Deck 27: Nutrition and Digestion

Question 1

What advantages are there to digestion? Would it not be simpler for a vertebrate to simply absorb carbohydrates, lipids, and proteins from its food and to use these molecules without breaking them down?

Answer 1

Digestion refers to the process of breakdown of food- both chemical and mechanical breakdown- into smaller particles such that the cells of the specific animal can absorb easily.
The advantages of digestion are that:
• Mechanical breakdown of food helps to break food particles into smaller forms on which enzymes can act effectively and efficiently.
• Chemical breakdown of food helps to breakdown the constituent nutrients of food into smaller chemical units so that they are easily absorbed by the body and cells for producing energy.
• Digestion thus helps in breaking the nutrients present in food into an easily absorbable form.
The cell linings in intestines have specialized folds called villi that help absorb most of the nutrients from food. For the nutrients to be absorbed from food, they must first be broken down in to simpler molecules that can pass through the cell membrane.
Carbohydrates, lipids and proteins are complex forms of nutrients that need to be further broken down to simple sugars, fatty acids and amino acids respectively, so that they can be readily absorbed by the cell.
The complex molecules cannot be absorbed and used by the cells as it is. Hence it would not be possible for a vertebrate to simply absorb carbohydrates, proteins and lipids from the food as it is.

Question 2

Which of the following animals possess an incomplete digestive system?

A) echinoderms
B) annelids
C) flatworms
D) arthropods
E) molluscs

Answer 2

Earlier primitive animals like the cnidarians have an incomplete digestive system as gut mainly consists of a blind and closed sac known as the gastrovascular cavity. Complete digestive system with mouth, digestive tract and anus has been observed form aschelminths.
Echinoderms have a complete digestive system with mouth, stomach, intestine and anus. In most of the echinoderms, it is the anus that is present on the top while the mouth is present on the underside of the animal.
Thus option (a) is incorrect.
Annelids also have a complete digestive system that consists of a mouth (present on underside of the head), a long unsegmented gut and anus.
Thus option (b) is incorrect.
The digestive system of arthropods is a complete digestive system. Their digestive tract is divided into three major segments: foregut consisting of mouth, esophagus and pharynx; midgut consisting of stomach and hindgut consisting of colon and anus. Some arthropods even have a crop that acts as a storage organ.
Thus option (d) is incorrect.
Molluscs have a complete digestive system with a mouth, esophagus, stomach and anus. Their mouth also contains teeth like structures called radula.Thus option (e) is incorrect.
Flatworms belong to the primitive class of planarians that have an incompete digestive system. They just have one opening that acts both as mouth and anus. The muscular pharynx is stuck out of the mouth while feeding.
Thus correct option is (c).

Question 3

Autotrophs synthesize all of their own complex molecules from simpler ones; heterotrophs are animals that consume other animals for their nutrients; herbivores subsist entirely on plant material; carnivores eat only meat; omnivores eat plant and animal matter; and insectivores eat arthropods. Once an animal obtains complex organic molecules from its diet, it can lose the ability to synthesize those molecules and expend less energy on biosynthetic processes. This is an evolutionary advantage.
What are five animals that can be classified as omnivores?

Answer 3

Animals which depend on other organisms as their source of nutrients are known as heterotrophs. Depending on their mode of nutrition animals can be classified as herbivores, carnivores or omnivores. Those animals which use both plants and animals as their source of nutrition are known as omnivores.
Five animals which are omnivores are badgers, bears, raccoons, skunks and squirrels.

Question 4

What might have been some evolutionary pressures acting on animals that led to the internalization of digestive systems?

Question 5

Ruminants need multiple stomach chambers in order to digest

A) starch.
B) proteins.
C) cellulose.
D) lignin.
E) emzymes.

Question 6

The Calorie is important because it measures the energy value of food we consume. Micronutrients in an animal's diet are necessary for certain enzymatic reactions and as parts of certain proteins. Minerals that are needed in large amounts are called macrominerals. Sodium is a good example and is needed for nerve and muscle functioning. Microminerals are needed in small amounts and are necessary for the functioning of various enzymes. Vitamins are chemically unrelated substances that occur in food in small amounts and are necessary for metabolic functioning.
What human food sources can be relied on to supply vitamins in the diet?

Question 7

Many digestive enzymes are produced in the pancreas and released into the duodenum. Why, then, has the mammalian stomach evolved the ability to produce pepsinogen?

Question 8

In a robin, the muscular digestive organ in which food is crushed into small bits is the

A) cloaca.
B) lumen.
C) stomach.
D) crop.
E) gizzard.

Question 9

In some of the simplest forms of life (protists and sponges), cells take in food and break it down via enzymes within the cell. This is intracellular digestion. In contrast, in extracellular digestion, the breakdown of food via enzymes usually occurs within a special organ or cavity.
Why can't a sponge carry out extracellular digestion?

Question 10

Human vegetarians, unlike true herbivores, have no highly specialized fermentation chambers. Why?

Question 11

Which of the following organs of the digestive system is different from the four others because it does NOT produce any secretions that aid in the digestive process?

A) Salivary gland
B) Pancreas
C) Liver
D) Stomach
E) Esophagus

Question 12

Predation is one of the most sophisticated feeding strategies. Some animals feed exclusively on fluids because fluids are an excellent source of nutrients. Continuous feeders are usually slow-moving sessile animals (e.g., tube worms and clams) that remain in one place and continuously "strain food" from the water. Discontinuous feeders are active animals that take in large meals that must be ground up or stored. Carnivores are good examples of animals using this type of feeding. Suspension feeders obtain their food by some sort of capture, trapping, or filtration structure. Deposit feeders include polychaete annelids, some snails, and some sea urchins. Molluscs use herbivory to obtain food.
Why is Desmodus a unique mammal with respect to its feeding strategy?

Question 13

Trace the fate of a hamburger from the mouth to the anus, identifying sites and mechanisms of digestion and absorption.

Question 14

Which of the following vitamins functions in the formation of a blood clot?

A) A
B) E
C) K
D) D
E) C

Question 15

A gastrovascular cavity is an incomplete digestive system becauseit has only one opening that serves as both a mouth an anus. Thecells and tissues of a one-way digestive system are specialized sothat ingestion, digestion, and elimination can happen concurrently.These different processes make this system more efficient interms of food processing and energy utilization. Digestion in mollusksconsists of three cycles: feeding, extracellular digestion, andintracellular digestion. Complete digestive tracts permit a one-wayflow of food for continuous feeding and specializations of digestive structures for handling foods unique to the diets of many animals. Insects have a complete digestive tract because it contains a mouth, esophagus, crop, gastric seca, stomach, intestine, rectum, and anus.
In ciliated protozoa, what structure functions as an anus?

Question 16

The tongue of some frogs and salamanders is unique in that it can be rapidly projected to capture an insect. Omnivore teeth function in tearing, ripping, chiseling, and grinding. The ruminant lifestyle evolved in those animals that eat large quantities of food quickly but then can take their time in chewing the food at a more comfortable and safe location.
How can some vertebrates digest cellulose?

Question 17

The processes involved with digesting and absorbing nutrients in mammals include: ingestion, peristalsis, segmentation, secretion, digestion, absorption, and defecation. Digestion is accomplished by enzymes from the stomach, pancreas, and intestinal epithelium and bile salts produced by the liver and released by the gallbladder.
Why does fat not require carrier proteins to cross the intestinal epithelium?