Lecture 8: Animal Digestion

Question 1

What are the 4 steps of food processing?

Answer 1

1. Ingestion
2. Digestion
3. Absorption
4. Elimination

Question 2

Define ingestion and where it occurs in a body with an alimentary canal. Which step of food processing is it?

Answer 2

Ingestion is the act of eating, this can vary between different animals.
Ingestion occurs in the mouth (oral cavity) of the alimentary canal and is the first step to processing food.

Question 3

Define digestion. What are the two kinds of digestion?

Which step of food processing is it?

Answer 3

Digestion is the process of breaking down the large organic molecules of food into smaller molecules animal bodies can use.
Digestion is the second step of food processing.
Two kinds:
mechanical and chemical digestion

Question 4

Define absorption and where it occurs in a body with an alimentary canal. Which step of food processing is it?

Answer 4

Absorption is how the nutrients enter the cells

Question 5

Define elimination and where it occurs in a body with an alimentary canal. Which step of food processing is it?

Answer 5

Elimination is how waste materials leave the body

Question 6

What are the 4 kinds of ingestion? describe and provide an example of each

Answer 6

1. Suspension and filter feeders: Aquatic animals that sift particles and small organisms out of water
   - ex. baleen whales, sponges
2. Substrate feeders: live on their food source either for a period of their lives or throughout their whole lives.
   - ex. caterpillars live on leaves until they metamorphosis
3. Fluid feeders: suck nutrient filled fluids from their food source
   - ex. nectar feeding birds like hummingbirds
4. Bulk feeders: eat large pieces of food or whole organisms
   - ex. humans

Question 7

What are the three big energy molecules that come from food? What process are they all important for?

Answer 7

• proteins
• carbohydrates
• fats
  Important in cellular respiration process for ATP production

Question 8

Why does digestion need to occur in animals?

Answer 8

Animals cannot use the large organic molecules (proteins, carbs, and fats) directly so they must be digested and broken down into their smaller components

Question 9

Compare and contrast mechanical and chemical digestion? Where does each occur?

Answer 9

Mechanical digestion is the physical break down of large food molecules into smaller particles.
This occurs firstly in the mouth with teeth grinding or chewing and secondly in the stomach with muscular contractions.

Whereas, chemical digestion is the breakdown of large food molecules into smaller compounds through the use of enzymes.
Chemical digestion occurs in the salivary glands of the mouth first and continues all the way through the alimentary canal.

Question 10

Define intracellular digestion.

Answer 10

The breakdown of food particles INSIDE cells. This occurs when cell membranes form a pocket around a large food particle (endocytosis) and the lysosome organelle releases digestive enzymes inside the cell to break down the large food particle

Question 11

Define extracellular digestion

Answer 11

The breakdown of food particles that occurs OUTSIDE of cells and within the digestive cavity (can be either gastrovascular or alimentary canal).
Extracellular digestion can include chemical and/or mechanical digestion.

Question 12

Compare and contrast intracellular and extracellular digestion?

Answer 12

Intracellular digestion and extracellular digestion are both forms of breaking down large food particles into smaller components so animals are able to absorb essential nutrients.

Intracellular digestion is the breakdown of food particles WITHIN cells. Whereas, extracellular digestion occurs outside of cells and within the digestive cavity.

Intracellular digestion is purely an enzymatic process of chemical digestion. Whereas, extracellular digestion can include chemical and/or mechanical digestion.

Intracellular digestion allows for an animal that is reliant on this form of digestion (only Porifera) to be able to digest and absorb nutrients from all areas within the body.
Whereas, in most other animals that rely on a combination of both extracellular and intracellular digestion, digestion and absorption occur in sequential orders at different stages of the digestive cavity.

Question 13

Which animals use only intracellular digestion?

Answer 13

PORIFERA (SPONGES) are the ONLY animals that depend completely on intracellular digestion

Question 14

T or F: A gastrovascular cavity has one opening where food enters and waste exits? give an example.

Answer 14

TRUE.

Phyla Porifera and species Hydra (from phyla cnidaria) are examples of animals with gastrovascular cavities

Question 15

T or F: in a gastrovascular cavity, digestion and absorption occur all throughout the cavity? why/why not?

