FEEDING HABITS

Organisms exhibit different feeding habits. These are:

Filter Feeding

Filter feeders which are also called microphagous feeders feed on very tiny organisms which cannot be easily picked to the satisfaction of the feeder. Filter feeders are mainly aquatic animals and they have to wallow in water through sieve-like structure into their body in order to collect reasonable quantity of their prey or food. Examples of filter feeders are mosquito larva, mussel, ducks and prawns.

 

Filter Feeding in Mosquito Larva

The mouth of mosquito larva, for example, has horny jaws and two small ciliated appendages or mouth brushes. These are used to create a current of water. The small coloidal particles or planktons, small plants and animals are filtered from water and ingested into the mouth as food.

 

Fluid Feeding

Animals which feed on any fluid materials are classified as fluid feeders. There are two major groups of fluid feeders. These are:

1) Wallowers: These organisms rest within or wallow in their food, e.g. the tapeworm in the intestine of man. The tapeworm lives within the digested food of its host and absorbs the food directly into its body. It has no alimentary canal and it uses its entire body surface to absorb already digested food of the host.

 

2) Suckers: Suckers are organisms, mainly insects, which feed by sucking fluid from plants and animals. Examples of suckers are bug, mosquito, butterfly, aphid, tsetse fly and housefly.

 

Saprophytic Feeding

Saprophytes are mainly non-green plants which do not have chloroplasts and therefore cannot manufacture their own food. They then feed on dead and decaying organic matter from which they derive their food. Examples of saprophytes are rhizopus, mushroom and mucor. Their body is adapted in the following ways:

1. They have hyphae instead of roots through which they pour out enzymes for digestion.
2. They are capable of carrying out extracellular digestion, i.e ., digestion of food outside the body cells of the plant.
3. The digested portion of the organic matter is later reabsorbed into the body.

 

Parasitic Feeding

Parasitic feeding is found in both plants and animals. Animal parasites are tapeworm, roundworm, liver fluke, louse, tick and guinea worm while plant parasites are cassytha, dodder and mistletoe. Parasites are structurally modified organisms that depend wholly or partially on other living organisms for their food and survival.

 

PROCESS OF FEEDING IN PROTOZOA, HYDRA AND MAMMALS

Feeding in Protozoa

Protozoa like Amoeba exhibits holozoic mode of nutrition. Amoeba feeds on micro-organisms like diatoms, desmids or other organic particles. It engulfs the food particles by putting out its pseudopodia which surround the food particle by forming a cup-shape when the two ends of the pseudopodia touch. The pseudopodia on meeting or touching, fused and enclosed the food into the body with little drop of water; this forms a food vacuole. The food is digested inside the food vacuole.

 

Feeding in Hydra

Hydra feeds mainly on small crustaceans or other smaller aquatic organisms. The food is captured by the action of nematocysts borne on the tentacle. The food is carried into the wide mouth by the tentacle. Enzymes are secreted into the enteron by the gland cells. Here digestion takes place extracellularly, i.e ., inside the body cells. The digested food is absorbed into the body while the undigested parts are sent back into the enteron and forced out through the mouth.

 

Feeding in Mammals

The process of feeding in mammals has already been discussed under alimentary canal and digestion of food in man.