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Feeding and Digestion – Part 1. Biology 155 A. Russo-Neustadt. I. Definitions. Ingestion = to bring food into the digestive system Digestion = to break food down into smaller molecules that can be absorbed by the body 1. Mechanical – physical , makes use of chewing, grinding, etc.

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Feeding and digestion part 1

Feeding and Digestion – Part 1

Biology 155

A. Russo-Neustadt


I definitions
I. Definitions

  • Ingestion = to bring food into the digestive system

  • Digestion = to break food down into smaller molecules that can be absorbed by the body

    1. Mechanical – physical, makes use of chewing, grinding, etc.

    2. Chemical - makes use of enzymes

    C. Egestion = elimination of non-digestible materials


Ii feeding mechanisms
II. Feeding Mechanisms:

  • Feeding on food dissolved (stays in solution) in the environment –

    • Rare

    • Animal takes up food across body surface

    • No need for a digestive system

      (Note that this mechanism is not mentioned in the textbook.)


Examples -

a. Tapeworms -

Marine invertebrates


Fig. 21.1C

B. Feeding on liquids –

1. Requires a specialized mouthpart to obtain fluids

2. Mouthparts are adapted for sucking or lapping

3. Other examples –

Plant sap – aphids

Blood – mosquitoes and vampire bats

Milk – young mammals

Lapping

Nectar as food source (also hummingbirds)

Sucking


C. Filter Feeding = feeding on small particles suspended (will settle out) in the environment

1. Must be aquatic

2. Requires specialized straining device

3. Continuous feeders

4. Indiscriminant feeders

Fig. 21.1A

c. Other examples – baleen whale, mollusks

a. sponges


D. Feeding on Large Particles – (will settle out) in the environment

1. Requires elaborate sensory systems to find prey

2. Requires elaborate motor systems to capture prey

3. Discontinuous feeders

4. Highly selective

Ex. Fish to mammals, insects

Figs. 21.1B (substrate feeders) and 21.1D


III. Intracellular versus Extracellular Digestion: (will settle out) in the environment

A. Intracellular = engulf (phagocytize) food particle and isolate it in a food vacuole inside a cell; digestive enzymes are secreted into the vacuole, where chemical digestion occurs

Problem = food must be smaller than a cell

Ex. Sponges and single celled organisms


Iii intracellular versus extracellular digestion continued
III. Intracellular versus Extracellular Digestion - continued

B. Extracellular = digestive enzymes are secreted into a cavity where chemical digestion generates small molecules that can be absorbed into the body

Advantage = can eat things larger than the size of a single cell


Ex. Jellyfish and their relatives (shown)

Flatworms (not shown)

Fig. 21.3A


2. Complete Digestive System = a True Gut, continuedsystem with both a mouth and an anus

Advantage = one-way traffic of food bolus, thus regional specialization is possible which increases digestive efficiency

Ex. Roundworms (shown here) through mammals (not shown)

Fig. 21.3B


IV. Example of a Generalized Complete Digestive Tract: continued

Salivary glands

Oral cavity

Mouth

esophagus

Fig. 21.4

liver

Stomach or crop and gizzard

Gall bladder

pancreas

Large intestine

Small intestine

Anus


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