Answer 15

TRUE. Because organisms with gastrovascular cavities have no circulatory system, instead the GVC extends throughout the entire body so the nutrients can be distributed to all cells in contact with the cavity

Question 16

T or F: in an alimentary canal, digestion and the processes involved occur sequentially through the animal’s body? why/why not?

Answer 16

TRUE. Ingestion through the mouth, moves through the digestive cavity, absorbed in a different area, waste out the anus

Question 17

In animals with alimentary canals, where does most of the digestion occur/what kind of digestion?
In animals with gastrovascular cavities?

Answer 17

In animals with alimentary canals, digestion occurs mostly inside the canal before entering the cells = EXTRACELLULAR. But some intracellular digestion will still occur.

Whereas, in animals with gastrovascular cavities, most of the digestion occurs within the cells = INTRACELLULAR

Question 18

Why does digestion not occur everywhere within an alimentary canal like it would in a GVC?

Answer 18

Digestion occurs in sequential stages within isolated compartments of the alimentary canal because the canal is not in contact with all body cells.
Most animals with ACs, also have a circulatory system to distribute nutrients.

Question 19

What are some advantages of having digestion occur sequentially in alimentary canals?

Answer 19

Animals with an AC can ingest more food before the digestion of the current meal is complete due to large storage compartments and sequential processing.
Beneficial for animals in nature who don’t receive regular meals.

Animals with an AC can ingest bigger food items

More diverse diet

Faster metabolism - breaking down large food molecules mechanically in the gut speeds up the process of the food particles being absorbed into body cells

Question 20

Why is a circulatory system beneficial for animals with an alimentary canal?

Answer 20

Because the alimentary canal is not in contact with all body cells, so the circulatory system distributes nutrients from where absorption occurs to other cells in different areas of the body.

Question 21

T or F: Alimentary canals are typically found in animals that have circulatory systems? why/why not?

Answer 21

TRUE.

Circulatory systems distribute nutrients to different body cells that are not in contact with the alimentary canal.

Question 22

What is a major difference between a gastrovascular cavity and an alimentary canal (complete gut)?

Answer 22

Gastrovascular cavities extend throughout the entire body of an animal and reaches all body cells. Whereas, an alimentary canal does not extend to all body cells and nutrient absorption is isolated to the small intestine.

Question 23

Is the trend in animal evolution toward increasing dependence on intra- or extracellular digestion? why?

Answer 23

Extracellular digestion because larger and more diverse food sources can be introduced into diets (key adaptation)

Question 24

T or F: Everything that happens in the alimentary canal is extracellular? why?

Answer 24

TRUE, it all occurs within the digestive cavity (AC).

Question 25

Where in the alimentary canal do carbohydrates, proteins, and fats begin chemical digestion?

Answer 25

Carbohydrates: ORAL CAVITY Proteins: STOMACH Fats: DUODENUM of the SMALL INTESTINE

Question 26

What are the structures and functions of the oral cavity? Which part of food processing occurs here? which of the 3 main food molecules begins chemical digestion here?

Answer 26

Both ingestion and some digestion occur in the oral cavity. Structures: tongue, teeth, salivary glands Functions: - tongue to move food around - teeth to mechanically digest (grind/chew) - salivary glands begin to chemically digest CARBOHYDRATES with enzymes

Question 27

What are the structures and functions of the esophagus?

Answer 27

The esophagus is the passage between the mouth and stomach that is regulated by muscular sphincters and the epiglottis. It is the passage way for food to move via peristalsis from the mouth to the stomach

Question 28

What is a sphincter?

Answer 28

Sphincters protect different compartments of the digestive tract

Question 29

What is the epiglottis?

Answer 29

The epiglottis is a flap that blocks the trachea while eating so that food does not enter the lungs

Question 30

What is peristalsis?

Answer 30

Wave-like muscle contractions in the esophagus that push chewed food down from the mouth to the stomach

Question 31

What are the 5 major compartments of the alimentary canal?

Answer 31

1. Oral cavity 2. Esophagus 3. Stomach 4. small intestine 5. large intestine

Question 32

Describe the function of the 3 accessory organs and to which major component of the alimentary canal are they CONNECTED to?

