Deck 27: Nutrition and Digestion

Question 1

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

Answer 1

The type of digestive system varies from one species to the other. The earliest cells used to simply engulf food, digest them with enzymes and then throw the waste out as vesicles. But such organisms were able to ingest only simpler molecules.
With increasing complexity of the organisms, increasing demands of energy and variety in availability of food, there has been evolution of the digestive system from a single gastrovascular cavity to the advanced alimentary canal of humans.
Some of the evolutionary pressures that may have acted on the animals, leading to internalization of digestive system are:
• Increasing complexity of organism prompting higher demands of energy, necessitating increased intake of food
• Change in types of food being eaten due to change of habitats and available prey
• Intake of harder and tougher food items
• Necessity to digest and absorb food better for higher energy reserves to combat phases of drought
• Ability to store ingested food and completely absorb nutrients sequentially; to facilitate complete absorption of nutrients from ingested food to combat higher energy demands.

Question 2

Ruminants need multiple stomach chambers in order to digest

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

Answer 2

C
Ruminants are one of the few categories of herbivores who have multiple chambers of digestive tract for digestion of food. In ruminants, the food is first eaten, fermented in one of the chamber, regurgitated and chewed and then finally digested.
Digestion of starch is done by salivary amylase present in the saliva of animals. it is an easy carbohydrate to digest.
Thus option (a)
Protein digestion does not require multiple chambers. In fact just like mammals, protein is digested by gastric enzymes that are released in the gut.
Thus option (b)
Lignin is a compound that is found in the cell walls of plants. The amount of lignin is higher in cell walls of older plants and this lignin is not digested by ruminants.
Thus option (d)
Enzymes are not digested by the body. Instead enzymes help in the process of digestion.
Thus option (e)
Ruminants have a specialized chamber called rumen where the food that they swallow is firsts ent to. The rumen is rich in bacteria that help ferment cellulose present in the cell walls of plants releasing high amounts of energy. The fermented food is then sent to reticulum from where it is regurgitated back into the mouth, where it is chewed again. This chewed and fermented food passes on to omasum and abomasum for digestion.
Thus ruminants need various chambers for digestion of cellulose.

Question 3

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?
TABLE 27.4 WATER-SOLUBLE VITAMINS

Answer 3

Vitamins are organic substances present in many types of food which are necessary in small amounts for certain metabolic activities of the body. Vitamins B and C are water soluble while vitamins A, D, E and K are fat soluble.
Green leafy vegetables and carrots are a rich source of Vitamin A. Vitamin B is obtained from cereals, lean meats and eggs. Citrus fruits provide Vitamin C. The best food which is a source of Vitamin D is fatty fish. Vitamin E and K are obtained from vegetable oils and broccoli respectively.

Question 4

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 5

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 6

In 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 7

Human vegetarians, unlike true herbivores, have no highly specialized fermentation chambers. Explain how this is reflected in the structure of the digestive systems of a human and a deer.

Question 8

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 9

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 10

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

Question 11

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

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

Question 12

A gastrovascular cavity is an incomplete digestive system because it has only one opening that serves as both a mouth an anus. The cells and tissues of a one-way digestive system are specialized so that ingestion, digestion, and elimination can happen concurrently. These different processes make this system more efficient in terms of food processing and energy utilization. Digestion in molluscs consists of three cycles: feeding, extracellular digestion, and intracellular digestion. Complete digestive tracts permit a one-way flow 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 13

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 14

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?

Question 15

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?

Question 16

Which of the following animals possess an incomplete digestive system?

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

Question 17

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?