Digestion

Question 1

Why do animals eat?

Answer 1

As heterotrophs, they eat for energy.

Question 2

Why is food broken down as it goes through the body?

Answer 2

Food is too bulky to be absorbed directly by the body’s cells

Question 3

Digestion

Answer 3

The process of breaking down food into molecules that are small enough to be absorbed

Question 4

Mechanical digestion

Answer 4

The physical breakdown of food through non-chemical processes

Question 5

Chemical digestion

Answer 5

The process of breaking down food with enzymes and chemicals

Question 6

Describe intracellular digestion

Answer 6

Food particle is enclosed by cell membrane through phagocytosis, digestion of food takes place in the digestive vacuole, products of digestion are absorbed into the cell, waste products are removed by exocytosis

Question 7

Sponges are … (and what 3 cells)

Answer 7

Suspension feeders who use intracellular digestion exclusively. They have no mouth or gut. choanocytes, archaeocytes, pinacocytes

Question 8

Extracellular digestion process

Answer 8

Digestion occurs within gut and not within cells

Question 9

What does extracellular digestion require?

Answer 9

A digestive tract and cells that secrete digestive enzymes into the gut

Question 10

Advantages of extracellular digestion?

Answer 10

Larger food masses can be ingested, cells lining the gut can become specialized for secreting particular enzymes or for absorption of nutrients

Question 11

Two types of digestive tracts

Answer 11

alimentary canal - mouth and anus (2 separate openings), gastrovascular cavity- mouth and anus (1 opening)

Question 12

Most animals with an incomplete gut use what form of digestion?

Answer 12

Intracellular and extracellular

Question 13

Disadvantage of an incomplete gut?

Answer 13

Newly ingested food is mixed with previous ingested food and waste

Question 14

Alimentary canal allows for

Answer 14

continuous and sequential processing of food, regional specialization of gut

Question 15

What animals have a complete gut?

Answer 15

vertebrates and other chordates

Question 16

Region 1 name and funtion

Answer 16

Region of reception - mouthparts for mechanical digestion such as jaws with teeth or beaks, mandibles. Mouth (buccal) cavity with salivary glands and tongues, pharynx

Question 17

What has a tongue?

Answer 17

vertebrates only

Question 18

Salivary glands function

Answer 18

Lubrication of food, secrete toxins to incapacitate prey, secrete salivary amylase (only in primate mammals, herbivorous molluscs, and some insects

Question 19

Functions of tongue

Answer 19

Mixing food with salivary gland secretion, capturing prey, detection of prey or conspecifics

Question 20

What animals use tongue for prey capture?

Answer 20

Frogs, salamanders, chameleons, anteaters, woodpeckers

Question 21

Tongues are used for chemoreception in all snakes and lizards to ____

Answer 21

detect prey, detect conspecifics (see if they are of the same species)

Question 22

Pharynx extends from what to what

Answer 22

Back of buccal cavity to the beginning of the esophagus

Question 23

In terrestrial vertebrates, the pharynx is what?

Answer 23

the passages for air and food cross

Question 24

Describe how a food bolus travels through the pharynx via (what is the food reflex?)

Answer 24

Swallowing reflex. Soft palate is pressed back against the pharynx to close the nasopharynx off, then the epiglottis tips down to close the trachea, and food travels downward via peristalsis and the epiglottis raises again so the trachea can reopen

Question 25

Region 2 name and function

Answer 25

Region of conduction and storage. Esophagus serves in conduction, crop serves for storage, peristalsis propels food toward stomach

Question 26

What layer of muscle is responsible for peristalsis mainly?

Answer 26

Inner circular muscles

Question 27

What allows food to enter the stomach?

Answer 27

The cardiac sphincter relaxes and allows food in.

Question 28

Function of the crop?

Answer 28

Food storage prior to the initiation of chemical digestion?

Question 29

Avian crop (5)

Answer 29

Present in most birds, allows for excess food storage temporarily, allows for ingestion of large quantities of abundant food, allows for parent to store and regurgitate food for younglings, well-developed in seed and grain-eating species to allow food to be softened prior to chemical digestion in stomach

Question 30

Bird stomach is called ____

Answer 30

proventriculus

Question 31

The gizzard is also known as the

Answer 31

ventriculus

Question 32

Region 3 name and function

Answer 32

Region of Early digestion and storage (and grinding), Stomach serves in early digestion of proteins Gizzard is not found in all animals, but it serves for grinding of food for it to absorbed

Question 33

What juice does the stomach produce and what are the 3 cells and their function? (4)

Answer 33

Gastric juice parietal cells secrete hydrochloric acid and look like crab claws Chief cells secrete pepsinogen which reacts with HCl to produce pepsin (which breaks down proteins) and they are located near the base of the structure Surface mucous cells produce mucus that coats the stomach lining so that the hydrochloric acid does not break down stomach lining and are located near the top of the structure

Question 34

Rugae

Answer 34

Smooth muscle folds in the stomach that churn the food

Question 35

What sphincter releases food to the duodenum?

Answer 35

Pyloric sphincter

Question 36

Why doesn't absorption of nutrients occur in the stomach?

Answer 36

It has not been digested enough

Question 37

Region 4

Answer 37

Region of terminal digestion and absorption

Question 38

Duodenum function

Answer 38

Duodenum receives bile from the liver and pancreatic juice to break down food.