Answer 32

1. liver: produces bile 2. gallbladder: stores and concentrates bile until it is needed in the duodenum. 3. pancreas: secretes alkaline pancreatic juice into the duodenum and neutralizes acid chyme - enzymes sent from the pancreas to the duodenum help complete the breakdown of carbs, proteins, and fats. These are connected to the duodenum in the small intestine.

Question 33

What are the structures and functions of the stomach? Which of the 3 main food molecule begins chemical digestion here?

Answer 33

Structure: The stomach is a compartment that contains RUGAE which are accordion-like folds that can expand to accommodate food. Function: The stomach performs MUSCLE CONTRACTIONS to MECHANICALLY break down food and released stomach ACID and ENZYMES to CHEMICALLY break down PROTEINS

Question 34

What is the result of the mechanical and chemical digestion in the stomach?

Answer 34

the chemical breakdown of proteins with stomach acid and enzymes combined with the mechanical churning creates ACIDIC CHYME.

Question 35

What are the structures and function of the small intestine? Which of the 3 major food molecules begins chemical digestion here?

Answer 35

Chyme that was created in the stomach enters the first segment of the small intestine called the DUODENUM through a sphincter. Structure: 1. first segment: Duodenum 2. second segment: jejunum and ileum 3. Villi: projections that grow off the circular folds of the intestinal lining 4. Microvilli: projections off the cells that line the villi 1. Major function of the duodenum is CHEMICAL DIGESTION of FATS though some absorption occurs here too. 2. Function of the jejunum and ileum is nutrient ABSORPTION 3 & 4. Function of villi and microvilli and circular folds: increase surface area for increased absorption of minerals.

Question 36

T or F: most chemical digestion occurs in the first segment of the small intestine (the duodenum)?

Answer 36

TRUE.

Question 37

Where is bile produced? Where is it sent? What is its function?

Answer 37

Bile is produced in the LIVER and stored in the GALLBLADDER where it is concentrated until it is needed in the DUODENUM where it begins to chemically digest FATS.

Question 38

T or F: Chemical digestion occurs in the accessory organs?

Answer 38

FALSE. The accessory organs produce the enzymes that are necessary for the chemical digestion that occurs in the duodenum of the small intestine.

Question 39

How does chyme move through the small intestine?

Answer 39

Peristalsis! Wave-like muscle contractions that move chyme.

Question 40

Which major component of the alimentary canal does the majority of nutrient absorption occur?

Answer 40

The second section of the following the duodenum of the SMALL INTESTINE (structures: jejunum and ileum)

Question 41

What are the 3 structures of the large intestine and their functions? Which is the major component of the 3?

Answer 41

Structure: 1. colon - the major component 2. cecum 3. rectum Function: collective main function is to absorb water and solidify species 1. the colon absorbs water 2. cecum: fermentation chamber - enlarged in herbivores 3. rectum: feces storage until elimination through anus

Question 42

What are two general adaptations for plant vs. meat based diets?

Answer 42

1. teeth | 2. digestive systems

Question 43

Contrast animal teeth that are adapted for meat vs. plant based diets?

Answer 43

- Carnivores have large canines and less molars - molars are usually sharp to tear flesh - possess carnassial pair of molars that have a space between them to hold bones - Herbivores generally lack large canines and have many flattened molars to grind and chew cellulose and plant materials - some herbivores do have large canines (ex. gorillas) for defense - must chew a lot before ingesting plant material because cellulose is hard to break down - usually have a large space (diastema) between their incisors and their molars for elongated faces that allows them to see surroundings while they eat.

Question 44

How do carnivore digestive systems differ from herbivore digestive systems?

Answer 44

Carnivores: - Stomach is much more expandable than a herbivores to be able to store food for longer periods of time and eat as much as they can at once. - reduced cecum because they do not need to ferment much - reduced large intestine, likely cause nutrients from meat are easier to break down Herbivores: - enlarged cecum for fermenting (with bacteria) hard to digest plant materials like fibres - alimentary canal is more extensive because plants take longer to digest and more surface area to absorb