Sheep Continuous Feeder or Discontinuous Feeder

Animal Getting & Using Food:

As noted earlier, only a few protists and animals can absorb nutrients directly from their external environment via intracellular digestion. Most animals must work for their nutrients. The number of specializations that have evolved for food procurement (feeding) and extracellular digestion are almost as numerous as the number of animal species. What follows is a brief discussion of the major feeding strategies animals use.

ContinuousVS Discontinuous Feeder:

One variable related to the structure of digestive systems is whether an animal is a continuous or discontinuous feeder. Manycontinuous feeders are slow moving or completely sessile animals (they remain permanently in one place).

For Example , aquatic suspension feeders, such as tube worms and barnacles, remain in one place and continuously "strain" small food particles from the water.Discontinuous feeders tend to be active, sometimes highly mobile, animals. Typically, discontinuous feeders have more digestive specializations than continuous feeders because discontinuous feeders take in large meals that must be either ground up or stored, or both.

Many carnivores,  For Example , pursue and capture relatively large prey. When successful, they must eat large meals so that they need not spend their time in the continuous pursuit of prey. Thus, carnivores have digestive systems that permit the storage and gradual digestion of large, relatively infrequent meals.

Herbivores spend more time eating than carnivores do, but they are also discontinuous feeders. They need to move from area to area when food is exhausted and, at least in natural environments, must limit their grazing time to avoid excessive exposure to predators. Thus, their digestive systems permit relatively rapid food gathering and gradual digestion.

Suspension Feeders:

Suspension feeding is the removal of suspended food particles from the surrounding water by some sort of capture, trapping, or filtration structure.

This feeding strategy involves three steps:

(1) Transport of water past the feeding structure.

(2) Removal of nutrients from the water.

(3) Transport of the nutrients to the mouth of the digestive system. Sponges, ascidians, branchiopods, ectoprocts, entoprocts, phoronids, most bivalves, and many crustaceans, polychaetes, gastropods, and some nonvertebrate chordates are suspension feeders.

Deposit feeder:

Deposit feeding involves primarily omnivorous animals. These animals obtain their nutrients from the sediments of soft-bottom habitats (muds and sands) or terrestrial soils. Direct deposit feeders simply swallow large quantities of sediment (mud, soil, sand, organic matter). The usable nutrients are digested, and the remains pass out the anus.

Direct deposit feeding occurs in many polychaete annelids, Some snails, some sea urchins, and in most earthworms. Other direct deposit feeders utilize tentacle like structures to consume sediment. Examples  include sea cucumbers, most sipunculans, certain clams, and several types of polychaetes.

Herbivory:

Herbivory (L. herba, herb + vorare, to eat) is the consumption of macroscopic plants. This common feeding strategY requires the ability to "bite and chew" large pieces of plant matter (macroher bivory). Although biting and chewing mechanisms evolved within the architectural framework of a number of invertebrate lineages, they are often characterized by the development o hard surfaces (e.g., teeth) that powerful muscles manipulate.

Invertebrates that evolved macroherbivory include molluscs, polychaete worms, arthropods, and sea urchins. Many molluscs have a radula. A radula is a muscularized, belt-like rasp armed with chitinous teeth. Molluscs use the radula to scrape algae off rocks or to tear the leaves off terrestrial plants. Polychaetes have sets of large chitinous teeth on an eversible proboscis or pharynx that is used to scrape off algae.

This toothed pharynx is also suitable for carnivory when plant material is scarce. Macroherbivory is found in almost every group of arthropods. For Example , insects and crustaceans have large, powerful mandibles capable of biting off plant material and subsequently grinding and chewing it before passing the plant material to the mouth.

Predation:

Predation (L. praedator, a plunderer, pillager) is one of the most sophisticated feeding strategies, since it requires the capture of live prey. Only a few generalizations about the many kinds of predation are presented here.

Predators can be classified by how they capture their prey:

Motile stalkers, lurking predators, sessile opportunists, or grazers. Motile stalkers actively pursue their prey. Examples  include ciliate protozoa, nemerteans, polychaete worms, gastropods, octopuses and squids, crabs, sea stars, and many vertebrates. Lurking predators sit and wait for their prey to come within seizing distance.