Question 39

Bile

Answer 39

A fat emulsifier, which increases the surface area of fat

Question 40

Pancreatic juice composition and function of each enzyme (6)

Answer 40

Introduced in the duodenum 3 proteases Trypsin, chymotrypsin, carboxypeptidase - break down smaller proteins into even smaller proteins Pancreatic Lipase - turns fats into fatty acids and glycerol which can then be absorbed Pancreatic amylase - turns starch into maltose Nucleases turn DNA/RNA into nucleotides which can then be absorbed

Question 41

Gastric bypass surgery

Answer 41

Staples are used to permanently close off part of the stomach and this small pouch is attached directly to the jejunum. As a result this bypasses a large part of the stomach and the entire duodenum.

Question 42

How does gastric bypass result in weight loss?

Answer 42

The stomach is smaller, so the feeling of hunger will be satiated by less food. Also, food is not digested as entirely by the time it reaches the region of terminal digestion and absorption.

Question 43

Enzymes secreted by the epithelial cells lining the small intestine (5)

Answer 43

Aminopeptidase - turns even smaller proteins into amino acids, which can be absorbed Maltase - turns maltose into glucose, which can be absorbed Sucrase - turns sucrose into fructose and glucose, which can both be absorbed Lactase - turns lactose into galactose and glucose, which can be absorbed Alkaline phosphatase - breaks down a variety of phosphate compounds, e.g ATP, which can be absorbed

Question 44

How has the surface area adapted? (5)

Answer 44

Increased length Coiling Folding - spiral folds (sharks) or longitudinal folds (lampreys) Villi: tissue-level fingerlike projections from epithelial tissue Microvilli : Cellular-level fingerlike projections from the cell membrane

Question 45

Surface area of a cylinder is equal to what equation

Answer 45

2 pi r squared + 2 pi r h

Question 46

Mammalian small intestine is very ___ and shows ____

Answer 46

small; extensive coiling

Question 47

Sharks and rays increase the surface area available for absorption through___

Answer 47

Spiral valves in their intestines

Question 48

Microvilli and villi increase the surface area more than ____ compared to a smooth cylinder the same diameter

Answer 48

1000 ; the surface area of the inner lining of the small intestine is that of a football field (4500 square meters)

Question 49

Fatty acids and glycerol are transported from the lumen across the cell membrane into epithelial tissue via ___

Answer 49

simple diffusion

Question 50

Describe how simple sugars and amino acids are transported from the lumen across the cell membrane of epithelial tissue.

Answer 50

If concentration in lumen is higher, then it is done via facilitated diffusion via protein channels down the concentration gradient. If the concentration in the lumen is lower, then it is done via active transport via protein channels against the concentration gradient.

Question 51

Where do fats go from the epithelial cells of the small intestine?

Answer 51

Into lacteals, a part of the lymphatic system. This is done via simple diffusion. Fats pass through the thoracic duct into the circulatory system.

Question 52

Where do amino acids and simple sugars go from the epithelial cells of the small intestine?

Answer 52

They diffuse into blood capillaries and enter the circulatory system via facilitated diffusion down the concentration gradient.

Question 53

Region 5 name

Answer 53

Region of water absorption and concentration of solids

Question 54

Large intestine is the site of (3)

Answer 54

reabsorption of water reabsorption of salts considerable microbial activity (bacteria comprises 1/3 of dry weight of feces, bacteria degrade organic wastes, bacteria synthsize vitamin k and b, which are absorbed)

Question 55

Specialization of herbivores (3)

Answer 55

Herbivores have longer guts Herbivores cannot digest cellulose directly, which leads to a direct relationship with microbes that can produce cellulase

Question 56

Frogs in relation to digestion (4)

Answer 56

Most tadpoles are herbivorous and eat primarily algae. After metamorphosis, the frogs shift to a carnivorous diet consuming insects Dietary shift is reflected in differences between the digestive tracts of tadpoles and frogs. Their gut goes from a long spiral in a tadpole to a tube that does not take up as much space.

Question 57

Three major strategies of herbivorous animals (3)

Answer 57

Large, 4-chambered stomachs, coupled with rumination - in cows, deer, bison Large multi-chambered stomachs, usually without rumination - sloth, some marsupials Enlarged caecum - Seen in herbivorous non-ruminants, such as horses, rabbits, rodents

Question 58

4 chambers and their function in rumination species

Answer 58

Rumen - house microbes and digest cellulose Reticulum - House microbes and digest cellulose Omasum - absorption of water and minerals Abomasum - Functions in early digestion of proteins

Question 59

Rumination

Answer 59

Chewing the cud, which is partly digested food from the first stomach of ruminants to the mouth for further chewing

Question 60

Large multi-chambered stomachs without rumination resemble ____

Answer 60

The stomach of ruminants

Question 61

Enlarged caecum strategy (2)

Answer 61

Enhances digestion of plant matter Coprophagy - Keeps balance of flora in the gut as well as introduces another source of nutrients that are created in the lower large intestine and passed in the dung

Question 62

Is the ruminant herbivore or non-ruminant herbivore more efficient?

Answer 62

The nonruminant herbivore is more efficient since their strategy does not rely on regurgitation of cud and simply passes through their gut. The enlarged cecum strategy is inefficient as it requires coprophagy but is still more efficient than ruminant behaviors.