested from the cytoplasm into the surrounding water. Amoeba is using HOLOZOIC method of nutrition.

FEEDING HABITS IN HYDRA

Hydra is a carnivorous organism that sting its prey with specialized organelles called NEMATOCYST. It also uses the tentacles to push the food into its mouth. The organism feed on smaller micro-organism that swim around in the aquatic habita e.g. Daphina & flea & insect larvae. With the food in the gastro vascular cavity, specialized cell secrete digestive enzyme that soften the tissue of the prey into pieces. The food particles are then taken to gastro- dermal cell by phagocytosis and food molecules are hydrolyzed within food vacuoles after digestion of the meal. Undigested material remaining in the gastro- vascular cavity are eliminated through the single opening which functions as mouth and anus.