11th Class Biology Digestion and Absorption Nutrition


Category : 11th Class

The substance used for nutrition are called nutrients. Nutreology is the study of food and their use in diet and therapy.

Types of nutrition

(1) Autotrophic / Holophytic : The individuals, which synthesizes their own food. It can be grouped into two following categories –

(i) Photoautotrophs : The individual, which synthesizes their own food from \[C{{O}_{2}}\] and \[{{H}_{2}}O\] in presence of sunlight. Examples – Green plants, euglena, green sulphur bacteria, chlorobium.

(ii) Chemoautotrophs : The individuals which synthesizes their food with the help of chemical. Examples – Sulphur bacteria, nitrite bacteria, nitrate bacteria, nitrosomonas, nitrifying bacteria– nitrosomonas, nitrobacter etc.

(2) Heterotrophic : The animals derive organic food materials by consuming bodies or products of other living or dead plants or animals. Heterotrophs are of following three types on the basis of their mode of feeding.

(i) Holotrophic or Holozoic : These individuals ingest mostly solid food. Example – Animals.        

(ii) Saprotrophic or Saprobiotic : They feed on dead organic matter. They absorb food through their body surface, organic fluids formed due to putrefaction of dead organism. Example – Bacteria, fungi, some protozoans etc.

(iii) Parasitic : These individuals derive their food from the body of their host. These may live inside or upon the bodies of their hosts, or may only periodically visit them for feeding. e.g., Ectoparasites (Lice) and endoparasites (Ascaris, Taenia solium).

(3) Myxotrophic nutrition : They carry out autotrophic as well as heterotrophic nutrition. Example – Euglena.

Modes of animal nutrition

On the basis of food, holozoic or holotrophic or ingestive nutritionally animals are classified into following –

(1) Herbivorous : The animal which exclusively feeds on plants. Their length of alimentary canal is more as compared to others. Examples – Tadpole larva of frog, rabbit, cow, horse, sheep etc.

(2) Carnivorous : The animal which kills and feeds on other animals. The length of their alimentary canal is minimum. Examples – Tiger, lion etc.

(3) Omnivorous : The animal which can take both plant and animal product as food. They have maximum type of digestive enzymes. Example - Human, Dog, Prawn.

(4) Insectivorous : The animal which feeds on insects. Example - Frog, Common bats, wall lizards.

(5) Sanguivorous : The animal which feeds on blood of other animal. Examples - Leech, body louse, mosquito, vampire bat etc.

(6) Carrion Eaters (scavengers) : They feeds on dead animals also termed as scavengers. Examples - Hyaena, neltura, kites etc.

(7) Cannibalus : Organisms which feeds on its own species. Examples - Cockroaches, some fishes, frog, snakes etc.

(8) Detritus : Animals feed chiefly upon organic matters present in the humus. Examples - Earthworm.

(9) Coprophagus or pseudorumination or refection : Animals which feeds on their own faeces. Example - Rabbit, Guinea pig

(10) Larvivorous : Feeds on larva. Example - Gambusia (mosquito fish) and Dragon fly.

(11) Frugivorous : Feeding on fruits. Example - Parrot, Bat, Squirrel.

(12) Food robbers : Feed upon food formed in alimentary canal. Example - Ascaris, Taenia solium.

(13) Filter feeder : Paramecium, Unio, Sponge.

Feeding mechanism

(1) Feeding mechanism in liquid feeders (fluid feeders) are as follows -

(i) Diffusion : Many parasitic organisms (protozoans, tapeworm) absorb the dissolved organic food through general body surface.

(ii) Pinocytosis (cell drinking) : Ingestion of liquid food by invagination through surface of body. Pinocytosis channels are formed at body surface to enclose the fluid food from surrounding medium. Lower ends of channels are pinched off as pinocytic vesicle or pinosomes.

(iii) Blood sucking : Their mouthparts are modified for sucking blood. Examples - Vampire bat, mosquito etc.

(2) Feeding mechanism in microphagus animals (filter feeders) : The food of such animals (paramecium, sponges, corals, bivalves, tadpole etc.) is suspended in water fluid and they have filtering devices (clusters of pseudopodia, cilia, flagella, sheets of mucous etc.) or feeding on small microscopic animals like – Amoeba, Paramecium etc.

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