Examples  include certain species of praying mantises, shrimp, crabs, spiders, polychaetes, and many vertebrates. Sessile opportunists usually are not very mobile. They can only capture prey when the prey organism comes into contact with them.

Examples  include certain protozoa, barnacles, and cnidarians. Grazing carnivores move about the substrate picking up small organisms. Their diet usually consists largely of sessile and slow-moving animals, such as sponges, ectoprocts, tunicates, snails, worms, and small crustaceans.

Surface Nutrients Absorption:

Some highly specialized animals have dispensed entirely with all mechanisms for prey capture, ingestion of food particles, and digestive processes. Instead they directly absorb nutrients from the external medium across their body surfaces. This medium may be nutrient-rich seawater, fluid in other animals' digestive tracts, or the body fluids of other animals.

For Example , some free-living protozoa, such as Chilomonas, absorb all of their nutrients across their body surface. The endoparasitic protozoa, cestode worms, endoparasitic gastropods, and crustaceans (all of which lack mouths and digestive systems) also absorb all of their nutrients across their body surface. A few nonparasitic multicellular animals also lack a mouth and digestive system and absorb nutrients across their body surface.

Examples include the gutless bivalves and pogonophoran worms. Interestingly, many pogonophoran worms absorb some nutrients from seawater across their body surface and also

Diversity of Animal as Digestive Structure:

Invertebrates

In primitive, multicellular animals, such as cnidarians, the gut is a blind (closed) sac called a Gastrovascular Cavity . It has only one opening that is both entrance and exit; thus, it is an incomplete digestive tract. Some specialized cells in the cavity secrete digestive enzymes that begin the process of extracellular digestion.

Other phagocytic cells that line the cavity engulf food material and continue intracellular digestion inside food vacuoles. Some flatworms have similar digestive patterns. The development of the anus and complete digestive tract in the aschelminths was an evolutionary breakthrough.

A complete digestive tract permits the one-way flow of ingested food without mixing it with previously ingested food or waste. Complete digestive tracts also have the advantage of progressive digestive processing in specialized regions along the system. Food can be digested efficiently in a series of distinctly different steps.

Instead, threeExamples further illustrate digestive systems in protozoa and invertebrates:

(1) The incomplete digestive system of a ciliated protozoan is an Example  of an intracellular digestive system

(2) The bivalve mollusc is an Example  of an invertebrate that has both intracellular and extracellular digestion;

(3) An insect is an Example of an invertebrate that has extracellular digestion and a complete digestive tract.

Fluids Feeders:

The biological fluids of animals and plants are a rich source of nutrients. Feeding on this fluid is called Fluid Feeding . Fluid feeding is especially characteristic of some parasites, such as the intestinal nematodes that bite and rasp off host tissue or suck blood. External parasites (ectoparasites), such as leeches, ticks, mites, lampreys, and certain crustaceans, use a wide variety of mouthparts to feed on body fluids.

For Example , the sea lamprey has a funnel structure surrounding its mouth. The funnel is lined with over 200 rasping teeth and a rasplike tongue. The lamprey uses the funnel like a suction cup to grip its fish host, and then with its tongue, rasps a hole in the fish's body wall. The lamprey then sucks blood and body fluids from the wound. Insects have the most highly developed sucking structures for fluid feeding.

For Example , butterflies, moths, and aphids have tube like mouthparts that enable them to suck up plant fluids. Blood sucking mosquitoes have complex mouthparts with piercing stylets. Most pollen- and nectar-feeding birds have long bills and tongues. In fact, the bill is often specialized (in shape, length, and curvature) for particular types of flowers.

The tongues of some birds have a brush like tip or are hollow, or both, to collect the nectar from flowers. Other nectar-feeding birds have short bills; they make a hole in the base of a flower and use their tongue to obtain nectar through the hole.

The only mammals that feed exclusively on blood are the vampire bats, such as Desmodus, of tropical South and Central America. These bats attack birds, cattle, and horses, using knife sharp front teeth to pierce the surface blood vessels, and then lap at the oozing wound.

Nectar feeding bats have a long tongue to extract the nectar from flowering plants, and compared to the blood-feeding bats, have reduced dentition. In like manner, the nectar-feeding honey possum has a long, brush-tipped tongue and reduced dentition.

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Source: https://www.zaheenlog.com/2022/04/SuspensionDeposit%20Feeder%20Herbivore.html

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